1 # SPDX-License-Identifier: GPL-2.0 1 # SPDX-License-Identifier: GPL-2.0
2 # 2 #
3 # General architecture dependent options 3 # General architecture dependent options
4 # 4 #
5 5
6 # 6 #
7 # Note: arch/$(SRCARCH)/Kconfig needs to be in 7 # Note: arch/$(SRCARCH)/Kconfig needs to be included first so that it can
8 # override the default values in this file. 8 # override the default values in this file.
9 # 9 #
10 source "arch/$(SRCARCH)/Kconfig" 10 source "arch/$(SRCARCH)/Kconfig"
11 11
12 config ARCH_CONFIGURES_CPU_MITIGATIONS 12 config ARCH_CONFIGURES_CPU_MITIGATIONS
13 bool 13 bool
14 14
15 if !ARCH_CONFIGURES_CPU_MITIGATIONS 15 if !ARCH_CONFIGURES_CPU_MITIGATIONS
16 config CPU_MITIGATIONS 16 config CPU_MITIGATIONS
17 def_bool y 17 def_bool y
18 endif 18 endif
19 19
20 # <<
21 # Selected by architectures that need custom D <<
22 # IOMMUs not handled by dma-iommu. Drivers mu <<
23 # <<
24 config ARCH_HAS_DMA_OPS <<
25 depends on HAS_DMA <<
26 select DMA_OPS_HELPERS <<
27 bool <<
28 <<
29 menu "General architecture-dependent options" 20 menu "General architecture-dependent options"
30 21
31 config ARCH_HAS_SUBPAGE_FAULTS 22 config ARCH_HAS_SUBPAGE_FAULTS
32 bool 23 bool
33 help 24 help
34 Select if the architecture can check 25 Select if the architecture can check permissions at sub-page
35 granularity (e.g. arm64 MTE). The pr 26 granularity (e.g. arm64 MTE). The probe_user_*() functions
36 must be implemented. 27 must be implemented.
37 28
38 config HOTPLUG_SMT 29 config HOTPLUG_SMT
39 bool 30 bool
40 31
41 config SMT_NUM_THREADS_DYNAMIC 32 config SMT_NUM_THREADS_DYNAMIC
42 bool 33 bool
43 34
44 # Selected by HOTPLUG_CORE_SYNC_DEAD or HOTPLU 35 # Selected by HOTPLUG_CORE_SYNC_DEAD or HOTPLUG_CORE_SYNC_FULL
45 config HOTPLUG_CORE_SYNC 36 config HOTPLUG_CORE_SYNC
46 bool 37 bool
47 38
48 # Basic CPU dead synchronization selected by a 39 # Basic CPU dead synchronization selected by architecture
49 config HOTPLUG_CORE_SYNC_DEAD 40 config HOTPLUG_CORE_SYNC_DEAD
50 bool 41 bool
51 select HOTPLUG_CORE_SYNC 42 select HOTPLUG_CORE_SYNC
52 43
53 # Full CPU synchronization with alive state se 44 # Full CPU synchronization with alive state selected by architecture
54 config HOTPLUG_CORE_SYNC_FULL 45 config HOTPLUG_CORE_SYNC_FULL
55 bool 46 bool
56 select HOTPLUG_CORE_SYNC_DEAD if HOTPL 47 select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU
57 select HOTPLUG_CORE_SYNC 48 select HOTPLUG_CORE_SYNC
58 49
59 config HOTPLUG_SPLIT_STARTUP 50 config HOTPLUG_SPLIT_STARTUP
60 bool 51 bool
61 select HOTPLUG_CORE_SYNC_FULL 52 select HOTPLUG_CORE_SYNC_FULL
62 53
63 config HOTPLUG_PARALLEL 54 config HOTPLUG_PARALLEL
64 bool 55 bool
65 select HOTPLUG_SPLIT_STARTUP 56 select HOTPLUG_SPLIT_STARTUP
66 57
67 config GENERIC_ENTRY 58 config GENERIC_ENTRY
68 bool 59 bool
69 60
70 config KPROBES 61 config KPROBES
71 bool "Kprobes" 62 bool "Kprobes"
72 depends on HAVE_KPROBES 63 depends on HAVE_KPROBES
73 select KALLSYMS 64 select KALLSYMS
74 select EXECMEM 65 select EXECMEM
75 select NEED_TASKS_RCU 66 select NEED_TASKS_RCU
76 help 67 help
77 Kprobes allows you to trap at almost 68 Kprobes allows you to trap at almost any kernel address and
78 execute a callback function. regist 69 execute a callback function. register_kprobe() establishes
79 a probepoint and specifies the callb 70 a probepoint and specifies the callback. Kprobes is useful
80 for kernel debugging, non-intrusive 71 for kernel debugging, non-intrusive instrumentation and testing.
81 If in doubt, say "N". 72 If in doubt, say "N".
82 73
83 config JUMP_LABEL 74 config JUMP_LABEL
84 bool "Optimize very unlikely/likely br 75 bool "Optimize very unlikely/likely branches"
85 depends on HAVE_ARCH_JUMP_LABEL 76 depends on HAVE_ARCH_JUMP_LABEL
86 select OBJTOOL if HAVE_JUMP_LABEL_HACK 77 select OBJTOOL if HAVE_JUMP_LABEL_HACK
87 help 78 help
88 This option enables a transparent br 79 This option enables a transparent branch optimization that
89 makes certain almost-always-true or 80 makes certain almost-always-true or almost-always-false branch
90 conditions even cheaper to execute w 81 conditions even cheaper to execute within the kernel.
91 82
92 Certain performance-sensitive kernel 83 Certain performance-sensitive kernel code, such as trace points,
93 scheduler functionality, networking 84 scheduler functionality, networking code and KVM have such
94 branches and include support for thi 85 branches and include support for this optimization technique.
95 86
96 If it is detected that the compiler 87 If it is detected that the compiler has support for "asm goto",
97 the kernel will compile such branche 88 the kernel will compile such branches with just a nop
98 instruction. When the condition flag 89 instruction. When the condition flag is toggled to true, the
99 nop will be converted to a jump inst 90 nop will be converted to a jump instruction to execute the
100 conditional block of instructions. 91 conditional block of instructions.
101 92
102 This technique lowers overhead and s 93 This technique lowers overhead and stress on the branch prediction
103 of the processor and generally makes 94 of the processor and generally makes the kernel faster. The update
104 of the condition is slower, but thos 95 of the condition is slower, but those are always very rare.
105 96
106 ( On 32-bit x86, the necessary optio 97 ( On 32-bit x86, the necessary options added to the compiler
107 flags may increase the size of the 98 flags may increase the size of the kernel slightly. )
108 99
109 config STATIC_KEYS_SELFTEST 100 config STATIC_KEYS_SELFTEST
110 bool "Static key selftest" 101 bool "Static key selftest"
111 depends on JUMP_LABEL 102 depends on JUMP_LABEL
112 help 103 help
113 Boot time self-test of the branch pa 104 Boot time self-test of the branch patching code.
114 105
115 config STATIC_CALL_SELFTEST 106 config STATIC_CALL_SELFTEST
116 bool "Static call selftest" 107 bool "Static call selftest"
117 depends on HAVE_STATIC_CALL 108 depends on HAVE_STATIC_CALL
118 help 109 help
119 Boot time self-test of the call patc 110 Boot time self-test of the call patching code.
120 111
121 config OPTPROBES 112 config OPTPROBES
122 def_bool y 113 def_bool y
123 depends on KPROBES && HAVE_OPTPROBES 114 depends on KPROBES && HAVE_OPTPROBES
124 select NEED_TASKS_RCU 115 select NEED_TASKS_RCU
125 116
126 config KPROBES_ON_FTRACE 117 config KPROBES_ON_FTRACE
127 def_bool y 118 def_bool y
128 depends on KPROBES && HAVE_KPROBES_ON_ 119 depends on KPROBES && HAVE_KPROBES_ON_FTRACE
129 depends on DYNAMIC_FTRACE_WITH_REGS 120 depends on DYNAMIC_FTRACE_WITH_REGS
130 help 121 help
131 If function tracer is enabled and th 122 If function tracer is enabled and the arch supports full
132 passing of pt_regs to function traci 123 passing of pt_regs to function tracing, then kprobes can
133 optimize on top of function tracing. 124 optimize on top of function tracing.
134 125
135 config UPROBES 126 config UPROBES
136 def_bool n 127 def_bool n
137 depends on ARCH_SUPPORTS_UPROBES 128 depends on ARCH_SUPPORTS_UPROBES
138 help 129 help
139 Uprobes is the user-space counterpar 130 Uprobes is the user-space counterpart to kprobes: they
140 enable instrumentation applications 131 enable instrumentation applications (such as 'perf probe')
141 to establish unintrusive probes in u 132 to establish unintrusive probes in user-space binaries and
142 libraries, by executing handler func 133 libraries, by executing handler functions when the probes
143 are hit by user-space applications. 134 are hit by user-space applications.
144 135
145 ( These probes come in the form of s 136 ( These probes come in the form of single-byte breakpoints,
146 managed by the kernel and kept tra 137 managed by the kernel and kept transparent to the probed
147 application. ) 138 application. )
148 139
149 config HAVE_64BIT_ALIGNED_ACCESS 140 config HAVE_64BIT_ALIGNED_ACCESS
150 def_bool 64BIT && !HAVE_EFFICIENT_UNAL 141 def_bool 64BIT && !HAVE_EFFICIENT_UNALIGNED_ACCESS
151 help 142 help
152 Some architectures require 64 bit ac 143 Some architectures require 64 bit accesses to be 64 bit
153 aligned, which also requires structs 144 aligned, which also requires structs containing 64 bit values
154 to be 64 bit aligned too. This inclu 145 to be 64 bit aligned too. This includes some 32 bit
155 architectures which can do 64 bit ac 146 architectures which can do 64 bit accesses, as well as 64 bit
156 architectures without unaligned acce 147 architectures without unaligned access.
157 148
158 This symbol should be selected by an 149 This symbol should be selected by an architecture if 64 bit
159 accesses are required to be 64 bit a 150 accesses are required to be 64 bit aligned in this way even
160 though it is not a 64 bit architectu 151 though it is not a 64 bit architecture.
161 152
162 See Documentation/core-api/unaligned 153 See Documentation/core-api/unaligned-memory-access.rst for
163 more information on the topic of una 154 more information on the topic of unaligned memory accesses.
164 155
165 config HAVE_EFFICIENT_UNALIGNED_ACCESS 156 config HAVE_EFFICIENT_UNALIGNED_ACCESS
166 bool 157 bool
167 help 158 help
168 Some architectures are unable to per 159 Some architectures are unable to perform unaligned accesses
169 without the use of get_unaligned/put 160 without the use of get_unaligned/put_unaligned. Others are
170 unable to perform such accesses effi 161 unable to perform such accesses efficiently (e.g. trap on
171 unaligned access and require fixing 162 unaligned access and require fixing it up in the exception
172 handler.) 163 handler.)
173 164
174 This symbol should be selected by an 165 This symbol should be selected by an architecture if it can
175 perform unaligned accesses efficient 166 perform unaligned accesses efficiently to allow different
176 code paths to be selected for these 167 code paths to be selected for these cases. Some network
177 drivers, for example, could opt to n 168 drivers, for example, could opt to not fix up alignment
178 problems with received packets if do 169 problems with received packets if doing so would not help
179 much. 170 much.
180 171
181 See Documentation/core-api/unaligned 172 See Documentation/core-api/unaligned-memory-access.rst for more
182 information on the topic of unaligne 173 information on the topic of unaligned memory accesses.
183 174
184 config ARCH_USE_BUILTIN_BSWAP 175 config ARCH_USE_BUILTIN_BSWAP
185 bool 176 bool
186 help 177 help
187 Modern versions of GCC (since 4.4) h 178 Modern versions of GCC (since 4.4) have builtin functions
188 for handling byte-swapping. Using th 179 for handling byte-swapping. Using these, instead of the old
189 inline assembler that the architectu 180 inline assembler that the architecture code provides in the
190 __arch_bswapXX() macros, allows the 181 __arch_bswapXX() macros, allows the compiler to see what's
191 happening and offers more opportunit 182 happening and offers more opportunity for optimisation. In
192 particular, the compiler will be abl 183 particular, the compiler will be able to combine the byteswap
193 with a nearby load or store and use 184 with a nearby load or store and use load-and-swap or
194 store-and-swap instructions if the a 185 store-and-swap instructions if the architecture has them. It
195 should almost *never* result in code 186 should almost *never* result in code which is worse than the
196 hand-coded assembler in <asm/swab.h> 187 hand-coded assembler in <asm/swab.h>. But just in case it
197 does, the use of the builtins is opt 188 does, the use of the builtins is optional.
198 189
199 Any architecture with load-and-swap 190 Any architecture with load-and-swap or store-and-swap
200 instructions should set this. And it 191 instructions should set this. And it shouldn't hurt to set it
201 on architectures that don't have suc 192 on architectures that don't have such instructions.
202 193
203 config KRETPROBES 194 config KRETPROBES
204 def_bool y 195 def_bool y
205 depends on KPROBES && (HAVE_KRETPROBES 196 depends on KPROBES && (HAVE_KRETPROBES || HAVE_RETHOOK)
206 197
207 config KRETPROBE_ON_RETHOOK 198 config KRETPROBE_ON_RETHOOK
208 def_bool y 199 def_bool y
209 depends on HAVE_RETHOOK 200 depends on HAVE_RETHOOK
210 depends on KRETPROBES 201 depends on KRETPROBES
211 select RETHOOK 202 select RETHOOK
212 203
213 config USER_RETURN_NOTIFIER 204 config USER_RETURN_NOTIFIER
214 bool 205 bool
215 depends on HAVE_USER_RETURN_NOTIFIER 206 depends on HAVE_USER_RETURN_NOTIFIER
216 help 207 help
217 Provide a kernel-internal notificati 208 Provide a kernel-internal notification when a cpu is about to
218 switch to user mode. 209 switch to user mode.
219 210
220 config HAVE_IOREMAP_PROT 211 config HAVE_IOREMAP_PROT
221 bool 212 bool
222 213
223 config HAVE_KPROBES 214 config HAVE_KPROBES
224 bool 215 bool
225 216
226 config HAVE_KRETPROBES 217 config HAVE_KRETPROBES
227 bool 218 bool
228 219
229 config HAVE_OPTPROBES 220 config HAVE_OPTPROBES
230 bool 221 bool
231 222
232 config HAVE_KPROBES_ON_FTRACE 223 config HAVE_KPROBES_ON_FTRACE
233 bool 224 bool
234 225
235 config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE 226 config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
236 bool 227 bool
237 help 228 help
238 Since kretprobes modifies return add 229 Since kretprobes modifies return address on the stack, the
239 stacktrace may see the kretprobe tra 230 stacktrace may see the kretprobe trampoline address instead
240 of correct one. If the architecture 231 of correct one. If the architecture stacktrace code and
241 unwinder can adjust such entries, se 232 unwinder can adjust such entries, select this configuration.
242 233
243 config HAVE_FUNCTION_ERROR_INJECTION 234 config HAVE_FUNCTION_ERROR_INJECTION
244 bool 235 bool
245 236
246 config HAVE_NMI 237 config HAVE_NMI
247 bool 238 bool
248 239
249 config HAVE_FUNCTION_DESCRIPTORS 240 config HAVE_FUNCTION_DESCRIPTORS
250 bool 241 bool
251 242
252 config TRACE_IRQFLAGS_SUPPORT 243 config TRACE_IRQFLAGS_SUPPORT
253 bool 244 bool
254 245
255 config TRACE_IRQFLAGS_NMI_SUPPORT 246 config TRACE_IRQFLAGS_NMI_SUPPORT
256 bool 247 bool
257 248
258 # 249 #
259 # An arch should select this if it provides al 250 # An arch should select this if it provides all these things:
260 # 251 #
261 # task_pt_regs() in asm/process 252 # task_pt_regs() in asm/processor.h or asm/ptrace.h
262 # arch_has_single_step() if there is ha 253 # arch_has_single_step() if there is hardware single-step support
263 # arch_has_block_step() if there is ha 254 # arch_has_block_step() if there is hardware block-step support
264 # asm/syscall.h supplying asm- 255 # asm/syscall.h supplying asm-generic/syscall.h interface
265 # linux/regset.h user_regset in 256 # linux/regset.h user_regset interfaces
266 # CORE_DUMP_USE_REGSET #define'd in l 257 # CORE_DUMP_USE_REGSET #define'd in linux/elf.h
267 # TIF_SYSCALL_TRACE calls ptrace_r 258 # TIF_SYSCALL_TRACE calls ptrace_report_syscall_{entry,exit}
268 # TIF_NOTIFY_RESUME calls resume_u 259 # TIF_NOTIFY_RESUME calls resume_user_mode_work()
269 # 260 #
270 config HAVE_ARCH_TRACEHOOK 261 config HAVE_ARCH_TRACEHOOK
271 bool 262 bool
272 263
273 config HAVE_DMA_CONTIGUOUS 264 config HAVE_DMA_CONTIGUOUS
274 bool 265 bool
275 266
276 config GENERIC_SMP_IDLE_THREAD 267 config GENERIC_SMP_IDLE_THREAD
277 bool 268 bool
278 269
279 config GENERIC_IDLE_POLL_SETUP 270 config GENERIC_IDLE_POLL_SETUP
280 bool 271 bool
281 272
282 config ARCH_HAS_FORTIFY_SOURCE 273 config ARCH_HAS_FORTIFY_SOURCE
283 bool 274 bool
284 help 275 help
285 An architecture should select this w 276 An architecture should select this when it can successfully
286 build and run with CONFIG_FORTIFY_SO 277 build and run with CONFIG_FORTIFY_SOURCE.
287 278
288 # 279 #
289 # Select if the arch provides a historic keepi 280 # Select if the arch provides a historic keepinit alias for the retain_initrd
290 # command line option 281 # command line option
291 # 282 #
292 config ARCH_HAS_KEEPINITRD 283 config ARCH_HAS_KEEPINITRD
293 bool 284 bool
294 285
295 # Select if arch has all set_memory_ro/rw/x/nx 286 # Select if arch has all set_memory_ro/rw/x/nx() functions in asm/cacheflush.h
296 config ARCH_HAS_SET_MEMORY 287 config ARCH_HAS_SET_MEMORY
297 bool 288 bool
298 289
299 # Select if arch has all set_direct_map_invali 290 # Select if arch has all set_direct_map_invalid/default() functions
300 config ARCH_HAS_SET_DIRECT_MAP 291 config ARCH_HAS_SET_DIRECT_MAP
301 bool 292 bool
302 293
303 # 294 #
304 # Select if the architecture provides the arch 295 # Select if the architecture provides the arch_dma_set_uncached symbol to
305 # either provide an uncached segment alias for 296 # either provide an uncached segment alias for a DMA allocation, or
306 # to remap the page tables in place. 297 # to remap the page tables in place.
307 # 298 #
308 config ARCH_HAS_DMA_SET_UNCACHED 299 config ARCH_HAS_DMA_SET_UNCACHED
309 bool 300 bool
310 301
311 # 302 #
312 # Select if the architectures provides the arc 303 # Select if the architectures provides the arch_dma_clear_uncached symbol
313 # to undo an in-place page table remap for unc 304 # to undo an in-place page table remap for uncached access.
314 # 305 #
315 config ARCH_HAS_DMA_CLEAR_UNCACHED 306 config ARCH_HAS_DMA_CLEAR_UNCACHED
316 bool 307 bool
317 308
318 config ARCH_HAS_CPU_FINALIZE_INIT 309 config ARCH_HAS_CPU_FINALIZE_INIT
319 bool 310 bool
320 311
321 # The architecture has a per-task state that i 312 # The architecture has a per-task state that includes the mm's PASID
322 config ARCH_HAS_CPU_PASID 313 config ARCH_HAS_CPU_PASID
323 bool 314 bool
324 select IOMMU_MM_DATA 315 select IOMMU_MM_DATA
325 316
326 config HAVE_ARCH_THREAD_STRUCT_WHITELIST 317 config HAVE_ARCH_THREAD_STRUCT_WHITELIST
327 bool 318 bool
328 help 319 help
329 An architecture should select this t 320 An architecture should select this to provide hardened usercopy
330 knowledge about what region of the t 321 knowledge about what region of the thread_struct should be
331 whitelisted for copying to userspace 322 whitelisted for copying to userspace. Normally this is only the
332 FPU registers. Specifically, arch_th 323 FPU registers. Specifically, arch_thread_struct_whitelist()
333 should be implemented. Without this, 324 should be implemented. Without this, the entire thread_struct
334 field in task_struct will be left wh 325 field in task_struct will be left whitelisted.
335 326
336 # Select if arch wants to size task_struct dyn 327 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
337 config ARCH_WANTS_DYNAMIC_TASK_STRUCT 328 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
338 bool 329 bool
339 330
340 config ARCH_WANTS_NO_INSTR 331 config ARCH_WANTS_NO_INSTR
341 bool 332 bool
342 help 333 help
343 An architecture should select this i 334 An architecture should select this if the noinstr macro is being used on
344 functions to denote that the toolcha 335 functions to denote that the toolchain should avoid instrumenting such
345 functions and is required for correc 336 functions and is required for correctness.
346 337
347 config ARCH_32BIT_OFF_T 338 config ARCH_32BIT_OFF_T
348 bool 339 bool
349 depends on !64BIT 340 depends on !64BIT
350 help 341 help
351 All new 32-bit architectures should 342 All new 32-bit architectures should have 64-bit off_t type on
352 userspace side which corresponds to 343 userspace side which corresponds to the loff_t kernel type. This
353 is the requirement for modern ABIs. 344 is the requirement for modern ABIs. Some existing architectures
354 still support 32-bit off_t. This opt 345 still support 32-bit off_t. This option is enabled for all such
355 architectures explicitly. 346 architectures explicitly.
356 347
357 # Selected by 64 bit architectures which have 348 # Selected by 64 bit architectures which have a 32 bit f_tinode in struct ustat
358 config ARCH_32BIT_USTAT_F_TINODE 349 config ARCH_32BIT_USTAT_F_TINODE
359 bool 350 bool
360 351
361 config HAVE_ASM_MODVERSIONS 352 config HAVE_ASM_MODVERSIONS
362 bool 353 bool
363 help 354 help
364 This symbol should be selected by an 355 This symbol should be selected by an architecture if it provides
365 <asm/asm-prototypes.h> to support th 356 <asm/asm-prototypes.h> to support the module versioning for symbols
366 exported from assembly code. 357 exported from assembly code.
367 358
368 config HAVE_REGS_AND_STACK_ACCESS_API 359 config HAVE_REGS_AND_STACK_ACCESS_API
369 bool 360 bool
370 help 361 help
371 This symbol should be selected by an 362 This symbol should be selected by an architecture if it supports
372 the API needed to access registers a 363 the API needed to access registers and stack entries from pt_regs,
373 declared in asm/ptrace.h 364 declared in asm/ptrace.h
374 For example the kprobes-based event 365 For example the kprobes-based event tracer needs this API.
375 366
376 config HAVE_RSEQ 367 config HAVE_RSEQ
377 bool 368 bool
378 depends on HAVE_REGS_AND_STACK_ACCESS_ 369 depends on HAVE_REGS_AND_STACK_ACCESS_API
379 help 370 help
380 This symbol should be selected by an 371 This symbol should be selected by an architecture if it
381 supports an implementation of restar 372 supports an implementation of restartable sequences.
382 373
383 config HAVE_RUST 374 config HAVE_RUST
384 bool 375 bool
385 help 376 help
386 This symbol should be selected by an 377 This symbol should be selected by an architecture if it
387 supports Rust. 378 supports Rust.
388 379
389 config HAVE_FUNCTION_ARG_ACCESS_API 380 config HAVE_FUNCTION_ARG_ACCESS_API
390 bool 381 bool
391 help 382 help
392 This symbol should be selected by an 383 This symbol should be selected by an architecture if it supports
393 the API needed to access function ar 384 the API needed to access function arguments from pt_regs,
394 declared in asm/ptrace.h 385 declared in asm/ptrace.h
395 386
396 config HAVE_HW_BREAKPOINT 387 config HAVE_HW_BREAKPOINT
397 bool 388 bool
398 depends on PERF_EVENTS 389 depends on PERF_EVENTS
399 390
400 config HAVE_MIXED_BREAKPOINTS_REGS 391 config HAVE_MIXED_BREAKPOINTS_REGS
401 bool 392 bool
402 depends on HAVE_HW_BREAKPOINT 393 depends on HAVE_HW_BREAKPOINT
403 help 394 help
404 Depending on the arch implementation 395 Depending on the arch implementation of hardware breakpoints,
405 some of them have separate registers 396 some of them have separate registers for data and instruction
406 breakpoints addresses, others have m 397 breakpoints addresses, others have mixed registers to store
407 them but define the access type in a 398 them but define the access type in a control register.
408 Select this option if your arch impl 399 Select this option if your arch implements breakpoints under the
409 latter fashion. 400 latter fashion.
410 401
411 config HAVE_USER_RETURN_NOTIFIER 402 config HAVE_USER_RETURN_NOTIFIER
412 bool 403 bool
413 404
414 config HAVE_PERF_EVENTS_NMI 405 config HAVE_PERF_EVENTS_NMI
415 bool 406 bool
416 help 407 help
417 System hardware can generate an NMI 408 System hardware can generate an NMI using the perf event
418 subsystem. Also has support for cal 409 subsystem. Also has support for calculating CPU cycle events
419 to determine how many clock cycles i 410 to determine how many clock cycles in a given period.
420 411
421 config HAVE_HARDLOCKUP_DETECTOR_PERF 412 config HAVE_HARDLOCKUP_DETECTOR_PERF
422 bool 413 bool
423 depends on HAVE_PERF_EVENTS_NMI 414 depends on HAVE_PERF_EVENTS_NMI
424 help 415 help
425 The arch chooses to use the generic 416 The arch chooses to use the generic perf-NMI-based hardlockup
426 detector. Must define HAVE_PERF_EVEN 417 detector. Must define HAVE_PERF_EVENTS_NMI.
427 418
428 config HAVE_HARDLOCKUP_DETECTOR_ARCH 419 config HAVE_HARDLOCKUP_DETECTOR_ARCH
429 bool 420 bool
430 help 421 help
431 The arch provides its own hardlockup 422 The arch provides its own hardlockup detector implementation instead
432 of the generic ones. 423 of the generic ones.
433 424
434 It uses the same command line parame 425 It uses the same command line parameters, and sysctl interface,
435 as the generic hardlockup detectors. 426 as the generic hardlockup detectors.
436 427
437 config HAVE_PERF_REGS 428 config HAVE_PERF_REGS
438 bool 429 bool
439 help 430 help
440 Support selective register dumps for 431 Support selective register dumps for perf events. This includes
441 bit-mapping of each registers and a 432 bit-mapping of each registers and a unique architecture id.
442 433
443 config HAVE_PERF_USER_STACK_DUMP 434 config HAVE_PERF_USER_STACK_DUMP
444 bool 435 bool
445 help 436 help
446 Support user stack dumps for perf ev 437 Support user stack dumps for perf event samples. This needs
447 access to the user stack pointer whi 438 access to the user stack pointer which is not unified across
448 architectures. 439 architectures.
449 440
450 config HAVE_ARCH_JUMP_LABEL 441 config HAVE_ARCH_JUMP_LABEL
451 bool 442 bool
452 443
453 config HAVE_ARCH_JUMP_LABEL_RELATIVE 444 config HAVE_ARCH_JUMP_LABEL_RELATIVE
454 bool 445 bool
455 446
456 config MMU_GATHER_TABLE_FREE 447 config MMU_GATHER_TABLE_FREE
457 bool 448 bool
458 449
459 config MMU_GATHER_RCU_TABLE_FREE 450 config MMU_GATHER_RCU_TABLE_FREE
460 bool 451 bool
461 select MMU_GATHER_TABLE_FREE 452 select MMU_GATHER_TABLE_FREE
462 453
463 config MMU_GATHER_PAGE_SIZE 454 config MMU_GATHER_PAGE_SIZE
464 bool 455 bool
465 456
466 config MMU_GATHER_NO_RANGE 457 config MMU_GATHER_NO_RANGE
467 bool 458 bool
468 select MMU_GATHER_MERGE_VMAS 459 select MMU_GATHER_MERGE_VMAS
469 460
470 config MMU_GATHER_NO_FLUSH_CACHE 461 config MMU_GATHER_NO_FLUSH_CACHE
471 bool 462 bool
472 463
473 config MMU_GATHER_MERGE_VMAS 464 config MMU_GATHER_MERGE_VMAS
474 bool 465 bool
475 466
476 config MMU_GATHER_NO_GATHER 467 config MMU_GATHER_NO_GATHER
477 bool 468 bool
478 depends on MMU_GATHER_TABLE_FREE 469 depends on MMU_GATHER_TABLE_FREE
479 470
480 config ARCH_WANT_IRQS_OFF_ACTIVATE_MM 471 config ARCH_WANT_IRQS_OFF_ACTIVATE_MM
481 bool 472 bool
482 help 473 help
483 Temporary select until all architect 474 Temporary select until all architectures can be converted to have
484 irqs disabled over activate_mm. Arch 475 irqs disabled over activate_mm. Architectures that do IPI based TLB
485 shootdowns should enable this. 476 shootdowns should enable this.
486 477
487 # Use normal mm refcounting for MMU_LAZY_TLB k 478 # Use normal mm refcounting for MMU_LAZY_TLB kernel thread references.
488 # MMU_LAZY_TLB_REFCOUNT=n can improve the scal 479 # MMU_LAZY_TLB_REFCOUNT=n can improve the scalability of context switching
489 # to/from kernel threads when the same mm is r 480 # to/from kernel threads when the same mm is running on a lot of CPUs (a large
490 # multi-threaded application), by reducing con 481 # multi-threaded application), by reducing contention on the mm refcount.
491 # 482 #
492 # This can be disabled if the architecture ens 483 # This can be disabled if the architecture ensures no CPUs are using an mm as a
493 # "lazy tlb" beyond its final refcount (i.e., 484 # "lazy tlb" beyond its final refcount (i.e., by the time __mmdrop frees the mm
494 # or its kernel page tables). This could be ar 485 # or its kernel page tables). This could be arranged by arch_exit_mmap(), or
495 # final exit(2) TLB flush, for example. 486 # final exit(2) TLB flush, for example.
496 # 487 #
497 # To implement this, an arch *must*: 488 # To implement this, an arch *must*:
498 # Ensure the _lazy_tlb variants of mmgrab/mmdr 489 # Ensure the _lazy_tlb variants of mmgrab/mmdrop are used when manipulating
499 # the lazy tlb reference of a kthread's ->acti 490 # the lazy tlb reference of a kthread's ->active_mm (non-arch code has been
500 # converted already). 491 # converted already).
501 config MMU_LAZY_TLB_REFCOUNT 492 config MMU_LAZY_TLB_REFCOUNT
502 def_bool y 493 def_bool y
503 depends on !MMU_LAZY_TLB_SHOOTDOWN 494 depends on !MMU_LAZY_TLB_SHOOTDOWN
504 495
505 # This option allows MMU_LAZY_TLB_REFCOUNT=n. 496 # This option allows MMU_LAZY_TLB_REFCOUNT=n. It ensures no CPUs are using an
506 # mm as a lazy tlb beyond its last reference c 497 # mm as a lazy tlb beyond its last reference count, by shooting down these
507 # users before the mm is deallocated. __mmdrop 498 # users before the mm is deallocated. __mmdrop() first IPIs all CPUs that may
508 # be using the mm as a lazy tlb, so that they 499 # be using the mm as a lazy tlb, so that they may switch themselves to using
509 # init_mm for their active mm. mm_cpumask(mm) 500 # init_mm for their active mm. mm_cpumask(mm) is used to determine which CPUs
510 # may be using mm as a lazy tlb mm. 501 # may be using mm as a lazy tlb mm.
511 # 502 #
512 # To implement this, an arch *must*: 503 # To implement this, an arch *must*:
513 # - At the time of the final mmdrop of the mm, 504 # - At the time of the final mmdrop of the mm, ensure mm_cpumask(mm) contains
514 # at least all possible CPUs in which the mm 505 # at least all possible CPUs in which the mm is lazy.
515 # - It must meet the requirements for MMU_LAZY 506 # - It must meet the requirements for MMU_LAZY_TLB_REFCOUNT=n (see above).
516 config MMU_LAZY_TLB_SHOOTDOWN 507 config MMU_LAZY_TLB_SHOOTDOWN
517 bool 508 bool
518 509
519 config ARCH_HAVE_NMI_SAFE_CMPXCHG 510 config ARCH_HAVE_NMI_SAFE_CMPXCHG
520 bool 511 bool
521 512
522 config ARCH_HAVE_EXTRA_ELF_NOTES 513 config ARCH_HAVE_EXTRA_ELF_NOTES
523 bool 514 bool
524 help 515 help
525 An architecture should select this i 516 An architecture should select this in order to enable adding an
526 arch-specific ELF note section to co 517 arch-specific ELF note section to core files. It must provide two
527 functions: elf_coredump_extra_notes_ 518 functions: elf_coredump_extra_notes_size() and
528 elf_coredump_extra_notes_write() whi 519 elf_coredump_extra_notes_write() which are invoked by the ELF core
529 dumper. 520 dumper.
530 521
531 config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS 522 config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
532 bool 523 bool
533 524
534 config HAVE_ALIGNED_STRUCT_PAGE 525 config HAVE_ALIGNED_STRUCT_PAGE
535 bool 526 bool
536 help 527 help
537 This makes sure that struct pages ar 528 This makes sure that struct pages are double word aligned and that
538 e.g. the SLUB allocator can perform 529 e.g. the SLUB allocator can perform double word atomic operations
539 on a struct page for better performa 530 on a struct page for better performance. However selecting this
540 might increase the size of a struct 531 might increase the size of a struct page by a word.
541 532
542 config HAVE_CMPXCHG_LOCAL 533 config HAVE_CMPXCHG_LOCAL
543 bool 534 bool
544 535
545 config HAVE_CMPXCHG_DOUBLE 536 config HAVE_CMPXCHG_DOUBLE
546 bool 537 bool
547 538
548 config ARCH_WEAK_RELEASE_ACQUIRE 539 config ARCH_WEAK_RELEASE_ACQUIRE
549 bool 540 bool
550 541
551 config ARCH_WANT_IPC_PARSE_VERSION 542 config ARCH_WANT_IPC_PARSE_VERSION
552 bool 543 bool
553 544
554 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION 545 config ARCH_WANT_COMPAT_IPC_PARSE_VERSION
555 bool 546 bool
556 547
557 config ARCH_WANT_OLD_COMPAT_IPC 548 config ARCH_WANT_OLD_COMPAT_IPC
558 select ARCH_WANT_COMPAT_IPC_PARSE_VERS 549 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
559 bool 550 bool
560 551
561 config HAVE_ARCH_SECCOMP 552 config HAVE_ARCH_SECCOMP
562 bool 553 bool
563 help 554 help
564 An arch should select this symbol to 555 An arch should select this symbol to support seccomp mode 1 (the fixed
565 syscall policy), and must provide an 556 syscall policy), and must provide an overrides for __NR_seccomp_sigreturn,
566 and compat syscalls if the asm-gener 557 and compat syscalls if the asm-generic/seccomp.h defaults need adjustment:
567 - __NR_seccomp_read_32 558 - __NR_seccomp_read_32
568 - __NR_seccomp_write_32 559 - __NR_seccomp_write_32
569 - __NR_seccomp_exit_32 560 - __NR_seccomp_exit_32
570 - __NR_seccomp_sigreturn_32 561 - __NR_seccomp_sigreturn_32
571 562
572 config HAVE_ARCH_SECCOMP_FILTER 563 config HAVE_ARCH_SECCOMP_FILTER
573 bool 564 bool
574 select HAVE_ARCH_SECCOMP 565 select HAVE_ARCH_SECCOMP
575 help 566 help
576 An arch should select this symbol if 567 An arch should select this symbol if it provides all of these things:
577 - all the requirements for HAVE_ARCH 568 - all the requirements for HAVE_ARCH_SECCOMP
578 - syscall_get_arch() 569 - syscall_get_arch()
579 - syscall_get_arguments() 570 - syscall_get_arguments()
580 - syscall_rollback() 571 - syscall_rollback()
581 - syscall_set_return_value() 572 - syscall_set_return_value()
582 - SIGSYS siginfo_t support 573 - SIGSYS siginfo_t support
583 - secure_computing is called from a 574 - secure_computing is called from a ptrace_event()-safe context
584 - secure_computing return value is c 575 - secure_computing return value is checked and a return value of -1
585 results in the system call being s 576 results in the system call being skipped immediately.
586 - seccomp syscall wired up 577 - seccomp syscall wired up
587 - if !HAVE_SPARSE_SYSCALL_NR, have S 578 - if !HAVE_SPARSE_SYSCALL_NR, have SECCOMP_ARCH_NATIVE,
588 SECCOMP_ARCH_NATIVE_NR, SECCOMP_AR 579 SECCOMP_ARCH_NATIVE_NR, SECCOMP_ARCH_NATIVE_NAME defined. If
589 COMPAT is supported, have the SECC 580 COMPAT is supported, have the SECCOMP_ARCH_COMPAT* defines too.
590 581
591 config SECCOMP 582 config SECCOMP
592 prompt "Enable seccomp to safely execu 583 prompt "Enable seccomp to safely execute untrusted bytecode"
593 def_bool y 584 def_bool y
594 depends on HAVE_ARCH_SECCOMP 585 depends on HAVE_ARCH_SECCOMP
595 help 586 help
596 This kernel feature is useful for nu 587 This kernel feature is useful for number crunching applications
597 that may need to handle untrusted by 588 that may need to handle untrusted bytecode during their
598 execution. By using pipes or other t 589 execution. By using pipes or other transports made available
599 to the process as file descriptors s 590 to the process as file descriptors supporting the read/write
600 syscalls, it's possible to isolate t 591 syscalls, it's possible to isolate those applications in their
601 own address space using seccomp. Onc 592 own address space using seccomp. Once seccomp is enabled via
602 prctl(PR_SET_SECCOMP) or the seccomp 593 prctl(PR_SET_SECCOMP) or the seccomp() syscall, it cannot be
603 disabled and the task is only allowe 594 disabled and the task is only allowed to execute a few safe
604 syscalls defined by each seccomp mod 595 syscalls defined by each seccomp mode.
605 596
606 If unsure, say Y. 597 If unsure, say Y.
607 598
608 config SECCOMP_FILTER 599 config SECCOMP_FILTER
609 def_bool y 600 def_bool y
610 depends on HAVE_ARCH_SECCOMP_FILTER && 601 depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET
611 help 602 help
612 Enable tasks to build secure computi 603 Enable tasks to build secure computing environments defined
613 in terms of Berkeley Packet Filter p 604 in terms of Berkeley Packet Filter programs which implement
614 task-defined system call filtering p 605 task-defined system call filtering polices.
615 606
616 See Documentation/userspace-api/secc 607 See Documentation/userspace-api/seccomp_filter.rst for details.
617 608
618 config SECCOMP_CACHE_DEBUG 609 config SECCOMP_CACHE_DEBUG
619 bool "Show seccomp filter cache status 610 bool "Show seccomp filter cache status in /proc/pid/seccomp_cache"
620 depends on SECCOMP_FILTER && !HAVE_SPA 611 depends on SECCOMP_FILTER && !HAVE_SPARSE_SYSCALL_NR
621 depends on PROC_FS 612 depends on PROC_FS
622 help 613 help
623 This enables the /proc/pid/seccomp_c 614 This enables the /proc/pid/seccomp_cache interface to monitor
624 seccomp cache data. The file format 615 seccomp cache data. The file format is subject to change. Reading
625 the file requires CAP_SYS_ADMIN. 616 the file requires CAP_SYS_ADMIN.
626 617
627 This option is for debugging only. E 618 This option is for debugging only. Enabling presents the risk that
628 an adversary may be able to infer th 619 an adversary may be able to infer the seccomp filter logic.
629 620
630 If unsure, say N. 621 If unsure, say N.
631 622
632 config HAVE_ARCH_STACKLEAK 623 config HAVE_ARCH_STACKLEAK
633 bool 624 bool
634 help 625 help
635 An architecture should select this i 626 An architecture should select this if it has the code which
636 fills the used part of the kernel st 627 fills the used part of the kernel stack with the STACKLEAK_POISON
637 value before returning from system c 628 value before returning from system calls.
638 629
639 config HAVE_STACKPROTECTOR 630 config HAVE_STACKPROTECTOR
640 bool 631 bool
641 help 632 help
642 An arch should select this symbol if 633 An arch should select this symbol if:
643 - it has implemented a stack canary 634 - it has implemented a stack canary (e.g. __stack_chk_guard)
644 635
645 config STACKPROTECTOR 636 config STACKPROTECTOR
646 bool "Stack Protector buffer overflow 637 bool "Stack Protector buffer overflow detection"
647 depends on HAVE_STACKPROTECTOR 638 depends on HAVE_STACKPROTECTOR
648 depends on $(cc-option,-fstack-protect 639 depends on $(cc-option,-fstack-protector)
649 default y 640 default y
650 help 641 help
651 This option turns on the "stack-prot 642 This option turns on the "stack-protector" GCC feature. This
652 feature puts, at the beginning of fu 643 feature puts, at the beginning of functions, a canary value on
653 the stack just before the return add 644 the stack just before the return address, and validates
654 the value just before actually retur 645 the value just before actually returning. Stack based buffer
655 overflows (that need to overwrite th 646 overflows (that need to overwrite this return address) now also
656 overwrite the canary, which gets det 647 overwrite the canary, which gets detected and the attack is then
657 neutralized via a kernel panic. 648 neutralized via a kernel panic.
658 649
659 Functions will have the stack-protec 650 Functions will have the stack-protector canary logic added if they
660 have an 8-byte or larger character a 651 have an 8-byte or larger character array on the stack.
661 652
662 This feature requires gcc version 4. 653 This feature requires gcc version 4.2 or above, or a distribution
663 gcc with the feature backported ("-f 654 gcc with the feature backported ("-fstack-protector").
664 655
665 On an x86 "defconfig" build, this fe 656 On an x86 "defconfig" build, this feature adds canary checks to
666 about 3% of all kernel functions, wh 657 about 3% of all kernel functions, which increases kernel code size
667 by about 0.3%. 658 by about 0.3%.
668 659
669 config STACKPROTECTOR_STRONG 660 config STACKPROTECTOR_STRONG
670 bool "Strong Stack Protector" 661 bool "Strong Stack Protector"
671 depends on STACKPROTECTOR 662 depends on STACKPROTECTOR
672 depends on $(cc-option,-fstack-protect 663 depends on $(cc-option,-fstack-protector-strong)
673 default y 664 default y
674 help 665 help
675 Functions will have the stack-protec 666 Functions will have the stack-protector canary logic added in any
676 of the following conditions: 667 of the following conditions:
677 668
678 - local variable's address used as p 669 - local variable's address used as part of the right hand side of an
679 assignment or function argument 670 assignment or function argument
680 - local variable is an array (or uni 671 - local variable is an array (or union containing an array),
681 regardless of array type or length 672 regardless of array type or length
682 - uses register local variables 673 - uses register local variables
683 674
684 This feature requires gcc version 4. 675 This feature requires gcc version 4.9 or above, or a distribution
685 gcc with the feature backported ("-f 676 gcc with the feature backported ("-fstack-protector-strong").
686 677
687 On an x86 "defconfig" build, this fe 678 On an x86 "defconfig" build, this feature adds canary checks to
688 about 20% of all kernel functions, w 679 about 20% of all kernel functions, which increases the kernel code
689 size by about 2%. 680 size by about 2%.
690 681
691 config ARCH_SUPPORTS_SHADOW_CALL_STACK 682 config ARCH_SUPPORTS_SHADOW_CALL_STACK
692 bool 683 bool
693 help 684 help
694 An architecture should select this i 685 An architecture should select this if it supports the compiler's
695 Shadow Call Stack and implements run 686 Shadow Call Stack and implements runtime support for shadow stack
696 switching. 687 switching.
697 688
698 config SHADOW_CALL_STACK 689 config SHADOW_CALL_STACK
699 bool "Shadow Call Stack" 690 bool "Shadow Call Stack"
700 depends on ARCH_SUPPORTS_SHADOW_CALL_S 691 depends on ARCH_SUPPORTS_SHADOW_CALL_STACK
701 depends on DYNAMIC_FTRACE_WITH_ARGS || 692 depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
702 depends on MMU 693 depends on MMU
703 help 694 help
704 This option enables the compiler's S 695 This option enables the compiler's Shadow Call Stack, which
705 uses a shadow stack to protect funct 696 uses a shadow stack to protect function return addresses from
706 being overwritten by an attacker. Mo 697 being overwritten by an attacker. More information can be found
707 in the compiler's documentation: 698 in the compiler's documentation:
708 699
709 - Clang: https://clang.llvm.org/docs 700 - Clang: https://clang.llvm.org/docs/ShadowCallStack.html
710 - GCC: https://gcc.gnu.org/onlinedoc 701 - GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options
711 702
712 Note that security guarantees in the 703 Note that security guarantees in the kernel differ from the
713 ones documented for user space. The 704 ones documented for user space. The kernel must store addresses
714 of shadow stacks in memory, which me 705 of shadow stacks in memory, which means an attacker capable of
715 reading and writing arbitrary memory 706 reading and writing arbitrary memory may be able to locate them
716 and hijack control flow by modifying 707 and hijack control flow by modifying the stacks.
717 708
718 config DYNAMIC_SCS 709 config DYNAMIC_SCS
719 bool 710 bool
720 help 711 help
721 Set by the arch code if it relies on 712 Set by the arch code if it relies on code patching to insert the
722 shadow call stack push and pop instr 713 shadow call stack push and pop instructions rather than on the
723 compiler. 714 compiler.
724 715
725 config LTO 716 config LTO
726 bool 717 bool
727 help 718 help
728 Selected if the kernel will be built 719 Selected if the kernel will be built using the compiler's LTO feature.
729 720
730 config LTO_CLANG 721 config LTO_CLANG
731 bool 722 bool
732 select LTO 723 select LTO
733 help 724 help
734 Selected if the kernel will be built 725 Selected if the kernel will be built using Clang's LTO feature.
735 726
736 config ARCH_SUPPORTS_LTO_CLANG 727 config ARCH_SUPPORTS_LTO_CLANG
737 bool 728 bool
738 help 729 help
739 An architecture should select this o 730 An architecture should select this option if it supports:
740 - compiling with Clang, 731 - compiling with Clang,
741 - compiling inline assembly with Cla 732 - compiling inline assembly with Clang's integrated assembler,
742 - and linking with LLD. 733 - and linking with LLD.
743 734
744 config ARCH_SUPPORTS_LTO_CLANG_THIN 735 config ARCH_SUPPORTS_LTO_CLANG_THIN
745 bool 736 bool
746 help 737 help
747 An architecture should select this o 738 An architecture should select this option if it can support Clang's
748 ThinLTO mode. 739 ThinLTO mode.
749 740
750 config HAS_LTO_CLANG 741 config HAS_LTO_CLANG
751 def_bool y 742 def_bool y
752 depends on CC_IS_CLANG && LD_IS_LLD && 743 depends on CC_IS_CLANG && LD_IS_LLD && AS_IS_LLVM
753 depends on $(success,$(NM) --help | he 744 depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
754 depends on $(success,$(AR) --help | he 745 depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)
755 depends on ARCH_SUPPORTS_LTO_CLANG 746 depends on ARCH_SUPPORTS_LTO_CLANG
756 depends on !FTRACE_MCOUNT_USE_RECORDMC 747 depends on !FTRACE_MCOUNT_USE_RECORDMCOUNT
757 # https://github.com/ClangBuiltLinux/l 748 # https://github.com/ClangBuiltLinux/linux/issues/1721
758 depends on (!KASAN || KASAN_HW_TAGS || 749 depends on (!KASAN || KASAN_HW_TAGS || CLANG_VERSION >= 170000) || !DEBUG_INFO
759 depends on (!KCOV || CLANG_VERSION >= 750 depends on (!KCOV || CLANG_VERSION >= 170000) || !DEBUG_INFO
760 depends on !GCOV_KERNEL 751 depends on !GCOV_KERNEL
761 help 752 help
762 The compiler and Kconfig options sup 753 The compiler and Kconfig options support building with Clang's
763 LTO. 754 LTO.
764 755
765 choice 756 choice
766 prompt "Link Time Optimization (LTO)" 757 prompt "Link Time Optimization (LTO)"
767 default LTO_NONE 758 default LTO_NONE
768 help 759 help
769 This option enables Link Time Optimi 760 This option enables Link Time Optimization (LTO), which allows the
770 compiler to optimize binaries global 761 compiler to optimize binaries globally.
771 762
772 If unsure, select LTO_NONE. Note tha 763 If unsure, select LTO_NONE. Note that LTO is very resource-intensive
773 so it's disabled by default. 764 so it's disabled by default.
774 765
775 config LTO_NONE 766 config LTO_NONE
776 bool "None" 767 bool "None"
777 help 768 help
778 Build the kernel normally, without L 769 Build the kernel normally, without Link Time Optimization (LTO).
779 770
780 config LTO_CLANG_FULL 771 config LTO_CLANG_FULL
781 bool "Clang Full LTO (EXPERIMENTAL)" 772 bool "Clang Full LTO (EXPERIMENTAL)"
782 depends on HAS_LTO_CLANG 773 depends on HAS_LTO_CLANG
783 depends on !COMPILE_TEST 774 depends on !COMPILE_TEST
784 select LTO_CLANG 775 select LTO_CLANG
785 help 776 help
786 This option enables Clang's full Lin 777 This option enables Clang's full Link Time Optimization (LTO), which
787 allows the compiler to optimize the 778 allows the compiler to optimize the kernel globally. If you enable
788 this option, the compiler generates 779 this option, the compiler generates LLVM bitcode instead of ELF
789 object files, and the actual compila 780 object files, and the actual compilation from bitcode happens at
790 the LTO link step, which may take se 781 the LTO link step, which may take several minutes depending on the
791 kernel configuration. More informati 782 kernel configuration. More information can be found from LLVM's
792 documentation: 783 documentation:
793 784
794 https://llvm.org/docs/LinkTimeOpti 785 https://llvm.org/docs/LinkTimeOptimization.html
795 786
796 During link time, this option can us 787 During link time, this option can use a large amount of RAM, and
797 may take much longer than the ThinLT 788 may take much longer than the ThinLTO option.
798 789
799 config LTO_CLANG_THIN 790 config LTO_CLANG_THIN
800 bool "Clang ThinLTO (EXPERIMENTAL)" 791 bool "Clang ThinLTO (EXPERIMENTAL)"
801 depends on HAS_LTO_CLANG && ARCH_SUPPO 792 depends on HAS_LTO_CLANG && ARCH_SUPPORTS_LTO_CLANG_THIN
802 select LTO_CLANG 793 select LTO_CLANG
803 help 794 help
804 This option enables Clang's ThinLTO, 795 This option enables Clang's ThinLTO, which allows for parallel
805 optimization and faster incremental 796 optimization and faster incremental compiles compared to the
806 CONFIG_LTO_CLANG_FULL option. More i 797 CONFIG_LTO_CLANG_FULL option. More information can be found
807 from Clang's documentation: 798 from Clang's documentation:
808 799
809 https://clang.llvm.org/docs/ThinLT 800 https://clang.llvm.org/docs/ThinLTO.html
810 801
811 If unsure, say Y. 802 If unsure, say Y.
812 endchoice 803 endchoice
813 804
814 config ARCH_SUPPORTS_CFI_CLANG 805 config ARCH_SUPPORTS_CFI_CLANG
815 bool 806 bool
816 help 807 help
817 An architecture should select this o 808 An architecture should select this option if it can support Clang's
818 Control-Flow Integrity (CFI) checkin 809 Control-Flow Integrity (CFI) checking.
819 810
820 config ARCH_USES_CFI_TRAPS 811 config ARCH_USES_CFI_TRAPS
821 bool 812 bool
822 813
823 config CFI_CLANG 814 config CFI_CLANG
824 bool "Use Clang's Control Flow Integri 815 bool "Use Clang's Control Flow Integrity (CFI)"
825 depends on ARCH_SUPPORTS_CFI_CLANG 816 depends on ARCH_SUPPORTS_CFI_CLANG
826 depends on $(cc-option,-fsanitize=kcfi 817 depends on $(cc-option,-fsanitize=kcfi)
827 help 818 help
828 This option enables Clang's forward- 819 This option enables Clang's forward-edge Control Flow Integrity
829 (CFI) checking, where the compiler i 820 (CFI) checking, where the compiler injects a runtime check to each
830 indirect function call to ensure the 821 indirect function call to ensure the target is a valid function with
831 the correct static type. This restri 822 the correct static type. This restricts possible call targets and
832 makes it more difficult for an attac 823 makes it more difficult for an attacker to exploit bugs that allow
833 the modification of stored function 824 the modification of stored function pointers. More information can be
834 found from Clang's documentation: 825 found from Clang's documentation:
835 826
836 https://clang.llvm.org/docs/Contro 827 https://clang.llvm.org/docs/ControlFlowIntegrity.html
837 828
838 config CFI_ICALL_NORMALIZE_INTEGERS <<
839 bool "Normalize CFI tags for integers" <<
840 depends on CFI_CLANG <<
841 depends on HAVE_CFI_ICALL_NORMALIZE_IN <<
842 help <<
843 This option normalizes the CFI tags <<
844 integer types of the same size and s <<
845 tag. <<
846 <<
847 The option is separate from CONFIG_R <<
848 When working with build systems that <<
849 convenient to be able to turn on thi <<
850 turned on. <<
851 <<
852 This option is necessary for using C <<
853 <<
854 config HAVE_CFI_ICALL_NORMALIZE_INTEGERS_CLANG <<
855 def_bool y <<
856 depends on $(cc-option,-fsanitize=kcfi <<
857 # With GCOV/KASAN we need this fix: ht <<
858 depends on CLANG_VERSION >= 190103 || <<
859 <<
860 config HAVE_CFI_ICALL_NORMALIZE_INTEGERS_RUSTC <<
861 def_bool y <<
862 depends on HAVE_CFI_ICALL_NORMALIZE_IN <<
863 depends on RUSTC_VERSION >= 107900 <<
864 # With GCOV/KASAN we need this fix: ht <<
865 depends on (RUSTC_LLVM_VERSION >= 1901 <<
866 (!GCOV_KERNEL && !KASAN_GENERI <<
867 <<
868 config CFI_PERMISSIVE 829 config CFI_PERMISSIVE
869 bool "Use CFI in permissive mode" 830 bool "Use CFI in permissive mode"
870 depends on CFI_CLANG 831 depends on CFI_CLANG
871 help 832 help
872 When selected, Control Flow Integrit 833 When selected, Control Flow Integrity (CFI) violations result in a
873 warning instead of a kernel panic. T 834 warning instead of a kernel panic. This option should only be used
874 for finding indirect call type misma 835 for finding indirect call type mismatches during development.
875 836
876 If unsure, say N. 837 If unsure, say N.
877 838
878 config HAVE_ARCH_WITHIN_STACK_FRAMES 839 config HAVE_ARCH_WITHIN_STACK_FRAMES
879 bool 840 bool
880 help 841 help
881 An architecture should select this i 842 An architecture should select this if it can walk the kernel stack
882 frames to determine if an object is 843 frames to determine if an object is part of either the arguments
883 or local variables (i.e. that it exc 844 or local variables (i.e. that it excludes saved return addresses,
884 and similar) by implementing an inli 845 and similar) by implementing an inline arch_within_stack_frames(),
885 which is used by CONFIG_HARDENED_USE 846 which is used by CONFIG_HARDENED_USERCOPY.
886 847
887 config HAVE_CONTEXT_TRACKING_USER 848 config HAVE_CONTEXT_TRACKING_USER
888 bool 849 bool
889 help 850 help
890 Provide kernel/user boundaries probe 851 Provide kernel/user boundaries probes necessary for subsystems
891 that need it, such as userspace RCU 852 that need it, such as userspace RCU extended quiescent state.
892 Syscalls need to be wrapped inside u 853 Syscalls need to be wrapped inside user_exit()-user_enter(), either
893 optimized behind static key or throu 854 optimized behind static key or through the slow path using TIF_NOHZ
894 flag. Exceptions handlers must be wr 855 flag. Exceptions handlers must be wrapped as well. Irqs are already
895 protected inside ct_irq_enter/ct_irq 856 protected inside ct_irq_enter/ct_irq_exit() but preemption or signal
896 handling on irq exit still need to b 857 handling on irq exit still need to be protected.
897 858
898 config HAVE_CONTEXT_TRACKING_USER_OFFSTACK 859 config HAVE_CONTEXT_TRACKING_USER_OFFSTACK
899 bool 860 bool
900 help 861 help
901 Architecture neither relies on excep 862 Architecture neither relies on exception_enter()/exception_exit()
902 nor on schedule_user(). Also preempt 863 nor on schedule_user(). Also preempt_schedule_notrace() and
903 preempt_schedule_irq() can't be call 864 preempt_schedule_irq() can't be called in a preemptible section
904 while context tracking is CT_STATE_U !! 865 while context tracking is CONTEXT_USER. This feature reflects a sane
905 entry implementation where the follo 866 entry implementation where the following requirements are met on
906 critical entry code, ie: before user 867 critical entry code, ie: before user_exit() or after user_enter():
907 868
908 - Critical entry code isn't preempti 869 - Critical entry code isn't preemptible (or better yet:
909 not interruptible). 870 not interruptible).
910 - No use of RCU read side critical s 871 - No use of RCU read side critical sections, unless ct_nmi_enter()
911 got called. 872 got called.
912 - No use of instrumentation, unless 873 - No use of instrumentation, unless instrumentation_begin() got
913 called. 874 called.
914 875
915 config HAVE_TIF_NOHZ 876 config HAVE_TIF_NOHZ
916 bool 877 bool
917 help 878 help
918 Arch relies on TIF_NOHZ and syscall 879 Arch relies on TIF_NOHZ and syscall slow path to implement context
919 tracking calls to user_enter()/user_ 880 tracking calls to user_enter()/user_exit().
920 881
921 config HAVE_VIRT_CPU_ACCOUNTING 882 config HAVE_VIRT_CPU_ACCOUNTING
922 bool 883 bool
923 884
924 config HAVE_VIRT_CPU_ACCOUNTING_IDLE 885 config HAVE_VIRT_CPU_ACCOUNTING_IDLE
925 bool 886 bool
926 help 887 help
927 Architecture has its own way to acco 888 Architecture has its own way to account idle CPU time and therefore
928 doesn't implement vtime_account_idle 889 doesn't implement vtime_account_idle().
929 890
930 config ARCH_HAS_SCALED_CPUTIME 891 config ARCH_HAS_SCALED_CPUTIME
931 bool 892 bool
932 893
933 config HAVE_VIRT_CPU_ACCOUNTING_GEN 894 config HAVE_VIRT_CPU_ACCOUNTING_GEN
934 bool 895 bool
935 default y if 64BIT 896 default y if 64BIT
936 help 897 help
937 With VIRT_CPU_ACCOUNTING_GEN, cputim 898 With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
938 Before enabling this option, arch co 899 Before enabling this option, arch code must be audited
939 to ensure there are no races in conc 900 to ensure there are no races in concurrent read/write of
940 cputime_t. For example, reading/writ 901 cputime_t. For example, reading/writing 64-bit cputime_t on
941 some 32-bit arches may require multi 902 some 32-bit arches may require multiple accesses, so proper
942 locking is needed to protect against 903 locking is needed to protect against concurrent accesses.
943 904
944 config HAVE_IRQ_TIME_ACCOUNTING 905 config HAVE_IRQ_TIME_ACCOUNTING
945 bool 906 bool
946 help 907 help
947 Archs need to ensure they use a high 908 Archs need to ensure they use a high enough resolution clock to
948 support irq time accounting and then 909 support irq time accounting and then call enable_sched_clock_irqtime().
949 910
950 config HAVE_MOVE_PUD 911 config HAVE_MOVE_PUD
951 bool 912 bool
952 help 913 help
953 Architectures that select this are a 914 Architectures that select this are able to move page tables at the
954 PUD level. If there are only 3 page 915 PUD level. If there are only 3 page table levels, the move effectively
955 happens at the PGD level. 916 happens at the PGD level.
956 917
957 config HAVE_MOVE_PMD 918 config HAVE_MOVE_PMD
958 bool 919 bool
959 help 920 help
960 Archs that select this are able to m 921 Archs that select this are able to move page tables at the PMD level.
961 922
962 config HAVE_ARCH_TRANSPARENT_HUGEPAGE 923 config HAVE_ARCH_TRANSPARENT_HUGEPAGE
963 bool 924 bool
964 925
965 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 926 config HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
966 bool 927 bool
967 928
968 config HAVE_ARCH_HUGE_VMAP 929 config HAVE_ARCH_HUGE_VMAP
969 bool 930 bool
970 931
971 # 932 #
972 # Archs that select this would be capable of 933 # Archs that select this would be capable of PMD-sized vmaps (i.e.,
973 # arch_vmap_pmd_supported() returns true). Th 934 # arch_vmap_pmd_supported() returns true). The VM_ALLOW_HUGE_VMAP flag
974 # must be used to enable allocations to use h 935 # must be used to enable allocations to use hugepages.
975 # 936 #
976 config HAVE_ARCH_HUGE_VMALLOC 937 config HAVE_ARCH_HUGE_VMALLOC
977 depends on HAVE_ARCH_HUGE_VMAP 938 depends on HAVE_ARCH_HUGE_VMAP
978 bool 939 bool
979 940
980 config ARCH_WANT_HUGE_PMD_SHARE 941 config ARCH_WANT_HUGE_PMD_SHARE
981 bool 942 bool
982 943
983 # Archs that want to use pmd_mkwrite on kernel 944 # Archs that want to use pmd_mkwrite on kernel memory need it defined even
984 # if there are no userspace memory management 945 # if there are no userspace memory management features that use it
985 config ARCH_WANT_KERNEL_PMD_MKWRITE 946 config ARCH_WANT_KERNEL_PMD_MKWRITE
986 bool 947 bool
987 948
988 config ARCH_WANT_PMD_MKWRITE 949 config ARCH_WANT_PMD_MKWRITE
989 def_bool TRANSPARENT_HUGEPAGE || ARCH_ 950 def_bool TRANSPARENT_HUGEPAGE || ARCH_WANT_KERNEL_PMD_MKWRITE
990 951
991 config HAVE_ARCH_SOFT_DIRTY 952 config HAVE_ARCH_SOFT_DIRTY
992 bool 953 bool
993 954
994 config HAVE_MOD_ARCH_SPECIFIC 955 config HAVE_MOD_ARCH_SPECIFIC
995 bool 956 bool
996 help 957 help
997 The arch uses struct mod_arch_specif 958 The arch uses struct mod_arch_specific to store data. Many arches
998 just need a simple module loader wit 959 just need a simple module loader without arch specific data - those
999 should not enable this. 960 should not enable this.
1000 961
1001 config MODULES_USE_ELF_RELA 962 config MODULES_USE_ELF_RELA
1002 bool 963 bool
1003 help 964 help
1004 Modules only use ELF RELA relocatio 965 Modules only use ELF RELA relocations. Modules with ELF REL
1005 relocations will give an error. 966 relocations will give an error.
1006 967
1007 config MODULES_USE_ELF_REL 968 config MODULES_USE_ELF_REL
1008 bool 969 bool
1009 help 970 help
1010 Modules only use ELF REL relocation 971 Modules only use ELF REL relocations. Modules with ELF RELA
1011 relocations will give an error. 972 relocations will give an error.
1012 973
1013 config ARCH_WANTS_MODULES_DATA_IN_VMALLOC 974 config ARCH_WANTS_MODULES_DATA_IN_VMALLOC
1014 bool 975 bool
1015 help 976 help
1016 For architectures like powerpc/32 w 977 For architectures like powerpc/32 which have constraints on module
1017 allocation and need to allocate mod 978 allocation and need to allocate module data outside of module area.
1018 979
1019 config ARCH_WANTS_EXECMEM_LATE 980 config ARCH_WANTS_EXECMEM_LATE
1020 bool 981 bool
1021 help 982 help
1022 For architectures that do not alloc 983 For architectures that do not allocate executable memory early on
1023 boot, but rather require its initia 984 boot, but rather require its initialization late when there is
1024 enough entropy for module space ran 985 enough entropy for module space randomization, for instance
1025 arm64. 986 arm64.
1026 987
1027 config HAVE_IRQ_EXIT_ON_IRQ_STACK 988 config HAVE_IRQ_EXIT_ON_IRQ_STACK
1028 bool 989 bool
1029 help 990 help
1030 Architecture doesn't only execute t 991 Architecture doesn't only execute the irq handler on the irq stack
1031 but also irq_exit(). This way we ca 992 but also irq_exit(). This way we can process softirqs on this irq
1032 stack instead of switching to a new 993 stack instead of switching to a new one when we call __do_softirq()
1033 in the end of an hardirq. 994 in the end of an hardirq.
1034 This spares a stack switch and impr 995 This spares a stack switch and improves cache usage on softirq
1035 processing. 996 processing.
1036 997
1037 config HAVE_SOFTIRQ_ON_OWN_STACK 998 config HAVE_SOFTIRQ_ON_OWN_STACK
1038 bool 999 bool
1039 help 1000 help
1040 Architecture provides a function to 1001 Architecture provides a function to run __do_softirq() on a
1041 separate stack. 1002 separate stack.
1042 1003
1043 config SOFTIRQ_ON_OWN_STACK 1004 config SOFTIRQ_ON_OWN_STACK
1044 def_bool HAVE_SOFTIRQ_ON_OWN_STACK && 1005 def_bool HAVE_SOFTIRQ_ON_OWN_STACK && !PREEMPT_RT
1045 1006
1046 config ALTERNATE_USER_ADDRESS_SPACE 1007 config ALTERNATE_USER_ADDRESS_SPACE
1047 bool 1008 bool
1048 help 1009 help
1049 Architectures set this when the CPU 1010 Architectures set this when the CPU uses separate address
1050 spaces for kernel and user space po 1011 spaces for kernel and user space pointers. In this case, the
1051 access_ok() check on a __user point 1012 access_ok() check on a __user pointer is skipped.
1052 1013
1053 config PGTABLE_LEVELS 1014 config PGTABLE_LEVELS
1054 int 1015 int
1055 default 2 1016 default 2
1056 1017
1057 config ARCH_HAS_ELF_RANDOMIZE 1018 config ARCH_HAS_ELF_RANDOMIZE
1058 bool 1019 bool
1059 help 1020 help
1060 An architecture supports choosing r 1021 An architecture supports choosing randomized locations for
1061 stack, mmap, brk, and ET_DYN. Defin 1022 stack, mmap, brk, and ET_DYN. Defined functions:
1062 - arch_mmap_rnd() 1023 - arch_mmap_rnd()
1063 - arch_randomize_brk() 1024 - arch_randomize_brk()
1064 1025
1065 config HAVE_ARCH_MMAP_RND_BITS 1026 config HAVE_ARCH_MMAP_RND_BITS
1066 bool 1027 bool
1067 help 1028 help
1068 An arch should select this symbol i 1029 An arch should select this symbol if it supports setting a variable
1069 number of bits for use in establish 1030 number of bits for use in establishing the base address for mmap
1070 allocations, has MMU enabled and pr 1031 allocations, has MMU enabled and provides values for both:
1071 - ARCH_MMAP_RND_BITS_MIN 1032 - ARCH_MMAP_RND_BITS_MIN
1072 - ARCH_MMAP_RND_BITS_MAX 1033 - ARCH_MMAP_RND_BITS_MAX
1073 1034
1074 config HAVE_EXIT_THREAD 1035 config HAVE_EXIT_THREAD
1075 bool 1036 bool
1076 help 1037 help
1077 An architecture implements exit_thr 1038 An architecture implements exit_thread.
1078 1039
1079 config ARCH_MMAP_RND_BITS_MIN 1040 config ARCH_MMAP_RND_BITS_MIN
1080 int 1041 int
1081 1042
1082 config ARCH_MMAP_RND_BITS_MAX 1043 config ARCH_MMAP_RND_BITS_MAX
1083 int 1044 int
1084 1045
1085 config ARCH_MMAP_RND_BITS_DEFAULT 1046 config ARCH_MMAP_RND_BITS_DEFAULT
1086 int 1047 int
1087 1048
1088 config ARCH_MMAP_RND_BITS 1049 config ARCH_MMAP_RND_BITS
1089 int "Number of bits to use for ASLR o 1050 int "Number of bits to use for ASLR of mmap base address" if EXPERT
1090 range ARCH_MMAP_RND_BITS_MIN ARCH_MMA 1051 range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX
1091 default ARCH_MMAP_RND_BITS_DEFAULT if 1052 default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT
1092 default ARCH_MMAP_RND_BITS_MIN 1053 default ARCH_MMAP_RND_BITS_MIN
1093 depends on HAVE_ARCH_MMAP_RND_BITS 1054 depends on HAVE_ARCH_MMAP_RND_BITS
1094 help 1055 help
1095 This value can be used to select th 1056 This value can be used to select the number of bits to use to
1096 determine the random offset to the 1057 determine the random offset to the base address of vma regions
1097 resulting from mmap allocations. Th 1058 resulting from mmap allocations. This value will be bounded
1098 by the architecture's minimum and m 1059 by the architecture's minimum and maximum supported values.
1099 1060
1100 This value can be changed after boo 1061 This value can be changed after boot using the
1101 /proc/sys/vm/mmap_rnd_bits tunable 1062 /proc/sys/vm/mmap_rnd_bits tunable
1102 1063
1103 config HAVE_ARCH_MMAP_RND_COMPAT_BITS 1064 config HAVE_ARCH_MMAP_RND_COMPAT_BITS
1104 bool 1065 bool
1105 help 1066 help
1106 An arch should select this symbol i 1067 An arch should select this symbol if it supports running applications
1107 in compatibility mode, supports set 1068 in compatibility mode, supports setting a variable number of bits for
1108 use in establishing the base addres 1069 use in establishing the base address for mmap allocations, has MMU
1109 enabled and provides values for bot 1070 enabled and provides values for both:
1110 - ARCH_MMAP_RND_COMPAT_BITS_MIN 1071 - ARCH_MMAP_RND_COMPAT_BITS_MIN
1111 - ARCH_MMAP_RND_COMPAT_BITS_MAX 1072 - ARCH_MMAP_RND_COMPAT_BITS_MAX
1112 1073
1113 config ARCH_MMAP_RND_COMPAT_BITS_MIN 1074 config ARCH_MMAP_RND_COMPAT_BITS_MIN
1114 int 1075 int
1115 1076
1116 config ARCH_MMAP_RND_COMPAT_BITS_MAX 1077 config ARCH_MMAP_RND_COMPAT_BITS_MAX
1117 int 1078 int
1118 1079
1119 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT 1080 config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
1120 int 1081 int
1121 1082
1122 config ARCH_MMAP_RND_COMPAT_BITS 1083 config ARCH_MMAP_RND_COMPAT_BITS
1123 int "Number of bits to use for ASLR o 1084 int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT
1124 range ARCH_MMAP_RND_COMPAT_BITS_MIN A 1085 range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX
1125 default ARCH_MMAP_RND_COMPAT_BITS_DEF 1086 default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT
1126 default ARCH_MMAP_RND_COMPAT_BITS_MIN 1087 default ARCH_MMAP_RND_COMPAT_BITS_MIN
1127 depends on HAVE_ARCH_MMAP_RND_COMPAT_ 1088 depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS
1128 help 1089 help
1129 This value can be used to select th 1090 This value can be used to select the number of bits to use to
1130 determine the random offset to the 1091 determine the random offset to the base address of vma regions
1131 resulting from mmap allocations for 1092 resulting from mmap allocations for compatible applications This
1132 value will be bounded by the archit 1093 value will be bounded by the architecture's minimum and maximum
1133 supported values. 1094 supported values.
1134 1095
1135 This value can be changed after boo 1096 This value can be changed after boot using the
1136 /proc/sys/vm/mmap_rnd_compat_bits t 1097 /proc/sys/vm/mmap_rnd_compat_bits tunable
1137 1098
1138 config HAVE_ARCH_COMPAT_MMAP_BASES 1099 config HAVE_ARCH_COMPAT_MMAP_BASES
1139 bool 1100 bool
1140 help 1101 help
1141 This allows 64bit applications to i 1102 This allows 64bit applications to invoke 32-bit mmap() syscall
1142 and vice-versa 32-bit applications 1103 and vice-versa 32-bit applications to call 64-bit mmap().
1143 Required for applications doing dif 1104 Required for applications doing different bitness syscalls.
1144 1105
1145 config HAVE_PAGE_SIZE_4KB 1106 config HAVE_PAGE_SIZE_4KB
1146 bool 1107 bool
1147 1108
1148 config HAVE_PAGE_SIZE_8KB 1109 config HAVE_PAGE_SIZE_8KB
1149 bool 1110 bool
1150 1111
1151 config HAVE_PAGE_SIZE_16KB 1112 config HAVE_PAGE_SIZE_16KB
1152 bool 1113 bool
1153 1114
1154 config HAVE_PAGE_SIZE_32KB 1115 config HAVE_PAGE_SIZE_32KB
1155 bool 1116 bool
1156 1117
1157 config HAVE_PAGE_SIZE_64KB 1118 config HAVE_PAGE_SIZE_64KB
1158 bool 1119 bool
1159 1120
1160 config HAVE_PAGE_SIZE_256KB 1121 config HAVE_PAGE_SIZE_256KB
1161 bool 1122 bool
1162 1123
1163 choice 1124 choice
1164 prompt "MMU page size" 1125 prompt "MMU page size"
1165 1126
1166 config PAGE_SIZE_4KB 1127 config PAGE_SIZE_4KB
1167 bool "4KiB pages" 1128 bool "4KiB pages"
1168 depends on HAVE_PAGE_SIZE_4KB 1129 depends on HAVE_PAGE_SIZE_4KB
1169 help 1130 help
1170 This option select the standard 4Ki 1131 This option select the standard 4KiB Linux page size and the only
1171 available option on many architectu 1132 available option on many architectures. Using 4KiB page size will
1172 minimize memory consumption and is 1133 minimize memory consumption and is therefore recommended for low
1173 memory systems. 1134 memory systems.
1174 Some software that is written for x 1135 Some software that is written for x86 systems makes incorrect
1175 assumptions about the page size and 1136 assumptions about the page size and only runs on 4KiB pages.
1176 1137
1177 config PAGE_SIZE_8KB 1138 config PAGE_SIZE_8KB
1178 bool "8KiB pages" 1139 bool "8KiB pages"
1179 depends on HAVE_PAGE_SIZE_8KB 1140 depends on HAVE_PAGE_SIZE_8KB
1180 help 1141 help
1181 This option is the only supported p 1142 This option is the only supported page size on a few older
1182 processors, and can be slightly fas 1143 processors, and can be slightly faster than 4KiB pages.
1183 1144
1184 config PAGE_SIZE_16KB 1145 config PAGE_SIZE_16KB
1185 bool "16KiB pages" 1146 bool "16KiB pages"
1186 depends on HAVE_PAGE_SIZE_16KB 1147 depends on HAVE_PAGE_SIZE_16KB
1187 help 1148 help
1188 This option is usually a good compr 1149 This option is usually a good compromise between memory
1189 consumption and performance for typ 1150 consumption and performance for typical desktop and server
1190 workloads, often saving a level of 1151 workloads, often saving a level of page table lookups compared
1191 to 4KB pages as well as reducing TL 1152 to 4KB pages as well as reducing TLB pressure and overhead of
1192 per-page operations in the kernel a 1153 per-page operations in the kernel at the expense of a larger
1193 page cache. 1154 page cache.
1194 1155
1195 config PAGE_SIZE_32KB 1156 config PAGE_SIZE_32KB
1196 bool "32KiB pages" 1157 bool "32KiB pages"
1197 depends on HAVE_PAGE_SIZE_32KB 1158 depends on HAVE_PAGE_SIZE_32KB
1198 help 1159 help
1199 Using 32KiB page size will result i 1160 Using 32KiB page size will result in slightly higher performance
1200 kernel at the price of higher memor 1161 kernel at the price of higher memory consumption compared to
1201 16KiB pages. This option is availa 1162 16KiB pages. This option is available only on cnMIPS cores.
1202 Note that you will need a suitable 1163 Note that you will need a suitable Linux distribution to
1203 support this. 1164 support this.
1204 1165
1205 config PAGE_SIZE_64KB 1166 config PAGE_SIZE_64KB
1206 bool "64KiB pages" 1167 bool "64KiB pages"
1207 depends on HAVE_PAGE_SIZE_64KB 1168 depends on HAVE_PAGE_SIZE_64KB
1208 help 1169 help
1209 Using 64KiB page size will result i 1170 Using 64KiB page size will result in slightly higher performance
1210 kernel at the price of much higher 1171 kernel at the price of much higher memory consumption compared to
1211 4KiB or 16KiB pages. 1172 4KiB or 16KiB pages.
1212 This is not suitable for general-pu 1173 This is not suitable for general-purpose workloads but the
1213 better performance may be worth the 1174 better performance may be worth the cost for certain types of
1214 supercomputing or database applicat 1175 supercomputing or database applications that work mostly with
1215 large in-memory data rather than sm 1176 large in-memory data rather than small files.
1216 1177
1217 config PAGE_SIZE_256KB 1178 config PAGE_SIZE_256KB
1218 bool "256KiB pages" 1179 bool "256KiB pages"
1219 depends on HAVE_PAGE_SIZE_256KB 1180 depends on HAVE_PAGE_SIZE_256KB
1220 help 1181 help
1221 256KiB pages have little practical 1182 256KiB pages have little practical value due to their extreme
1222 memory usage. The kernel will only 1183 memory usage. The kernel will only be able to run applications
1223 that have been compiled with '-zmax 1184 that have been compiled with '-zmax-page-size' set to 256KiB
1224 (the default is 64KiB or 4KiB on mo 1185 (the default is 64KiB or 4KiB on most architectures).
1225 1186
1226 endchoice 1187 endchoice
1227 1188
1228 config PAGE_SIZE_LESS_THAN_64KB 1189 config PAGE_SIZE_LESS_THAN_64KB
1229 def_bool y 1190 def_bool y
1230 depends on !PAGE_SIZE_64KB 1191 depends on !PAGE_SIZE_64KB
1231 depends on PAGE_SIZE_LESS_THAN_256KB 1192 depends on PAGE_SIZE_LESS_THAN_256KB
1232 1193
1233 config PAGE_SIZE_LESS_THAN_256KB 1194 config PAGE_SIZE_LESS_THAN_256KB
1234 def_bool y 1195 def_bool y
1235 depends on !PAGE_SIZE_256KB 1196 depends on !PAGE_SIZE_256KB
1236 1197
1237 config PAGE_SHIFT 1198 config PAGE_SHIFT
1238 int 1199 int
1239 default 12 if PAGE_SIZE_4KB 1200 default 12 if PAGE_SIZE_4KB
1240 default 13 if PAGE_SIZE_8KB 1201 default 13 if PAGE_SIZE_8KB
1241 default 14 if PAGE_SIZE_16KB 1202 default 14 if PAGE_SIZE_16KB
1242 default 15 if PAGE_SIZE_32KB 1203 default 15 if PAGE_SIZE_32KB
1243 default 16 if PAGE_SIZE_64KB 1204 default 16 if PAGE_SIZE_64KB
1244 default 18 if PAGE_SIZE_256KB 1205 default 18 if PAGE_SIZE_256KB
1245 1206
1246 # This allows to use a set of generic functio 1207 # This allows to use a set of generic functions to determine mmap base
1247 # address by giving priority to top-down sche 1208 # address by giving priority to top-down scheme only if the process
1248 # is not in legacy mode (compat task, unlimit 1209 # is not in legacy mode (compat task, unlimited stack size or
1249 # sysctl_legacy_va_layout). 1210 # sysctl_legacy_va_layout).
1250 # Architecture that selects this option can p 1211 # Architecture that selects this option can provide its own version of:
1251 # - STACK_RND_MASK 1212 # - STACK_RND_MASK
1252 config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT 1213 config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
1253 bool 1214 bool
1254 depends on MMU 1215 depends on MMU
1255 select ARCH_HAS_ELF_RANDOMIZE 1216 select ARCH_HAS_ELF_RANDOMIZE
1256 1217
1257 config HAVE_OBJTOOL 1218 config HAVE_OBJTOOL
1258 bool 1219 bool
1259 1220
1260 config HAVE_JUMP_LABEL_HACK 1221 config HAVE_JUMP_LABEL_HACK
1261 bool 1222 bool
1262 1223
1263 config HAVE_NOINSTR_HACK 1224 config HAVE_NOINSTR_HACK
1264 bool 1225 bool
1265 1226
1266 config HAVE_NOINSTR_VALIDATION 1227 config HAVE_NOINSTR_VALIDATION
1267 bool 1228 bool
1268 1229
1269 config HAVE_UACCESS_VALIDATION 1230 config HAVE_UACCESS_VALIDATION
1270 bool 1231 bool
1271 select OBJTOOL 1232 select OBJTOOL
1272 1233
1273 config HAVE_STACK_VALIDATION 1234 config HAVE_STACK_VALIDATION
1274 bool 1235 bool
1275 help 1236 help
1276 Architecture supports objtool compi 1237 Architecture supports objtool compile-time frame pointer rule
1277 validation. 1238 validation.
1278 1239
1279 config HAVE_RELIABLE_STACKTRACE 1240 config HAVE_RELIABLE_STACKTRACE
1280 bool 1241 bool
1281 help 1242 help
1282 Architecture has either save_stack_ 1243 Architecture has either save_stack_trace_tsk_reliable() or
1283 arch_stack_walk_reliable() function 1244 arch_stack_walk_reliable() function which only returns a stack trace
1284 if it can guarantee the trace is re 1245 if it can guarantee the trace is reliable.
1285 1246
1286 config HAVE_ARCH_HASH 1247 config HAVE_ARCH_HASH
1287 bool 1248 bool
1288 default n 1249 default n
1289 help 1250 help
1290 If this is set, the architecture pr 1251 If this is set, the architecture provides an <asm/hash.h>
1291 file which provides platform-specif 1252 file which provides platform-specific implementations of some
1292 functions in <linux/hash.h> or fs/n 1253 functions in <linux/hash.h> or fs/namei.c.
1293 1254
1294 config HAVE_ARCH_NVRAM_OPS 1255 config HAVE_ARCH_NVRAM_OPS
1295 bool 1256 bool
1296 1257
1297 config ISA_BUS_API 1258 config ISA_BUS_API
1298 def_bool ISA 1259 def_bool ISA
1299 1260
1300 # 1261 #
1301 # ABI hall of shame 1262 # ABI hall of shame
1302 # 1263 #
1303 config CLONE_BACKWARDS 1264 config CLONE_BACKWARDS
1304 bool 1265 bool
1305 help 1266 help
1306 Architecture has tls passed as the 1267 Architecture has tls passed as the 4th argument of clone(2),
1307 not the 5th one. 1268 not the 5th one.
1308 1269
1309 config CLONE_BACKWARDS2 1270 config CLONE_BACKWARDS2
1310 bool 1271 bool
1311 help 1272 help
1312 Architecture has the first two argu 1273 Architecture has the first two arguments of clone(2) swapped.
1313 1274
1314 config CLONE_BACKWARDS3 1275 config CLONE_BACKWARDS3
1315 bool 1276 bool
1316 help 1277 help
1317 Architecture has tls passed as the 1278 Architecture has tls passed as the 3rd argument of clone(2),
1318 not the 5th one. 1279 not the 5th one.
1319 1280
1320 config ODD_RT_SIGACTION 1281 config ODD_RT_SIGACTION
1321 bool 1282 bool
1322 help 1283 help
1323 Architecture has unusual rt_sigacti 1284 Architecture has unusual rt_sigaction(2) arguments
1324 1285
1325 config OLD_SIGSUSPEND 1286 config OLD_SIGSUSPEND
1326 bool 1287 bool
1327 help 1288 help
1328 Architecture has old sigsuspend(2) 1289 Architecture has old sigsuspend(2) syscall, of one-argument variety
1329 1290
1330 config OLD_SIGSUSPEND3 1291 config OLD_SIGSUSPEND3
1331 bool 1292 bool
1332 help 1293 help
1333 Even weirder antique ABI - three-ar 1294 Even weirder antique ABI - three-argument sigsuspend(2)
1334 1295
1335 config OLD_SIGACTION 1296 config OLD_SIGACTION
1336 bool 1297 bool
1337 help 1298 help
1338 Architecture has old sigaction(2) s 1299 Architecture has old sigaction(2) syscall. Nope, not the same
1339 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 1300 as OLD_SIGSUSPEND | OLD_SIGSUSPEND3 - alpha has sigsuspend(2),
1340 but fairly different variant of sig 1301 but fairly different variant of sigaction(2), thanks to OSF/1
1341 compatibility... 1302 compatibility...
1342 1303
1343 config COMPAT_OLD_SIGACTION 1304 config COMPAT_OLD_SIGACTION
1344 bool 1305 bool
1345 1306
1346 config COMPAT_32BIT_TIME 1307 config COMPAT_32BIT_TIME
1347 bool "Provide system calls for 32-bit 1308 bool "Provide system calls for 32-bit time_t"
1348 default !64BIT || COMPAT 1309 default !64BIT || COMPAT
1349 help 1310 help
1350 This enables 32 bit time_t support 1311 This enables 32 bit time_t support in addition to 64 bit time_t support.
1351 This is relevant on all 32-bit arch 1312 This is relevant on all 32-bit architectures, and 64-bit architectures
1352 as part of compat syscall handling. 1313 as part of compat syscall handling.
1353 1314
1354 config ARCH_NO_PREEMPT 1315 config ARCH_NO_PREEMPT
1355 bool 1316 bool
1356 1317
1357 config ARCH_SUPPORTS_RT 1318 config ARCH_SUPPORTS_RT
1358 bool 1319 bool
1359 1320
1360 config CPU_NO_EFFICIENT_FFS 1321 config CPU_NO_EFFICIENT_FFS
1361 def_bool n 1322 def_bool n
1362 1323
1363 config HAVE_ARCH_VMAP_STACK 1324 config HAVE_ARCH_VMAP_STACK
1364 def_bool n 1325 def_bool n
1365 help 1326 help
1366 An arch should select this symbol i 1327 An arch should select this symbol if it can support kernel stacks
1367 in vmalloc space. This means: 1328 in vmalloc space. This means:
1368 1329
1369 - vmalloc space must be large enoug 1330 - vmalloc space must be large enough to hold many kernel stacks.
1370 This may rule out many 32-bit arc 1331 This may rule out many 32-bit architectures.
1371 1332
1372 - Stacks in vmalloc space need to w 1333 - Stacks in vmalloc space need to work reliably. For example, if
1373 vmap page tables are created on d 1334 vmap page tables are created on demand, either this mechanism
1374 needs to work while the stack poi 1335 needs to work while the stack points to a virtual address with
1375 unpopulated page tables or arch c 1336 unpopulated page tables or arch code (switch_to() and switch_mm(),
1376 most likely) needs to ensure that 1337 most likely) needs to ensure that the stack's page table entries
1377 are populated before running on a 1338 are populated before running on a possibly unpopulated stack.
1378 1339
1379 - If the stack overflows into a gua 1340 - If the stack overflows into a guard page, something reasonable
1380 should happen. The definition of 1341 should happen. The definition of "reasonable" is flexible, but
1381 instantly rebooting without loggi 1342 instantly rebooting without logging anything would be unfriendly.
1382 1343
1383 config VMAP_STACK 1344 config VMAP_STACK
1384 default y 1345 default y
1385 bool "Use a virtually-mapped stack" 1346 bool "Use a virtually-mapped stack"
1386 depends on HAVE_ARCH_VMAP_STACK 1347 depends on HAVE_ARCH_VMAP_STACK
1387 depends on !KASAN || KASAN_HW_TAGS || 1348 depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC
1388 help 1349 help
1389 Enable this if you want the use vir 1350 Enable this if you want the use virtually-mapped kernel stacks
1390 with guard pages. This causes kern 1351 with guard pages. This causes kernel stack overflows to be
1391 caught immediately rather than caus 1352 caught immediately rather than causing difficult-to-diagnose
1392 corruption. 1353 corruption.
1393 1354
1394 To use this with software KASAN mod 1355 To use this with software KASAN modes, the architecture must support
1395 backing virtual mappings with real 1356 backing virtual mappings with real shadow memory, and KASAN_VMALLOC
1396 must be enabled. 1357 must be enabled.
1397 1358
1398 config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET 1359 config HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
1399 def_bool n 1360 def_bool n
1400 help 1361 help
1401 An arch should select this symbol i 1362 An arch should select this symbol if it can support kernel stack
1402 offset randomization with calls to 1363 offset randomization with calls to add_random_kstack_offset()
1403 during syscall entry and choose_ran 1364 during syscall entry and choose_random_kstack_offset() during
1404 syscall exit. Careful removal of -f 1365 syscall exit. Careful removal of -fstack-protector-strong and
1405 -fstack-protector should also be ap 1366 -fstack-protector should also be applied to the entry code and
1406 closely examined, as the artificial 1367 closely examined, as the artificial stack bump looks like an array
1407 to the compiler, so it will attempt 1368 to the compiler, so it will attempt to add canary checks regardless
1408 of the static branch state. 1369 of the static branch state.
1409 1370
1410 config RANDOMIZE_KSTACK_OFFSET 1371 config RANDOMIZE_KSTACK_OFFSET
1411 bool "Support for randomizing kernel 1372 bool "Support for randomizing kernel stack offset on syscall entry" if EXPERT
1412 default y 1373 default y
1413 depends on HAVE_ARCH_RANDOMIZE_KSTACK 1374 depends on HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
1414 depends on INIT_STACK_NONE || !CC_IS_ 1375 depends on INIT_STACK_NONE || !CC_IS_CLANG || CLANG_VERSION >= 140000
1415 help 1376 help
1416 The kernel stack offset can be rand 1377 The kernel stack offset can be randomized (after pt_regs) by
1417 roughly 5 bits of entropy, frustrat 1378 roughly 5 bits of entropy, frustrating memory corruption
1418 attacks that depend on stack addres 1379 attacks that depend on stack address determinism or
1419 cross-syscall address exposures. 1380 cross-syscall address exposures.
1420 1381
1421 The feature is controlled via the " 1382 The feature is controlled via the "randomize_kstack_offset=on/off"
1422 kernel boot param, and if turned of 1383 kernel boot param, and if turned off has zero overhead due to its use
1423 of static branches (see JUMP_LABEL) 1384 of static branches (see JUMP_LABEL).
1424 1385
1425 If unsure, say Y. 1386 If unsure, say Y.
1426 1387
1427 config RANDOMIZE_KSTACK_OFFSET_DEFAULT 1388 config RANDOMIZE_KSTACK_OFFSET_DEFAULT
1428 bool "Default state of kernel stack o 1389 bool "Default state of kernel stack offset randomization"
1429 depends on RANDOMIZE_KSTACK_OFFSET 1390 depends on RANDOMIZE_KSTACK_OFFSET
1430 help 1391 help
1431 Kernel stack offset randomization i 1392 Kernel stack offset randomization is controlled by kernel boot param
1432 "randomize_kstack_offset=on/off", a 1393 "randomize_kstack_offset=on/off", and this config chooses the default
1433 boot state. 1394 boot state.
1434 1395
1435 config ARCH_OPTIONAL_KERNEL_RWX 1396 config ARCH_OPTIONAL_KERNEL_RWX
1436 def_bool n 1397 def_bool n
1437 1398
1438 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT 1399 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1439 def_bool n 1400 def_bool n
1440 1401
1441 config ARCH_HAS_STRICT_KERNEL_RWX 1402 config ARCH_HAS_STRICT_KERNEL_RWX
1442 def_bool n 1403 def_bool n
1443 1404
1444 config STRICT_KERNEL_RWX 1405 config STRICT_KERNEL_RWX
1445 bool "Make kernel text and rodata rea 1406 bool "Make kernel text and rodata read-only" if ARCH_OPTIONAL_KERNEL_RWX
1446 depends on ARCH_HAS_STRICT_KERNEL_RWX 1407 depends on ARCH_HAS_STRICT_KERNEL_RWX
1447 default !ARCH_OPTIONAL_KERNEL_RWX || 1408 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1448 help 1409 help
1449 If this is set, kernel text and rod 1410 If this is set, kernel text and rodata memory will be made read-only,
1450 and non-text memory will be made no 1411 and non-text memory will be made non-executable. This provides
1451 protection against certain security 1412 protection against certain security exploits (e.g. executing the heap
1452 or modifying text) 1413 or modifying text)
1453 1414
1454 These features are considered stand 1415 These features are considered standard security practice these days.
1455 You should say Y here in almost all 1416 You should say Y here in almost all cases.
1456 1417
1457 config ARCH_HAS_STRICT_MODULE_RWX 1418 config ARCH_HAS_STRICT_MODULE_RWX
1458 def_bool n 1419 def_bool n
1459 1420
1460 config STRICT_MODULE_RWX 1421 config STRICT_MODULE_RWX
1461 bool "Set loadable kernel module data 1422 bool "Set loadable kernel module data as NX and text as RO" if ARCH_OPTIONAL_KERNEL_RWX
1462 depends on ARCH_HAS_STRICT_MODULE_RWX 1423 depends on ARCH_HAS_STRICT_MODULE_RWX && MODULES
1463 default !ARCH_OPTIONAL_KERNEL_RWX || 1424 default !ARCH_OPTIONAL_KERNEL_RWX || ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
1464 help 1425 help
1465 If this is set, module text and rod 1426 If this is set, module text and rodata memory will be made read-only,
1466 and non-text memory will be made no 1427 and non-text memory will be made non-executable. This provides
1467 protection against certain security 1428 protection against certain security exploits (e.g. writing to text)
1468 1429
1469 # select if the architecture provides an asm/ 1430 # select if the architecture provides an asm/dma-direct.h header
1470 config ARCH_HAS_PHYS_TO_DMA 1431 config ARCH_HAS_PHYS_TO_DMA
1471 bool 1432 bool
1472 1433
1473 config HAVE_ARCH_COMPILER_H 1434 config HAVE_ARCH_COMPILER_H
1474 bool 1435 bool
1475 help 1436 help
1476 An architecture can select this if 1437 An architecture can select this if it provides an
1477 asm/compiler.h header that should b 1438 asm/compiler.h header that should be included after
1478 linux/compiler-*.h in order to over 1439 linux/compiler-*.h in order to override macro definitions that those
1479 headers generally provide. 1440 headers generally provide.
1480 1441
1481 config HAVE_ARCH_PREL32_RELOCATIONS 1442 config HAVE_ARCH_PREL32_RELOCATIONS
1482 bool 1443 bool
1483 help 1444 help
1484 May be selected by an architecture 1445 May be selected by an architecture if it supports place-relative
1485 32-bit relocations, both in the too 1446 32-bit relocations, both in the toolchain and in the module loader,
1486 in which case relative references c 1447 in which case relative references can be used in special sections
1487 for PCI fixup, initcalls etc which 1448 for PCI fixup, initcalls etc which are only half the size on 64 bit
1488 architectures, and don't require ru 1449 architectures, and don't require runtime relocation on relocatable
1489 kernels. 1450 kernels.
1490 1451
1491 config ARCH_USE_MEMREMAP_PROT 1452 config ARCH_USE_MEMREMAP_PROT
1492 bool 1453 bool
1493 1454
1494 config LOCK_EVENT_COUNTS 1455 config LOCK_EVENT_COUNTS
1495 bool "Locking event counts collection 1456 bool "Locking event counts collection"
1496 depends on DEBUG_FS 1457 depends on DEBUG_FS
1497 help 1458 help
1498 Enable light-weight counting of var 1459 Enable light-weight counting of various locking related events
1499 in the system with minimal performa 1460 in the system with minimal performance impact. This reduces
1500 the chance of application behavior 1461 the chance of application behavior change because of timing
1501 differences. The counts are reporte 1462 differences. The counts are reported via debugfs.
1502 1463
1503 # Select if the architecture has support for 1464 # Select if the architecture has support for applying RELR relocations.
1504 config ARCH_HAS_RELR 1465 config ARCH_HAS_RELR
1505 bool 1466 bool
1506 1467
1507 config RELR 1468 config RELR
1508 bool "Use RELR relocation packing" 1469 bool "Use RELR relocation packing"
1509 depends on ARCH_HAS_RELR && TOOLS_SUP 1470 depends on ARCH_HAS_RELR && TOOLS_SUPPORT_RELR
1510 default y 1471 default y
1511 help 1472 help
1512 Store the kernel's dynamic relocati 1473 Store the kernel's dynamic relocations in the RELR relocation packing
1513 format. Requires a compatible linke 1474 format. Requires a compatible linker (LLD supports this feature), as
1514 well as compatible NM and OBJCOPY u 1475 well as compatible NM and OBJCOPY utilities (llvm-nm and llvm-objcopy
1515 are compatible). 1476 are compatible).
1516 1477
1517 config ARCH_HAS_MEM_ENCRYPT 1478 config ARCH_HAS_MEM_ENCRYPT
1518 bool 1479 bool
1519 1480
1520 config ARCH_HAS_CC_PLATFORM 1481 config ARCH_HAS_CC_PLATFORM
1521 bool 1482 bool
1522 1483
1523 config HAVE_SPARSE_SYSCALL_NR 1484 config HAVE_SPARSE_SYSCALL_NR
1524 bool 1485 bool
1525 help 1486 help
1526 An architecture should select this 1487 An architecture should select this if its syscall numbering is sparse
1527 to save space. For example, MIPS ar 1488 to save space. For example, MIPS architecture has a syscall array with
1528 entries at 4000, 5000 and 6000 loca 1489 entries at 4000, 5000 and 6000 locations. This option turns on syscall
1529 related optimizations for a given a 1490 related optimizations for a given architecture.
1530 1491
1531 config ARCH_HAS_VDSO_DATA 1492 config ARCH_HAS_VDSO_DATA
1532 bool 1493 bool
1533 1494
1534 config HAVE_STATIC_CALL 1495 config HAVE_STATIC_CALL
1535 bool 1496 bool
1536 1497
1537 config HAVE_STATIC_CALL_INLINE 1498 config HAVE_STATIC_CALL_INLINE
1538 bool 1499 bool
1539 depends on HAVE_STATIC_CALL 1500 depends on HAVE_STATIC_CALL
1540 select OBJTOOL 1501 select OBJTOOL
1541 1502
1542 config HAVE_PREEMPT_DYNAMIC 1503 config HAVE_PREEMPT_DYNAMIC
1543 bool 1504 bool
1544 1505
1545 config HAVE_PREEMPT_DYNAMIC_CALL 1506 config HAVE_PREEMPT_DYNAMIC_CALL
1546 bool 1507 bool
1547 depends on HAVE_STATIC_CALL 1508 depends on HAVE_STATIC_CALL
1548 select HAVE_PREEMPT_DYNAMIC 1509 select HAVE_PREEMPT_DYNAMIC
1549 help 1510 help
1550 An architecture should select this 1511 An architecture should select this if it can handle the preemption
1551 model being selected at boot time u 1512 model being selected at boot time using static calls.
1552 1513
1553 Where an architecture selects HAVE_ 1514 Where an architecture selects HAVE_STATIC_CALL_INLINE, any call to a
1554 preemption function will be patched 1515 preemption function will be patched directly.
1555 1516
1556 Where an architecture does not sele 1517 Where an architecture does not select HAVE_STATIC_CALL_INLINE, any
1557 call to a preemption function will 1518 call to a preemption function will go through a trampoline, and the
1558 trampoline will be patched. 1519 trampoline will be patched.
1559 1520
1560 It is strongly advised to support i 1521 It is strongly advised to support inline static call to avoid any
1561 overhead. 1522 overhead.
1562 1523
1563 config HAVE_PREEMPT_DYNAMIC_KEY 1524 config HAVE_PREEMPT_DYNAMIC_KEY
1564 bool 1525 bool
1565 depends on HAVE_ARCH_JUMP_LABEL 1526 depends on HAVE_ARCH_JUMP_LABEL
1566 select HAVE_PREEMPT_DYNAMIC 1527 select HAVE_PREEMPT_DYNAMIC
1567 help 1528 help
1568 An architecture should select this 1529 An architecture should select this if it can handle the preemption
1569 model being selected at boot time u 1530 model being selected at boot time using static keys.
1570 1531
1571 Each preemption function will be gi 1532 Each preemption function will be given an early return based on a
1572 static key. This should have slight 1533 static key. This should have slightly lower overhead than non-inline
1573 static calls, as this effectively i 1534 static calls, as this effectively inlines each trampoline into the
1574 start of its callee. This may avoid 1535 start of its callee. This may avoid redundant work, and may
1575 integrate better with CFI schemes. 1536 integrate better with CFI schemes.
1576 1537
1577 This will have greater overhead tha 1538 This will have greater overhead than using inline static calls as
1578 the call to the preemption function 1539 the call to the preemption function cannot be entirely elided.
1579 1540
1580 config ARCH_WANT_LD_ORPHAN_WARN 1541 config ARCH_WANT_LD_ORPHAN_WARN
1581 bool 1542 bool
1582 help 1543 help
1583 An arch should select this symbol o 1544 An arch should select this symbol once all linker sections are explicitly
1584 included, size-asserted, or discard 1545 included, size-asserted, or discarded in the linker scripts. This is
1585 important because we never want exp 1546 important because we never want expected sections to be placed heuristically
1586 by the linker, since the locations 1547 by the linker, since the locations of such sections can change between linker
1587 versions. 1548 versions.
1588 1549
1589 config HAVE_ARCH_PFN_VALID 1550 config HAVE_ARCH_PFN_VALID
1590 bool 1551 bool
1591 1552
1592 config ARCH_SUPPORTS_DEBUG_PAGEALLOC 1553 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
1593 bool 1554 bool
1594 1555
1595 config ARCH_SUPPORTS_PAGE_TABLE_CHECK 1556 config ARCH_SUPPORTS_PAGE_TABLE_CHECK
1596 bool 1557 bool
1597 1558
1598 config ARCH_SPLIT_ARG64 1559 config ARCH_SPLIT_ARG64
1599 bool 1560 bool
1600 help 1561 help
1601 If a 32-bit architecture requires 6 1562 If a 32-bit architecture requires 64-bit arguments to be split into
1602 pairs of 32-bit arguments, select t 1563 pairs of 32-bit arguments, select this option.
1603 1564
1604 config ARCH_HAS_ELFCORE_COMPAT 1565 config ARCH_HAS_ELFCORE_COMPAT
1605 bool 1566 bool
1606 1567
1607 config ARCH_HAS_PARANOID_L1D_FLUSH 1568 config ARCH_HAS_PARANOID_L1D_FLUSH
1608 bool 1569 bool
1609 1570
1610 config ARCH_HAVE_TRACE_MMIO_ACCESS 1571 config ARCH_HAVE_TRACE_MMIO_ACCESS
1611 bool 1572 bool
1612 1573
1613 config DYNAMIC_SIGFRAME 1574 config DYNAMIC_SIGFRAME
1614 bool 1575 bool
1615 1576
1616 # Select, if arch has a named attribute group 1577 # Select, if arch has a named attribute group bound to NUMA device nodes.
1617 config HAVE_ARCH_NODE_DEV_GROUP 1578 config HAVE_ARCH_NODE_DEV_GROUP
1618 bool 1579 bool
1619 1580
1620 config ARCH_HAS_HW_PTE_YOUNG 1581 config ARCH_HAS_HW_PTE_YOUNG
1621 bool 1582 bool
1622 help 1583 help
1623 Architectures that select this opti 1584 Architectures that select this option are capable of setting the
1624 accessed bit in PTE entries when us 1585 accessed bit in PTE entries when using them as part of linear address
1625 translations. Architectures that re 1586 translations. Architectures that require runtime check should select
1626 this option and override arch_has_h 1587 this option and override arch_has_hw_pte_young().
1627 1588
1628 config ARCH_HAS_NONLEAF_PMD_YOUNG 1589 config ARCH_HAS_NONLEAF_PMD_YOUNG
1629 bool 1590 bool
1630 help 1591 help
1631 Architectures that select this opti 1592 Architectures that select this option are capable of setting the
1632 accessed bit in non-leaf PMD entrie 1593 accessed bit in non-leaf PMD entries when using them as part of linear
1633 address translations. Page table wa 1594 address translations. Page table walkers that clear the accessed bit
1634 may use this capability to reduce t 1595 may use this capability to reduce their search space.
1635 1596
1636 config ARCH_HAS_KERNEL_FPU_SUPPORT 1597 config ARCH_HAS_KERNEL_FPU_SUPPORT
1637 bool 1598 bool
1638 help 1599 help
1639 Architectures that select this opti 1600 Architectures that select this option can run floating-point code in
1640 the kernel, as described in Documen 1601 the kernel, as described in Documentation/core-api/floating-point.rst.
1641 1602
1642 source "kernel/gcov/Kconfig" 1603 source "kernel/gcov/Kconfig"
1643 1604
1644 source "scripts/gcc-plugins/Kconfig" 1605 source "scripts/gcc-plugins/Kconfig"
1645 1606
1646 config FUNCTION_ALIGNMENT_4B 1607 config FUNCTION_ALIGNMENT_4B
1647 bool 1608 bool
1648 1609
1649 config FUNCTION_ALIGNMENT_8B 1610 config FUNCTION_ALIGNMENT_8B
1650 bool 1611 bool
1651 1612
1652 config FUNCTION_ALIGNMENT_16B 1613 config FUNCTION_ALIGNMENT_16B
1653 bool 1614 bool
1654 1615
1655 config FUNCTION_ALIGNMENT_32B 1616 config FUNCTION_ALIGNMENT_32B
1656 bool 1617 bool
1657 1618
1658 config FUNCTION_ALIGNMENT_64B 1619 config FUNCTION_ALIGNMENT_64B
1659 bool 1620 bool
1660 1621
1661 config FUNCTION_ALIGNMENT 1622 config FUNCTION_ALIGNMENT
1662 int 1623 int
1663 default 64 if FUNCTION_ALIGNMENT_64B 1624 default 64 if FUNCTION_ALIGNMENT_64B
1664 default 32 if FUNCTION_ALIGNMENT_32B 1625 default 32 if FUNCTION_ALIGNMENT_32B
1665 default 16 if FUNCTION_ALIGNMENT_16B 1626 default 16 if FUNCTION_ALIGNMENT_16B
1666 default 8 if FUNCTION_ALIGNMENT_8B 1627 default 8 if FUNCTION_ALIGNMENT_8B
1667 default 4 if FUNCTION_ALIGNMENT_4B 1628 default 4 if FUNCTION_ALIGNMENT_4B
1668 default 0 1629 default 0
1669 1630
1670 config CC_HAS_MIN_FUNCTION_ALIGNMENT 1631 config CC_HAS_MIN_FUNCTION_ALIGNMENT
1671 # Detect availability of the GCC opti 1632 # Detect availability of the GCC option -fmin-function-alignment which
1672 # guarantees minimal alignment for al 1633 # guarantees minimal alignment for all functions, unlike
1673 # -falign-functions which the compile 1634 # -falign-functions which the compiler ignores for cold functions.
1674 def_bool $(cc-option, -fmin-function- 1635 def_bool $(cc-option, -fmin-function-alignment=8)
1675 1636
1676 config CC_HAS_SANE_FUNCTION_ALIGNMENT 1637 config CC_HAS_SANE_FUNCTION_ALIGNMENT
1677 # Set if the guaranteed alignment wit 1638 # Set if the guaranteed alignment with -fmin-function-alignment is
1678 # available or extra care is required 1639 # available or extra care is required in the kernel. Clang provides
1679 # strict alignment always, even with 1640 # strict alignment always, even with -falign-functions.
1680 def_bool CC_HAS_MIN_FUNCTION_ALIGNMEN 1641 def_bool CC_HAS_MIN_FUNCTION_ALIGNMENT || CC_IS_CLANG
1681 1642
1682 config ARCH_NEED_CMPXCHG_1_EMU 1643 config ARCH_NEED_CMPXCHG_1_EMU
1683 bool 1644 bool
1684 1645
1685 endmenu 1646 endmenu
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