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