1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2012 Regents of the University of California
4 */
5
6 #include <linux/cpu.h>
7 #include <linux/kernel.h>
8 #include <linux/init.h>
9 #include <linux/randomize_kstack.h>
10 #include <linux/sched.h>
11 #include <linux/sched/debug.h>
12 #include <linux/sched/signal.h>
13 #include <linux/signal.h>
14 #include <linux/kdebug.h>
15 #include <linux/uaccess.h>
16 #include <linux/kprobes.h>
17 #include <linux/uprobes.h>
18 #include <asm/uprobes.h>
19 #include <linux/mm.h>
20 #include <linux/module.h>
21 #include <linux/irq.h>
22 #include <linux/kexec.h>
23 #include <linux/entry-common.h>
24
25 #include <asm/asm-prototypes.h>
26 #include <asm/bug.h>
27 #include <asm/cfi.h>
28 #include <asm/csr.h>
29 #include <asm/processor.h>
30 #include <asm/ptrace.h>
31 #include <asm/syscall.h>
32 #include <asm/thread_info.h>
33 #include <asm/vector.h>
34 #include <asm/irq_stack.h>
35
36 int show_unhandled_signals = 1;
37
38 static DEFINE_SPINLOCK(die_lock);
39
40 static int copy_code(struct pt_regs *regs, u16 *val, const u16 *insns)
41 {
42 const void __user *uaddr = (__force const void __user *)insns;
43
44 if (!user_mode(regs))
45 return get_kernel_nofault(*val, insns);
46
47 /* The user space code from other tasks cannot be accessed. */
48 if (regs != task_pt_regs(current))
49 return -EPERM;
50
51 return copy_from_user_nofault(val, uaddr, sizeof(*val));
52 }
53
54 static void dump_instr(const char *loglvl, struct pt_regs *regs)
55 {
56 char str[sizeof("0000 ") * 12 + 2 + 1], *p = str;
57 const u16 *insns = (u16 *)instruction_pointer(regs);
58 long bad;
59 u16 val;
60 int i;
61
62 for (i = -10; i < 2; i++) {
63 bad = copy_code(regs, &val, &insns[i]);
64 if (!bad) {
65 p += sprintf(p, i == 0 ? "(%04hx) " : "%04hx ", val);
66 } else {
67 printk("%sCode: Unable to access instruction at 0x%px.\n",
68 loglvl, &insns[i]);
69 return;
70 }
71 }
72 printk("%sCode: %s\n", loglvl, str);
73 }
74
75 void die(struct pt_regs *regs, const char *str)
76 {
77 static int die_counter;
78 int ret;
79 long cause;
80 unsigned long flags;
81
82 oops_enter();
83
84 spin_lock_irqsave(&die_lock, flags);
85 console_verbose();
86 bust_spinlocks(1);
87
88 pr_emerg("%s [#%d]\n", str, ++die_counter);
89 print_modules();
90 if (regs) {
91 show_regs(regs);
92 dump_instr(KERN_EMERG, regs);
93 }
94
95 cause = regs ? regs->cause : -1;
96 ret = notify_die(DIE_OOPS, str, regs, 0, cause, SIGSEGV);
97
98 if (kexec_should_crash(current))
99 crash_kexec(regs);
100
101 bust_spinlocks(0);
102 add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
103 spin_unlock_irqrestore(&die_lock, flags);
104 oops_exit();
105
106 if (in_interrupt())
107 panic("Fatal exception in interrupt");
108 if (panic_on_oops)
109 panic("Fatal exception");
110 if (ret != NOTIFY_STOP)
111 make_task_dead(SIGSEGV);
112 }
113
114 void do_trap(struct pt_regs *regs, int signo, int code, unsigned long addr)
115 {
116 struct task_struct *tsk = current;
117
118 if (show_unhandled_signals && unhandled_signal(tsk, signo)
119 && printk_ratelimit()) {
120 pr_info("%s[%d]: unhandled signal %d code 0x%x at 0x" REG_FMT,
121 tsk->comm, task_pid_nr(tsk), signo, code, addr);
122 print_vma_addr(KERN_CONT " in ", instruction_pointer(regs));
123 pr_cont("\n");
124 __show_regs(regs);
125 dump_instr(KERN_INFO, regs);
126 }
127
128 force_sig_fault(signo, code, (void __user *)addr);
129 }
130
131 static void do_trap_error(struct pt_regs *regs, int signo, int code,
132 unsigned long addr, const char *str)
133 {
134 current->thread.bad_cause = regs->cause;
135
136 if (user_mode(regs)) {
137 do_trap(regs, signo, code, addr);
138 } else {
139 if (!fixup_exception(regs))
140 die(regs, str);
141 }
142 }
143
144 #if defined(CONFIG_XIP_KERNEL) && defined(CONFIG_RISCV_ALTERNATIVE)
145 #define __trap_section __noinstr_section(".xip.traps")
146 #else
147 #define __trap_section noinstr
148 #endif
149 #define DO_ERROR_INFO(name, signo, code, str) \
150 asmlinkage __visible __trap_section void name(struct pt_regs *regs) \
151 { \
152 if (user_mode(regs)) { \
153 irqentry_enter_from_user_mode(regs); \
154 do_trap_error(regs, signo, code, regs->epc, "Oops - " str); \
155 irqentry_exit_to_user_mode(regs); \
156 } else { \
157 irqentry_state_t state = irqentry_nmi_enter(regs); \
158 do_trap_error(regs, signo, code, regs->epc, "Oops - " str); \
159 irqentry_nmi_exit(regs, state); \
160 } \
161 }
162
163 DO_ERROR_INFO(do_trap_unknown,
164 SIGILL, ILL_ILLTRP, "unknown exception");
165 DO_ERROR_INFO(do_trap_insn_misaligned,
166 SIGBUS, BUS_ADRALN, "instruction address misaligned");
167 DO_ERROR_INFO(do_trap_insn_fault,
168 SIGSEGV, SEGV_ACCERR, "instruction access fault");
169
170 asmlinkage __visible __trap_section void do_trap_insn_illegal(struct pt_regs *regs)
171 {
172 bool handled;
173
174 if (user_mode(regs)) {
175 irqentry_enter_from_user_mode(regs);
176
177 local_irq_enable();
178
179 handled = riscv_v_first_use_handler(regs);
180
181 local_irq_disable();
182
183 if (!handled)
184 do_trap_error(regs, SIGILL, ILL_ILLOPC, regs->epc,
185 "Oops - illegal instruction");
186
187 irqentry_exit_to_user_mode(regs);
188 } else {
189 irqentry_state_t state = irqentry_nmi_enter(regs);
190
191 do_trap_error(regs, SIGILL, ILL_ILLOPC, regs->epc,
192 "Oops - illegal instruction");
193
194 irqentry_nmi_exit(regs, state);
195 }
196 }
197
198 DO_ERROR_INFO(do_trap_load_fault,
199 SIGSEGV, SEGV_ACCERR, "load access fault");
200
201 asmlinkage __visible __trap_section void do_trap_load_misaligned(struct pt_regs *regs)
202 {
203 if (user_mode(regs)) {
204 irqentry_enter_from_user_mode(regs);
205
206 if (handle_misaligned_load(regs))
207 do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
208 "Oops - load address misaligned");
209
210 irqentry_exit_to_user_mode(regs);
211 } else {
212 irqentry_state_t state = irqentry_nmi_enter(regs);
213
214 if (handle_misaligned_load(regs))
215 do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
216 "Oops - load address misaligned");
217
218 irqentry_nmi_exit(regs, state);
219 }
220 }
221
222 asmlinkage __visible __trap_section void do_trap_store_misaligned(struct pt_regs *regs)
223 {
224 if (user_mode(regs)) {
225 irqentry_enter_from_user_mode(regs);
226
227 if (handle_misaligned_store(regs))
228 do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
229 "Oops - store (or AMO) address misaligned");
230
231 irqentry_exit_to_user_mode(regs);
232 } else {
233 irqentry_state_t state = irqentry_nmi_enter(regs);
234
235 if (handle_misaligned_store(regs))
236 do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
237 "Oops - store (or AMO) address misaligned");
238
239 irqentry_nmi_exit(regs, state);
240 }
241 }
242 DO_ERROR_INFO(do_trap_store_fault,
243 SIGSEGV, SEGV_ACCERR, "store (or AMO) access fault");
244 DO_ERROR_INFO(do_trap_ecall_s,
245 SIGILL, ILL_ILLTRP, "environment call from S-mode");
246 DO_ERROR_INFO(do_trap_ecall_m,
247 SIGILL, ILL_ILLTRP, "environment call from M-mode");
248
249 static inline unsigned long get_break_insn_length(unsigned long pc)
250 {
251 bug_insn_t insn;
252
253 if (get_kernel_nofault(insn, (bug_insn_t *)pc))
254 return 0;
255
256 return GET_INSN_LENGTH(insn);
257 }
258
259 static bool probe_single_step_handler(struct pt_regs *regs)
260 {
261 bool user = user_mode(regs);
262
263 return user ? uprobe_single_step_handler(regs) : kprobe_single_step_handler(regs);
264 }
265
266 static bool probe_breakpoint_handler(struct pt_regs *regs)
267 {
268 bool user = user_mode(regs);
269
270 return user ? uprobe_breakpoint_handler(regs) : kprobe_breakpoint_handler(regs);
271 }
272
273 void handle_break(struct pt_regs *regs)
274 {
275 if (probe_single_step_handler(regs))
276 return;
277
278 if (probe_breakpoint_handler(regs))
279 return;
280
281 current->thread.bad_cause = regs->cause;
282
283 if (user_mode(regs))
284 force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)regs->epc);
285 #ifdef CONFIG_KGDB
286 else if (notify_die(DIE_TRAP, "EBREAK", regs, 0, regs->cause, SIGTRAP)
287 == NOTIFY_STOP)
288 return;
289 #endif
290 else if (report_bug(regs->epc, regs) == BUG_TRAP_TYPE_WARN ||
291 handle_cfi_failure(regs) == BUG_TRAP_TYPE_WARN)
292 regs->epc += get_break_insn_length(regs->epc);
293 else
294 die(regs, "Kernel BUG");
295 }
296
297 asmlinkage __visible __trap_section void do_trap_break(struct pt_regs *regs)
298 {
299 if (user_mode(regs)) {
300 irqentry_enter_from_user_mode(regs);
301
302 handle_break(regs);
303
304 irqentry_exit_to_user_mode(regs);
305 } else {
306 irqentry_state_t state = irqentry_nmi_enter(regs);
307
308 handle_break(regs);
309
310 irqentry_nmi_exit(regs, state);
311 }
312 }
313
314 asmlinkage __visible __trap_section __no_stack_protector
315 void do_trap_ecall_u(struct pt_regs *regs)
316 {
317 if (user_mode(regs)) {
318 long syscall = regs->a7;
319
320 regs->epc += 4;
321 regs->orig_a0 = regs->a0;
322 regs->a0 = -ENOSYS;
323
324 riscv_v_vstate_discard(regs);
325
326 syscall = syscall_enter_from_user_mode(regs, syscall);
327
328 add_random_kstack_offset();
329
330 if (syscall >= 0 && syscall < NR_syscalls)
331 syscall_handler(regs, syscall);
332
333 /*
334 * Ultimately, this value will get limited by KSTACK_OFFSET_MAX(),
335 * so the maximum stack offset is 1k bytes (10 bits).
336 *
337 * The actual entropy will be further reduced by the compiler when
338 * applying stack alignment constraints: 16-byte (i.e. 4-bit) aligned
339 * for RV32I or RV64I.
340 *
341 * The resulting 6 bits of entropy is seen in SP[9:4].
342 */
343 choose_random_kstack_offset(get_random_u16());
344
345 syscall_exit_to_user_mode(regs);
346 } else {
347 irqentry_state_t state = irqentry_nmi_enter(regs);
348
349 do_trap_error(regs, SIGILL, ILL_ILLTRP, regs->epc,
350 "Oops - environment call from U-mode");
351
352 irqentry_nmi_exit(regs, state);
353 }
354
355 }
356
357 #ifdef CONFIG_MMU
358 asmlinkage __visible noinstr void do_page_fault(struct pt_regs *regs)
359 {
360 irqentry_state_t state = irqentry_enter(regs);
361
362 handle_page_fault(regs);
363
364 local_irq_disable();
365
366 irqentry_exit(regs, state);
367 }
368 #endif
369
370 static void noinstr handle_riscv_irq(struct pt_regs *regs)
371 {
372 struct pt_regs *old_regs;
373
374 irq_enter_rcu();
375 old_regs = set_irq_regs(regs);
376 handle_arch_irq(regs);
377 set_irq_regs(old_regs);
378 irq_exit_rcu();
379 }
380
381 asmlinkage void noinstr do_irq(struct pt_regs *regs)
382 {
383 irqentry_state_t state = irqentry_enter(regs);
384
385 if (IS_ENABLED(CONFIG_IRQ_STACKS) && on_thread_stack())
386 call_on_irq_stack(regs, handle_riscv_irq);
387 else
388 handle_riscv_irq(regs);
389
390 irqentry_exit(regs, state);
391 }
392
393 #ifdef CONFIG_GENERIC_BUG
394 int is_valid_bugaddr(unsigned long pc)
395 {
396 bug_insn_t insn;
397
398 if (pc < VMALLOC_START)
399 return 0;
400 if (get_kernel_nofault(insn, (bug_insn_t *)pc))
401 return 0;
402 if ((insn & __INSN_LENGTH_MASK) == __INSN_LENGTH_32)
403 return (insn == __BUG_INSN_32);
404 else
405 return ((insn & __COMPRESSED_INSN_MASK) == __BUG_INSN_16);
406 }
407 #endif /* CONFIG_GENERIC_BUG */
408
409 #ifdef CONFIG_VMAP_STACK
410 DEFINE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)],
411 overflow_stack)__aligned(16);
412
413 asmlinkage void handle_bad_stack(struct pt_regs *regs)
414 {
415 unsigned long tsk_stk = (unsigned long)current->stack;
416 unsigned long ovf_stk = (unsigned long)this_cpu_ptr(overflow_stack);
417
418 console_verbose();
419
420 pr_emerg("Insufficient stack space to handle exception!\n");
421 pr_emerg("Task stack: [0x%016lx..0x%016lx]\n",
422 tsk_stk, tsk_stk + THREAD_SIZE);
423 pr_emerg("Overflow stack: [0x%016lx..0x%016lx]\n",
424 ovf_stk, ovf_stk + OVERFLOW_STACK_SIZE);
425
426 __show_regs(regs);
427 panic("Kernel stack overflow");
428
429 for (;;)
430 wait_for_interrupt();
431 }
432 #endif
433
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