1 /*
2 * Copyright (C) 1991, 1992 Linus Torvalds
3 * Copyright (C) 2000, 2001, 2002 Andi Kleen, SuSE Labs
4 */
5 #include <linux/kallsyms.h>
6 #include <linux/kprobes.h>
7 #include <linux/uaccess.h>
8 #include <linux/utsname.h>
9 #include <linux/hardirq.h>
10 #include <linux/kdebug.h>
11 #include <linux/module.h>
12 #include <linux/ptrace.h>
13 #include <linux/sched/debug.h>
14 #include <linux/sched/task_stack.h>
15 #include <linux/ftrace.h>
16 #include <linux/kexec.h>
17 #include <linux/bug.h>
18 #include <linux/nmi.h>
19 #include <linux/sysfs.h>
20 #include <linux/kasan.h>
21
22 #include <asm/cpu_entry_area.h>
23 #include <asm/stacktrace.h>
24 #include <asm/unwind.h>
25
26 int panic_on_unrecovered_nmi;
27 int panic_on_io_nmi;
28 static int die_counter;
29
30 static struct pt_regs exec_summary_regs;
31
in_task_stack(unsigned long * stack,struct task_struct * task,struct stack_info * info)32 bool noinstr in_task_stack(unsigned long *stack, struct task_struct *task,
33 struct stack_info *info)
34 {
35 unsigned long *begin = task_stack_page(task);
36 unsigned long *end = task_stack_page(task) + THREAD_SIZE;
37
38 if (stack < begin || stack >= end)
39 return false;
40
41 info->type = STACK_TYPE_TASK;
42 info->begin = begin;
43 info->end = end;
44 info->next_sp = NULL;
45
46 return true;
47 }
48
49 /* Called from get_stack_info_noinstr - so must be noinstr too */
in_entry_stack(unsigned long * stack,struct stack_info * info)50 bool noinstr in_entry_stack(unsigned long *stack, struct stack_info *info)
51 {
52 struct entry_stack *ss = cpu_entry_stack(smp_processor_id());
53
54 void *begin = ss;
55 void *end = ss + 1;
56
57 if ((void *)stack < begin || (void *)stack >= end)
58 return false;
59
60 info->type = STACK_TYPE_ENTRY;
61 info->begin = begin;
62 info->end = end;
63 info->next_sp = NULL;
64
65 return true;
66 }
67
printk_stack_address(unsigned long address,int reliable,const char * log_lvl)68 static void printk_stack_address(unsigned long address, int reliable,
69 const char *log_lvl)
70 {
71 touch_nmi_watchdog();
72 printk("%s %s%pBb\n", log_lvl, reliable ? "" : "? ", (void *)address);
73 }
74
copy_code(struct pt_regs * regs,u8 * buf,unsigned long src,unsigned int nbytes)75 static int copy_code(struct pt_regs *regs, u8 *buf, unsigned long src,
76 unsigned int nbytes)
77 {
78 if (!user_mode(regs))
79 return copy_from_kernel_nofault(buf, (u8 *)src, nbytes);
80
81 /* The user space code from other tasks cannot be accessed. */
82 if (regs != task_pt_regs(current))
83 return -EPERM;
84
85 /*
86 * Even if named copy_from_user_nmi() this can be invoked from
87 * other contexts and will not try to resolve a pagefault, which is
88 * the correct thing to do here as this code can be called from any
89 * context.
90 */
91 return copy_from_user_nmi(buf, (void __user *)src, nbytes);
92 }
93
94 /*
95 * There are a couple of reasons for the 2/3rd prologue, courtesy of Linus:
96 *
97 * In case where we don't have the exact kernel image (which, if we did, we can
98 * simply disassemble and navigate to the RIP), the purpose of the bigger
99 * prologue is to have more context and to be able to correlate the code from
100 * the different toolchains better.
101 *
102 * In addition, it helps in recreating the register allocation of the failing
103 * kernel and thus make sense of the register dump.
104 *
105 * What is more, the additional complication of a variable length insn arch like
106 * x86 warrants having longer byte sequence before rIP so that the disassembler
107 * can "sync" up properly and find instruction boundaries when decoding the
108 * opcode bytes.
109 *
110 * Thus, the 2/3rds prologue and 64 byte OPCODE_BUFSIZE is just a random
111 * guesstimate in attempt to achieve all of the above.
112 */
show_opcodes(struct pt_regs * regs,const char * loglvl)113 void show_opcodes(struct pt_regs *regs, const char *loglvl)
114 {
115 #define PROLOGUE_SIZE 42
116 #define EPILOGUE_SIZE 21
117 #define OPCODE_BUFSIZE (PROLOGUE_SIZE + 1 + EPILOGUE_SIZE)
118 u8 opcodes[OPCODE_BUFSIZE];
119 unsigned long prologue = regs->ip - PROLOGUE_SIZE;
120
121 switch (copy_code(regs, opcodes, prologue, sizeof(opcodes))) {
122 case 0:
123 printk("%sCode: %" __stringify(PROLOGUE_SIZE) "ph <%02x> %"
124 __stringify(EPILOGUE_SIZE) "ph\n", loglvl, opcodes,
125 opcodes[PROLOGUE_SIZE], opcodes + PROLOGUE_SIZE + 1);
126 break;
127 case -EPERM:
128 /* No access to the user space stack of other tasks. Ignore. */
129 break;
130 default:
131 printk("%sCode: Unable to access opcode bytes at 0x%lx.\n",
132 loglvl, prologue);
133 break;
134 }
135 }
136
show_ip(struct pt_regs * regs,const char * loglvl)137 void show_ip(struct pt_regs *regs, const char *loglvl)
138 {
139 #ifdef CONFIG_X86_32
140 printk("%sEIP: %pS\n", loglvl, (void *)regs->ip);
141 #else
142 printk("%sRIP: %04x:%pS\n", loglvl, (int)regs->cs, (void *)regs->ip);
143 #endif
144 show_opcodes(regs, loglvl);
145 }
146
show_iret_regs(struct pt_regs * regs,const char * log_lvl)147 void show_iret_regs(struct pt_regs *regs, const char *log_lvl)
148 {
149 show_ip(regs, log_lvl);
150 printk("%sRSP: %04x:%016lx EFLAGS: %08lx", log_lvl, (int)regs->ss,
151 regs->sp, regs->flags);
152 }
153
show_regs_if_on_stack(struct stack_info * info,struct pt_regs * regs,bool partial,const char * log_lvl)154 static void show_regs_if_on_stack(struct stack_info *info, struct pt_regs *regs,
155 bool partial, const char *log_lvl)
156 {
157 /*
158 * These on_stack() checks aren't strictly necessary: the unwind code
159 * has already validated the 'regs' pointer. The checks are done for
160 * ordering reasons: if the registers are on the next stack, we don't
161 * want to print them out yet. Otherwise they'll be shown as part of
162 * the wrong stack. Later, when show_trace_log_lvl() switches to the
163 * next stack, this function will be called again with the same regs so
164 * they can be printed in the right context.
165 */
166 if (!partial && on_stack(info, regs, sizeof(*regs))) {
167 __show_regs(regs, SHOW_REGS_SHORT, log_lvl);
168
169 } else if (partial && on_stack(info, (void *)regs + IRET_FRAME_OFFSET,
170 IRET_FRAME_SIZE)) {
171 /*
172 * When an interrupt or exception occurs in entry code, the
173 * full pt_regs might not have been saved yet. In that case
174 * just print the iret frame.
175 */
176 show_iret_regs(regs, log_lvl);
177 }
178 }
179
180 /*
181 * This function reads pointers from the stack and dereferences them. The
182 * pointers may not have their KMSAN shadow set up properly, which may result
183 * in false positive reports. Disable instrumentation to avoid those.
184 */
185 __no_kmsan_checks
show_trace_log_lvl(struct task_struct * task,struct pt_regs * regs,unsigned long * stack,const char * log_lvl)186 static void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
187 unsigned long *stack, const char *log_lvl)
188 {
189 struct unwind_state state;
190 struct stack_info stack_info = {0};
191 unsigned long visit_mask = 0;
192 int graph_idx = 0;
193 bool partial = false;
194
195 printk("%sCall Trace:\n", log_lvl);
196
197 unwind_start(&state, task, regs, stack);
198 stack = stack ? : get_stack_pointer(task, regs);
199 regs = unwind_get_entry_regs(&state, &partial);
200
201 /*
202 * Iterate through the stacks, starting with the current stack pointer.
203 * Each stack has a pointer to the next one.
204 *
205 * x86-64 can have several stacks:
206 * - task stack
207 * - interrupt stack
208 * - HW exception stacks (double fault, nmi, debug, mce)
209 * - entry stack
210 *
211 * x86-32 can have up to four stacks:
212 * - task stack
213 * - softirq stack
214 * - hardirq stack
215 * - entry stack
216 */
217 for ( ; stack; stack = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {
218 const char *stack_name;
219
220 if (get_stack_info(stack, task, &stack_info, &visit_mask)) {
221 /*
222 * We weren't on a valid stack. It's possible that
223 * we overflowed a valid stack into a guard page.
224 * See if the next page up is valid so that we can
225 * generate some kind of backtrace if this happens.
226 */
227 stack = (unsigned long *)PAGE_ALIGN((unsigned long)stack);
228 if (get_stack_info(stack, task, &stack_info, &visit_mask))
229 break;
230 }
231
232 stack_name = stack_type_name(stack_info.type);
233 if (stack_name)
234 printk("%s <%s>\n", log_lvl, stack_name);
235
236 if (regs)
237 show_regs_if_on_stack(&stack_info, regs, partial, log_lvl);
238
239 /*
240 * Scan the stack, printing any text addresses we find. At the
241 * same time, follow proper stack frames with the unwinder.
242 *
243 * Addresses found during the scan which are not reported by
244 * the unwinder are considered to be additional clues which are
245 * sometimes useful for debugging and are prefixed with '?'.
246 * This also serves as a failsafe option in case the unwinder
247 * goes off in the weeds.
248 */
249 for (; stack < stack_info.end; stack++) {
250 unsigned long real_addr;
251 int reliable = 0;
252 unsigned long addr = READ_ONCE_NOCHECK(*stack);
253 unsigned long *ret_addr_p =
254 unwind_get_return_address_ptr(&state);
255
256 if (!__kernel_text_address(addr))
257 continue;
258
259 /*
260 * Don't print regs->ip again if it was already printed
261 * by show_regs_if_on_stack().
262 */
263 if (regs && stack == ®s->ip)
264 goto next;
265
266 if (stack == ret_addr_p)
267 reliable = 1;
268
269 /*
270 * When function graph tracing is enabled for a
271 * function, its return address on the stack is
272 * replaced with the address of an ftrace handler
273 * (return_to_handler). In that case, before printing
274 * the "real" address, we want to print the handler
275 * address as an "unreliable" hint that function graph
276 * tracing was involved.
277 */
278 real_addr = ftrace_graph_ret_addr(task, &graph_idx,
279 addr, stack);
280 if (real_addr != addr)
281 printk_stack_address(addr, 0, log_lvl);
282 printk_stack_address(real_addr, reliable, log_lvl);
283
284 if (!reliable)
285 continue;
286
287 next:
288 /*
289 * Get the next frame from the unwinder. No need to
290 * check for an error: if anything goes wrong, the rest
291 * of the addresses will just be printed as unreliable.
292 */
293 unwind_next_frame(&state);
294
295 /* if the frame has entry regs, print them */
296 regs = unwind_get_entry_regs(&state, &partial);
297 if (regs)
298 show_regs_if_on_stack(&stack_info, regs, partial, log_lvl);
299 }
300
301 if (stack_name)
302 printk("%s </%s>\n", log_lvl, stack_name);
303 }
304 }
305
show_stack(struct task_struct * task,unsigned long * sp,const char * loglvl)306 void show_stack(struct task_struct *task, unsigned long *sp,
307 const char *loglvl)
308 {
309 task = task ? : current;
310
311 /*
312 * Stack frames below this one aren't interesting. Don't show them
313 * if we're printing for %current.
314 */
315 if (!sp && task == current)
316 sp = get_stack_pointer(current, NULL);
317
318 show_trace_log_lvl(task, NULL, sp, loglvl);
319 }
320
show_stack_regs(struct pt_regs * regs)321 void show_stack_regs(struct pt_regs *regs)
322 {
323 show_trace_log_lvl(current, regs, NULL, KERN_DEFAULT);
324 }
325
326 static arch_spinlock_t die_lock = __ARCH_SPIN_LOCK_UNLOCKED;
327 static int die_owner = -1;
328 static unsigned int die_nest_count;
329
oops_begin(void)330 unsigned long oops_begin(void)
331 {
332 int cpu;
333 unsigned long flags;
334
335 oops_enter();
336
337 /* racy, but better than risking deadlock. */
338 raw_local_irq_save(flags);
339 cpu = smp_processor_id();
340 if (!arch_spin_trylock(&die_lock)) {
341 if (cpu == die_owner)
342 /* nested oops. should stop eventually */;
343 else
344 arch_spin_lock(&die_lock);
345 }
346 die_nest_count++;
347 die_owner = cpu;
348 console_verbose();
349 bust_spinlocks(1);
350 return flags;
351 }
352 NOKPROBE_SYMBOL(oops_begin);
353
354 void __noreturn rewind_stack_and_make_dead(int signr);
355
oops_end(unsigned long flags,struct pt_regs * regs,int signr)356 void oops_end(unsigned long flags, struct pt_regs *regs, int signr)
357 {
358 if (regs && kexec_should_crash(current))
359 crash_kexec(regs);
360
361 bust_spinlocks(0);
362 die_owner = -1;
363 add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
364 die_nest_count--;
365 if (!die_nest_count)
366 /* Nest count reaches zero, release the lock. */
367 arch_spin_unlock(&die_lock);
368 raw_local_irq_restore(flags);
369 oops_exit();
370
371 /* Executive summary in case the oops scrolled away */
372 __show_regs(&exec_summary_regs, SHOW_REGS_ALL, KERN_DEFAULT);
373
374 if (!signr)
375 return;
376 if (in_interrupt())
377 panic("Fatal exception in interrupt");
378 if (panic_on_oops)
379 panic("Fatal exception");
380
381 /*
382 * We're not going to return, but we might be on an IST stack or
383 * have very little stack space left. Rewind the stack and kill
384 * the task.
385 * Before we rewind the stack, we have to tell KASAN that we're going to
386 * reuse the task stack and that existing poisons are invalid.
387 */
388 kasan_unpoison_task_stack(current);
389 rewind_stack_and_make_dead(signr);
390 }
391 NOKPROBE_SYMBOL(oops_end);
392
__die_header(const char * str,struct pt_regs * regs,long err)393 static void __die_header(const char *str, struct pt_regs *regs, long err)
394 {
395 const char *pr = "";
396
397 /* Save the regs of the first oops for the executive summary later. */
398 if (!die_counter)
399 exec_summary_regs = *regs;
400
401 if (IS_ENABLED(CONFIG_PREEMPTION))
402 pr = IS_ENABLED(CONFIG_PREEMPT_RT) ? " PREEMPT_RT" : " PREEMPT";
403
404 printk(KERN_DEFAULT
405 "%s: %04lx [#%d]%s%s%s%s%s\n", str, err & 0xffff, ++die_counter,
406 pr,
407 IS_ENABLED(CONFIG_SMP) ? " SMP" : "",
408 debug_pagealloc_enabled() ? " DEBUG_PAGEALLOC" : "",
409 IS_ENABLED(CONFIG_KASAN) ? " KASAN" : "",
410 IS_ENABLED(CONFIG_PAGE_TABLE_ISOLATION) ?
411 (boot_cpu_has(X86_FEATURE_PTI) ? " PTI" : " NOPTI") : "");
412 }
413 NOKPROBE_SYMBOL(__die_header);
414
__die_body(const char * str,struct pt_regs * regs,long err)415 static int __die_body(const char *str, struct pt_regs *regs, long err)
416 {
417 show_regs(regs);
418 print_modules();
419
420 if (notify_die(DIE_OOPS, str, regs, err,
421 current->thread.trap_nr, SIGSEGV) == NOTIFY_STOP)
422 return 1;
423
424 return 0;
425 }
426 NOKPROBE_SYMBOL(__die_body);
427
__die(const char * str,struct pt_regs * regs,long err)428 int __die(const char *str, struct pt_regs *regs, long err)
429 {
430 __die_header(str, regs, err);
431 return __die_body(str, regs, err);
432 }
433 NOKPROBE_SYMBOL(__die);
434
435 /*
436 * This is gone through when something in the kernel has done something bad
437 * and is about to be terminated:
438 */
die(const char * str,struct pt_regs * regs,long err)439 void die(const char *str, struct pt_regs *regs, long err)
440 {
441 unsigned long flags = oops_begin();
442 int sig = SIGSEGV;
443
444 if (__die(str, regs, err))
445 sig = 0;
446 oops_end(flags, regs, sig);
447 }
448
die_addr(const char * str,struct pt_regs * regs,long err,long gp_addr)449 void die_addr(const char *str, struct pt_regs *regs, long err, long gp_addr)
450 {
451 unsigned long flags = oops_begin();
452 int sig = SIGSEGV;
453
454 __die_header(str, regs, err);
455 if (gp_addr)
456 kasan_non_canonical_hook(gp_addr);
457 if (__die_body(str, regs, err))
458 sig = 0;
459 oops_end(flags, regs, sig);
460 }
461
show_regs(struct pt_regs * regs)462 void show_regs(struct pt_regs *regs)
463 {
464 enum show_regs_mode print_kernel_regs;
465
466 show_regs_print_info(KERN_DEFAULT);
467
468 print_kernel_regs = user_mode(regs) ? SHOW_REGS_USER : SHOW_REGS_ALL;
469 __show_regs(regs, print_kernel_regs, KERN_DEFAULT);
470
471 /*
472 * When in-kernel, we also print out the stack at the time of the fault..
473 */
474 if (!user_mode(regs))
475 show_trace_log_lvl(current, regs, NULL, KERN_DEFAULT);
476 }
477