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
26static int die_counter;
27
28static struct pt_regs exec_summary_regs;
29
30bool noinstr in_task_stack(unsigned long *stack, struct task_struct *task,
31 struct stack_info *info)
32{
33 unsigned long *begin = task_stack_page(task);
34 unsigned long *end = task_stack_page(task) + THREAD_SIZE;
35
36 if (stack < begin || stack >= end)
37 return false;
38
39 info->type = STACK_TYPE_TASK;
40 info->begin = begin;
41 info->end = end;
42 info->next_sp = NULL;
43
44 return true;
45}
46
47/* Called from get_stack_info_noinstr - so must be noinstr too */
48bool noinstr in_entry_stack(unsigned long *stack, struct stack_info *info)
49{
50 struct entry_stack *ss = cpu_entry_stack(smp_processor_id());
51
52 void *begin = ss;
53 void *end = ss + 1;
54
55 if ((void *)stack < begin || (void *)stack >= end)
56 return false;
57
58 info->type = STACK_TYPE_ENTRY;
59 info->begin = begin;
60 info->end = end;
61 info->next_sp = NULL;
62
63 return true;
64}
65
66static void printk_stack_address(unsigned long address, int reliable,
67 const char *log_lvl)
68{
69 touch_nmi_watchdog();
70 printk("%s %s%pBb\n", log_lvl, reliable ? "" : "? ", (void *)address);
71}
72
73static int copy_code(struct pt_regs *regs, u8 *buf, unsigned long src,
74 unsigned int nbytes)
75{
76 if (!user_mode(regs))
77 return copy_from_kernel_nofault(dst: buf, src: (u8 *)src, size: nbytes);
78
79 /* The user space code from other tasks cannot be accessed. */
80 if (regs != task_pt_regs(current))
81 return -EPERM;
82
83 /*
84 * Even if named copy_from_user_nmi() this can be invoked from
85 * other contexts and will not try to resolve a pagefault, which is
86 * the correct thing to do here as this code can be called from any
87 * context.
88 */
89 return copy_from_user_nmi(to: buf, from: (void __user *)src, n: nbytes);
90}
91
92/*
93 * There are a couple of reasons for the 2/3rd prologue, courtesy of Linus:
94 *
95 * In case where we don't have the exact kernel image (which, if we did, we can
96 * simply disassemble and navigate to the RIP), the purpose of the bigger
97 * prologue is to have more context and to be able to correlate the code from
98 * the different toolchains better.
99 *
100 * In addition, it helps in recreating the register allocation of the failing
101 * kernel and thus make sense of the register dump.
102 *
103 * What is more, the additional complication of a variable length insn arch like
104 * x86 warrants having longer byte sequence before rIP so that the disassembler
105 * can "sync" up properly and find instruction boundaries when decoding the
106 * opcode bytes.
107 *
108 * Thus, the 2/3rds prologue and 64 byte OPCODE_BUFSIZE is just a random
109 * guesstimate in attempt to achieve all of the above.
110 */
111void show_opcodes(struct pt_regs *regs, const char *loglvl)
112{
113#define PROLOGUE_SIZE 42
114#define EPILOGUE_SIZE 21
115#define OPCODE_BUFSIZE (PROLOGUE_SIZE + 1 + EPILOGUE_SIZE)
116 u8 opcodes[OPCODE_BUFSIZE];
117 unsigned long prologue = regs->ip - PROLOGUE_SIZE;
118
119 switch (copy_code(regs, buf: opcodes, src: prologue, nbytes: sizeof(opcodes))) {
120 case 0:
121 printk("%sCode: %" __stringify(PROLOGUE_SIZE) "ph <%02x> %"
122 __stringify(EPILOGUE_SIZE) "ph\n", loglvl, opcodes,
123 opcodes[PROLOGUE_SIZE], opcodes + PROLOGUE_SIZE + 1);
124 break;
125 case -EPERM:
126 /* No access to the user space stack of other tasks. Ignore. */
127 break;
128 default:
129 printk("%sCode: Unable to access opcode bytes at 0x%lx.\n",
130 loglvl, prologue);
131 break;
132 }
133}
134
135void show_ip(struct pt_regs *regs, const char *loglvl)
136{
137#ifdef CONFIG_X86_32
138 printk("%sEIP: %pS\n", loglvl, (void *)regs->ip);
139#else
140 printk("%sRIP: %04x:%pS\n", loglvl, (int)regs->cs, (void *)regs->ip);
141#endif
142 show_opcodes(regs, loglvl);
143}
144
145void show_iret_regs(struct pt_regs *regs, const char *log_lvl)
146{
147 show_ip(regs, loglvl: log_lvl);
148 printk("%sRSP: %04x:%016lx EFLAGS: %08lx", log_lvl, (int)regs->ss,
149 regs->sp, regs->flags);
150}
151
152static void show_regs_if_on_stack(struct stack_info *info, struct pt_regs *regs,
153 bool partial, const char *log_lvl)
154{
155 /*
156 * These on_stack() checks aren't strictly necessary: the unwind code
157 * has already validated the 'regs' pointer. The checks are done for
158 * ordering reasons: if the registers are on the next stack, we don't
159 * want to print them out yet. Otherwise they'll be shown as part of
160 * the wrong stack. Later, when show_trace_log_lvl() switches to the
161 * next stack, this function will be called again with the same regs so
162 * they can be printed in the right context.
163 */
164 if (!partial && on_stack(info, addr: regs, len: sizeof(*regs))) {
165 __show_regs(regs, SHOW_REGS_SHORT, log_lvl);
166
167 } else if (partial && on_stack(info, addr: (void *)regs + IRET_FRAME_OFFSET,
168 IRET_FRAME_SIZE)) {
169 /*
170 * When an interrupt or exception occurs in entry code, the
171 * full pt_regs might not have been saved yet. In that case
172 * just print the iret frame.
173 */
174 show_iret_regs(regs, log_lvl);
175 }
176}
177
178/*
179 * This function reads pointers from the stack and dereferences them. The
180 * pointers may not have their KMSAN shadow set up properly, which may result
181 * in false positive reports. Disable instrumentation to avoid those.
182 */
183__no_kmsan_checks
184static void __show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
185 unsigned long *stack, const char *log_lvl)
186{
187 struct unwind_state state;
188 struct stack_info stack_info = {0};
189 unsigned long visit_mask = 0;
190 int graph_idx = 0;
191 bool partial = false;
192
193 printk("%sCall Trace:\n", log_lvl);
194
195 unwind_start(state: &state, task, regs, first_frame: stack);
196 stack = stack ?: get_stack_pointer(task, regs);
197 regs = unwind_get_entry_regs(state: &state, partial: &partial);
198
199 /*
200 * Iterate through the stacks, starting with the current stack pointer.
201 * Each stack has a pointer to the next one.
202 *
203 * x86-64 can have several stacks:
204 * - task stack
205 * - interrupt stack
206 * - HW exception stacks (double fault, nmi, debug, mce)
207 * - entry stack
208 *
209 * x86-32 can have up to four stacks:
210 * - task stack
211 * - softirq stack
212 * - hardirq stack
213 * - entry stack
214 */
215 for (; stack; stack = stack_info.next_sp) {
216 const char *stack_name;
217
218 stack = PTR_ALIGN(stack, sizeof(long));
219
220 if (get_stack_info(stack, task, info: &stack_info, visit_mask: &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, info: &stack_info, visit_mask: &visit_mask))
229 break;
230 }
231
232 stack_name = stack_type_name(type: 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(info: &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: &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 == &regs->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, idx: &graph_idx,
279 ret: addr, retp: stack);
280 if (real_addr != addr)
281 printk_stack_address(address: addr, reliable: 0, log_lvl);
282 printk_stack_address(address: real_addr, reliable, log_lvl);
283
284 if (!reliable)
285 continue;
286
287next:
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: &state);
294
295 /* if the frame has entry regs, print them */
296 regs = unwind_get_entry_regs(state: &state, partial: &partial);
297 if (regs)
298 show_regs_if_on_stack(info: &stack_info, regs, partial, log_lvl);
299 }
300
301 if (stack_name)
302 printk("%s </%s>\n", log_lvl, stack_name);
303 }
304}
305
306static void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
307 unsigned long *stack, const char *log_lvl)
308{
309 /*
310 * Disable KASAN to avoid false positives during walking another
311 * task's stacks, as values on these stacks may change concurrently
312 * with task execution.
313 */
314 bool disable_kasan = task && task != current;
315
316 if (disable_kasan)
317 kasan_disable_current();
318
319 __show_trace_log_lvl(task, regs, stack, log_lvl);
320
321 if (disable_kasan)
322 kasan_enable_current();
323}
324
325void show_stack(struct task_struct *task, unsigned long *sp,
326 const char *loglvl)
327{
328 task = task ? : current;
329
330 /*
331 * Stack frames below this one aren't interesting. Don't show them
332 * if we're printing for %current.
333 */
334 if (!sp && task == current)
335 sp = get_stack_pointer(current, NULL);
336
337 show_trace_log_lvl(task, NULL, stack: sp, log_lvl: loglvl);
338}
339
340void show_stack_regs(struct pt_regs *regs)
341{
342 show_trace_log_lvl(current, regs, NULL, KERN_DEFAULT);
343}
344
345static arch_spinlock_t die_lock = __ARCH_SPIN_LOCK_UNLOCKED;
346static int die_owner = -1;
347static unsigned int die_nest_count;
348
349unsigned long oops_begin(void)
350{
351 int cpu;
352 unsigned long flags;
353
354 oops_enter();
355
356 /* racy, but better than risking deadlock. */
357 raw_local_irq_save(flags);
358 cpu = smp_processor_id();
359 if (!arch_spin_trylock(&die_lock)) {
360 if (cpu == die_owner)
361 /* nested oops. should stop eventually */;
362 else
363 arch_spin_lock(&die_lock);
364 }
365 die_nest_count++;
366 die_owner = cpu;
367 console_verbose();
368 bust_spinlocks(yes: 1);
369 return flags;
370}
371NOKPROBE_SYMBOL(oops_begin);
372
373void __noreturn rewind_stack_and_make_dead(int signr);
374
375void oops_end(unsigned long flags, struct pt_regs *regs, int signr)
376{
377 if (regs && kexec_should_crash(current))
378 crash_kexec(regs);
379
380 bust_spinlocks(yes: 0);
381 die_owner = -1;
382 add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
383 die_nest_count--;
384 if (!die_nest_count)
385 /* Nest count reaches zero, release the lock. */
386 arch_spin_unlock(&die_lock);
387 raw_local_irq_restore(flags);
388 oops_exit();
389
390 /* Executive summary in case the oops scrolled away */
391 __show_regs(regs: &exec_summary_regs, SHOW_REGS_ALL, KERN_DEFAULT);
392
393 if (!signr)
394 return;
395 if (in_interrupt())
396 panic(fmt: "Fatal exception in interrupt");
397 if (panic_on_oops)
398 panic(fmt: "Fatal exception");
399
400 /*
401 * We're not going to return, but we might be on an IST stack or
402 * have very little stack space left. Rewind the stack and kill
403 * the task.
404 * Before we rewind the stack, we have to tell KASAN that we're going to
405 * reuse the task stack and that existing poisons are invalid.
406 */
407 kasan_unpoison_task_stack(current);
408 rewind_stack_and_make_dead(signr);
409}
410NOKPROBE_SYMBOL(oops_end);
411
412static void __die_header(const char *str, struct pt_regs *regs, long err)
413{
414 /* Save the regs of the first oops for the executive summary later. */
415 if (!die_counter)
416 exec_summary_regs = *regs;
417
418 printk(KERN_DEFAULT
419 "Oops: %s: %04lx [#%d]%s%s%s%s\n", str, err & 0xffff,
420 ++die_counter,
421 IS_ENABLED(CONFIG_SMP) ? " SMP" : "",
422 debug_pagealloc_enabled() ? " DEBUG_PAGEALLOC" : "",
423 IS_ENABLED(CONFIG_KASAN) ? " KASAN" : "",
424 IS_ENABLED(CONFIG_MITIGATION_PAGE_TABLE_ISOLATION) ?
425 (boot_cpu_has(X86_FEATURE_PTI) ? " PTI" : " NOPTI") : "");
426}
427NOKPROBE_SYMBOL(__die_header);
428
429static int __die_body(const char *str, struct pt_regs *regs, long err)
430{
431 show_regs(regs);
432 print_modules();
433
434 if (notify_die(val: DIE_OOPS, str, regs, err,
435 current->thread.trap_nr, SIGSEGV) == NOTIFY_STOP)
436 return 1;
437
438 return 0;
439}
440NOKPROBE_SYMBOL(__die_body);
441
442int __die(const char *str, struct pt_regs *regs, long err)
443{
444 __die_header(str, regs, err);
445 return __die_body(str, regs, err);
446}
447NOKPROBE_SYMBOL(__die);
448
449/*
450 * This is gone through when something in the kernel has done something bad
451 * and is about to be terminated:
452 */
453void die(const char *str, struct pt_regs *regs, long err)
454{
455 unsigned long flags = oops_begin();
456 int sig = SIGSEGV;
457
458 if (__die(str, regs, err))
459 sig = 0;
460 oops_end(flags, regs, signr: sig);
461}
462
463void die_addr(const char *str, struct pt_regs *regs, long err, long gp_addr)
464{
465 unsigned long flags = oops_begin();
466 int sig = SIGSEGV;
467
468 __die_header(str, regs, err);
469 if (gp_addr)
470 kasan_non_canonical_hook(addr: gp_addr);
471 if (__die_body(str, regs, err))
472 sig = 0;
473 oops_end(flags, regs, signr: sig);
474}
475
476void show_regs(struct pt_regs *regs)
477{
478 enum show_regs_mode print_kernel_regs;
479
480 show_regs_print_info(KERN_DEFAULT);
481
482 print_kernel_regs = user_mode(regs) ? SHOW_REGS_USER : SHOW_REGS_ALL;
483 __show_regs(regs, print_kernel_regs, KERN_DEFAULT);
484
485 /*
486 * When in-kernel, we also print out the stack at the time of the fault..
487 */
488 if (!user_mode(regs))
489 show_trace_log_lvl(current, regs, NULL, KERN_DEFAULT);
490}
491

source code of linux/arch/x86/kernel/dumpstack.c