GNU Linux-libre 4.14.266-gnu1
[releases.git] / arch / x86 / kernel / dumpstack.c
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 unsigned int code_bytes = 64;
29 static int die_counter;
30
31 bool in_task_stack(unsigned long *stack, struct task_struct *task,
32                    struct stack_info *info)
33 {
34         unsigned long *begin = task_stack_page(task);
35         unsigned long *end   = task_stack_page(task) + THREAD_SIZE;
36
37         if (stack < begin || stack >= end)
38                 return false;
39
40         info->type      = STACK_TYPE_TASK;
41         info->begin     = begin;
42         info->end       = end;
43         info->next_sp   = NULL;
44
45         return true;
46 }
47
48 bool 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
66 static void printk_stack_address(unsigned long address, int reliable,
67                                  char *log_lvl)
68 {
69         touch_nmi_watchdog();
70         printk("%s %s%pB\n", log_lvl, reliable ? "" : "? ", (void *)address);
71 }
72
73 void show_iret_regs(struct pt_regs *regs)
74 {
75         printk(KERN_DEFAULT "RIP: %04x:%pS\n", (int)regs->cs, (void *)regs->ip);
76         printk(KERN_DEFAULT "RSP: %04x:%016lx EFLAGS: %08lx", (int)regs->ss,
77                 regs->sp, regs->flags);
78 }
79
80 static void show_regs_if_on_stack(struct stack_info *info, struct pt_regs *regs,
81                                   bool partial)
82 {
83         /*
84          * These on_stack() checks aren't strictly necessary: the unwind code
85          * has already validated the 'regs' pointer.  The checks are done for
86          * ordering reasons: if the registers are on the next stack, we don't
87          * want to print them out yet.  Otherwise they'll be shown as part of
88          * the wrong stack.  Later, when show_trace_log_lvl() switches to the
89          * next stack, this function will be called again with the same regs so
90          * they can be printed in the right context.
91          */
92         if (!partial && on_stack(info, regs, sizeof(*regs))) {
93                 __show_regs(regs, 0);
94
95         } else if (partial && on_stack(info, (void *)regs + IRET_FRAME_OFFSET,
96                                        IRET_FRAME_SIZE)) {
97                 /*
98                  * When an interrupt or exception occurs in entry code, the
99                  * full pt_regs might not have been saved yet.  In that case
100                  * just print the iret frame.
101                  */
102                 show_iret_regs(regs);
103         }
104 }
105
106 void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
107                         unsigned long *stack, char *log_lvl)
108 {
109         struct unwind_state state;
110         struct stack_info stack_info = {0};
111         unsigned long visit_mask = 0;
112         int graph_idx = 0;
113         bool partial = false;
114
115         printk("%sCall Trace:\n", log_lvl);
116
117         unwind_start(&state, task, regs, stack);
118         stack = stack ? : get_stack_pointer(task, regs);
119         regs = unwind_get_entry_regs(&state, &partial);
120
121         /*
122          * Iterate through the stacks, starting with the current stack pointer.
123          * Each stack has a pointer to the next one.
124          *
125          * x86-64 can have several stacks:
126          * - task stack
127          * - interrupt stack
128          * - HW exception stacks (double fault, nmi, debug, mce)
129          * - entry stack
130          *
131          * x86-32 can have up to four stacks:
132          * - task stack
133          * - softirq stack
134          * - hardirq stack
135          * - entry stack
136          */
137         for ( ; stack; stack = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {
138                 const char *stack_name;
139
140                 if (get_stack_info(stack, task, &stack_info, &visit_mask)) {
141                         /*
142                          * We weren't on a valid stack.  It's possible that
143                          * we overflowed a valid stack into a guard page.
144                          * See if the next page up is valid so that we can
145                          * generate some kind of backtrace if this happens.
146                          */
147                         stack = (unsigned long *)PAGE_ALIGN((unsigned long)stack);
148                         if (get_stack_info(stack, task, &stack_info, &visit_mask))
149                                 break;
150                 }
151
152                 stack_name = stack_type_name(stack_info.type);
153                 if (stack_name)
154                         printk("%s <%s>\n", log_lvl, stack_name);
155
156                 if (regs)
157                         show_regs_if_on_stack(&stack_info, regs, partial);
158
159                 /*
160                  * Scan the stack, printing any text addresses we find.  At the
161                  * same time, follow proper stack frames with the unwinder.
162                  *
163                  * Addresses found during the scan which are not reported by
164                  * the unwinder are considered to be additional clues which are
165                  * sometimes useful for debugging and are prefixed with '?'.
166                  * This also serves as a failsafe option in case the unwinder
167                  * goes off in the weeds.
168                  */
169                 for (; stack < stack_info.end; stack++) {
170                         unsigned long real_addr;
171                         int reliable = 0;
172                         unsigned long addr = READ_ONCE_NOCHECK(*stack);
173                         unsigned long *ret_addr_p =
174                                 unwind_get_return_address_ptr(&state);
175
176                         if (!__kernel_text_address(addr))
177                                 continue;
178
179                         /*
180                          * Don't print regs->ip again if it was already printed
181                          * by show_regs_if_on_stack().
182                          */
183                         if (regs && stack == &regs->ip)
184                                 goto next;
185
186                         if (stack == ret_addr_p)
187                                 reliable = 1;
188
189                         /*
190                          * When function graph tracing is enabled for a
191                          * function, its return address on the stack is
192                          * replaced with the address of an ftrace handler
193                          * (return_to_handler).  In that case, before printing
194                          * the "real" address, we want to print the handler
195                          * address as an "unreliable" hint that function graph
196                          * tracing was involved.
197                          */
198                         real_addr = ftrace_graph_ret_addr(task, &graph_idx,
199                                                           addr, stack);
200                         if (real_addr != addr)
201                                 printk_stack_address(addr, 0, log_lvl);
202                         printk_stack_address(real_addr, reliable, log_lvl);
203
204                         if (!reliable)
205                                 continue;
206
207 next:
208                         /*
209                          * Get the next frame from the unwinder.  No need to
210                          * check for an error: if anything goes wrong, the rest
211                          * of the addresses will just be printed as unreliable.
212                          */
213                         unwind_next_frame(&state);
214
215                         /* if the frame has entry regs, print them */
216                         regs = unwind_get_entry_regs(&state, &partial);
217                         if (regs)
218                                 show_regs_if_on_stack(&stack_info, regs, partial);
219                 }
220
221                 if (stack_name)
222                         printk("%s </%s>\n", log_lvl, stack_name);
223         }
224 }
225
226 void show_stack(struct task_struct *task, unsigned long *sp)
227 {
228         task = task ? : current;
229
230         /*
231          * Stack frames below this one aren't interesting.  Don't show them
232          * if we're printing for %current.
233          */
234         if (!sp && task == current)
235                 sp = get_stack_pointer(current, NULL);
236
237         show_trace_log_lvl(task, NULL, sp, KERN_DEFAULT);
238 }
239
240 void show_stack_regs(struct pt_regs *regs)
241 {
242         show_trace_log_lvl(current, regs, NULL, KERN_DEFAULT);
243 }
244
245 static arch_spinlock_t die_lock = __ARCH_SPIN_LOCK_UNLOCKED;
246 static int die_owner = -1;
247 static unsigned int die_nest_count;
248
249 unsigned long oops_begin(void)
250 {
251         int cpu;
252         unsigned long flags;
253
254         oops_enter();
255
256         /* racy, but better than risking deadlock. */
257         raw_local_irq_save(flags);
258         cpu = smp_processor_id();
259         if (!arch_spin_trylock(&die_lock)) {
260                 if (cpu == die_owner)
261                         /* nested oops. should stop eventually */;
262                 else
263                         arch_spin_lock(&die_lock);
264         }
265         die_nest_count++;
266         die_owner = cpu;
267         console_verbose();
268         bust_spinlocks(1);
269         return flags;
270 }
271 EXPORT_SYMBOL_GPL(oops_begin);
272 NOKPROBE_SYMBOL(oops_begin);
273
274 void __noreturn rewind_stack_do_exit(int signr);
275
276 void oops_end(unsigned long flags, struct pt_regs *regs, int signr)
277 {
278         if (regs && kexec_should_crash(current))
279                 crash_kexec(regs);
280
281         bust_spinlocks(0);
282         die_owner = -1;
283         add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
284         die_nest_count--;
285         if (!die_nest_count)
286                 /* Nest count reaches zero, release the lock. */
287                 arch_spin_unlock(&die_lock);
288         raw_local_irq_restore(flags);
289         oops_exit();
290
291         if (!signr)
292                 return;
293         if (in_interrupt())
294                 panic("Fatal exception in interrupt");
295         if (panic_on_oops)
296                 panic("Fatal exception");
297
298         /*
299          * We're not going to return, but we might be on an IST stack or
300          * have very little stack space left.  Rewind the stack and kill
301          * the task.
302          * Before we rewind the stack, we have to tell KASAN that we're going to
303          * reuse the task stack and that existing poisons are invalid.
304          */
305         kasan_unpoison_task_stack(current);
306         rewind_stack_do_exit(signr);
307 }
308 NOKPROBE_SYMBOL(oops_end);
309
310 int __die(const char *str, struct pt_regs *regs, long err)
311 {
312 #ifdef CONFIG_X86_32
313         unsigned short ss;
314         unsigned long sp;
315 #endif
316         printk(KERN_DEFAULT
317                "%s: %04lx [#%d]%s%s%s%s%s\n", str, err & 0xffff, ++die_counter,
318                IS_ENABLED(CONFIG_PREEMPT) ? " PREEMPT"         : "",
319                IS_ENABLED(CONFIG_SMP)     ? " SMP"             : "",
320                debug_pagealloc_enabled()  ? " DEBUG_PAGEALLOC" : "",
321                IS_ENABLED(CONFIG_KASAN)   ? " KASAN"           : "",
322                IS_ENABLED(CONFIG_PAGE_TABLE_ISOLATION) ?
323                (boot_cpu_has(X86_FEATURE_PTI) ? " PTI" : " NOPTI") : "");
324
325         if (notify_die(DIE_OOPS, str, regs, err,
326                         current->thread.trap_nr, SIGSEGV) == NOTIFY_STOP)
327                 return 1;
328
329         print_modules();
330         show_regs(regs);
331 #ifdef CONFIG_X86_32
332         if (user_mode(regs)) {
333                 sp = regs->sp;
334                 ss = regs->ss;
335         } else {
336                 sp = kernel_stack_pointer(regs);
337                 savesegment(ss, ss);
338         }
339         printk(KERN_EMERG "EIP: %pS SS:ESP: %04x:%08lx\n",
340                (void *)regs->ip, ss, sp);
341 #else
342         /* Executive summary in case the oops scrolled away */
343         printk(KERN_ALERT "RIP: %pS RSP: %016lx\n", (void *)regs->ip, regs->sp);
344 #endif
345         return 0;
346 }
347 NOKPROBE_SYMBOL(__die);
348
349 /*
350  * This is gone through when something in the kernel has done something bad
351  * and is about to be terminated:
352  */
353 void die(const char *str, struct pt_regs *regs, long err)
354 {
355         unsigned long flags = oops_begin();
356         int sig = SIGSEGV;
357
358         if (__die(str, regs, err))
359                 sig = 0;
360         oops_end(flags, regs, sig);
361 }
362
363 static int __init code_bytes_setup(char *s)
364 {
365         ssize_t ret;
366         unsigned long val;
367
368         if (!s)
369                 return -EINVAL;
370
371         ret = kstrtoul(s, 0, &val);
372         if (ret)
373                 return ret;
374
375         code_bytes = val;
376         if (code_bytes > 8192)
377                 code_bytes = 8192;
378
379         return 1;
380 }
381 __setup("code_bytes=", code_bytes_setup);