the-tree/kernel/stacktrace.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  * kernel/stacktrace.c
0004  *
0005  * Stack trace management functions
0006  *
0007  *  Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
0008  */
0009 #include <linux/sched/task_stack.h>
0010 #include <linux/sched/debug.h>
0011 #include <linux/sched.h>
0012 #include <linux/kernel.h>
0013 #include <linux/export.h>
0014 #include <linux/kallsyms.h>
0015 #include <linux/stacktrace.h>
0016 #include <linux/interrupt.h>
0017
0018 /**
0019  * stack_trace_print - Print the entries in the stack trace
0020  * @entries:    Pointer to storage array
0021  * @nr_entries: Number of entries in the storage array
0022  * @spaces: Number of leading spaces to print
0023  */
0024 void stack_trace_print(const unsigned long *entries, unsigned int nr_entries,
0025                int spaces)
0026 {
0027     unsigned int i;
0028
0029     if (WARN_ON(!entries))
0030         return;
0031
0032     for (i = 0; i < nr_entries; i++)
0033         printk("%*c%pS\n", 1 + spaces, ' ', (void *)entries[i]);
0034 }
0035 EXPORT_SYMBOL_GPL(stack_trace_print);
0036
0037 /**
0038  * stack_trace_snprint - Print the entries in the stack trace into a buffer
0039  * @buf:    Pointer to the print buffer
0040  * @size:   Size of the print buffer
0041  * @entries:    Pointer to storage array
0042  * @nr_entries: Number of entries in the storage array
0043  * @spaces: Number of leading spaces to print
0044  *
0045  * Return: Number of bytes printed.
0046  */
0047 int stack_trace_snprint(char *buf, size_t size, const unsigned long *entries,
0048             unsigned int nr_entries, int spaces)
0049 {
0050     unsigned int generated, i, total = 0;
0051
0052     if (WARN_ON(!entries))
0053         return 0;
0054
0055     for (i = 0; i < nr_entries && size; i++) {
0056         generated = snprintf(buf, size, "%*c%pS\n", 1 + spaces, ' ',
0057                      (void *)entries[i]);
0058
0059         total += generated;
0060         if (generated >= size) {
0061             buf += size;
0062             size = 0;
0063         } else {
0064             buf += generated;
0065             size -= generated;
0066         }
0067     }
0068
0069     return total;
0070 }
0071 EXPORT_SYMBOL_GPL(stack_trace_snprint);
0072
0073 #ifdef CONFIG_ARCH_STACKWALK
0074
0075 struct stacktrace_cookie {
0076     unsigned long   *store;
0077     unsigned int    size;
0078     unsigned int    skip;
0079     unsigned int    len;
0080 };
0081
0082 static bool stack_trace_consume_entry(void *cookie, unsigned long addr)
0083 {
0084     struct stacktrace_cookie *c = cookie;
0085
0086     if (c->len >= c->size)
0087         return false;
0088
0089     if (c->skip > 0) {
0090         c->skip--;
0091         return true;
0092     }
0093     c->store[c->len++] = addr;
0094     return c->len < c->size;
0095 }
0096
0097 static bool stack_trace_consume_entry_nosched(void *cookie, unsigned long addr)
0098 {
0099     if (in_sched_functions(addr))
0100         return true;
0101     return stack_trace_consume_entry(cookie, addr);
0102 }
0103
0104 /**
0105  * stack_trace_save - Save a stack trace into a storage array
0106  * @store:  Pointer to storage array
0107  * @size:   Size of the storage array
0108  * @skipnr: Number of entries to skip at the start of the stack trace
0109  *
0110  * Return: Number of trace entries stored.
0111  */
0112 unsigned int stack_trace_save(unsigned long *store, unsigned int size,
0113                   unsigned int skipnr)
0114 {
0115     stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
0116     struct stacktrace_cookie c = {
0117         .store  = store,
0118         .size   = size,
0119         .skip   = skipnr + 1,
0120     };
0121
0122     arch_stack_walk(consume_entry, &c, current, NULL);
0123     return c.len;
0124 }
0125 EXPORT_SYMBOL_GPL(stack_trace_save);
0126
0127 /**
0128  * stack_trace_save_tsk - Save a task stack trace into a storage array
0129  * @task:   The task to examine
0130  * @store:  Pointer to storage array
0131  * @size:   Size of the storage array
0132  * @skipnr: Number of entries to skip at the start of the stack trace
0133  *
0134  * Return: Number of trace entries stored.
0135  */
0136 unsigned int stack_trace_save_tsk(struct task_struct *tsk, unsigned long *store,
0137                   unsigned int size, unsigned int skipnr)
0138 {
0139     stack_trace_consume_fn consume_entry = stack_trace_consume_entry_nosched;
0140     struct stacktrace_cookie c = {
0141         .store  = store,
0142         .size   = size,
0143         /* skip this function if they are tracing us */
0144         .skip   = skipnr + (current == tsk),
0145     };
0146
0147     if (!try_get_task_stack(tsk))
0148         return 0;
0149
0150     arch_stack_walk(consume_entry, &c, tsk, NULL);
0151     put_task_stack(tsk);
0152     return c.len;
0153 }
0154
0155 /**
0156  * stack_trace_save_regs - Save a stack trace based on pt_regs into a storage array
0157  * @regs:   Pointer to pt_regs to examine
0158  * @store:  Pointer to storage array
0159  * @size:   Size of the storage array
0160  * @skipnr: Number of entries to skip at the start of the stack trace
0161  *
0162  * Return: Number of trace entries stored.
0163  */
0164 unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store,
0165                    unsigned int size, unsigned int skipnr)
0166 {
0167     stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
0168     struct stacktrace_cookie c = {
0169         .store  = store,
0170         .size   = size,
0171         .skip   = skipnr,
0172     };
0173
0174     arch_stack_walk(consume_entry, &c, current, regs);
0175     return c.len;
0176 }
0177
0178 #ifdef CONFIG_HAVE_RELIABLE_STACKTRACE
0179 /**
0180  * stack_trace_save_tsk_reliable - Save task stack with verification
0181  * @tsk:    Pointer to the task to examine
0182  * @store:  Pointer to storage array
0183  * @size:   Size of the storage array
0184  *
0185  * Return:  An error if it detects any unreliable features of the
0186  *      stack. Otherwise it guarantees that the stack trace is
0187  *      reliable and returns the number of entries stored.
0188  *
0189  * If the task is not 'current', the caller *must* ensure the task is inactive.
0190  */
0191 int stack_trace_save_tsk_reliable(struct task_struct *tsk, unsigned long *store,
0192                   unsigned int size)
0193 {
0194     stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
0195     struct stacktrace_cookie c = {
0196         .store  = store,
0197         .size   = size,
0198     };
0199     int ret;
0200
0201     /*
0202      * If the task doesn't have a stack (e.g., a zombie), the stack is
0203      * "reliably" empty.
0204      */
0205     if (!try_get_task_stack(tsk))
0206         return 0;
0207
0208     ret = arch_stack_walk_reliable(consume_entry, &c, tsk);
0209     put_task_stack(tsk);
0210     return ret ? ret : c.len;
0211 }
0212 #endif
0213
0214 #ifdef CONFIG_USER_STACKTRACE_SUPPORT
0215 /**
0216  * stack_trace_save_user - Save a user space stack trace into a storage array
0217  * @store:  Pointer to storage array
0218  * @size:   Size of the storage array
0219  *
0220  * Return: Number of trace entries stored.
0221  */
0222 unsigned int stack_trace_save_user(unsigned long *store, unsigned int size)
0223 {
0224     stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
0225     struct stacktrace_cookie c = {
0226         .store  = store,
0227         .size   = size,
0228     };
0229
0230     /* Trace user stack if not a kernel thread */
0231     if (current->flags & PF_KTHREAD)
0232         return 0;
0233
0234     arch_stack_walk_user(consume_entry, &c, task_pt_regs(current));
0235
0236     return c.len;
0237 }
0238 #endif
0239
0240 #else /* CONFIG_ARCH_STACKWALK */
0241
0242 /*
0243  * Architectures that do not implement save_stack_trace_*()
0244  * get these weak aliases and once-per-bootup warnings
0245  * (whenever this facility is utilized - for example by procfs):
0246  */
0247 __weak void
0248 save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
0249 {
0250     WARN_ONCE(1, KERN_INFO "save_stack_trace_tsk() not implemented yet.\n");
0251 }
0252
0253 __weak void
0254 save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
0255 {
0256     WARN_ONCE(1, KERN_INFO "save_stack_trace_regs() not implemented yet.\n");
0257 }
0258
0259 /**
0260  * stack_trace_save - Save a stack trace into a storage array
0261  * @store:  Pointer to storage array
0262  * @size:   Size of the storage array
0263  * @skipnr: Number of entries to skip at the start of the stack trace
0264  *
0265  * Return: Number of trace entries stored
0266  */
0267 unsigned int stack_trace_save(unsigned long *store, unsigned int size,
0268                   unsigned int skipnr)
0269 {
0270     struct stack_trace trace = {
0271         .entries    = store,
0272         .max_entries    = size,
0273         .skip       = skipnr + 1,
0274     };
0275
0276     save_stack_trace(&trace);
0277     return trace.nr_entries;
0278 }
0279 EXPORT_SYMBOL_GPL(stack_trace_save);
0280
0281 /**
0282  * stack_trace_save_tsk - Save a task stack trace into a storage array
0283  * @task:   The task to examine
0284  * @store:  Pointer to storage array
0285  * @size:   Size of the storage array
0286  * @skipnr: Number of entries to skip at the start of the stack trace
0287  *
0288  * Return: Number of trace entries stored
0289  */
0290 unsigned int stack_trace_save_tsk(struct task_struct *task,
0291                   unsigned long *store, unsigned int size,
0292                   unsigned int skipnr)
0293 {
0294     struct stack_trace trace = {
0295         .entries    = store,
0296         .max_entries    = size,
0297         /* skip this function if they are tracing us */
0298         .skip   = skipnr + (current == task),
0299     };
0300
0301     save_stack_trace_tsk(task, &trace);
0302     return trace.nr_entries;
0303 }
0304
0305 /**
0306  * stack_trace_save_regs - Save a stack trace based on pt_regs into a storage array
0307  * @regs:   Pointer to pt_regs to examine
0308  * @store:  Pointer to storage array
0309  * @size:   Size of the storage array
0310  * @skipnr: Number of entries to skip at the start of the stack trace
0311  *
0312  * Return: Number of trace entries stored
0313  */
0314 unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store,
0315                    unsigned int size, unsigned int skipnr)
0316 {
0317     struct stack_trace trace = {
0318         .entries    = store,
0319         .max_entries    = size,
0320         .skip       = skipnr,
0321     };
0322
0323     save_stack_trace_regs(regs, &trace);
0324     return trace.nr_entries;
0325 }
0326
0327 #ifdef CONFIG_HAVE_RELIABLE_STACKTRACE
0328 /**
0329  * stack_trace_save_tsk_reliable - Save task stack with verification
0330  * @tsk:    Pointer to the task to examine
0331  * @store:  Pointer to storage array
0332  * @size:   Size of the storage array
0333  *
0334  * Return:  An error if it detects any unreliable features of the
0335  *      stack. Otherwise it guarantees that the stack trace is
0336  *      reliable and returns the number of entries stored.
0337  *
0338  * If the task is not 'current', the caller *must* ensure the task is inactive.
0339  */
0340 int stack_trace_save_tsk_reliable(struct task_struct *tsk, unsigned long *store,
0341                   unsigned int size)
0342 {
0343     struct stack_trace trace = {
0344         .entries    = store,
0345         .max_entries    = size,
0346     };
0347     int ret = save_stack_trace_tsk_reliable(tsk, &trace);
0348
0349     return ret ? ret : trace.nr_entries;
0350 }
0351 #endif
0352
0353 #ifdef CONFIG_USER_STACKTRACE_SUPPORT
0354 /**
0355  * stack_trace_save_user - Save a user space stack trace into a storage array
0356  * @store:  Pointer to storage array
0357  * @size:   Size of the storage array
0358  *
0359  * Return: Number of trace entries stored
0360  */
0361 unsigned int stack_trace_save_user(unsigned long *store, unsigned int size)
0362 {
0363     struct stack_trace trace = {
0364         .entries    = store,
0365         .max_entries    = size,
0366     };
0367
0368     save_stack_trace_user(&trace);
0369     return trace.nr_entries;
0370 }
0371 #endif /* CONFIG_USER_STACKTRACE_SUPPORT */
0372
0373 #endif /* !CONFIG_ARCH_STACKWALK */
0374
0375 static inline bool in_irqentry_text(unsigned long ptr)
0376 {
0377     return (ptr >= (unsigned long)&__irqentry_text_start &&
0378         ptr < (unsigned long)&__irqentry_text_end) ||
0379         (ptr >= (unsigned long)&__softirqentry_text_start &&
0380          ptr < (unsigned long)&__softirqentry_text_end);
0381 }
0382
0383 /**
0384  * filter_irq_stacks - Find first IRQ stack entry in trace
0385  * @entries:    Pointer to stack trace array
0386  * @nr_entries: Number of entries in the storage array
0387  *
0388  * Return: Number of trace entries until IRQ stack starts.
0389  */
0390 unsigned int filter_irq_stacks(unsigned long *entries, unsigned int nr_entries)
0391 {
0392     unsigned int i;
0393
0394     for (i = 0; i < nr_entries; i++) {
0395         if (in_irqentry_text(entries[i])) {
0396             /* Include the irqentry function into the stack. */
0397             return i + 1;
0398         }
0399     }
0400     return nr_entries;
0401 }
0402 EXPORT_SYMBOL_GPL(filter_irq_stacks);