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4b48512c2e
My commit b0c51f1584 ("stacktrace: Don't skip first entry on
noncurrent tasks") adds one or zero to skipnr by "!!(current == tsk)".
But the C99 standard says:
The == (equal to) and != (not equal to) operators are
...
Each of the operators yields 1 if the specified relation is true and 0
if it is false.
So there is no need to prepend the above expression by "!!" -- remove it.
Reported-by: Joe Perches <joe@perches.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20191111092647.27419-1-jslaby@suse.cz
Signed-off-by: Ingo Molnar <mingo@kernel.org>
378 lines
9.7 KiB
C
378 lines
9.7 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* kernel/stacktrace.c
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*
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* Stack trace management functions
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*
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* Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
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*/
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#include <linux/sched/task_stack.h>
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#include <linux/sched/debug.h>
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#include <linux/sched.h>
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#include <linux/kernel.h>
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#include <linux/export.h>
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#include <linux/kallsyms.h>
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#include <linux/stacktrace.h>
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/**
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* stack_trace_print - Print the entries in the stack trace
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* @entries: Pointer to storage array
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* @nr_entries: Number of entries in the storage array
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* @spaces: Number of leading spaces to print
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*/
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void stack_trace_print(const unsigned long *entries, unsigned int nr_entries,
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int spaces)
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{
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unsigned int i;
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if (WARN_ON(!entries))
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return;
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for (i = 0; i < nr_entries; i++)
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printk("%*c%pS\n", 1 + spaces, ' ', (void *)entries[i]);
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}
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EXPORT_SYMBOL_GPL(stack_trace_print);
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/**
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* stack_trace_snprint - Print the entries in the stack trace into a buffer
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* @buf: Pointer to the print buffer
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* @size: Size of the print buffer
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* @entries: Pointer to storage array
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* @nr_entries: Number of entries in the storage array
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* @spaces: Number of leading spaces to print
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*
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* Return: Number of bytes printed.
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*/
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int stack_trace_snprint(char *buf, size_t size, const unsigned long *entries,
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unsigned int nr_entries, int spaces)
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{
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unsigned int generated, i, total = 0;
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if (WARN_ON(!entries))
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return 0;
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for (i = 0; i < nr_entries && size; i++) {
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generated = snprintf(buf, size, "%*c%pS\n", 1 + spaces, ' ',
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(void *)entries[i]);
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total += generated;
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if (generated >= size) {
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buf += size;
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size = 0;
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} else {
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buf += generated;
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size -= generated;
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}
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}
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return total;
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}
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EXPORT_SYMBOL_GPL(stack_trace_snprint);
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#ifdef CONFIG_ARCH_STACKWALK
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struct stacktrace_cookie {
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unsigned long *store;
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unsigned int size;
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unsigned int skip;
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unsigned int len;
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};
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static bool stack_trace_consume_entry(void *cookie, unsigned long addr,
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bool reliable)
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{
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struct stacktrace_cookie *c = cookie;
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if (c->len >= c->size)
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return false;
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if (c->skip > 0) {
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c->skip--;
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return true;
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}
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c->store[c->len++] = addr;
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return c->len < c->size;
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}
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static bool stack_trace_consume_entry_nosched(void *cookie, unsigned long addr,
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bool reliable)
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{
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if (in_sched_functions(addr))
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return true;
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return stack_trace_consume_entry(cookie, addr, reliable);
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}
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/**
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* stack_trace_save - Save a stack trace into a storage array
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* @store: Pointer to storage array
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* @size: Size of the storage array
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* @skipnr: Number of entries to skip at the start of the stack trace
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*
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* Return: Number of trace entries stored.
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*/
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unsigned int stack_trace_save(unsigned long *store, unsigned int size,
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unsigned int skipnr)
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{
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stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
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struct stacktrace_cookie c = {
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.store = store,
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.size = size,
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.skip = skipnr + 1,
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};
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arch_stack_walk(consume_entry, &c, current, NULL);
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return c.len;
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}
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EXPORT_SYMBOL_GPL(stack_trace_save);
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/**
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* stack_trace_save_tsk - Save a task stack trace into a storage array
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* @task: The task to examine
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* @store: Pointer to storage array
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* @size: Size of the storage array
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* @skipnr: Number of entries to skip at the start of the stack trace
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*
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* Return: Number of trace entries stored.
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*/
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unsigned int stack_trace_save_tsk(struct task_struct *tsk, unsigned long *store,
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unsigned int size, unsigned int skipnr)
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{
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stack_trace_consume_fn consume_entry = stack_trace_consume_entry_nosched;
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struct stacktrace_cookie c = {
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.store = store,
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.size = size,
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/* skip this function if they are tracing us */
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.skip = skipnr + (current == tsk),
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};
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if (!try_get_task_stack(tsk))
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return 0;
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arch_stack_walk(consume_entry, &c, tsk, NULL);
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put_task_stack(tsk);
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return c.len;
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}
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/**
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* stack_trace_save_regs - Save a stack trace based on pt_regs into a storage array
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* @regs: Pointer to pt_regs to examine
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* @store: Pointer to storage array
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* @size: Size of the storage array
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* @skipnr: Number of entries to skip at the start of the stack trace
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*
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* Return: Number of trace entries stored.
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*/
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unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store,
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unsigned int size, unsigned int skipnr)
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{
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stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
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struct stacktrace_cookie c = {
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.store = store,
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.size = size,
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.skip = skipnr,
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};
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arch_stack_walk(consume_entry, &c, current, regs);
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return c.len;
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}
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#ifdef CONFIG_HAVE_RELIABLE_STACKTRACE
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/**
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* stack_trace_save_tsk_reliable - Save task stack with verification
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* @tsk: Pointer to the task to examine
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* @store: Pointer to storage array
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* @size: Size of the storage array
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*
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* Return: An error if it detects any unreliable features of the
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* stack. Otherwise it guarantees that the stack trace is
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* reliable and returns the number of entries stored.
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*
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* If the task is not 'current', the caller *must* ensure the task is inactive.
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*/
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int stack_trace_save_tsk_reliable(struct task_struct *tsk, unsigned long *store,
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unsigned int size)
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{
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stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
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struct stacktrace_cookie c = {
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.store = store,
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.size = size,
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};
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int ret;
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/*
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* If the task doesn't have a stack (e.g., a zombie), the stack is
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* "reliably" empty.
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*/
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if (!try_get_task_stack(tsk))
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return 0;
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ret = arch_stack_walk_reliable(consume_entry, &c, tsk);
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put_task_stack(tsk);
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return ret ? ret : c.len;
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}
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#endif
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#ifdef CONFIG_USER_STACKTRACE_SUPPORT
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/**
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* stack_trace_save_user - Save a user space stack trace into a storage array
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* @store: Pointer to storage array
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* @size: Size of the storage array
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*
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* Return: Number of trace entries stored.
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*/
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unsigned int stack_trace_save_user(unsigned long *store, unsigned int size)
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{
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stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
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struct stacktrace_cookie c = {
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.store = store,
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.size = size,
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};
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mm_segment_t fs;
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/* Trace user stack if not a kernel thread */
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if (current->flags & PF_KTHREAD)
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return 0;
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fs = get_fs();
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set_fs(USER_DS);
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arch_stack_walk_user(consume_entry, &c, task_pt_regs(current));
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set_fs(fs);
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return c.len;
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}
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#endif
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#else /* CONFIG_ARCH_STACKWALK */
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/*
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* Architectures that do not implement save_stack_trace_*()
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* get these weak aliases and once-per-bootup warnings
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* (whenever this facility is utilized - for example by procfs):
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*/
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__weak void
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save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
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{
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WARN_ONCE(1, KERN_INFO "save_stack_trace_tsk() not implemented yet.\n");
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}
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__weak void
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save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
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{
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WARN_ONCE(1, KERN_INFO "save_stack_trace_regs() not implemented yet.\n");
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}
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/**
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* stack_trace_save - Save a stack trace into a storage array
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* @store: Pointer to storage array
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* @size: Size of the storage array
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* @skipnr: Number of entries to skip at the start of the stack trace
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*
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* Return: Number of trace entries stored
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*/
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unsigned int stack_trace_save(unsigned long *store, unsigned int size,
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unsigned int skipnr)
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{
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struct stack_trace trace = {
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.entries = store,
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.max_entries = size,
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.skip = skipnr + 1,
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};
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save_stack_trace(&trace);
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return trace.nr_entries;
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}
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EXPORT_SYMBOL_GPL(stack_trace_save);
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/**
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* stack_trace_save_tsk - Save a task stack trace into a storage array
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* @task: The task to examine
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* @store: Pointer to storage array
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* @size: Size of the storage array
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* @skipnr: Number of entries to skip at the start of the stack trace
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*
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* Return: Number of trace entries stored
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*/
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unsigned int stack_trace_save_tsk(struct task_struct *task,
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unsigned long *store, unsigned int size,
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unsigned int skipnr)
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{
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struct stack_trace trace = {
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.entries = store,
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.max_entries = size,
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/* skip this function if they are tracing us */
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.skip = skipnr + (current == task),
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};
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save_stack_trace_tsk(task, &trace);
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return trace.nr_entries;
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}
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/**
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* stack_trace_save_regs - Save a stack trace based on pt_regs into a storage array
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* @regs: Pointer to pt_regs to examine
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* @store: Pointer to storage array
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* @size: Size of the storage array
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* @skipnr: Number of entries to skip at the start of the stack trace
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*
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* Return: Number of trace entries stored
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*/
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unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store,
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unsigned int size, unsigned int skipnr)
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{
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struct stack_trace trace = {
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.entries = store,
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.max_entries = size,
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.skip = skipnr,
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};
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save_stack_trace_regs(regs, &trace);
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return trace.nr_entries;
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}
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#ifdef CONFIG_HAVE_RELIABLE_STACKTRACE
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/**
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* stack_trace_save_tsk_reliable - Save task stack with verification
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* @tsk: Pointer to the task to examine
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* @store: Pointer to storage array
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* @size: Size of the storage array
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*
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* Return: An error if it detects any unreliable features of the
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* stack. Otherwise it guarantees that the stack trace is
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* reliable and returns the number of entries stored.
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*
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* If the task is not 'current', the caller *must* ensure the task is inactive.
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*/
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int stack_trace_save_tsk_reliable(struct task_struct *tsk, unsigned long *store,
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unsigned int size)
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{
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struct stack_trace trace = {
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.entries = store,
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.max_entries = size,
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};
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int ret = save_stack_trace_tsk_reliable(tsk, &trace);
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return ret ? ret : trace.nr_entries;
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}
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#endif
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#ifdef CONFIG_USER_STACKTRACE_SUPPORT
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/**
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* stack_trace_save_user - Save a user space stack trace into a storage array
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* @store: Pointer to storage array
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* @size: Size of the storage array
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*
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* Return: Number of trace entries stored
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*/
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unsigned int stack_trace_save_user(unsigned long *store, unsigned int size)
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{
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struct stack_trace trace = {
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.entries = store,
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.max_entries = size,
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};
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save_stack_trace_user(&trace);
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return trace.nr_entries;
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}
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#endif /* CONFIG_USER_STACKTRACE_SUPPORT */
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#endif /* !CONFIG_ARCH_STACKWALK */
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