![Zhengyuan Liu](/assets/img/avatar_default.png)
It looks weird that the stack_trace_filter file can be written by root but shows that it does not have write permission by ll command. Link: http://lkml.kernel.org/r/1518054113-28096-1-git-send-email-liuzhengyuan@kylinos.cn Signed-off-by: Zhengyuan Liu <liuzhengyuan@kylinos.cn> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
489 lines
11 KiB
C
489 lines
11 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
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*
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*/
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#include <linux/sched/task_stack.h>
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#include <linux/stacktrace.h>
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#include <linux/kallsyms.h>
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#include <linux/seq_file.h>
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#include <linux/spinlock.h>
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#include <linux/uaccess.h>
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#include <linux/ftrace.h>
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#include <linux/module.h>
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#include <linux/sysctl.h>
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#include <linux/init.h>
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#include <asm/setup.h>
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#include "trace.h"
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static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] =
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{ [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX };
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unsigned stack_trace_index[STACK_TRACE_ENTRIES];
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/*
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* Reserve one entry for the passed in ip. This will allow
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* us to remove most or all of the stack size overhead
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* added by the stack tracer itself.
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*/
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struct stack_trace stack_trace_max = {
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.max_entries = STACK_TRACE_ENTRIES - 1,
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.entries = &stack_dump_trace[0],
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};
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unsigned long stack_trace_max_size;
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arch_spinlock_t stack_trace_max_lock =
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(arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
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DEFINE_PER_CPU(int, disable_stack_tracer);
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static DEFINE_MUTEX(stack_sysctl_mutex);
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int stack_tracer_enabled;
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static int last_stack_tracer_enabled;
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void stack_trace_print(void)
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{
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long i;
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int size;
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pr_emerg(" Depth Size Location (%d entries)\n"
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" ----- ---- --------\n",
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stack_trace_max.nr_entries);
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for (i = 0; i < stack_trace_max.nr_entries; i++) {
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if (stack_dump_trace[i] == ULONG_MAX)
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break;
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if (i+1 == stack_trace_max.nr_entries ||
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stack_dump_trace[i+1] == ULONG_MAX)
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size = stack_trace_index[i];
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else
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size = stack_trace_index[i] - stack_trace_index[i+1];
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pr_emerg("%3ld) %8d %5d %pS\n", i, stack_trace_index[i],
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size, (void *)stack_dump_trace[i]);
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}
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}
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/*
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* When arch-specific code overrides this function, the following
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* data should be filled up, assuming stack_trace_max_lock is held to
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* prevent concurrent updates.
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* stack_trace_index[]
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* stack_trace_max
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* stack_trace_max_size
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*/
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void __weak
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check_stack(unsigned long ip, unsigned long *stack)
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{
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unsigned long this_size, flags; unsigned long *p, *top, *start;
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static int tracer_frame;
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int frame_size = READ_ONCE(tracer_frame);
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int i, x;
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this_size = ((unsigned long)stack) & (THREAD_SIZE-1);
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this_size = THREAD_SIZE - this_size;
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/* Remove the frame of the tracer */
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this_size -= frame_size;
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if (this_size <= stack_trace_max_size)
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return;
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/* we do not handle interrupt stacks yet */
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if (!object_is_on_stack(stack))
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return;
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/* Can't do this from NMI context (can cause deadlocks) */
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if (in_nmi())
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return;
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local_irq_save(flags);
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arch_spin_lock(&stack_trace_max_lock);
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/* In case another CPU set the tracer_frame on us */
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if (unlikely(!frame_size))
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this_size -= tracer_frame;
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/* a race could have already updated it */
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if (this_size <= stack_trace_max_size)
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goto out;
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stack_trace_max_size = this_size;
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stack_trace_max.nr_entries = 0;
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stack_trace_max.skip = 3;
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save_stack_trace(&stack_trace_max);
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/* Skip over the overhead of the stack tracer itself */
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for (i = 0; i < stack_trace_max.nr_entries; i++) {
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if (stack_dump_trace[i] == ip)
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break;
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}
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/*
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* Some archs may not have the passed in ip in the dump.
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* If that happens, we need to show everything.
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*/
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if (i == stack_trace_max.nr_entries)
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i = 0;
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/*
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* Now find where in the stack these are.
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*/
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x = 0;
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start = stack;
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top = (unsigned long *)
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(((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
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/*
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* Loop through all the entries. One of the entries may
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* for some reason be missed on the stack, so we may
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* have to account for them. If they are all there, this
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* loop will only happen once. This code only takes place
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* on a new max, so it is far from a fast path.
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*/
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while (i < stack_trace_max.nr_entries) {
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int found = 0;
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stack_trace_index[x] = this_size;
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p = start;
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for (; p < top && i < stack_trace_max.nr_entries; p++) {
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if (stack_dump_trace[i] == ULONG_MAX)
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break;
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/*
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* The READ_ONCE_NOCHECK is used to let KASAN know that
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* this is not a stack-out-of-bounds error.
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*/
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if ((READ_ONCE_NOCHECK(*p)) == stack_dump_trace[i]) {
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stack_dump_trace[x] = stack_dump_trace[i++];
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this_size = stack_trace_index[x++] =
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(top - p) * sizeof(unsigned long);
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found = 1;
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/* Start the search from here */
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start = p + 1;
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/*
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* We do not want to show the overhead
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* of the stack tracer stack in the
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* max stack. If we haven't figured
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* out what that is, then figure it out
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* now.
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*/
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if (unlikely(!tracer_frame)) {
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tracer_frame = (p - stack) *
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sizeof(unsigned long);
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stack_trace_max_size -= tracer_frame;
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}
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}
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}
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if (!found)
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i++;
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}
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stack_trace_max.nr_entries = x;
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for (; x < i; x++)
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stack_dump_trace[x] = ULONG_MAX;
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if (task_stack_end_corrupted(current)) {
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stack_trace_print();
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BUG();
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}
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out:
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arch_spin_unlock(&stack_trace_max_lock);
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local_irq_restore(flags);
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}
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static void
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stack_trace_call(unsigned long ip, unsigned long parent_ip,
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struct ftrace_ops *op, struct pt_regs *pt_regs)
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{
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unsigned long stack;
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preempt_disable_notrace();
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/* no atomic needed, we only modify this variable by this cpu */
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__this_cpu_inc(disable_stack_tracer);
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if (__this_cpu_read(disable_stack_tracer) != 1)
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goto out;
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/* If rcu is not watching, then save stack trace can fail */
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if (!rcu_is_watching())
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goto out;
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ip += MCOUNT_INSN_SIZE;
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check_stack(ip, &stack);
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out:
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__this_cpu_dec(disable_stack_tracer);
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/* prevent recursion in schedule */
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preempt_enable_notrace();
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}
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static struct ftrace_ops trace_ops __read_mostly =
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{
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.func = stack_trace_call,
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.flags = FTRACE_OPS_FL_RECURSION_SAFE,
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};
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static ssize_t
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stack_max_size_read(struct file *filp, char __user *ubuf,
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size_t count, loff_t *ppos)
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{
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unsigned long *ptr = filp->private_data;
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char buf[64];
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int r;
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r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
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if (r > sizeof(buf))
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r = sizeof(buf);
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return simple_read_from_buffer(ubuf, count, ppos, buf, r);
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}
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static ssize_t
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stack_max_size_write(struct file *filp, const char __user *ubuf,
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size_t count, loff_t *ppos)
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{
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long *ptr = filp->private_data;
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unsigned long val, flags;
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int ret;
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ret = kstrtoul_from_user(ubuf, count, 10, &val);
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if (ret)
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return ret;
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local_irq_save(flags);
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/*
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* In case we trace inside arch_spin_lock() or after (NMI),
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* we will cause circular lock, so we also need to increase
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* the percpu disable_stack_tracer here.
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*/
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__this_cpu_inc(disable_stack_tracer);
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arch_spin_lock(&stack_trace_max_lock);
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*ptr = val;
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arch_spin_unlock(&stack_trace_max_lock);
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__this_cpu_dec(disable_stack_tracer);
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local_irq_restore(flags);
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return count;
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}
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static const struct file_operations stack_max_size_fops = {
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.open = tracing_open_generic,
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.read = stack_max_size_read,
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.write = stack_max_size_write,
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.llseek = default_llseek,
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};
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static void *
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__next(struct seq_file *m, loff_t *pos)
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{
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long n = *pos - 1;
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if (n > stack_trace_max.nr_entries || stack_dump_trace[n] == ULONG_MAX)
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return NULL;
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m->private = (void *)n;
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return &m->private;
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}
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static void *
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t_next(struct seq_file *m, void *v, loff_t *pos)
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{
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(*pos)++;
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return __next(m, pos);
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}
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static void *t_start(struct seq_file *m, loff_t *pos)
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{
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local_irq_disable();
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__this_cpu_inc(disable_stack_tracer);
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arch_spin_lock(&stack_trace_max_lock);
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if (*pos == 0)
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return SEQ_START_TOKEN;
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return __next(m, pos);
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}
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static void t_stop(struct seq_file *m, void *p)
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{
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arch_spin_unlock(&stack_trace_max_lock);
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__this_cpu_dec(disable_stack_tracer);
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local_irq_enable();
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}
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static void trace_lookup_stack(struct seq_file *m, long i)
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{
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unsigned long addr = stack_dump_trace[i];
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seq_printf(m, "%pS\n", (void *)addr);
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}
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static void print_disabled(struct seq_file *m)
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{
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seq_puts(m, "#\n"
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"# Stack tracer disabled\n"
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"#\n"
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"# To enable the stack tracer, either add 'stacktrace' to the\n"
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"# kernel command line\n"
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"# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"
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"#\n");
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}
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static int t_show(struct seq_file *m, void *v)
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{
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long i;
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int size;
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if (v == SEQ_START_TOKEN) {
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seq_printf(m, " Depth Size Location"
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" (%d entries)\n"
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" ----- ---- --------\n",
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stack_trace_max.nr_entries);
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if (!stack_tracer_enabled && !stack_trace_max_size)
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print_disabled(m);
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return 0;
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}
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i = *(long *)v;
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if (i >= stack_trace_max.nr_entries ||
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stack_dump_trace[i] == ULONG_MAX)
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return 0;
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if (i+1 == stack_trace_max.nr_entries ||
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stack_dump_trace[i+1] == ULONG_MAX)
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size = stack_trace_index[i];
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else
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size = stack_trace_index[i] - stack_trace_index[i+1];
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seq_printf(m, "%3ld) %8d %5d ", i, stack_trace_index[i], size);
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trace_lookup_stack(m, i);
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return 0;
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}
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static const struct seq_operations stack_trace_seq_ops = {
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.start = t_start,
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.next = t_next,
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.stop = t_stop,
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.show = t_show,
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};
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static int stack_trace_open(struct inode *inode, struct file *file)
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{
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return seq_open(file, &stack_trace_seq_ops);
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}
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static const struct file_operations stack_trace_fops = {
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.open = stack_trace_open,
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.read = seq_read,
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.llseek = seq_lseek,
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.release = seq_release,
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};
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#ifdef CONFIG_DYNAMIC_FTRACE
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static int
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stack_trace_filter_open(struct inode *inode, struct file *file)
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{
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struct ftrace_ops *ops = inode->i_private;
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return ftrace_regex_open(ops, FTRACE_ITER_FILTER,
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inode, file);
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}
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static const struct file_operations stack_trace_filter_fops = {
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.open = stack_trace_filter_open,
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.read = seq_read,
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.write = ftrace_filter_write,
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.llseek = tracing_lseek,
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.release = ftrace_regex_release,
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};
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#endif /* CONFIG_DYNAMIC_FTRACE */
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int
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stack_trace_sysctl(struct ctl_table *table, int write,
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void __user *buffer, size_t *lenp,
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loff_t *ppos)
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{
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int ret;
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mutex_lock(&stack_sysctl_mutex);
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ret = proc_dointvec(table, write, buffer, lenp, ppos);
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if (ret || !write ||
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(last_stack_tracer_enabled == !!stack_tracer_enabled))
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goto out;
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last_stack_tracer_enabled = !!stack_tracer_enabled;
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if (stack_tracer_enabled)
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register_ftrace_function(&trace_ops);
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else
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unregister_ftrace_function(&trace_ops);
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out:
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mutex_unlock(&stack_sysctl_mutex);
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return ret;
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}
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static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata;
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static __init int enable_stacktrace(char *str)
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{
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if (strncmp(str, "_filter=", 8) == 0)
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strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE);
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stack_tracer_enabled = 1;
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last_stack_tracer_enabled = 1;
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return 1;
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}
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__setup("stacktrace", enable_stacktrace);
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static __init int stack_trace_init(void)
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{
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struct dentry *d_tracer;
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d_tracer = tracing_init_dentry();
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if (IS_ERR(d_tracer))
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return 0;
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trace_create_file("stack_max_size", 0644, d_tracer,
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&stack_trace_max_size, &stack_max_size_fops);
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trace_create_file("stack_trace", 0444, d_tracer,
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NULL, &stack_trace_fops);
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#ifdef CONFIG_DYNAMIC_FTRACE
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trace_create_file("stack_trace_filter", 0644, d_tracer,
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&trace_ops, &stack_trace_filter_fops);
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#endif
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if (stack_trace_filter_buf[0])
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ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1);
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if (stack_tracer_enabled)
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register_ftrace_function(&trace_ops);
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return 0;
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}
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device_initcall(stack_trace_init);
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