![Anton Vorontsov](/assets/img/avatar_default.png)
It seems that 'ftrace_enabled' flag should not be used inside the tracer functions. The ftrace core is using this flag for internal purposes, and the flag wasn't meant to be used in tracers' runtime checks. stack tracer is the only tracer that abusing the flag. So stop it from serving as a bad example. Also, there is a local 'stack_trace_disabled' flag in the stack tracer, which is never updated; so it can be removed as well. Link: http://lkml.kernel.org/r/1342637761-9655-1-git-send-email-anton.vorontsov@linaro.org Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
394 lines
8.3 KiB
C
394 lines
8.3 KiB
C
/*
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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/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/debugfs.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 <linux/fs.h>
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#include <asm/setup.h>
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#include "trace.h"
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#define STACK_TRACE_ENTRIES 500
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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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static unsigned stack_dump_index[STACK_TRACE_ENTRIES];
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static struct stack_trace max_stack_trace = {
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.max_entries = STACK_TRACE_ENTRIES,
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.entries = stack_dump_trace,
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};
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static unsigned long max_stack_size;
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static arch_spinlock_t max_stack_lock =
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(arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
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static DEFINE_PER_CPU(int, trace_active);
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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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static inline void check_stack(void)
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{
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unsigned long this_size, flags;
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unsigned long *p, *top, *start;
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int i;
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this_size = ((unsigned long)&this_size) & (THREAD_SIZE-1);
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this_size = THREAD_SIZE - this_size;
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if (this_size <= max_stack_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(&this_size))
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return;
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local_irq_save(flags);
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arch_spin_lock(&max_stack_lock);
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/* a race could have already updated it */
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if (this_size <= max_stack_size)
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goto out;
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max_stack_size = this_size;
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max_stack_trace.nr_entries = 0;
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max_stack_trace.skip = 3;
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save_stack_trace(&max_stack_trace);
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/*
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* Now find where in the stack these are.
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*/
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i = 0;
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start = &this_size;
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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 < max_stack_trace.nr_entries) {
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int found = 0;
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stack_dump_index[i] = this_size;
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p = start;
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for (; p < top && i < max_stack_trace.nr_entries; p++) {
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if (*p == stack_dump_trace[i]) {
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this_size = stack_dump_index[i++] =
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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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}
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if (!found)
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i++;
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}
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out:
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arch_spin_unlock(&max_stack_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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int cpu;
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preempt_disable_notrace();
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cpu = raw_smp_processor_id();
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/* no atomic needed, we only modify this variable by this cpu */
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if (per_cpu(trace_active, cpu)++ != 0)
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goto out;
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check_stack();
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out:
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per_cpu(trace_active, cpu)--;
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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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int cpu;
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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 trace_active here.
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*/
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cpu = smp_processor_id();
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per_cpu(trace_active, cpu)++;
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arch_spin_lock(&max_stack_lock);
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*ptr = val;
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arch_spin_unlock(&max_stack_lock);
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per_cpu(trace_active, cpu)--;
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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 >= max_stack_trace.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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int cpu;
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local_irq_disable();
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cpu = smp_processor_id();
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per_cpu(trace_active, cpu)++;
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arch_spin_lock(&max_stack_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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int cpu;
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arch_spin_unlock(&max_stack_lock);
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cpu = smp_processor_id();
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per_cpu(trace_active, cpu)--;
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local_irq_enable();
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}
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static int 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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return 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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max_stack_trace.nr_entries - 1);
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if (!stack_tracer_enabled && !max_stack_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 >= max_stack_trace.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 == max_stack_trace.nr_entries ||
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stack_dump_trace[i+1] == ULONG_MAX)
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size = stack_dump_index[i];
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else
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size = stack_dump_index[i] - stack_dump_index[i+1];
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seq_printf(m, "%3ld) %8d %5d ", i, stack_dump_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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static int
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stack_trace_filter_open(struct inode *inode, struct file *file)
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{
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return ftrace_regex_open(&trace_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 = ftrace_regex_lseek,
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.release = ftrace_regex_release,
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};
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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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trace_create_file("stack_max_size", 0644, d_tracer,
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&max_stack_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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trace_create_file("stack_trace_filter", 0444, d_tracer,
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NULL, &stack_trace_filter_fops);
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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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