e447e1df2e
If the stack tracing is disabled (by default) the stack_trace file will only contain the header: # cat /debug/tracing/stack_trace Depth Size Location (0 entries) ----- ---- -------- This can be frustrating to a developer that does not realize that the stack tracer is disabled. This patch adds the following text: # cat /debug/tracing/stack_trace Depth Size Location (0 entries) ----- ---- -------- # # Stack tracer disabled # # To enable the stack tracer, either add 'stacktrace' to the # kernel command line # or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled' # Signed-off-by: Steven Rostedt <srostedt@redhat.com>
375 lines
7.7 KiB
C
375 lines
7.7 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 "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 raw_spinlock_t max_stack_lock =
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(raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
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static int stack_trace_disabled __read_mostly;
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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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__raw_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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__raw_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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{
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int cpu, resched;
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if (unlikely(!ftrace_enabled || stack_trace_disabled))
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return;
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resched = ftrace_preempt_disable();
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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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ftrace_preempt_enable(resched);
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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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};
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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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char buf[64];
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int ret;
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if (count >= sizeof(buf))
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return -EINVAL;
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if (copy_from_user(&buf, ubuf, count))
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return -EFAULT;
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buf[count] = 0;
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ret = strict_strtoul(buf, 10, &val);
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if (ret < 0)
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return ret;
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local_irq_save(flags);
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__raw_spin_lock(&max_stack_lock);
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*ptr = val;
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__raw_spin_unlock(&max_stack_lock);
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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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};
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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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long i;
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(*pos)++;
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if (v == SEQ_START_TOKEN)
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i = 0;
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else {
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i = *(long *)v;
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i++;
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}
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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 NULL;
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m->private = (void *)i;
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return &m->private;
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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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void *t = SEQ_START_TOKEN;
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loff_t l = 0;
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local_irq_disable();
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__raw_spin_lock(&max_stack_lock);
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if (*pos == 0)
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return SEQ_START_TOKEN;
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for (; t && l < *pos; t = t_next(m, t, &l))
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;
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return t;
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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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__raw_spin_unlock(&max_stack_lock);
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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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#ifdef CONFIG_KALLSYMS
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char str[KSYM_SYMBOL_LEN];
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sprint_symbol(str, addr);
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return seq_printf(m, "%s\n", str);
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#else
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return seq_printf(m, "%p\n", (void*)addr);
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#endif
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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);
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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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int ret;
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ret = seq_open(file, &stack_trace_seq_ops);
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return ret;
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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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};
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int
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stack_trace_sysctl(struct ctl_table *table, int write,
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struct file *file, 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, file, 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 __init int enable_stacktrace(char *str)
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{
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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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struct dentry *entry;
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d_tracer = tracing_init_dentry();
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entry = debugfs_create_file("stack_max_size", 0644, d_tracer,
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&max_stack_size, &stack_max_size_fops);
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if (!entry)
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pr_warning("Could not create debugfs 'stack_max_size' entry\n");
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entry = debugfs_create_file("stack_trace", 0444, d_tracer,
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NULL, &stack_trace_fops);
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if (!entry)
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pr_warning("Could not create debugfs 'stack_trace' entry\n");
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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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