/* * trace stack traces * * Copyright (C) 2004-2008, Soeren Sandmann * Copyright (C) 2007 Steven Rostedt <srostedt@redhat.com> * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com> */ #include <linux/kallsyms.h> #include <linux/debugfs.h> #include <linux/hrtimer.h> #include <linux/uaccess.h> #include <linux/ftrace.h> #include <linux/module.h> #include <linux/irq.h> #include <linux/fs.h> #include <asm/stacktrace.h> #include "trace.h" static struct trace_array *sysprof_trace; static int __read_mostly tracer_enabled; /* * 1 msec sample interval by default: */ static unsigned long sample_period = 1000000; static const unsigned int sample_max_depth = 512; static DEFINE_MUTEX(sample_timer_lock); /* * Per CPU hrtimers that do the profiling: */ static DEFINE_PER_CPU(struct hrtimer, stack_trace_hrtimer); struct stack_frame { const void __user *next_fp; unsigned long return_address; }; static int copy_stack_frame(const void __user *fp, struct stack_frame *frame) { int ret; if (!access_ok(VERIFY_READ, fp, sizeof(*frame))) return 0; ret = 1; pagefault_disable(); if (__copy_from_user_inatomic(frame, fp, sizeof(*frame))) ret = 0; pagefault_enable(); return ret; } struct backtrace_info { struct trace_array_cpu *data; struct trace_array *tr; int pos; }; static void backtrace_warning_symbol(void *data, char *msg, unsigned long symbol) { /* Ignore warnings */ } static void backtrace_warning(void *data, char *msg) { /* Ignore warnings */ } static int backtrace_stack(void *data, char *name) { /* Don't bother with IRQ stacks for now */ return -1; } static void backtrace_address(void *data, unsigned long addr, int reliable) { struct backtrace_info *info = data; if (info->pos < sample_max_depth && reliable) { __trace_special(info->tr, info->data, 1, addr, 0); info->pos++; } } static const struct stacktrace_ops backtrace_ops = { .warning = backtrace_warning, .warning_symbol = backtrace_warning_symbol, .stack = backtrace_stack, .address = backtrace_address, .walk_stack = print_context_stack, }; static int trace_kernel(struct pt_regs *regs, struct trace_array *tr, struct trace_array_cpu *data) { struct backtrace_info info; unsigned long bp; char *stack; info.tr = tr; info.data = data; info.pos = 1; __trace_special(info.tr, info.data, 1, regs->ip, 0); stack = ((char *)regs + sizeof(struct pt_regs)); #ifdef CONFIG_FRAME_POINTER bp = regs->bp; #else bp = 0; #endif dump_trace(NULL, regs, (void *)stack, bp, &backtrace_ops, &info); return info.pos; } static void timer_notify(struct pt_regs *regs, int cpu) { struct trace_array_cpu *data; struct stack_frame frame; struct trace_array *tr; const void __user *fp; int is_user; int i; if (!regs) return; tr = sysprof_trace; data = tr->data[cpu]; is_user = user_mode(regs); if (!current || current->pid == 0) return; if (is_user && current->state != TASK_RUNNING) return; __trace_special(tr, data, 0, 0, current->pid); if (!is_user) i = trace_kernel(regs, tr, data); else i = 0; /* * Trace user stack if we are not a kernel thread */ if (current->mm && i < sample_max_depth) { regs = (struct pt_regs *)current->thread.sp0 - 1; fp = (void __user *)regs->bp; __trace_special(tr, data, 2, regs->ip, 0); while (i < sample_max_depth) { frame.next_fp = NULL; frame.return_address = 0; if (!copy_stack_frame(fp, &frame)) break; if ((unsigned long)fp < regs->sp) break; __trace_special(tr, data, 2, frame.return_address, (unsigned long)fp); fp = frame.next_fp; i++; } } /* * Special trace entry if we overflow the max depth: */ if (i == sample_max_depth) __trace_special(tr, data, -1, -1, -1); __trace_special(tr, data, 3, current->pid, i); } static enum hrtimer_restart stack_trace_timer_fn(struct hrtimer *hrtimer) { /* trace here */ timer_notify(get_irq_regs(), smp_processor_id()); hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period)); return HRTIMER_RESTART; } static void start_stack_timer(void *unused) { struct hrtimer *hrtimer = &__get_cpu_var(stack_trace_hrtimer); hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); hrtimer->function = stack_trace_timer_fn; hrtimer_start(hrtimer, ns_to_ktime(sample_period), HRTIMER_MODE_REL_PINNED); } static void start_stack_timers(void) { on_each_cpu(start_stack_timer, NULL, 1); } static void stop_stack_timer(int cpu) { struct hrtimer *hrtimer = &per_cpu(stack_trace_hrtimer, cpu); hrtimer_cancel(hrtimer); } static void stop_stack_timers(void) { int cpu; for_each_online_cpu(cpu) stop_stack_timer(cpu); } static void stop_stack_trace(struct trace_array *tr) { mutex_lock(&sample_timer_lock); stop_stack_timers(); tracer_enabled = 0; mutex_unlock(&sample_timer_lock); } static int stack_trace_init(struct trace_array *tr) { sysprof_trace = tr; tracing_start_cmdline_record(); mutex_lock(&sample_timer_lock); start_stack_timers(); tracer_enabled = 1; mutex_unlock(&sample_timer_lock); return 0; } static void stack_trace_reset(struct trace_array *tr) { tracing_stop_cmdline_record(); stop_stack_trace(tr); } static struct tracer stack_trace __read_mostly = { .name = "sysprof", .init = stack_trace_init, .reset = stack_trace_reset, #ifdef CONFIG_FTRACE_SELFTEST .selftest = trace_selftest_startup_sysprof, #endif }; __init static int init_stack_trace(void) { return register_tracer(&stack_trace); } device_initcall(init_stack_trace); #define MAX_LONG_DIGITS 22 static ssize_t sysprof_sample_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos) { char buf[MAX_LONG_DIGITS]; int r; r = sprintf(buf, "%ld\n", nsecs_to_usecs(sample_period)); return simple_read_from_buffer(ubuf, cnt, ppos, buf, r); } static ssize_t sysprof_sample_write(struct file *filp, const char __user *ubuf, size_t cnt, loff_t *ppos) { char buf[MAX_LONG_DIGITS]; unsigned long val; if (cnt > MAX_LONG_DIGITS-1) cnt = MAX_LONG_DIGITS-1; if (copy_from_user(&buf, ubuf, cnt)) return -EFAULT; buf[cnt] = 0; val = simple_strtoul(buf, NULL, 10); /* * Enforce a minimum sample period of 100 usecs: */ if (val < 100) val = 100; mutex_lock(&sample_timer_lock); stop_stack_timers(); sample_period = val * 1000; start_stack_timers(); mutex_unlock(&sample_timer_lock); return cnt; } static const struct file_operations sysprof_sample_fops = { .read = sysprof_sample_read, .write = sysprof_sample_write, }; void init_tracer_sysprof_debugfs(struct dentry *d_tracer) { trace_create_file("sysprof_sample_period", 0644, d_tracer, NULL, &sysprof_sample_fops); }