kernel/trace/trace_syscalls.c

   1 #include <linux/ftrace.h>
   2 #include <linux/kernel.h>
   3
   4 #include <asm/syscall.h>
   5
   6 #include "trace_output.h"
   7 #include "trace.h"
   8
   9 static atomic_t refcount;
  10
  11 void start_ftrace_syscalls(void)
  12 {
  13         unsigned long flags;
  14         struct task_struct *g, *t;
  15
  16         if (atomic_inc_return(&refcount) != 1)
  17                 goto out;
  18
  19         read_lock_irqsave(&tasklist_lock, flags);
  20
  21         do_each_thread(g, t) {
  22                 set_tsk_thread_flag(t, TIF_SYSCALL_FTRACE);
  23         } while_each_thread(g, t);
  24
  25         read_unlock_irqrestore(&tasklist_lock, flags);
  26 out:
  27         atomic_dec(&refcount);
  28 }
  29
  30 void stop_ftrace_syscalls(void)
  31 {
  32         unsigned long flags;
  33         struct task_struct *g, *t;
  34
  35         if (atomic_dec_return(&refcount))
  36                 goto out;
  37
  38         read_lock_irqsave(&tasklist_lock, flags);
  39
  40         do_each_thread(g, t) {
  41                 clear_tsk_thread_flag(t, TIF_SYSCALL_FTRACE);
  42         } while_each_thread(g, t);
  43
  44         read_unlock_irqrestore(&tasklist_lock, flags);
  45 out:
  46         atomic_inc(&refcount);
  47 }
  48
  49 void ftrace_syscall_enter(struct pt_regs *regs)
  50 {
  51         int syscall_nr;
  52
  53         syscall_nr = syscall_get_nr(current, regs);
  54
  55         trace_printk("syscall %d enter\n", syscall_nr);
  56 }
  57
  58 void ftrace_syscall_exit(struct pt_regs *regs)
  59 {
  60         int syscall_nr;
  61
  62         syscall_nr = syscall_get_nr(current, regs);
  63
  64         trace_printk("syscall %d exit\n", syscall_nr);
  65 }
  66
  67 static int init_syscall_tracer(struct trace_array *tr)
  68 {
  69         start_ftrace_syscalls();
  70
  71         return 0;
  72 }
  73
  74 static void reset_syscall_tracer(struct trace_array *tr)
  75 {
  76         stop_ftrace_syscalls();
  77 }
  78
  79 static struct trace_event syscall_enter_event = {
  80         .type           = TRACE_SYSCALL_ENTER,
  81 };
  82
  83 static struct trace_event syscall_exit_event = {
  84         .type           = TRACE_SYSCALL_EXIT,
  85 };
  86
  87 static struct tracer syscall_tracer __read_mostly = {
  88         .name           = "syscall",
  89         .init           = init_syscall_tracer,
  90         .reset          = reset_syscall_tracer
  91 };
  92
  93 __init int register_ftrace_syscalls(void)
  94 {
  95         int ret;
  96
  97         ret = register_ftrace_event(&syscall_enter_event);
  98         if (!ret) {
  99                 printk(KERN_WARNING "event %d failed to register\n",
 100                        syscall_enter_event.type);
 101                 WARN_ON_ONCE(1);
 102         }
 103
 104         ret = register_ftrace_event(&syscall_exit_event);
 105         if (!ret) {
 106                 printk(KERN_WARNING "event %d failed to register\n",
 107                        syscall_exit_event.type);
 108                 WARN_ON_ONCE(1);
 109         }
 110
 111         return register_tracer(&syscall_tracer);
 112 }
 113 device_initcall(register_ftrace_syscalls);