oprofile: Implement performance counter multiplexing
[linux-2.6.git] / arch / x86 / oprofile / backtrace.c
1 /**
2  * @file backtrace.c
3  *
4  * @remark Copyright 2002 OProfile authors
5  * @remark Read the file COPYING
6  *
7  * @author John Levon
8  * @author David Smith
9  */
10
11 #include <linux/oprofile.h>
12 #include <linux/sched.h>
13 #include <linux/mm.h>
14 #include <asm/ptrace.h>
15 #include <asm/uaccess.h>
16 #include <asm/stacktrace.h>
17
18 static void backtrace_warning_symbol(void *data, char *msg,
19                                      unsigned long symbol)
20 {
21         /* Ignore warnings */
22 }
23
24 static void backtrace_warning(void *data, char *msg)
25 {
26         /* Ignore warnings */
27 }
28
29 static int backtrace_stack(void *data, char *name)
30 {
31         /* Yes, we want all stacks */
32         return 0;
33 }
34
35 static void backtrace_address(void *data, unsigned long addr, int reliable)
36 {
37         unsigned int *depth = data;
38
39         if ((*depth)--)
40                 oprofile_add_trace(addr);
41 }
42
43 static struct stacktrace_ops backtrace_ops = {
44         .warning = backtrace_warning,
45         .warning_symbol = backtrace_warning_symbol,
46         .stack = backtrace_stack,
47         .address = backtrace_address,
48 };
49
50 struct frame_head {
51         struct frame_head *bp;
52         unsigned long ret;
53 } __attribute__((packed));
54
55 static struct frame_head *dump_user_backtrace(struct frame_head *head)
56 {
57         struct frame_head bufhead[2];
58
59         /* Also check accessibility of one struct frame_head beyond */
60         if (!access_ok(VERIFY_READ, head, sizeof(bufhead)))
61                 return NULL;
62         if (__copy_from_user_inatomic(bufhead, head, sizeof(bufhead)))
63                 return NULL;
64
65         oprofile_add_trace(bufhead[0].ret);
66
67         /* frame pointers should strictly progress back up the stack
68          * (towards higher addresses) */
69         if (head >= bufhead[0].bp)
70                 return NULL;
71
72         return bufhead[0].bp;
73 }
74
75 void
76 x86_backtrace(struct pt_regs * const regs, unsigned int depth)
77 {
78         struct frame_head *head = (struct frame_head *)frame_pointer(regs);
79
80         if (!user_mode_vm(regs)) {
81                 unsigned long stack = kernel_stack_pointer(regs);
82                 if (depth)
83                         dump_trace(NULL, regs, (unsigned long *)stack, 0,
84                                    &backtrace_ops, &depth);
85                 return;
86         }
87
88         while (depth-- && head)
89                 head = dump_user_backtrace(head);
90 }