Merge master.kernel.org:/pub/scm/linux/kernel/git/davej/agpgart
[linux-2.6] / arch / i386 / 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
17 struct frame_head {
18         struct frame_head * ebp;
19         unsigned long ret;
20 } __attribute__((packed));
21
22 static struct frame_head *
23 dump_backtrace(struct frame_head * head)
24 {
25         struct frame_head bufhead[2];
26
27         /* Also check accessibility of one struct frame_head beyond */
28         if (!access_ok(VERIFY_READ, head, sizeof(bufhead)))
29                 return NULL;
30         if (__copy_from_user_inatomic(bufhead, head, sizeof(bufhead)))
31                 return NULL;
32
33         oprofile_add_trace(bufhead[0].ret);
34
35         /* frame pointers should strictly progress back up the stack
36          * (towards higher addresses) */
37         if (head >= bufhead[0].ebp)
38                 return NULL;
39
40         return bufhead[0].ebp;
41 }
42
43 /*
44  * |             | /\ Higher addresses
45  * |             |
46  * --------------- stack base (address of current_thread_info)
47  * | thread info |
48  * .             .
49  * |    stack    |
50  * --------------- saved regs->ebp value if valid (frame_head address)
51  * .             .
52  * --------------- struct pt_regs stored on stack (struct pt_regs *)
53  * |             |
54  * .             .
55  * |             |
56  * --------------- %esp
57  * |             |
58  * |             | \/ Lower addresses
59  *
60  * Thus, &pt_regs <-> stack base restricts the valid(ish) ebp values
61  */
62 #ifdef CONFIG_FRAME_POINTER
63 static int valid_kernel_stack(struct frame_head * head, struct pt_regs * regs)
64 {
65         unsigned long headaddr = (unsigned long)head;
66         unsigned long stack = (unsigned long)regs;
67         unsigned long stack_base = (stack & ~(THREAD_SIZE - 1)) + THREAD_SIZE;
68
69         return headaddr > stack && headaddr < stack_base;
70 }
71 #else
72 /* without fp, it's just junk */
73 static int valid_kernel_stack(struct frame_head * head, struct pt_regs * regs)
74 {
75         return 0;
76 }
77 #endif
78
79
80 void
81 x86_backtrace(struct pt_regs * const regs, unsigned int depth)
82 {
83         struct frame_head *head;
84
85 #ifdef CONFIG_X86_64
86         head = (struct frame_head *)regs->rbp;
87 #else
88         head = (struct frame_head *)regs->ebp;
89 #endif
90
91         if (!user_mode_vm(regs)) {
92                 while (depth-- && valid_kernel_stack(head, regs))
93                         head = dump_backtrace(head);
94                 return;
95         }
96
97         while (depth-- && head)
98                 head = dump_backtrace(head);
99 }