1 /*
2 * Arm specific backtracing code for oprofile
3 *
4 * Copyright 2005 Openedhand Ltd.
5 *
6 * Author: Richard Purdie <rpurdie@openedhand.com>
7 *
8 * Based on i386 oprofile backtrace code by John Levon, David Smith
9 *
10 * This program is free software; you can redistribute it and/or modify
11 * it under the terms of the GNU General Public License version 2 as
12 * published by the Free Software Foundation.
13 *
14 */
15
16 #include <linux/oprofile.h>
17 #include <linux/sched.h>
18 #include <linux/mm.h>
19 #include <linux/uaccess.h>
20 #include <asm/ptrace.h>
21 #include <asm/stacktrace.h>
22
23 static int report_trace(struct stackframe *frame, void *d)
24 {
25 unsigned int *depth = d;
26
27 if (*depth) {
28 oprofile_add_trace(frame->pc);
29 (*depth)--;
30 }
31
32 return *depth == 0;
33 }
34
35 /*
36 * The registers we're interested in are at the end of the variable
37 * length saved register structure. The fp points at the end of this
38 * structure so the address of this struct is:
39 * (struct frame_tail *)(xxx->fp)-1
40 */
41 struct frame_tail {
42 struct frame_tail *fp;
43 unsigned long sp;
44 unsigned long lr;
45 } __attribute__((packed));
46
47 static struct frame_tail* user_backtrace(struct frame_tail *tail)
48 {
49 struct frame_tail buftail[2];
50
51 /* Also check accessibility of one struct frame_tail beyond */
52 if (!access_ok(VERIFY_READ, tail, sizeof(buftail)))
53 return NULL;
54 if (__copy_from_user_inatomic(buftail, tail, sizeof(buftail)))
55 return NULL;
56
57 oprofile_add_trace(buftail[0].lr);
58
59 /* frame pointers should strictly progress back up the stack
60 * (towards higher addresses) */
61 if (tail >= buftail[0].fp)
62 return NULL;
63
64 return buftail[0].fp-1;
65 }
66
67 void arm_backtrace(struct pt_regs * const regs, unsigned int depth)
68 {
69 struct frame_tail *tail = ((struct frame_tail *) regs->ARM_fp) - 1;
70
71 if (!user_mode(regs)) {
72 struct stackframe frame;
73 frame.fp = regs->ARM_fp;
74 frame.sp = regs->ARM_sp;
75 frame.lr = regs->ARM_lr;
76 frame.pc = regs->ARM_pc;
77 walk_stackframe(&frame, report_trace, &depth);
78 return;
79 }
80
81 while (depth-- && tail && !((unsigned long) tail & 3))
82 tail = user_backtrace(tail);
83 }
84
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