1 /*
2 * OpenRISC unwinder.c
3 *
4 * Reusable arch specific api for unwinding stacks.
5 *
6 * Copyright (C) 2017 Stafford Horne <shorne@gmail.com>
7 *
8 * This file is licensed under the terms of the GNU General Public License
9 * version 2. This program is licensed "as is" without any warranty of any
10 * kind, whether express or implied.
11 */
12
13 #include <linux/sched/task_stack.h>
14 #include <linux/kernel.h>
15
16 #include <asm/unwinder.h>
17
18 #ifdef CONFIG_FRAME_POINTER
19 struct or1k_frameinfo {
20 unsigned long *fp;
21 unsigned long ra;
22 unsigned long top;
23 };
24
25 /*
26 * Verify a frameinfo structure. The return address should be a valid text
27 * address. The frame pointer may be null if its the last frame, otherwise
28 * the frame pointer should point to a location in the stack after the the
29 * top of the next frame up.
30 */
31 static inline int or1k_frameinfo_valid(struct or1k_frameinfo *frameinfo)
32 {
33 return (frameinfo->fp == NULL ||
34 (!kstack_end(frameinfo->fp) &&
35 frameinfo->fp > &frameinfo->top)) &&
36 __kernel_text_address(frameinfo->ra);
37 }
38
39 /*
40 * Create a stack trace doing scanning which is frame pointer aware. We can
41 * get reliable stack traces by matching the previously found frame
42 * pointer with the top of the stack address every time we find a valid
43 * or1k_frameinfo.
44 *
45 * Ideally the stack parameter will be passed as FP, but it can not be
46 * guaranteed. Therefore we scan each address looking for the first sign
47 * of a return address.
48 *
49 * The OpenRISC stack frame looks something like the following. The
50 * location SP is held in r1 and location FP is held in r2 when frame pointers
51 * enabled.
52 *
53 * SP -> (top of stack)
54 * - (callee saved registers)
55 * - (local variables)
56 * FP-8 -> previous FP \
57 * FP-4 -> return address |- or1k_frameinfo
58 * FP -> (previous top of stack) /
59 */
60 void unwind_stack(void *data, unsigned long *stack,
61 void (*trace)(void *data, unsigned long addr, int reliable))
62 {
63 unsigned long *next_fp = NULL;
64 struct or1k_frameinfo *frameinfo = NULL;
65 int reliable = 0;
66
67 while (!kstack_end(stack)) {
68 frameinfo = container_of(stack,
69 struct or1k_frameinfo,
70 top);
71
72 if (__kernel_text_address(frameinfo->ra)) {
73 if (or1k_frameinfo_valid(frameinfo) &&
74 (next_fp == NULL ||
75 next_fp == &frameinfo->top)) {
76 reliable = 1;
77 next_fp = frameinfo->fp;
78 } else
79 reliable = 0;
80
81 trace(data, frameinfo->ra, reliable);
82 }
83 stack++;
84 }
85 }
86
87 #else /* CONFIG_FRAME_POINTER */
88
89 /*
90 * Create a stack trace by doing a simple scan treating all text addresses
91 * as return addresses.
92 */
93 void unwind_stack(void *data, unsigned long *stack,
94 void (*trace)(void *data, unsigned long addr, int reliable))
95 {
96 unsigned long addr;
97
98 while (!kstack_end(stack)) {
99 addr = *stack++;
100 if (__kernel_text_address(addr))
101 trace(data, addr, 0);
102 }
103 }
104 #endif /* CONFIG_FRAME_POINTER */
105