summaryrefslogtreecommitdiff
path: root/arch/arm/lib/backtrace.S
blob: 293a2716bd2047b8c2f57a3ea5863c5f31ac06f9 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
/* SPDX-License-Identifier: GPL-2.0-only */
/*
 *  linux/arch/arm/lib/backtrace.S
 *
 *  Copyright (C) 1995, 1996 Russell King
 *
 * 27/03/03 Ian Molton Clean up CONFIG_CPU
 */
#include <linux/kern_levels.h>
#include <linux/linkage.h>
#include <asm/assembler.h>
		.text

@ fp is 0 or stack frame

#define frame	r4
#define sv_fp	r5
#define sv_pc	r6
#define mask	r7
#define offset	r8
#define loglvl	r9

ENTRY(c_backtrace)

#if !defined(CONFIG_FRAME_POINTER) || !defined(CONFIG_PRINTK)
		ret	lr
ENDPROC(c_backtrace)
#else
		stmfd	sp!, {r4 - r9, lr}	@ Save an extra register so we have a location...
		movs	frame, r0		@ if frame pointer is zero
		beq	no_frame		@ we have no stack frames
		mov	loglvl, r2

		tst	r1, #0x10		@ 26 or 32-bit mode?
 ARM(		moveq	mask, #0xfc000003	)
 THUMB(		moveq	mask, #0xfc000000	)
 THUMB(		orreq	mask, #0x03		)
		movne	mask, #0		@ mask for 32-bit

1:		stmfd	sp!, {pc}		@ calculate offset of PC stored
		ldr	r0, [sp], #4		@ by stmfd for this CPU
		adr	r1, 1b
		sub	offset, r0, r1

/*
 * Stack frame layout:
 *             optionally saved caller registers (r4 - r10)
 *             saved fp
 *             saved sp
 *             saved lr
 *    frame => saved pc
 *             optionally saved arguments (r0 - r3)
 * saved sp => <next word>
 *
 * Functions start with the following code sequence:
 *                  mov   ip, sp
 *                  stmfd sp!, {r0 - r3} (optional)
 * corrected pc =>  stmfd sp!, {..., fp, ip, lr, pc}
 */
for_each_frame:	tst	frame, mask		@ Check for address exceptions
		bne	no_frame

1001:		ldr	sv_pc, [frame, #0]	@ get saved pc
1002:		ldr	sv_fp, [frame, #-12]	@ get saved fp

		sub	sv_pc, sv_pc, offset	@ Correct PC for prefetching
		bic	sv_pc, sv_pc, mask	@ mask PC/LR for the mode

1003:		ldr	r2, [sv_pc, #-4]	@ if stmfd sp!, {args} exists,
		ldr	r3, .Ldsi+4		@ adjust saved 'pc' back one
		teq	r3, r2, lsr #11		@ instruction
		subne	r0, sv_pc, #4		@ allow for mov
		subeq	r0, sv_pc, #8		@ allow for mov + stmia

		ldr	r1, [frame, #-4]	@ get saved lr
		mov	r2, frame
		bic	r1, r1, mask		@ mask PC/LR for the mode
		mov	r3, loglvl
		bl	dump_backtrace_entry

		ldr	r1, [sv_pc, #-4]	@ if stmfd sp!, {args} exists,
		ldr	r3, .Ldsi+4
		teq	r3, r1, lsr #11
		ldreq	r0, [frame, #-8]	@ get sp
		subeq	r0, r0, #4		@ point at the last arg
		mov	r2, loglvl
		bleq	dump_backtrace_stm	@ dump saved registers

1004:		ldr	r1, [sv_pc, #0]		@ if stmfd sp!, {..., fp, ip, lr, pc}
		ldr	r3, .Ldsi		@ instruction exists,
		teq	r3, r1, lsr #11
		subeq	r0, frame, #16
		mov	r2, loglvl
		bleq	dump_backtrace_stm	@ dump saved registers

		teq	sv_fp, #0		@ zero saved fp means
		beq	no_frame		@ no further frames

		cmp	sv_fp, frame		@ next frame must be
		mov	frame, sv_fp		@ above the current frame
#ifdef CONFIG_IRQSTACKS
		@
		@ Kernel stacks may be discontiguous in memory. If the next
		@ frame is below the previous frame, accept it as long as it
		@ lives in kernel memory.
		@
		cmpls	sv_fp, #PAGE_OFFSET
#endif
		bhi	for_each_frame

1006:		adr	r0, .Lbad
		mov	r1, loglvl
		mov	r2, frame
		bl	_printk
no_frame:	ldmfd	sp!, {r4 - r9, pc}
ENDPROC(c_backtrace)
		
		.pushsection __ex_table,"a"
		.align	3
		.long	1001b, 1006b
		.long	1002b, 1006b
		.long	1003b, 1006b
		.long	1004b, 1006b
		.popsection

.Lbad:		.asciz	"%sBacktrace aborted due to bad frame pointer <%p>\n"
		.align
.Ldsi:		.word	0xe92dd800 >> 11	@ stmfd sp!, {... fp, ip, lr, pc}
		.word	0xe92d0000 >> 11	@ stmfd sp!, {}

#endif