1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3 * linux/arch/arm/lib/backtrace.S
4 *
5 * Copyright (C) 1995, 1996 Russell King
6 *
7 * 27/03/03 Ian Molton Clean up CONFIG_CPU
8 */
9 #include <linux/kern_levels.h>
10 #include <linux/linkage.h>
11 #include <asm/assembler.h>
12 .text
13
14 @ fp is 0 or stack frame
15
16 #define frame r4
17 #define sv_fp r5
18 #define sv_pc r6
19 #define mask r7
20 #define offset r8
21 #define loglvl r9
22
23 ENTRY(c_backtrace)
24
25 #if !defined(CONFIG_FRAME_POINTER) || !defined
26 ret lr
27 ENDPROC(c_backtrace)
28 #else
29 stmfd sp!, {r4 - r9, lr}
30 movs frame, r0
31 beq no_frame
32 mov loglvl, r2
33
34 tst r1, #0x10
35 ARM( moveq mask, #0xfc000003
36 THUMB( moveq mask, #0xfc000000
37 THUMB( orreq mask, #0x03
38 movne mask, #0
39
40 1: stmfd sp!, {pc}
41 ldr r0, [sp], #4
42 adr r1, 1b
43 sub offset, r0, r1
44
45 /*
46 * Stack frame layout:
47 * optionally saved caller registe
48 * saved fp
49 * saved sp
50 * saved lr
51 * frame => saved pc
52 * optionally saved arguments (r0
53 * saved sp => <next word>
54 *
55 * Functions start with the following code seq
56 * mov ip, sp
57 * stmfd sp!, {r0 - r3} (opti
58 * corrected pc => stmfd sp!, {..., fp, ip, l
59 */
60 for_each_frame: tst frame, mask
61 bne no_frame
62
63 1001: ldr sv_pc, [frame, #0]
64 1002: ldr sv_fp, [frame, #-12]
65
66 sub sv_pc, sv_pc, offset
67 bic sv_pc, sv_pc, mask
68
69 1003: ldr r2, [sv_pc, #-4]
70 ldr r3, .Ldsi+4
71 teq r3, r2, lsr #11
72 subne r0, sv_pc, #4
73 subeq r0, sv_pc, #8
74
75 ldr r1, [frame, #-4]
76 mov r2, frame
77 bic r1, r1, mask
78 mov r3, loglvl
79 bl dump_backtrace_entry
80
81 ldr r1, [sv_pc, #-4]
82 ldr r3, .Ldsi+4
83 teq r3, r1, lsr #11
84 ldreq r0, [frame, #-8]
85 subeq r0, r0, #4
86 mov r2, loglvl
87 bleq dump_backtrace_stm
88
89 1004: ldr r1, [sv_pc, #0]
90 ldr r3, .Ldsi
91 teq r3, r1, lsr #11
92 subeq r0, frame, #16
93 mov r2, loglvl
94 bleq dump_backtrace_stm
95
96 teq sv_fp, #0
97 beq no_frame
98
99 cmp sv_fp, frame
100 mov frame, sv_fp
101 #ifdef CONFIG_IRQSTACKS
102 @
103 @ Kernel stacks may be discont
104 @ frame is below the previous
105 @ lives in kernel memory.
106 @
107 cmpls sv_fp, #PAGE_OFFSET
108 #endif
109 bhi for_each_frame
110
111 1006: adr r0, .Lbad
112 mov r1, loglvl
113 mov r2, frame
114 bl _printk
115 no_frame: ldmfd sp!, {r4 - r9, pc}
116 ENDPROC(c_backtrace)
117
118 .pushsection __ex_table,"a"
119 .align 3
120 .long 1001b, 1006b
121 .long 1002b, 1006b
122 .long 1003b, 1006b
123 .long 1004b, 1006b
124 .popsection
125
126 .Lbad: .asciz "%sBacktrace aborted d
127 .align
128 .Ldsi: .word 0xe92dd800 >> 11
129 .word 0xe92d0000 >> 11
130
131 #endif
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