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1/*
2 * linux/arch/arm/lib/backtrace.S
3 *
4 * Copyright (C) 1995, 1996 Russell King
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 *
10 * 27/03/03 Ian Molton Clean up CONFIG_CPU
11 *
12 */
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13#include <linux/linkage.h>
14#include <asm/assembler.h>
15 .text
16
17@ fp is 0 or stack frame
18
19#define frame r4
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20#define sv_fp r5
21#define sv_pc r6
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22#define mask r7
23#define offset r8
24
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25ENTRY(c_backtrace)
26
3ee357f0 27#if !defined(CONFIG_FRAME_POINTER) || !defined(CONFIG_PRINTK)
6ebbf2ce 28 ret lr
93ed3970 29ENDPROC(c_backtrace)
1da177e4 30#else
1da177e4 31 stmfd sp!, {r4 - r8, lr} @ Save an extra register so we have a location...
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32 movs frame, r0 @ if frame pointer is zero
33 beq no_frame @ we have no stack frames
34
35 tst r1, #0x10 @ 26 or 32-bit mode?
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36 ARM( moveq mask, #0xfc000003 )
37 THUMB( moveq mask, #0xfc000000 )
38 THUMB( orreq mask, #0x03 )
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39 movne mask, #0 @ mask for 32-bit
40
411: stmfd sp!, {pc} @ calculate offset of PC stored
42 ldr r0, [sp], #4 @ by stmfd for this CPU
43 adr r1, 1b
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44 sub offset, r0, r1
45
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46/*
47 * Stack frame layout:
48 * optionally saved caller registers (r4 - r10)
49 * saved fp
50 * saved sp
51 * saved lr
52 * frame => saved pc
53 * optionally saved arguments (r0 - r3)
54 * saved sp => <next word>
55 *
56 * Functions start with the following code sequence:
57 * mov ip, sp
58 * stmfd sp!, {r0 - r3} (optional)
59 * corrected pc => stmfd sp!, {..., fp, ip, lr, pc}
60 */
61for_each_frame: tst frame, mask @ Check for address exceptions
62 bne no_frame
63
641001: ldr sv_pc, [frame, #0] @ get saved pc
651002: ldr sv_fp, [frame, #-12] @ get saved fp
1da177e4 66
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67 sub sv_pc, sv_pc, offset @ Correct PC for prefetching
68 bic sv_pc, sv_pc, mask @ mask PC/LR for the mode
69
701003: ldr r2, [sv_pc, #-4] @ if stmfd sp!, {args} exists,
71 ldr r3, .Ldsi+4 @ adjust saved 'pc' back one
72 teq r3, r2, lsr #10 @ instruction
73 subne r0, sv_pc, #4 @ allow for mov
74 subeq r0, sv_pc, #8 @ allow for mov + stmia
75
76 ldr r1, [frame, #-4] @ get saved lr
77 mov r2, frame
78 bic r1, r1, mask @ mask PC/LR for the mode
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79 bl dump_backtrace_entry
80
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81 ldr r1, [sv_pc, #-4] @ if stmfd sp!, {args} exists,
82 ldr r3, .Ldsi+4
ef41b5c9 83 teq r3, r1, lsr #11
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84 ldreq r0, [frame, #-8] @ get sp
85 subeq r0, r0, #4 @ point at the last arg
86 bleq .Ldumpstm @ dump saved registers
1da177e4 87
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881004: ldr r1, [sv_pc, #0] @ if stmfd sp!, {..., fp, ip, lr, pc}
89 ldr r3, .Ldsi @ instruction exists,
ef41b5c9 90 teq r3, r1, lsr #11
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91 subeq r0, frame, #16
92 bleq .Ldumpstm @ dump saved registers
93
94 teq sv_fp, #0 @ zero saved fp means
95 beq no_frame @ no further frames
96
97 cmp sv_fp, frame @ next frame must be
98 mov frame, sv_fp @ above the current frame
99 bhi for_each_frame
100
1011006: adr r0, .Lbad
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102 mov r1, frame
103 bl printk
7ab3f8d5 104no_frame: ldmfd sp!, {r4 - r8, pc}
93ed3970 105ENDPROC(c_backtrace)
1da177e4 106
4260415f 107 .pushsection __ex_table,"a"
1da177e4 108 .align 3
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109 .long 1001b, 1006b
110 .long 1002b, 1006b
111 .long 1003b, 1006b
112 .long 1004b, 1006b
4260415f 113 .popsection
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114
115#define instr r4
116#define reg r5
117#define stack r6
118
7ab3f8d5 119.Ldumpstm: stmfd sp!, {instr, reg, stack, r7, lr}
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120 mov stack, r0
121 mov instr, r1
7ab3f8d5 122 mov reg, #10
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123 mov r7, #0
1241: mov r3, #1
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125 ARM( tst instr, r3, lsl reg )
126 THUMB( lsl r3, reg )
127 THUMB( tst instr, r3 )
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128 beq 2f
129 add r7, r7, #1
7ab3f8d5 130 teq r7, #6
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131 moveq r7, #0
132 adr r3, .Lcr
133 addne r3, r3, #1 @ skip newline
134 ldr r2, [stack], #-4
135 mov r1, reg
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136 adr r0, .Lfp
137 bl printk
1382: subs reg, reg, #1
139 bpl 1b
140 teq r7, #0
141 adrne r0, .Lcr
142 blne printk
7ab3f8d5 143 ldmfd sp!, {instr, reg, stack, r7, pc}
1da177e4 144
ef41b5c9 145.Lfp: .asciz " r%d:%08x%s"
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146.Lcr: .asciz "\n"
147.Lbad: .asciz "Backtrace aborted due to bad frame pointer <%p>\n"
148 .align
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149.Ldsi: .word 0xe92dd800 >> 11 @ stmfd sp!, {... fp, ip, lr, pc}
150 .word 0xe92d0000 >> 11 @ stmfd sp!, {}
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151
152#endif