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 */
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
20#define sv_fp	r5
21#define sv_pc	r6
22#define mask	r7
23#define offset	r8
24
25ENTRY(c_backtrace)
26
27#if !defined(CONFIG_FRAME_POINTER) || !defined(CONFIG_PRINTK)
28		ret	lr
29ENDPROC(c_backtrace)
30#else
31		stmfd	sp!, {r4 - r8, lr}	@ Save an extra register so we have a location...
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?
36 ARM(		moveq	mask, #0xfc000003	)
37 THUMB(		moveq	mask, #0xfc000000	)
38 THUMB(		orreq	mask, #0x03		)
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
44		sub	offset, r0, r1
45
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
66
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
79		bl	dump_backtrace_entry
80
81		ldr	r1, [sv_pc, #-4]	@ if stmfd sp!, {args} exists,
82		ldr	r3, .Ldsi+4
83		teq	r3, r1, lsr #11
84		ldreq	r0, [frame, #-8]	@ get sp
85		subeq	r0, r0, #4		@ point at the last arg
86		bleq	.Ldumpstm		@ dump saved registers
87
881004:		ldr	r1, [sv_pc, #0]		@ if stmfd sp!, {..., fp, ip, lr, pc}
89		ldr	r3, .Ldsi		@ instruction exists,
90		teq	r3, r1, lsr #11
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
102		mov	r1, frame
103		bl	printk
104no_frame:	ldmfd	sp!, {r4 - r8, pc}
105ENDPROC(c_backtrace)
106
107		.pushsection __ex_table,"a"
108		.align	3
109		.long	1001b, 1006b
110		.long	1002b, 1006b
111		.long	1003b, 1006b
112		.long	1004b, 1006b
113		.popsection
114
115#define instr r4
116#define reg   r5
117#define stack r6
118
119.Ldumpstm:	stmfd	sp!, {instr, reg, stack, r7, lr}
120		mov	stack, r0
121		mov	instr, r1
122		mov	reg, #10
123		mov	r7, #0
1241:		mov	r3, #1
125 ARM(		tst	instr, r3, lsl reg	)
126 THUMB(		lsl	r3, reg			)
127 THUMB(		tst	instr, r3		)
128		beq	2f
129		add	r7, r7, #1
130		teq	r7, #6
131		moveq	r7, #0
132		adr	r3, .Lcr
133		addne	r3, r3, #1		@ skip newline
134		ldr	r2, [stack], #-4
135		mov	r1, reg
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
143		ldmfd	sp!, {instr, reg, stack, r7, pc}
144
145.Lfp:		.asciz	" r%d:%08x%s"
146.Lcr:		.asciz	"\n"
147.Lbad:		.asciz	"Backtrace aborted due to bad frame pointer <%p>\n"
148		.align
149.Ldsi:		.word	0xe92dd800 >> 11	@ stmfd sp!, {... fp, ip, lr, pc}
150		.word	0xe92d0000 >> 11	@ stmfd sp!, {}
151
152#endif
153