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(__backtrace)
26		mov	r1, #0x10
27		mov	r0, fp
28
29ENTRY(c_backtrace)
30
31#if !defined(CONFIG_FRAME_POINTER) || !defined(CONFIG_PRINTK)
32		mov	pc, lr
33#else
34		stmfd	sp!, {r4 - r8, lr}	@ Save an extra register so we have a location...
35		movs	frame, r0		@ if frame pointer is zero
36		beq	no_frame		@ we have no stack frames
37
38		tst	r1, #0x10		@ 26 or 32-bit mode?
39		moveq	mask, #0xfc000003	@ mask for 26-bit
40		movne	mask, #0		@ mask for 32-bit
41
421:		stmfd	sp!, {pc}		@ calculate offset of PC stored
43		ldr	r0, [sp], #4		@ by stmfd for this CPU
44		adr	r1, 1b
45		sub	offset, r0, r1
46
47/*
48 * Stack frame layout:
49 *             optionally saved caller registers (r4 - r10)
50 *             saved fp
51 *             saved sp
52 *             saved lr
53 *    frame => saved pc
54 *             optionally saved arguments (r0 - r3)
55 * saved sp => <next word>
56 *
57 * Functions start with the following code sequence:
58 *                  mov   ip, sp
59 *                  stmfd sp!, {r0 - r3} (optional)
60 * corrected pc =>  stmfd sp!, {..., fp, ip, lr, pc}
61 */
62for_each_frame:	tst	frame, mask		@ Check for address exceptions
63		bne	no_frame
64
651001:		ldr	sv_pc, [frame, #0]	@ get saved pc
661002:		ldr	sv_fp, [frame, #-12]	@ get saved fp
67
68		sub	sv_pc, sv_pc, offset	@ Correct PC for prefetching
69		bic	sv_pc, sv_pc, mask	@ mask PC/LR for the mode
70
711003:		ldr	r2, [sv_pc, #-4]	@ if stmfd sp!, {args} exists,
72		ldr	r3, .Ldsi+4		@ adjust saved 'pc' back one
73		teq	r3, r2, lsr #10		@ instruction
74		subne	r0, sv_pc, #4		@ allow for mov
75		subeq	r0, sv_pc, #8		@ allow for mov + stmia
76
77		ldr	r1, [frame, #-4]	@ get saved lr
78		mov	r2, frame
79		bic	r1, r1, mask		@ mask PC/LR for the mode
80		bl	dump_backtrace_entry
81
82		ldr	r1, [sv_pc, #-4]	@ if stmfd sp!, {args} exists,
83		ldr	r3, .Ldsi+4
84		teq	r3, r1, lsr #10
85		ldreq	r0, [frame, #-8]	@ get sp
86		subeq	r0, r0, #4		@ point at the last arg
87		bleq	.Ldumpstm		@ dump saved registers
88
891004:		ldr	r1, [sv_pc, #0]		@ if stmfd sp!, {..., fp, ip, lr, pc}
90		ldr	r3, .Ldsi		@ instruction exists,
91		teq	r3, r1, lsr #10
92		subeq	r0, frame, #16
93		bleq	.Ldumpstm		@ dump saved registers
94
95		teq	sv_fp, #0		@ zero saved fp means
96		beq	no_frame		@ no further frames
97
98		cmp	sv_fp, frame		@ next frame must be
99		mov	frame, sv_fp		@ above the current frame
100		bhi	for_each_frame
101
1021006:		adr	r0, .Lbad
103		mov	r1, frame
104		bl	printk
105no_frame:	ldmfd	sp!, {r4 - r8, pc}
106
107		.section __ex_table,"a"
108		.align	3
109		.long	1001b, 1006b
110		.long	1002b, 1006b
111		.long	1003b, 1006b
112		.long	1004b, 1006b
113		.previous
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		tst	instr, r3, lsl reg
126		beq	2f
127		add	r7, r7, #1
128		teq	r7, #6
129		moveq	r7, #1
130		moveq	r1, #'\n'
131		movne	r1, #' '
132		ldr	r3, [stack], #-4
133		mov	r2, reg
134		adr	r0, .Lfp
135		bl	printk
1362:		subs	reg, reg, #1
137		bpl	1b
138		teq	r7, #0
139		adrne	r0, .Lcr
140		blne	printk
141		ldmfd	sp!, {instr, reg, stack, r7, pc}
142
143.Lfp:		.asciz	"%cr%d:%08x"
144.Lcr:		.asciz	"\n"
145.Lbad:		.asciz	"Backtrace aborted due to bad frame pointer <%p>\n"
146		.align
147.Ldsi:		.word	0xe92dd800 >> 10	@ stmfd sp!, {... fp, ip, lr, pc}
148		.word	0xe92d0000 >> 10	@ stmfd sp!, {}
149
150#endif
151