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/* 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
ENTRY(c_backtrace)
#if !defined(CONFIG_FRAME_POINTER) || !defined(CONFIG_PRINTK)
ret lr
ENDPROC(c_backtrace)
#else
stmfd sp!, {r4 - r8, 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
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
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
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
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
bhi for_each_frame
1006: adr r0, .Lbad
mov r1, frame
bl printk
no_frame: ldmfd sp!, {r4 - r8, 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 "Backtrace 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
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