1 /* SPDX-License-Identifier: GPL-2.0-only */
3 * linux/arch/arm/lib/backtrace.S
5 * Copyright (C) 1995, 1996 Russell King
7 * 27/03/03 Ian Molton Clean up CONFIG_CPU
9 #include <linux/kern_levels.h>
10 #include <linux/linkage.h>
11 #include <asm/assembler.h>
14 @ fp is 0 or stack frame
25 #if !defined(CONFIG_FRAME_POINTER) || !defined(CONFIG_PRINTK)
29 stmfd sp!, {r4 - r9, lr} @ Save an extra register so we have a location...
30 movs frame, r0 @ if frame pointer is zero
31 beq no_frame @ we have no stack frames
34 tst r1, #0x10 @ 26 or 32-bit mode?
35 ARM( moveq mask, #0xfc000003 )
36 THUMB( moveq mask, #0xfc000000 )
37 THUMB( orreq mask, #0x03 )
38 movne mask, #0 @ mask for 32-bit
40 1: stmfd sp!, {pc} @ calculate offset of PC stored
41 ldr r0, [sp], #4 @ by stmfd for this CPU
47 * optionally saved caller registers (r4 - r10)
52 * optionally saved arguments (r0 - r3)
53 * saved sp => <next word>
55 * Functions start with the following code sequence:
57 * stmfd sp!, {r0 - r3} (optional)
58 * corrected pc => stmfd sp!, {..., fp, ip, lr, pc}
60 for_each_frame: tst frame, mask @ Check for address exceptions
63 1001: ldr sv_pc, [frame, #0] @ get saved pc
64 1002: ldr sv_fp, [frame, #-12] @ get saved fp
66 sub sv_pc, sv_pc, offset @ Correct PC for prefetching
67 bic sv_pc, sv_pc, mask @ mask PC/LR for the mode
69 1003: ldr r2, [sv_pc, #-4] @ if stmfd sp!, {args} exists,
70 ldr r3, .Ldsi+4 @ adjust saved 'pc' back one
71 teq r3, r2, lsr #11 @ instruction
72 subne r0, sv_pc, #4 @ allow for mov
73 subeq r0, sv_pc, #8 @ allow for mov + stmia
75 ldr r1, [frame, #-4] @ get saved lr
77 bic r1, r1, mask @ mask PC/LR for the mode
79 bl dump_backtrace_entry
81 ldr r1, [sv_pc, #-4] @ if stmfd sp!, {args} exists,
84 ldreq r0, [frame, #-8] @ get sp
85 subeq r0, r0, #4 @ point at the last arg
87 bleq dump_backtrace_stm @ dump saved registers
89 1004: ldr r1, [sv_pc, #0] @ if stmfd sp!, {..., fp, ip, lr, pc}
90 ldr r3, .Ldsi @ instruction exists,
94 bleq dump_backtrace_stm @ dump saved registers
96 teq sv_fp, #0 @ zero saved fp means
97 beq no_frame @ no further frames
99 cmp sv_fp, frame @ next frame must be
100 mov frame, sv_fp @ above the current frame
107 no_frame: ldmfd sp!, {r4 - r9, pc}
110 .pushsection __ex_table,"a"
118 .Lbad: .asciz "%sBacktrace aborted due to bad frame pointer <%p>\n"
120 .Ldsi: .word 0xe92dd800 >> 11 @ stmfd sp!, {... fp, ip, lr, pc}
121 .word 0xe92d0000 >> 11 @ stmfd sp!, {}