1/* SPDX-License-Identifier: GPL-2.0-only */ 2/* 3 * linux/arch/arm/lib/backtrace.S 4 * 5 * Copyright (C) 1995, 1996 Russell King 6 * 7 * 27/03/03 Ian Molton Clean up CONFIG_CPU 8 */ 9#include <linux/kern_levels.h> 10#include <linux/linkage.h> 11#include <asm/assembler.h> 12 .text 13 14@ fp is 0 or stack frame 15 16#define frame r4 17#define sv_fp r5 18#define sv_pc r6 19#define mask r7 20#define offset r8 21#define loglvl r9 22 23ENTRY(c_backtrace) 24 25#if !defined(CONFIG_FRAME_POINTER) || !defined(CONFIG_PRINTK) 26 ret lr 27ENDPROC(c_backtrace) 28#else 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 32 mov loglvl, r2 33 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 39 401: stmfd sp!, {pc} @ calculate offset of PC stored 41 ldr r0, [sp], #4 @ by stmfd for this CPU 42 adr r1, 1b 43 sub offset, r0, r1 44 45/* 46 * Stack frame layout: 47 * optionally saved caller registers (r4 - r10) 48 * saved fp 49 * saved sp 50 * saved lr 51 * frame => saved pc 52 * optionally saved arguments (r0 - r3) 53 * saved sp => <next word> 54 * 55 * Functions start with the following code sequence: 56 * mov ip, sp 57 * stmfd sp!, {r0 - r3} (optional) 58 * corrected pc => stmfd sp!, {..., fp, ip, lr, pc} 59 */ 60for_each_frame: tst frame, mask @ Check for address exceptions 61 bne no_frame 62 631001: ldr sv_pc, [frame, #0] @ get saved pc 641002: ldr sv_fp, [frame, #-12] @ get saved fp 65 66 sub sv_pc, sv_pc, offset @ Correct PC for prefetching 67 bic sv_pc, sv_pc, mask @ mask PC/LR for the mode 68 691003: 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 74 75 ldr r1, [frame, #-4] @ get saved lr 76 mov r2, frame 77 bic r1, r1, mask @ mask PC/LR for the mode 78 mov r3, loglvl 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 mov r2, loglvl 87 bleq dump_backtrace_stm @ 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 #11 92 subeq r0, frame, #16 93 mov r2, loglvl 94 bleq dump_backtrace_stm @ dump saved registers 95 96 teq sv_fp, #0 @ zero saved fp means 97 beq no_frame @ no further frames 98 99 cmp sv_fp, frame @ next frame must be 100 mov frame, sv_fp @ above the current frame 101 bhi for_each_frame 102 1031006: adr r0, .Lbad 104 mov r1, loglvl 105 mov r2, frame 106 bl printk 107no_frame: ldmfd sp!, {r4 - r9, pc} 108ENDPROC(c_backtrace) 109 110 .pushsection __ex_table,"a" 111 .align 3 112 .long 1001b, 1006b 113 .long 1002b, 1006b 114 .long 1003b, 1006b 115 .long 1004b, 1006b 116 .popsection 117 118.Lbad: .asciz "%sBacktrace aborted due to bad frame pointer <%p>\n" 119 .align 120.Ldsi: .word 0xe92dd800 >> 11 @ stmfd sp!, {... fp, ip, lr, pc} 121 .word 0xe92d0000 >> 11 @ stmfd sp!, {} 122 123#endif 124