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 22ENTRY(c_backtrace) 23 24#if !defined(CONFIG_FRAME_POINTER) || !defined(CONFIG_PRINTK) 25 ret lr 26ENDPROC(c_backtrace) 27#else 28 stmfd sp!, {r4 - r8, lr} @ Save an extra register so we have a location... 29 movs frame, r0 @ if frame pointer is zero 30 beq no_frame @ we have no stack frames 31 32 tst r1, #0x10 @ 26 or 32-bit mode? 33 ARM( moveq mask, #0xfc000003 ) 34 THUMB( moveq mask, #0xfc000000 ) 35 THUMB( orreq mask, #0x03 ) 36 movne mask, #0 @ mask for 32-bit 37 381: stmfd sp!, {pc} @ calculate offset of PC stored 39 ldr r0, [sp], #4 @ by stmfd for this CPU 40 adr r1, 1b 41 sub offset, r0, r1 42 43/* 44 * Stack frame layout: 45 * optionally saved caller registers (r4 - r10) 46 * saved fp 47 * saved sp 48 * saved lr 49 * frame => saved pc 50 * optionally saved arguments (r0 - r3) 51 * saved sp => <next word> 52 * 53 * Functions start with the following code sequence: 54 * mov ip, sp 55 * stmfd sp!, {r0 - r3} (optional) 56 * corrected pc => stmfd sp!, {..., fp, ip, lr, pc} 57 */ 58for_each_frame: tst frame, mask @ Check for address exceptions 59 bne no_frame 60 611001: ldr sv_pc, [frame, #0] @ get saved pc 621002: ldr sv_fp, [frame, #-12] @ get saved fp 63 64 sub sv_pc, sv_pc, offset @ Correct PC for prefetching 65 bic sv_pc, sv_pc, mask @ mask PC/LR for the mode 66 671003: ldr r2, [sv_pc, #-4] @ if stmfd sp!, {args} exists, 68 ldr r3, .Ldsi+4 @ adjust saved 'pc' back one 69 teq r3, r2, lsr #11 @ instruction 70 subne r0, sv_pc, #4 @ allow for mov 71 subeq r0, sv_pc, #8 @ allow for mov + stmia 72 73 ldr r1, [frame, #-4] @ get saved lr 74 mov r2, frame 75 bic r1, r1, mask @ mask PC/LR for the mode 76 bl dump_backtrace_entry 77 78 ldr r1, [sv_pc, #-4] @ if stmfd sp!, {args} exists, 79 ldr r3, .Ldsi+4 80 teq r3, r1, lsr #11 81 ldreq r0, [frame, #-8] @ get sp 82 subeq r0, r0, #4 @ point at the last arg 83 bleq dump_backtrace_stm @ dump saved registers 84 851004: ldr r1, [sv_pc, #0] @ if stmfd sp!, {..., fp, ip, lr, pc} 86 ldr r3, .Ldsi @ instruction exists, 87 teq r3, r1, lsr #11 88 subeq r0, frame, #16 89 bleq dump_backtrace_stm @ dump saved registers 90 91 teq sv_fp, #0 @ zero saved fp means 92 beq no_frame @ no further frames 93 94 cmp sv_fp, frame @ next frame must be 95 mov frame, sv_fp @ above the current frame 96 bhi for_each_frame 97 981006: adr r0, .Lbad 99 mov r1, frame 100 bl printk 101no_frame: ldmfd sp!, {r4 - r8, pc} 102ENDPROC(c_backtrace) 103 104 .pushsection __ex_table,"a" 105 .align 3 106 .long 1001b, 1006b 107 .long 1002b, 1006b 108 .long 1003b, 1006b 109 .long 1004b, 1006b 110 .popsection 111 112.Lbad: .asciz "Backtrace aborted due to bad frame pointer <%p>\n" 113 .align 114.Ldsi: .word 0xe92dd800 >> 11 @ stmfd sp!, {... fp, ip, lr, pc} 115 .word 0xe92d0000 >> 11 @ stmfd sp!, {} 116 117#endif 118