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/kern_levels.h> 14#include <linux/linkage.h> 15#include <asm/assembler.h> 16 .text 17 18@ fp is 0 or stack frame 19 20#define frame r4 21#define sv_fp r5 22#define sv_pc r6 23#define mask r7 24#define offset r8 25 26ENTRY(c_backtrace) 27 28#if !defined(CONFIG_FRAME_POINTER) || !defined(CONFIG_PRINTK) 29 ret lr 30ENDPROC(c_backtrace) 31#else 32 stmfd sp!, {r4 - r8, lr} @ Save an extra register so we have a location... 33 movs frame, r0 @ if frame pointer is zero 34 beq no_frame @ we have no stack frames 35 36 tst r1, #0x10 @ 26 or 32-bit mode? 37 ARM( moveq mask, #0xfc000003 ) 38 THUMB( moveq mask, #0xfc000000 ) 39 THUMB( orreq mask, #0x03 ) 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 #11 85 ldreq r0, [frame, #-8] @ get sp 86 subeq r0, r0, #4 @ point at the last arg 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 bleq dump_backtrace_stm @ 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} 106ENDPROC(c_backtrace) 107 108 .pushsection __ex_table,"a" 109 .align 3 110 .long 1001b, 1006b 111 .long 1002b, 1006b 112 .long 1003b, 1006b 113 .long 1004b, 1006b 114 .popsection 115 116.Lbad: .asciz "Backtrace aborted due to bad frame pointer <%p>\n" 117 .align 118.Ldsi: .word 0xe92dd800 >> 11 @ stmfd sp!, {... fp, ip, lr, pc} 119 .word 0xe92d0000 >> 11 @ stmfd sp!, {} 120 121#endif 122