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 23 ENTRY(c_backtrace) 24 25 #if !defined(CONFIG_FRAME_POINTER) || !defined(CONFIG_PRINTK) 26 ret lr 27 ENDPROC(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 40 1: 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 */ 60 for_each_frame: tst frame, mask @ Check for address exceptions 61 bne no_frame 62 63 1001: ldr sv_pc, [frame, #0] @ get saved pc 64 1002: 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 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 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 89 1004: 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 #ifdef CONFIG_IRQSTACKS 102 @ 103 @ Kernel stacks may be discontiguous in memory. If the next 104 @ frame is below the previous frame, accept it as long as it 105 @ lives in kernel memory. 106 @ 107 cmpls sv_fp, #PAGE_OFFSET 108 #endif 109 bhi for_each_frame 110 111 1006: adr r0, .Lbad 112 mov r1, loglvl 113 mov r2, frame 114 bl _printk 115 no_frame: ldmfd sp!, {r4 - r9, pc} 116 ENDPROC(c_backtrace) 117 118 .pushsection __ex_table,"a" 119 .align 3 120 .long 1001b, 1006b 121 .long 1002b, 1006b 122 .long 1003b, 1006b 123 .long 1004b, 1006b 124 .popsection 125 126 .Lbad: .asciz "%sBacktrace aborted due to bad frame pointer <%p>\n" 127 .align 128 .Ldsi: .word 0xe92dd800 >> 11 @ stmfd sp!, {... fp, ip, lr, pc} 129 .word 0xe92d0000 >> 11 @ stmfd sp!, {} 130 131 #endif 132