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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 | /* SPDX-License-Identifier: GPL-2.0-only */ /* * linux/arch/arm/lib/backtrace.S * * Copyright (C) 1995, 1996 Russell King * * 27/03/03 Ian Molton Clean up CONFIG_CPU */ #include <linux/kern_levels.h> #include <linux/linkage.h> #include <asm/assembler.h> .text @ fp is 0 or stack frame #define frame r4 #define sv_fp r5 #define sv_pc r6 #define mask r7 #define offset r8 ENTRY(c_backtrace) #if !defined(CONFIG_FRAME_POINTER) || !defined(CONFIG_PRINTK) ret lr ENDPROC(c_backtrace) #else stmfd sp!, {r4 - r8, lr} @ Save an extra register so we have a location... movs frame, r0 @ if frame pointer is zero beq no_frame @ we have no stack frames tst r1, #0x10 @ 26 or 32-bit mode? ARM( moveq mask, #0xfc000003 ) THUMB( moveq mask, #0xfc000000 ) THUMB( orreq mask, #0x03 ) movne mask, #0 @ mask for 32-bit 1: stmfd sp!, {pc} @ calculate offset of PC stored ldr r0, [sp], #4 @ by stmfd for this CPU adr r1, 1b sub offset, r0, r1 /* * Stack frame layout: * optionally saved caller registers (r4 - r10) * saved fp * saved sp * saved lr * frame => saved pc * optionally saved arguments (r0 - r3) * saved sp => <next word> * * Functions start with the following code sequence: * mov ip, sp * stmfd sp!, {r0 - r3} (optional) * corrected pc => stmfd sp!, {..., fp, ip, lr, pc} */ for_each_frame: tst frame, mask @ Check for address exceptions bne no_frame 1001: ldr sv_pc, [frame, #0] @ get saved pc 1002: ldr sv_fp, [frame, #-12] @ get saved fp sub sv_pc, sv_pc, offset @ Correct PC for prefetching bic sv_pc, sv_pc, mask @ mask PC/LR for the mode 1003: ldr r2, [sv_pc, #-4] @ if stmfd sp!, {args} exists, ldr r3, .Ldsi+4 @ adjust saved 'pc' back one teq r3, r2, lsr #10 @ instruction subne r0, sv_pc, #4 @ allow for mov subeq r0, sv_pc, #8 @ allow for mov + stmia ldr r1, [frame, #-4] @ get saved lr mov r2, frame bic r1, r1, mask @ mask PC/LR for the mode bl dump_backtrace_entry ldr r1, [sv_pc, #-4] @ if stmfd sp!, {args} exists, ldr r3, .Ldsi+4 teq r3, r1, lsr #11 ldreq r0, [frame, #-8] @ get sp subeq r0, r0, #4 @ point at the last arg bleq dump_backtrace_stm @ dump saved registers 1004: ldr r1, [sv_pc, #0] @ if stmfd sp!, {..., fp, ip, lr, pc} ldr r3, .Ldsi @ instruction exists, teq r3, r1, lsr #11 subeq r0, frame, #16 bleq dump_backtrace_stm @ dump saved registers teq sv_fp, #0 @ zero saved fp means beq no_frame @ no further frames cmp sv_fp, frame @ next frame must be mov frame, sv_fp @ above the current frame bhi for_each_frame 1006: adr r0, .Lbad mov r1, frame bl printk no_frame: ldmfd sp!, {r4 - r8, pc} ENDPROC(c_backtrace) .pushsection __ex_table,"a" .align 3 .long 1001b, 1006b .long 1002b, 1006b .long 1003b, 1006b .long 1004b, 1006b .popsection .Lbad: .asciz "Backtrace aborted due to bad frame pointer <%p>\n" .align .Ldsi: .word 0xe92dd800 >> 11 @ stmfd sp!, {... fp, ip, lr, pc} .word 0xe92d0000 >> 11 @ stmfd sp!, {} #endif |