/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* linux/arch/arm/lib/backtrace.S
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*
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* Copyright (C) 1995, 1996 Russell King
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*
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* 27/03/03 Ian Molton Clean up CONFIG_CPU
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*/
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#include <linux/kern_levels.h>
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#include <linux/linkage.h>
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#include <asm/assembler.h>
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.text
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@ fp is 0 or stack frame
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#define frame r4
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#define sv_fp r5
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#define sv_pc r6
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#define mask r7
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#define offset r8
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#define loglvl r9
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ENTRY(c_backtrace)
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#if !defined(CONFIG_FRAME_POINTER) || !defined(CONFIG_PRINTK)
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ret lr
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ENDPROC(c_backtrace)
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#else
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stmfd sp!, {r4 - r9, lr} @ Save an extra register so we have a location...
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movs frame, r0 @ if frame pointer is zero
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beq no_frame @ we have no stack frames
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mov loglvl, r2
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tst r1, #0x10 @ 26 or 32-bit mode?
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ARM( moveq mask, #0xfc000003 )
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THUMB( moveq mask, #0xfc000000 )
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THUMB( orreq mask, #0x03 )
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movne mask, #0 @ mask for 32-bit
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1: stmfd sp!, {pc} @ calculate offset of PC stored
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ldr r0, [sp], #4 @ by stmfd for this CPU
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adr r1, 1b
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sub offset, r0, r1
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/*
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* Stack frame layout:
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* optionally saved caller registers (r4 - r10)
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* saved fp
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* saved sp
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* saved lr
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* frame => saved pc
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* optionally saved arguments (r0 - r3)
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* saved sp => <next word>
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*
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* Functions start with the following code sequence:
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* mov ip, sp
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* stmfd sp!, {r0 - r3} (optional)
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* corrected pc => stmfd sp!, {..., fp, ip, lr, pc}
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*/
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for_each_frame: tst frame, mask @ Check for address exceptions
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bne no_frame
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1001: ldr sv_pc, [frame, #0] @ get saved pc
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1002: ldr sv_fp, [frame, #-12] @ get saved fp
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sub sv_pc, sv_pc, offset @ Correct PC for prefetching
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bic sv_pc, sv_pc, mask @ mask PC/LR for the mode
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1003: ldr r2, [sv_pc, #-4] @ if stmfd sp!, {args} exists,
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ldr r3, .Ldsi+4 @ adjust saved 'pc' back one
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teq r3, r2, lsr #11 @ instruction
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subne r0, sv_pc, #4 @ allow for mov
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subeq r0, sv_pc, #8 @ allow for mov + stmia
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ldr r1, [frame, #-4] @ get saved lr
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mov r2, frame
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bic r1, r1, mask @ mask PC/LR for the mode
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mov r3, loglvl
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bl dump_backtrace_entry
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ldr r1, [sv_pc, #-4] @ if stmfd sp!, {args} exists,
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ldr r3, .Ldsi+4
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teq r3, r1, lsr #11
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ldreq r0, [frame, #-8] @ get sp
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subeq r0, r0, #4 @ point at the last arg
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mov r2, loglvl
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bleq dump_backtrace_stm @ dump saved registers
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1004: ldr r1, [sv_pc, #0] @ if stmfd sp!, {..., fp, ip, lr, pc}
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ldr r3, .Ldsi @ instruction exists,
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teq r3, r1, lsr #11
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subeq r0, frame, #16
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mov r2, loglvl
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bleq dump_backtrace_stm @ dump saved registers
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teq sv_fp, #0 @ zero saved fp means
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beq no_frame @ no further frames
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cmp sv_fp, frame @ next frame must be
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mov frame, sv_fp @ above the current frame
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bhi for_each_frame
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1006: adr r0, .Lbad
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mov r1, loglvl
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mov r2, frame
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bl printk
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no_frame: ldmfd sp!, {r4 - r9, pc}
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ENDPROC(c_backtrace)
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.pushsection __ex_table,"a"
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.align 3
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.long 1001b, 1006b
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.long 1002b, 1006b
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.long 1003b, 1006b
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.long 1004b, 1006b
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.popsection
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.Lbad: .asciz "%sBacktrace aborted due to bad frame pointer <%p>\n"
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.align
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.Ldsi: .word 0xe92dd800 >> 11 @ stmfd sp!, {... fp, ip, lr, pc}
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.word 0xe92d0000 >> 11 @ stmfd sp!, {}
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#endif
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