/* 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#define loglvl	r9 ENTRY(c_backtrace) #if !defined(CONFIG_FRAME_POINTER) || !defined(CONFIG_PRINTK)		ret	lrENDPROC(c_backtrace)#else		stmfd	sp!, {r4 - r9, 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		mov	loglvl, r2 		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 pc1002:		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 #11		@ 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		mov	r3, loglvl		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		mov	r2, loglvl		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		mov	r2, loglvl		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#ifdef CONFIG_IRQSTACKS		@		@ Kernel stacks may be discontiguous in memory. If the next		@ frame is below the previous frame, accept it as long as it		@ lives in kernel memory.		@		cmpls	sv_fp, #PAGE_OFFSET#endif		bhi	for_each_frame 1006:		adr	r0, .Lbad		mov	r1, loglvl		mov	r2, frame		bl	_printkno_frame:	ldmfd	sp!, {r4 - r9, 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	"%sBacktrace 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