From 849369d6c66d3054688672f97d31fceb8e8230fb Mon Sep 17 00:00:00 2001
From: root <root@artemis.panaceas.org>
Date: Fri, 25 Dec 2015 04:40:36 +0000
Subject: initial_commit

---
 arch/arm/lib/backtrace.S | 158 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 158 insertions(+)
 create mode 100644 arch/arm/lib/backtrace.S

(limited to 'arch/arm/lib/backtrace.S')

diff --git a/arch/arm/lib/backtrace.S b/arch/arm/lib/backtrace.S
new file mode 100644
index 00000000..a673297b
--- /dev/null
+++ b/arch/arm/lib/backtrace.S
@@ -0,0 +1,158 @@
+/*
+ *  linux/arch/arm/lib/backtrace.S
+ *
+ *  Copyright (C) 1995, 1996 Russell King
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * 27/03/03 Ian Molton Clean up CONFIG_CPU
+ *
+ */
+#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(__backtrace)
+		mov	r1, #0x10
+		mov	r0, fp
+
+ENTRY(c_backtrace)
+
+#if !defined(CONFIG_FRAME_POINTER) || !defined(CONFIG_PRINTK)
+		mov	pc, lr
+ENDPROC(__backtrace)
+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 #10
+		ldreq	r0, [frame, #-8]	@ get sp
+		subeq	r0, r0, #4		@ point at the last arg
+		bleq	.Ldumpstm		@ 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 #10
+		subeq	r0, frame, #16
+		bleq	.Ldumpstm		@ 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(__backtrace)
+ENDPROC(c_backtrace)
+		
+		.pushsection __ex_table,"a"
+		.align	3
+		.long	1001b, 1006b
+		.long	1002b, 1006b
+		.long	1003b, 1006b
+		.long	1004b, 1006b
+		.popsection
+
+#define instr r4
+#define reg   r5
+#define stack r6
+
+.Ldumpstm:	stmfd	sp!, {instr, reg, stack, r7, lr}
+		mov	stack, r0
+		mov	instr, r1
+		mov	reg, #10
+		mov	r7, #0
+1:		mov	r3, #1
+ ARM(		tst	instr, r3, lsl reg	)
+ THUMB(		lsl	r3, reg			)
+ THUMB(		tst	instr, r3		)
+		beq	2f
+		add	r7, r7, #1
+		teq	r7, #6
+		moveq	r7, #1
+		moveq	r1, #'\n'
+		movne	r1, #' '
+		ldr	r3, [stack], #-4
+		mov	r2, reg
+		adr	r0, .Lfp
+		bl	printk
+2:		subs	reg, reg, #1
+		bpl	1b
+		teq	r7, #0
+		adrne	r0, .Lcr
+		blne	printk
+		ldmfd	sp!, {instr, reg, stack, r7, pc}
+
+.Lfp:		.asciz	"%cr%d:%08x"
+.Lcr:		.asciz	"\n"
+.Lbad:		.asciz	"Backtrace aborted due to bad frame pointer <%p>\n"
+		.align
+.Ldsi:		.word	0xe92dd800 >> 10	@ stmfd sp!, {... fp, ip, lr, pc}
+		.word	0xe92d0000 >> 10	@ stmfd sp!, {}
+
+#endif
-- 
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