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Commit 24c66dfd authored by Russell King's avatar Russell King
Browse files

ARM: fix backtrace 



Recent kernels have changed their behaviour to be more inconsistent
when handling printk continuations.  With todays kernels, the output
looks sane on the console, but dmesg splits individual printk()s which
do not have the KERN_CONT prefix into separate lines.

Since the assembly code is not trivial to add the KERN_CONT, and we
ideally want to avoid using KERN_CONT (as multiple printk()s can race
between different threads), convert the assembly dumping the register
values to C code, and have the C code build the output a line at a
time before dumping to the console.

This avoids the KERN_CONT issue, and also avoids situations where the
output is intermixed with other console activity.

Signed-off-by: default avatarRussell King <rmk+kernel@armlinux.org.uk>
parent 6127d124

arch/arm/kernel/traps.c

+20 −0
Original line number Diff line number Diff line
@@ -74,6 +74,26 @@ void dump_backtrace_entry(unsigned long where, unsigned long from, unsigned long 
		dump_mem("", "Exception stack", frame + 4, frame + 4 + sizeof(struct pt_regs));

}



void dump_backtrace_stm(u32 *stack, u32 instruction)

{

	char str[80], *p;

	unsigned int x;

	int reg;



	for (reg = 10, x = 0, p = str; reg >= 0; reg--) {

		if (instruction & BIT(reg)) {

			p += sprintf(p, " r%d:%08x", reg, *stack--);

			if (++x == 6) {

				x = 0;

				p = str;

				printk("%s\n", str);

			}

		}

	}

	if (p != str)

		printk("%s\n", str);

}



#ifndef CONFIG_ARM_UNWIND

/*

 * Stack pointers should always be within the kernels view of

arch/arm/lib/backtrace.S

+3 −34
Original line number Diff line number Diff line
@@ -10,6 +10,7 @@ 
 * 27/03/03 Ian Molton Clean up CONFIG_CPU

 *

 */

#include <linux/kern_levels.h>

#include <linux/linkage.h>

#include <asm/assembler.h>

		.text
@@ -83,13 +84,13 @@ for_each_frame: tst frame, mask @ Check for address exceptions 
		teq	r3, r1, lsr #11

		ldreq	r0, [frame, #-8]	@ get sp

		subeq	r0, r0, #4		@ point at the last arg

		bleq	.Ldumpstm		@ dump saved registers

		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	.Ldumpstm		@ dump saved registers

		bleq	dump_backtrace_stm	@ dump saved registers



		teq	sv_fp, #0		@ zero saved fp means

		beq	no_frame		@ no further frames
@@ -112,38 +113,6 @@ ENDPROC(c_backtrace) 
		.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, #0

		adr	r3, .Lcr

		addne	r3, r3, #1		@ skip newline

		ldr	r2, [stack], #-4

		mov	r1, 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	" r%d:%08x%s"

.Lcr:		.asciz	"\n"

.Lbad:		.asciz	"Backtrace aborted due to bad frame pointer <%p>\n"

		.align

.Ldsi:		.word	0xe92dd800 >> 11	@ stmfd sp!, {... fp, ip, lr, pc}