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Commit 8e974b3b authored by Rasmus Villemoes's avatar Rasmus Villemoes Committed by Thomas Gleixner
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x86: Avoid pr_cont() in show_opcodes() 

If concurrent printk() messages are emitted, then pr_cont() is making it
extremly hard to decode which part of the output belongs to what. See the
convoluted example at:

  https://syzkaller.appspot.com/text?tag=CrashReport&x=139d342c400000



Avoid this by using a proper prefix for each line and by using %ph format
in show_opcodes() which emits the 'Code:' line in one go.

Signed-off-by: default avatarRasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: default avatarTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: joe@perches.com
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@suse.de>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lkml.kernel.org/r/1532009278-5953-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp
parent 9d3cce1e

arch/x86/kernel/dumpstack.c

+9 −19
Original line number Original line Diff line number Diff line
@@ -22,8 +22,6 @@ 
#include <asm/stacktrace.h>

#include <asm/stacktrace.h>

#include <asm/unwind.h>

#include <asm/unwind.h>





#define OPCODE_BUFSIZE 64



int panic_on_unrecovered_nmi;

int panic_on_unrecovered_nmi;

int panic_on_io_nmi;

int panic_on_io_nmi;

static int die_counter;

static int die_counter;
@@ -93,26 +91,18 @@ static void printk_stack_address(unsigned long address, int reliable, 
 */

 */

void show_opcodes(u8 *rip, const char *loglvl)

void show_opcodes(u8 *rip, const char *loglvl)

{

{

	unsigned int code_prologue = OPCODE_BUFSIZE * 2 / 3;

#define PROLOGUE_SIZE 42

#define EPILOGUE_SIZE 21

#define OPCODE_BUFSIZE (PROLOGUE_SIZE + 1 + EPILOGUE_SIZE)

	u8 opcodes[OPCODE_BUFSIZE];

	u8 opcodes[OPCODE_BUFSIZE];

	u8 *ip;

	int i;



	printk("%sCode: ", loglvl);



	ip = (u8 *)rip - code_prologue;

	if (probe_kernel_read(opcodes, ip, OPCODE_BUFSIZE)) {

		pr_cont("Bad RIP value.\n");

		return;

	}





	for (i = 0; i < OPCODE_BUFSIZE; i++, ip++) {

	if (probe_kernel_read(opcodes, rip - PROLOGUE_SIZE, OPCODE_BUFSIZE)) {

		if (ip == rip)

		printk("%sCode: Bad RIP value.\n", loglvl);

			pr_cont("<%02x> ", opcodes[i]);

	} else {

		else

		printk("%sCode: %" __stringify(PROLOGUE_SIZE) "ph <%02x> %"

			pr_cont("%02x ", opcodes[i]);

		       __stringify(EPILOGUE_SIZE) "ph\n", loglvl, opcodes,

		       opcodes[PROLOGUE_SIZE], opcodes + PROLOGUE_SIZE + 1);

	}

	}

	pr_cont("\n");

}

}





void show_ip(struct pt_regs *regs, const char *loglvl)

void show_ip(struct pt_regs *regs, const char *loglvl)