From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Rasmus Villemoes <mail@rasmusvillemoes.dk>,
Ingo Molnar <mingo@kernel.org>
Cc: mingo@redhat.com, linux-kernel@vger.kernel.org,
Tetsuo Handa <penguin-kernel@I-love.SKAURA.ne.jp>,
Andy Lutomirski <luto@amacapital.net>,
Borislav Petkov <bp@suse.de>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] x86: Avoid pr_cont() in show_opcodes()
Date: Tue, 17 Jul 2018 22:53:55 +0900 [thread overview]
Message-ID: <f486debf-e824-0d0c-c0c9-cf1e278ee9eb@i-love.sakura.ne.jp> (raw)
In-Reply-To: <12409dc4-c10a-d77a-f88d-165aa92b489e@rasmusvillemoes.dk>
On 2018/07/17 18:01, Rasmus Villemoes wrote:
> Why not this instead? Less stack use, less code, no intermediary
> snprintfs, no pr_cont...
Excellent! I didn't notice %ph extension.
> Not compile-tested, probably whitespace-damaged, but you get the idea.
Yes, it works well.
From 96d9d4d135994a081e54d33d23f5007c53d9b5dd Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Date: Tue, 17 Jul 2018 22:47:11 +0900
Subject: [PATCH v3] x86: Avoid pr_cont() in show_opcodes()
Since syzbot is confused by concurrent printk() messages [1],
this patch changes show_opcodes() to use %*ph format string.
When we start adding prefix to each line of printk() output,
we will be able to handle concurrent printk() messages.
[1] https://syzkaller.appspot.com/text?tag=CrashReport&x=139d342c400000
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SKAURA.ne.jp>
Signed-off-by: Rasmus Villemoes <mail@rasmusvillemoes.dk>
Cc: Borislav Petkov <bp@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
---
arch/x86/kernel/dumpstack.c | 25 +++++++------------------
1 file changed, 7 insertions(+), 18 deletions(-)
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 666a284..ffdd484 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -93,26 +93,15 @@ static void printk_stack_address(unsigned long address, int reliable,
*/
void show_opcodes(u8 *rip, const char *loglvl)
{
- unsigned int code_prologue = OPCODE_BUFSIZE * 2 / 3;
+ const unsigned int prologue = OPCODE_BUFSIZE * 2 / 3;
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 (ip == rip)
- pr_cont("<%02x> ", opcodes[i]);
- else
- pr_cont("%02x ", opcodes[i]);
- }
- pr_cont("\n");
+ if (probe_kernel_read(opcodes, rip - prologue, OPCODE_BUFSIZE))
+ printk("%sCode: Bad RIP value.\n", loglvl);
+ else
+ printk("%sCode: %*ph <%02x> %*ph\n", loglvl, prologue, opcodes,
+ opcodes[prologue], OPCODE_BUFSIZE - prologue - 1,
+ &opcodes[prologue + 1]);
}
void show_ip(struct pt_regs *regs, const char *loglvl)
--
1.8.3.1
next prev parent reply other threads:[~2018-07-17 13:54 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-07 6:07 [PATCH] x86: Avoid pr_cont() in show_opcodes() Tetsuo Handa
2018-07-07 11:12 ` Ingo Molnar
2018-07-07 13:54 ` Tetsuo Handa
2018-07-09 8:49 ` Peter Zijlstra
2018-07-09 13:22 ` David Laight
2018-07-09 19:11 ` Josh Poimboeuf
2018-07-10 11:55 ` Tetsuo Handa
2018-07-10 16:51 ` David Laight
2018-07-10 21:08 ` Tetsuo Handa
2018-07-16 12:47 ` Tetsuo Handa
2018-07-17 9:01 ` Rasmus Villemoes
2018-07-17 13:53 ` Tetsuo Handa [this message]
2018-07-17 14:24 ` Rasmus Villemoes
2018-07-17 20:54 ` Tetsuo Handa
2018-07-17 21:19 ` Joe Perches
2018-07-18 8:41 ` Joe Perches
2018-07-17 21:07 ` Andy Shevchenko
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