Messages in this thread Patch in this message | | | Subject | Re: [PATCH] x86: Avoid pr_cont() in show_opcodes() | From | Tetsuo Handa <> | Date | Tue, 17 Jul 2018 22:53:55 +0900 |
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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
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