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 <[email protected]> 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 <[email protected]> Signed-off-by: Rasmus Villemoes <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Josh Poimboeuf <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Andy Lutomirski <[email protected]> --- 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
