* [PATCH v5] x86: Avoid pr_cont() in show_opcodes().
@ 2018-07-18 9:54 Tetsuo Handa
2018-07-18 11:57 ` Ingo Molnar
0 siblings, 1 reply; 4+ messages in thread
From: Tetsuo Handa @ 2018-07-18 9:54 UTC (permalink / raw)
To: mingo, mingo, linux-kernel
Cc: joe, Tetsuo Handa, Rasmus Villemoes, Andy Lutomirski,
Borislav Petkov, Josh Poimboeuf, Linus Torvalds, Peter Zijlstra,
Thomas Gleixner
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.SAKURA.ne.jp>
Signed-off-by: Rasmus Villemoes <linux@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 | 29 +++++++++--------------------
1 file changed, 9 insertions(+), 20 deletions(-)
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 666a284..0821da3 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -22,8 +22,6 @@
#include <asm/stacktrace.h>
#include <asm/unwind.h>
-#define OPCODE_BUFSIZE 64
-
int panic_on_unrecovered_nmi;
int panic_on_io_nmi;
static int die_counter;
@@ -93,26 +91,17 @@ 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;
+#define PROLOGUE_SIZE 42
+#define EPILOGUE_SIZE 21
+#define OPCODE_BUFSIZE (PROLOGUE_SIZE + 1 + EPILOGUE_SIZE)
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_SIZE, OPCODE_BUFSIZE))
+ printk("%sCode: Bad RIP value.\n", loglvl);
+ else
+ printk("%sCode: %" __stringify(PROLOGUE_SIZE) "ph <%02x> %"
+ __stringify(EPILOGUE_SIZE) "ph\n", loglvl, opcodes,
+ opcodes[PROLOGUE_SIZE], opcodes + PROLOGUE_SIZE + 1);
}
void show_ip(struct pt_regs *regs, const char *loglvl)
--
1.8.3.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v5] x86: Avoid pr_cont() in show_opcodes().
2018-07-18 9:54 [PATCH v5] x86: Avoid pr_cont() in show_opcodes() Tetsuo Handa
@ 2018-07-18 11:57 ` Ingo Molnar
2018-07-19 13:54 ` Tetsuo Handa
0 siblings, 1 reply; 4+ messages in thread
From: Ingo Molnar @ 2018-07-18 11:57 UTC (permalink / raw)
To: Tetsuo Handa
Cc: mingo, linux-kernel, joe, Rasmus Villemoes, Andy Lutomirski,
Borislav Petkov, Josh Poimboeuf, Linus Torvalds, Peter Zijlstra,
Thomas Gleixner
* Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> wrote:
> 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.SAKURA.ne.jp>
> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Wasn't that variant of the patch written by Rasmus?
If so then the changelog should start with:
From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Thanks,
Ingo
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v5] x86: Avoid pr_cont() in show_opcodes().
2018-07-18 11:57 ` Ingo Molnar
@ 2018-07-19 13:54 ` Tetsuo Handa
2018-07-24 7:42 ` Ingo Molnar
0 siblings, 1 reply; 4+ messages in thread
From: Tetsuo Handa @ 2018-07-19 13:54 UTC (permalink / raw)
To: Ingo Molnar
Cc: mingo, linux-kernel, joe, Rasmus Villemoes, Andy Lutomirski,
Borislav Petkov, Josh Poimboeuf, Linus Torvalds, Peter Zijlstra,
Thomas Gleixner
On 2018/07/18 20:57, Ingo Molnar wrote:
>
> * Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> wrote:
>
>> 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.SAKURA.ne.jp>
>> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
>
> Wasn't that variant of the patch written by Rasmus?
Rasmus Villemoes taught me that we can use "%*ph" format string and pass
length as arguments for "*" part. Then, since Joe Perches suggested me to
use #define for length variable, I updated to use "#define length immediate"
and replaced "%*ph" with "%" __strigify(length) "ph" and removed length from
arguments. That is v5 patch.
>
> If so then the changelog should start with:
>
> From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
OK. I posted v6 patch with From: line updated.
>
> Thanks,
>
> Ingo
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v5] x86: Avoid pr_cont() in show_opcodes().
2018-07-19 13:54 ` Tetsuo Handa
@ 2018-07-24 7:42 ` Ingo Molnar
0 siblings, 0 replies; 4+ messages in thread
From: Ingo Molnar @ 2018-07-24 7:42 UTC (permalink / raw)
To: Tetsuo Handa
Cc: mingo, linux-kernel, joe, Rasmus Villemoes, Andy Lutomirski,
Borislav Petkov, Josh Poimboeuf, Linus Torvalds, Peter Zijlstra,
Thomas Gleixner
* Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> wrote:
> On 2018/07/18 20:57, Ingo Molnar wrote:
> >
> > * Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> wrote:
> >
> >> 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.SAKURA.ne.jp>
> >> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> >
> > Wasn't that variant of the patch written by Rasmus?
>
> Rasmus Villemoes taught me that we can use "%*ph" format string and pass
> length as arguments for "*" part. Then, since Joe Perches suggested me to
> use #define for length variable, I updated to use "#define length immediate"
> and replaced "%*ph" with "%" __strigify(length) "ph" and removed length from
> arguments. That is v5 patch.
>
> >
> > If so then the changelog should start with:
> >
> > From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
>
> OK. I posted v6 patch with From: line updated.
Please do that only if it was mainly written by him - otherwise just tell me that
it's yours and I'll apply it as such.
Thanks,
Ingo
^ permalink raw reply [flat|nested] 4+ messages in thread
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2018-07-18 9:54 [PATCH v5] x86: Avoid pr_cont() in show_opcodes() Tetsuo Handa
2018-07-18 11:57 ` Ingo Molnar
2018-07-19 13:54 ` Tetsuo Handa
2018-07-24 7:42 ` Ingo Molnar
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