* [PATCH v7] x86: Avoid pr_cont() in show_opcodes().
@ 2018-07-19 14:07 Tetsuo Handa
2018-07-19 14:11 ` Peter Zijlstra
2018-07-19 14:51 ` [tip:x86/debug] " tip-bot for Rasmus Villemoes
0 siblings, 2 replies; 3+ messages in thread
From: Tetsuo Handa @ 2018-07-19 14:07 UTC (permalink / raw)
To: mingo, mingo, linux-kernel
Cc: joe, Rasmus Villemoes, Tetsuo Handa, Andy Lutomirski,
Borislav Petkov, Josh Poimboeuf, Linus Torvalds, Peter Zijlstra,
Thomas Gleixner
From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
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: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
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 | 28 +++++++++-------------------
1 file changed, 9 insertions(+), 19 deletions(-)
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 666a284..9c86529 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 +91,18 @@ 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]);
+ 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);
}
- pr_cont("\n");
}
void show_ip(struct pt_regs *regs, const char *loglvl)
--
1.8.3.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v7] x86: Avoid pr_cont() in show_opcodes().
2018-07-19 14:07 [PATCH v7] x86: Avoid pr_cont() in show_opcodes() Tetsuo Handa
@ 2018-07-19 14:11 ` Peter Zijlstra
2018-07-19 14:51 ` [tip:x86/debug] " tip-bot for Rasmus Villemoes
1 sibling, 0 replies; 3+ messages in thread
From: Peter Zijlstra @ 2018-07-19 14:11 UTC (permalink / raw)
To: Tetsuo Handa
Cc: mingo, mingo, linux-kernel, joe, Rasmus Villemoes,
Andy Lutomirski, Borislav Petkov, Josh Poimboeuf, Linus Torvalds,
Thomas Gleixner
On Thu, Jul 19, 2018 at 11:07:58PM +0900, Tetsuo Handa wrote:
> From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
>
> 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: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> 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>
Thanks!
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
^ permalink raw reply [flat|nested] 3+ messages in thread
* [tip:x86/debug] x86: Avoid pr_cont() in show_opcodes()
2018-07-19 14:07 [PATCH v7] x86: Avoid pr_cont() in show_opcodes() Tetsuo Handa
2018-07-19 14:11 ` Peter Zijlstra
@ 2018-07-19 14:51 ` tip-bot for Rasmus Villemoes
1 sibling, 0 replies; 3+ messages in thread
From: tip-bot for Rasmus Villemoes @ 2018-07-19 14:51 UTC (permalink / raw)
To: linux-tip-commits
Cc: torvalds, jpoimboe, mingo, hpa, linux, penguin-kernel, luto,
peterz, linux-kernel, bp, tglx
Commit-ID: 8e974b3b8eddd42a8c43a18e8ea66a3e7b803a0d
Gitweb: https://git.kernel.org/tip/8e974b3b8eddd42a8c43a18e8ea66a3e7b803a0d
Author: Rasmus Villemoes <linux@rasmusvillemoes.dk>
AuthorDate: Thu, 19 Jul 2018 23:07:58 +0900
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Thu, 19 Jul 2018 16:46:23 +0200
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: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter 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
---
arch/x86/kernel/dumpstack.c | 28 +++++++++-------------------
1 file changed, 9 insertions(+), 19 deletions(-)
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 666a284116ac..9c8652974f8e 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 +91,18 @@ 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]);
+ 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);
}
- pr_cont("\n");
}
void show_ip(struct pt_regs *regs, const char *loglvl)
^ permalink raw reply related [flat|nested] 3+ messages in thread
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2018-07-19 14:07 [PATCH v7] x86: Avoid pr_cont() in show_opcodes() Tetsuo Handa
2018-07-19 14:11 ` Peter Zijlstra
2018-07-19 14:51 ` [tip:x86/debug] " tip-bot for Rasmus Villemoes
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