* Re: [PATCH] x86/debug: Handle warnings before the notifier chain
2017-07-24 10:04 [PATCH] x86/debug: Handle warnings before the notifier chain Alexander Shishkin
@ 2017-07-24 10:21 ` Peter Zijlstra
2017-08-29 11:53 ` Alexander Shishkin
2017-11-10 6:33 ` [tip:x86/urgent] x86/debug: Handle warnings before the notifier chain, to fix KGDB crash tip-bot for Alexander Shishkin
2017-11-10 9:41 ` tip-bot for Alexander Shishkin
2 siblings, 1 reply; 5+ messages in thread
From: Peter Zijlstra @ 2017-07-24 10:21 UTC (permalink / raw)
To: Alexander Shishkin
Cc: Thomas Gleixner, Ingo Molnar, Arjan van de Ven, Borislav Petkov,
Richard Weinberger, Ingo Molnar, linux-kernel, Jason Wessel
On Mon, Jul 24, 2017 at 01:04:28PM +0300, Alexander Shishkin wrote:
> Commit
>
> 9a93848fe787 ("x86/debug: Implement __WARN() using UD0")
>
> turned warnings into UD0, but the fixup code only runs after the
> notify_die() chain. This is a problem, in particular, with kgdb,
> which kicks in as if it was a BUG().
>
> Fix this by running the fixup code before the notifier chain in
> the invalid op handler path.
So arguable it might be nice to have kgdb trap on a WARN, but it
treating it as a BUG is obviously undesirable.
Jason, what would you want kgdb to do here?
> Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> Cc: Arjan van de Ven <arjan@linux.intel.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Richard Weinberger <richard.weinberger@gmail.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: linux-kernel@vger.kernel.org
> ---
> arch/x86/kernel/traps.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
> index bf54309b85..b2157d4a53 100644
> --- a/arch/x86/kernel/traps.c
> +++ b/arch/x86/kernel/traps.c
> @@ -221,9 +221,6 @@ do_trap_no_signal(struct task_struct *tsk, int trapnr, char *str,
> if (fixup_exception(regs, trapnr))
> return 0;
>
> - if (fixup_bug(regs, trapnr))
> - return 0;
> -
> tsk->thread.error_code = error_code;
> tsk->thread.trap_nr = trapnr;
> die(str, regs, error_code);
> @@ -304,6 +301,13 @@ static void do_error_trap(struct pt_regs *regs, long error_code, char *str,
>
> RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");
>
> + /*
> + * WARN*()s end up here; fix them up before we call the
> + * notifier chain.
> + */
> + if (!user_mode(regs) && fixup_bug(regs, trapnr))
> + return;
> +
> if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) !=
> NOTIFY_STOP) {
> cond_local_irq_enable(regs);
> --
> 2.13.2
>
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] x86/debug: Handle warnings before the notifier chain
2017-07-24 10:21 ` Peter Zijlstra
@ 2017-08-29 11:53 ` Alexander Shishkin
0 siblings, 0 replies; 5+ messages in thread
From: Alexander Shishkin @ 2017-08-29 11:53 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Thomas Gleixner, Ingo Molnar, Arjan van de Ven, Borislav Petkov,
Richard Weinberger, Ingo Molnar, linux-kernel, Jason Wessel
Peter Zijlstra <peterz@infradead.org> writes:
> On Mon, Jul 24, 2017 at 01:04:28PM +0300, Alexander Shishkin wrote:
>> Commit
>>
>> 9a93848fe787 ("x86/debug: Implement __WARN() using UD0")
>>
>> turned warnings into UD0, but the fixup code only runs after the
>> notify_die() chain. This is a problem, in particular, with kgdb,
>> which kicks in as if it was a BUG().
>>
>> Fix this by running the fixup code before the notifier chain in
>> the invalid op handler path.
>
> So arguable it might be nice to have kgdb trap on a WARN, but it
> treating it as a BUG is obviously undesirable.
>
> Jason, what would you want kgdb to do here?
Ping.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [tip:x86/urgent] x86/debug: Handle warnings before the notifier chain, to fix KGDB crash
2017-07-24 10:04 [PATCH] x86/debug: Handle warnings before the notifier chain Alexander Shishkin
2017-07-24 10:21 ` Peter Zijlstra
@ 2017-11-10 6:33 ` tip-bot for Alexander Shishkin
2017-11-10 9:41 ` tip-bot for Alexander Shishkin
2 siblings, 0 replies; 5+ messages in thread
From: tip-bot for Alexander Shishkin @ 2017-11-10 6:33 UTC (permalink / raw)
To: linux-tip-commits
Cc: hpa, mingo, daniel.thompson, peterz, idryomov, linux-kernel,
arjan, bp, alexander.shishkin, torvalds, richard.weinberger, tglx,
jason.wessel
Commit-ID: a8d6c1bd62ffefb075c9d3570f07659e2a36ecb3
Gitweb: https://git.kernel.org/tip/a8d6c1bd62ffefb075c9d3570f07659e2a36ecb3
Author: Alexander Shishkin <alexander.shishkin@linux.intel.com>
AuthorDate: Mon, 24 Jul 2017 13:04:28 +0300
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 10 Nov 2017 07:16:23 +0100
x86/debug: Handle warnings before the notifier chain, to fix KGDB crash
Commit:
9a93848fe787 ("x86/debug: Implement __WARN() using UD0")
turned warnings into UD0, but the fixup code only runs after the
notify_die() chain. This is a problem, in particular, with kgdb,
which kicks in as if it was a BUG().
Fix this by running the fixup code before the notifier chain in
the invalid op handler path.
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Tested-by: Ilya Dryomov <idryomov@gmail.com>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Richard Weinberger <richard.weinberger@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: <stable@vger.kernel.org> # v4.12+
Link: http://lkml.kernel.org/r/20170724100428.19173-1-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/kernel/traps.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 67db4f4..5a6b8f8 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -209,9 +209,6 @@ do_trap_no_signal(struct task_struct *tsk, int trapnr, char *str,
if (fixup_exception(regs, trapnr))
return 0;
- if (fixup_bug(regs, trapnr))
- return 0;
-
tsk->thread.error_code = error_code;
tsk->thread.trap_nr = trapnr;
die(str, regs, error_code);
@@ -292,6 +289,13 @@ static void do_error_trap(struct pt_regs *regs, long error_code, char *str,
RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");
+ /*
+ * WARN*()s end up here; fix them up before we call the
+ * notifier chain.
+ */
+ if (!user_mode(regs) && fixup_bug(regs, trapnr))
+ return;
+
if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) !=
NOTIFY_STOP) {
cond_local_irq_enable(regs);
^ permalink raw reply related [flat|nested] 5+ messages in thread* [tip:x86/urgent] x86/debug: Handle warnings before the notifier chain, to fix KGDB crash
2017-07-24 10:04 [PATCH] x86/debug: Handle warnings before the notifier chain Alexander Shishkin
2017-07-24 10:21 ` Peter Zijlstra
2017-11-10 6:33 ` [tip:x86/urgent] x86/debug: Handle warnings before the notifier chain, to fix KGDB crash tip-bot for Alexander Shishkin
@ 2017-11-10 9:41 ` tip-bot for Alexander Shishkin
2 siblings, 0 replies; 5+ messages in thread
From: tip-bot for Alexander Shishkin @ 2017-11-10 9:41 UTC (permalink / raw)
To: linux-tip-commits
Cc: arjan, linux-kernel, idryomov, mingo, alexander.shishkin, hpa,
tglx, torvalds, daniel.thompson, richard.weinberger, peterz,
jason.wessel, bp
Commit-ID: b8347c2196492f4e1cccde3d92fda1cc2cc7de7e
Gitweb: https://git.kernel.org/tip/b8347c2196492f4e1cccde3d92fda1cc2cc7de7e
Author: Alexander Shishkin <alexander.shishkin@linux.intel.com>
AuthorDate: Mon, 24 Jul 2017 13:04:28 +0300
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 10 Nov 2017 08:04:19 +0100
x86/debug: Handle warnings before the notifier chain, to fix KGDB crash
Commit:
9a93848fe787 ("x86/debug: Implement __WARN() using UD0")
turned warnings into UD0, but the fixup code only runs after the
notify_die() chain. This is a problem, in particular, with kgdb,
which kicks in as if it was a BUG().
Fix this by running the fixup code before the notifier chain in
the invalid op handler path.
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Tested-by: Ilya Dryomov <idryomov@gmail.com>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Richard Weinberger <richard.weinberger@gmail.com>
Cc: <stable@vger.kernel.org> # v4.12+
Link: http://lkml.kernel.org/r/20170724100428.19173-1-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/kernel/traps.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 67db4f4..5a6b8f8 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -209,9 +209,6 @@ do_trap_no_signal(struct task_struct *tsk, int trapnr, char *str,
if (fixup_exception(regs, trapnr))
return 0;
- if (fixup_bug(regs, trapnr))
- return 0;
-
tsk->thread.error_code = error_code;
tsk->thread.trap_nr = trapnr;
die(str, regs, error_code);
@@ -292,6 +289,13 @@ static void do_error_trap(struct pt_regs *regs, long error_code, char *str,
RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");
+ /*
+ * WARN*()s end up here; fix them up before we call the
+ * notifier chain.
+ */
+ if (!user_mode(regs) && fixup_bug(regs, trapnr))
+ return;
+
if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) !=
NOTIFY_STOP) {
cond_local_irq_enable(regs);
^ permalink raw reply related [flat|nested] 5+ messages in thread