[tip:x86/urgent] x86/debug: Handle warnings before the notifier chain, to fix KGDB crash

[tip-bot for Alexander Shishkin]

Commit-ID:  b8347c2196492f4e1cccde3d92fda1cc2cc7de7e
Gitweb: https://git.kernel.org/tip/b8347c2196492f4e1cccde3d92fda1cc2cc7de7e
Author: Alexander Shishkin 
AuthorDate: Mon, 24 Jul 2017 13:04:28 +0300
Committer:  Ingo Molnar 
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 
Tested-by: Ilya Dryomov 
Acked-by: Daniel Thompson 
Acked-by: Thomas Gleixner 
Cc: Jason Wessel 
Cc: Arjan van de Ven 
Cc: Borislav Petkov 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Richard Weinberger 
Cc:  # v4.12+
Link: 
http://lkml.kernel.org/r/20170724100428.19173-1-alexander.shish...@linux.intel.com
Signed-off-by: Ingo Molnar 
---
 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);

[tip:x86/urgent] x86/debug: Handle warnings before the notifier chain, to fix KGDB crash

[tip-bot for Alexander Shishkin]

Commit-ID:  b8347c2196492f4e1cccde3d92fda1cc2cc7de7e
Gitweb: https://git.kernel.org/tip/b8347c2196492f4e1cccde3d92fda1cc2cc7de7e
Author: Alexander Shishkin 
AuthorDate: Mon, 24 Jul 2017 13:04:28 +0300
Committer:  Ingo Molnar 
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 
Tested-by: Ilya Dryomov 
Acked-by: Daniel Thompson 
Acked-by: Thomas Gleixner 
Cc: Jason Wessel 
Cc: Arjan van de Ven 
Cc: Borislav Petkov 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Richard Weinberger 
Cc:  # v4.12+
Link: 
http://lkml.kernel.org/r/20170724100428.19173-1-alexander.shish...@linux.intel.com
Signed-off-by: Ingo Molnar 
---
 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);

[tip:x86/urgent] x86/debug: Handle warnings before the notifier chain, to fix KGDB crash

[tip-bot for Alexander Shishkin]

Commit-ID:  a8d6c1bd62ffefb075c9d3570f07659e2a36ecb3
Gitweb: https://git.kernel.org/tip/a8d6c1bd62ffefb075c9d3570f07659e2a36ecb3
Author: Alexander Shishkin 
AuthorDate: Mon, 24 Jul 2017 13:04:28 +0300
Committer:  Ingo Molnar 
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 
Tested-by: Ilya Dryomov 
Acked-by: Daniel Thompson 
Cc: Jason Wessel 
Cc: Arjan van de Ven 
Cc: Borislav Petkov 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Richard Weinberger 
Cc: Thomas Gleixner 
Cc:  # v4.12+
Link: 
http://lkml.kernel.org/r/20170724100428.19173-1-alexander.shish...@linux.intel.com
Signed-off-by: Ingo Molnar 
---
 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);

[tip:x86/urgent] x86/debug: Handle warnings before the notifier chain, to fix KGDB crash

[tip-bot for Alexander Shishkin]

Commit-ID:  a8d6c1bd62ffefb075c9d3570f07659e2a36ecb3
Gitweb: https://git.kernel.org/tip/a8d6c1bd62ffefb075c9d3570f07659e2a36ecb3
Author: Alexander Shishkin 
AuthorDate: Mon, 24 Jul 2017 13:04:28 +0300
Committer:  Ingo Molnar 
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 
Tested-by: Ilya Dryomov 
Acked-by: Daniel Thompson 
Cc: Jason Wessel 
Cc: Arjan van de Ven 
Cc: Borislav Petkov 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Richard Weinberger 
Cc: Thomas Gleixner 
Cc:  # v4.12+
Link: 
http://lkml.kernel.org/r/20170724100428.19173-1-alexander.shish...@linux.intel.com
Signed-off-by: Ingo Molnar 
---
 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);