The following commit has been merged into the x86/entry branch of tip:
Commit-ID: 4eb5acc39187a7ba578fbb44f7bb1965057309ae
Gitweb: https://git.kernel.org/tip/4eb5acc39187a7ba578fbb44f7bb1965057309ae
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Wed, 02 Sep 2020 15:25:56 +02:00
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Fri, 04 Sep 2020 15:12:53 +02:00
x86/debug: Move historical SYSENTER junk into exc_debug_kernel()
The historical SYSENTER junk is explicitly for from-kernel, so move it
to the #DB-from-kernel handler.
It is ordered after the notifier, which is important for KGDB which uses TF
single-step and needs to consume the event before that point.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Tested-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20200902133201.031099736@xxxxxxxxxxxxx
---
arch/x86/kernel/traps.c | 49 ++++++++++++++++++++--------------------
1 file changed, 25 insertions(+), 24 deletions(-)
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 24e09f8..2605686 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -783,7 +783,7 @@ static __always_inline unsigned long debug_read_clear_dr6(void)
*
* May run on IST stack.
*/
-static void handle_debug(struct pt_regs *regs, unsigned long dr6)
+static bool handle_debug(struct pt_regs *regs, unsigned long *dr6)
{
struct task_struct *tsk = current;
bool icebp;
@@ -793,15 +793,13 @@ static void handle_debug(struct pt_regs *regs, unsigned long dr6)
* then it's very likely the result of an icebp/int01 trap.
* User wants a sigtrap for that.
*/
- icebp = !dr6;
+ icebp = !*dr6;
/* Store the virtualized DR6 value */
- tsk->thread.debugreg6 = dr6;
+ tsk->thread.debugreg6 = *dr6;
- if (notify_die(DIE_DEBUG, "debug", regs, (long)&dr6, 0,
- SIGTRAP) == NOTIFY_STOP) {
- return;
- }
+ if (notify_die(DIE_DEBUG, "debug", regs, (long)dr6, 0, SIGTRAP) == NOTIFY_STOP)
+ return true;
/* It's safe to allow irq's after DR6 has been saved */
cond_local_irq_enable(regs);
@@ -815,25 +813,15 @@ static void handle_debug(struct pt_regs *regs, unsigned long dr6)
/*
* Reload dr6, the notifier might have changed it.
*/
- dr6 = tsk->thread.debugreg6;
+ *dr6 = tsk->thread.debugreg6;
- if (WARN_ON_ONCE((dr6 & DR_STEP) && !user_mode(regs))) {
- /*
- * Historical junk that used to handle SYSENTER single-stepping.
- * This should be unreachable now. If we survive for a while
- * without anyone hitting this warning, we'll turn this into
- * an oops.
- */
- tsk->thread.debugreg6 &= ~DR_STEP;
- set_tsk_thread_flag(tsk, TIF_SINGLESTEP);
- regs->flags &= ~X86_EFLAGS_TF;
- }
-
- if (dr6 & (DR_STEP | DR_TRAP_BITS) || icebp)
- send_sigtrap(regs, 0, get_si_code(dr6));
+ if (*dr6 & (DR_STEP | DR_TRAP_BITS) || icebp)
+ send_sigtrap(regs, 0, get_si_code(*dr6));
out:
cond_local_irq_disable(regs);
+
+ return false;
}
static __always_inline void exc_debug_kernel(struct pt_regs *regs,
@@ -876,7 +864,20 @@ static __always_inline void exc_debug_kernel(struct pt_regs *regs,
if (!dr6)
goto out;
- handle_debug(regs, dr6);
+ if (handle_debug(regs, &dr6))
+ goto out;
+
+ if (WARN_ON_ONCE(dr6 & DR_STEP)) {
+ /*
+ * Historical junk that used to handle SYSENTER single-stepping.
+ * This should be unreachable now. If we survive for a while
+ * without anyone hitting this warning, we'll turn this into
+ * an oops.
+ */
+ dr6 &= ~DR_STEP;
+ set_thread_flag(TIF_SINGLESTEP);
+ regs->flags &= ~X86_EFLAGS_TF;
+ }
out:
instrumentation_end();
@@ -906,7 +907,7 @@ static __always_inline void exc_debug_user(struct pt_regs *regs,
irqentry_enter_from_user_mode(regs);
instrumentation_begin();
- handle_debug(regs, dr6);
+ handle_debug(regs, &dr6);
instrumentation_end();
irqentry_exit_to_user_mode(regs);
|