From cd840e424f27fcc1ae8d14b7ec3ec4560ee6561a Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Fri, 29 May 2020 23:27:35 +0200
Subject: [PATCH] x86/entry, mce: Disallow #DB during #MC
#MC is fragile as heck, don't tempt fate.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200529213321.131187767@infradead.org
---
arch/x86/kernel/cpu/mce/core.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 068e6cab1286c..be499267bbb47 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -1943,22 +1943,34 @@ static __always_inline void exc_machine_check_user(struct pt_regs *regs)
/* MCE hit kernel mode */
DEFINE_IDTENTRY_MCE(exc_machine_check)
{
+ unsigned long dr7;
+
+ dr7 = local_db_save();
exc_machine_check_kernel(regs);
+ local_db_restore(dr7);
}
/* The user mode variant. */
DEFINE_IDTENTRY_MCE_USER(exc_machine_check)
{
+ unsigned long dr7;
+
+ dr7 = local_db_save();
exc_machine_check_user(regs);
+ local_db_restore(dr7);
}
#else
/* 32bit unified entry point */
DEFINE_IDTENTRY_MCE(exc_machine_check)
{
+ unsigned long dr7;
+
+ dr7 = local_db_save();
if (user_mode(regs))
exc_machine_check_user(regs);
else
exc_machine_check_kernel(regs);
+ local_db_restore(dr7);
}
#endif
--
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