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authorPeter Zijlstra <peterz@infradead.org>2020-10-27 10:15:06 +0100
committerThomas Gleixner <tglx@linutronix.de>2020-10-27 23:15:23 +0100
commita195f3d4528a2f88d6f986f6b1101775ad4891cf (patch)
treef61191d9faa00ce094e8a54b215e4de01262fec7 /arch
parent2a9baf5ad4884108b3c6d56a50e8105ccf8a4ee7 (diff)
x86/debug: Only clear/set ->virtual_dr6 for userspace #DB
The ->virtual_dr6 is the value used by ptrace_{get,set}_debugreg(6). A kernel #DB clearing it could mean spurious malfunction of ptrace() expectations. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Kyle Huey <me@kylehuey.com> Link: https://lore.kernel.org/r/20201027093608.028952500@infradead.org
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/traps.c12
1 files changed, 6 insertions, 6 deletions
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index b5208aa7351f..32b2d39272e0 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -793,12 +793,6 @@ static __always_inline unsigned long debug_read_clear_dr6(void)
set_debugreg(DR6_RESERVED, 6);
dr6 ^= DR6_RESERVED; /* Flip to positive polarity */
- /*
- * Clear the virtual DR6 value, ptrace routines will set bits here for
- * things we want signals for.
- */
- current->thread.virtual_dr6 = 0;
-
return dr6;
}
@@ -943,6 +937,12 @@ static __always_inline void exc_debug_user(struct pt_regs *regs,
instrumentation_begin();
/*
+ * Clear the virtual DR6 value, ptrace() routines will set bits here
+ * for things it wants signals for.
+ */
+ current->thread.virtual_dr6 = 0;
+
+ /*
* The SDM says "The processor clears the BTF flag when it
* generates a debug exception." Clear TIF_BLOCKSTEP to keep
* TIF_BLOCKSTEP in sync with the hardware BTF flag.

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