From a195f3d4528a2f88d6f986f6b1101775ad4891cf Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 27 Oct 2020 10:15:06 +0100 Subject: 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) Signed-off-by: Thomas Gleixner Tested-by: Kyle Huey Link: https://lore.kernel.org/r/20201027093608.028952500@infradead.org --- arch/x86/kernel/traps.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) (limited to 'arch/x86/kernel') 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; } @@ -942,6 +936,12 @@ static __always_inline void exc_debug_user(struct pt_regs *regs, irqentry_enter_from_user_mode(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 -- cgit v1.2.3