The following commit has been merged into the x86/urgent branch of tip:
Commit-ID: a195f3d4528a2f88d6f986f6b1101775ad4891cf
Gitweb:
https://git.kernel.org/tip/a195f3d4528a2f88d6f986f6b1101775ad4891cf
Author: Peter Zijlstra <pet...@infradead.org>
AuthorDate: Tue, 27 Oct 2020 10:15:06 +01:00
Committer: Thomas Gleixner <t...@linutronix.de>
CommitterDate: Tue, 27 Oct 2020 23:15:23 +01:00
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) <pet...@infradead.org>
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Tested-by: Kyle Huey <m...@kylehuey.com>
Link: https://lore.kernel.org/r/20201027093608.028952...@infradead.org
---
arch/x86/kernel/traps.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index b5208aa..32b2d39 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.
