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x86/debug: Sync BTF earlier 

Move the BTF sync near the DR6 load, as this will be the only common
code guaranteed to run on every #DB.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Daniel Thompson <daniel.thompson@linaro.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20200902133200.786888252@infradead.org
This commit is contained in:
Peter Zijlstra 2020-09-02 15:25:52 +02:00 committed by Thomas Gleixner
parent d5c678aed5
commit c182487da1
1 changed files with 7 additions and 7 deletions
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14
arch/x86/kernel/traps.c
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@ -749,6 +749,13 @@ static __always_inline unsigned long debug_read_clear_dr6(void)
/* Filter out all the reserved bits which are preset to 1 */
dr6 &= ~DR6_RESERVED;
/*
* 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.
*/
clear_thread_flag(TIF_BLOCKSTEP);
return dr6;
}
@ -782,13 +789,6 @@ static void handle_debug(struct pt_regs *regs, unsigned long dr6, bool user)
bool user_icebp;
int si_code;
/*
* 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.
*/
clear_thread_flag(TIF_BLOCKSTEP);
/*
* If DR6 is zero, no point in trying to handle it. The kernel is
* not using INT1.