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Date: Fri, 22 May 2020 22:47:39 +0200 From: Peter Zijlstra <peterz@...radead.org> To: tglx@...utronix.de, luto@...capital.net, peterz@...radead.org Cc: linux-kernel@...r.kernel.org, x86@...nel.org Subject: [RFC][PATCH 1/4] x86/entry: Introduce local_db_{rave,restore}() In order to allow other exceptions than #DB to disable breakpoints, provide a common helper. Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org> --- arch/x86/include/asm/debugreg.h | 23 +++++++++++++++++++++++ arch/x86/kernel/traps.c | 18 ++---------------- 2 files changed, 25 insertions(+), 16 deletions(-) --- a/arch/x86/include/asm/debugreg.h +++ b/arch/x86/include/asm/debugreg.h @@ -113,6 +113,29 @@ static inline void debug_stack_usage_inc static inline void debug_stack_usage_dec(void) { } #endif /* X86_64 */ +static __always_inline void local_db_save(unsigned long *dr7) +{ + get_debugreg(*dr7, 7); + set_debugreg(0, 7); + /* + * Ensure the compiler doesn't lower the above statements into + * the critical section; disabling breakpoints late would not + * be good. + */ + barrier(); +} + +static __always_inline void local_db_restore(unsigned long dr7) +{ + /* + * Ensure the compiler doesn't raise this statement into + * the critical section; enabling breakpoints early would + * not be good. + */ + barrier(); + set_debugreg(dr7, 7); +} + #ifdef CONFIG_CPU_SUP_AMD extern void set_dr_addr_mask(unsigned long mask, int dr); #else --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -727,15 +727,7 @@ static __always_inline void debug_enter( * Entry text is excluded for HW_BP_X and cpu_entry_area, which * includes the entry stack is excluded for everything. */ - get_debugreg(*dr7, 7); - set_debugreg(0, 7); - - /* - * Ensure the compiler doesn't lower the above statements into - * the critical section; disabling breakpoints late would not - * be good. - */ - barrier(); + local_db_save(dr7); /* * The Intel SDM says: @@ -756,13 +748,7 @@ static __always_inline void debug_enter( static __always_inline void debug_exit(unsigned long dr7) { - /* - * Ensure the compiler doesn't raise this statement into - * the critical section; enabling breakpoints early would - * not be good. - */ - barrier(); - set_debugreg(dr7, 7); + local_db_restore(dr7); } /*
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