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x86/entry: Introduce local_db_{save,restore}()

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In order to allow other exceptions than #DB to disable breakpoints,
provide common helpers.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200529213321.012060983@infradead.org
This commit is contained in:
Peter Zijlstra 2020-05-29 23:27:33 +02:00 committed by Thomas Gleixner
parent fdef24dfcc
commit e1de11d4d1
2 changed files with 32 additions and 16 deletions
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30
arch/x86/include/asm/debugreg.h
View File

@ -113,6 +113,36 @@ static inline void debug_stack_usage_inc(void) { }
static inline void debug_stack_usage_dec(void) { }
#endif /* X86_64 */
static __always_inline unsigned long local_db_save(void)
{
unsigned long dr7;
get_debugreg(dr7, 7);
dr7 &= ~0x400; /* architecturally set bit */
if (dr7)
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();
return dr7;
}
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();
if (dr7)
set_debugreg(dr7, 7);
}
#ifdef CONFIG_CPU_SUP_AMD
extern void set_dr_addr_mask(unsigned long mask, int dr);
#else

18
arch/x86/kernel/traps.c
View File

@ -727,15 +727,7 @@ static __always_inline void debug_enter(unsigned long *dr6, unsigned long *dr7)
* 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();
*dr7 = local_db_save();
/*
* The Intel SDM says:
@ -756,13 +748,7 @@ static __always_inline void debug_enter(unsigned long *dr6, unsigned long *dr7)
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);
}
/*