Commit e1de11d4 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Thomas Gleixner
Browse files

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



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

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200529213321.012060983@infradead.org
parent fdef24df

arch/x86/include/asm/debugreg.h

+30 −0
Original line number Diff line number Diff line
@@ -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

arch/x86/kernel/traps.c

+2 −16
Original line number Diff line number Diff line
@@ -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);

}



/*