1 files changed, 31 insertions, 17 deletions

diff --git a/arch/x86/include/asm/debugreg.h b/arch/x86/include/asm/debugreg.h
index 1a8609a15856..e89558a3fe4a 100644
--- a/arch/x86/include/asm/debugreg.h
+++ b/arch/x86/include/asm/debugreg.h
@@ -18,7 +18,7 @@ DECLARE_PER_CPU(unsigned long, cpu_dr7);
 	native_set_debugreg(register, value)
 #endif
 
-static inline unsigned long native_get_debugreg(int regno)
+static __always_inline unsigned long native_get_debugreg(int regno)
 {
 	unsigned long val = 0;	/* Damn you, gcc! */
 
@@ -47,7 +47,7 @@ static inline unsigned long native_get_debugreg(int regno)
 	return val;
 }
 
-static inline void native_set_debugreg(int regno, unsigned long value)
+static __always_inline void native_set_debugreg(int regno, unsigned long value)
 {
 	switch (regno) {
 	case 0:
@@ -85,7 +85,7 @@ static inline void hw_breakpoint_disable(void)
 	set_debugreg(0UL, 3);
 }
 
-static inline int hw_breakpoint_active(void)
+static __always_inline bool hw_breakpoint_active(void)
 {
 	return __this_cpu_read(cpu_dr7) & DR_GLOBAL_ENABLE_MASK;
 }
@@ -94,24 +94,38 @@ extern void aout_dump_debugregs(struct user *dump);
 
 extern void hw_breakpoint_restore(void);
 
-#ifdef CONFIG_X86_64
-DECLARE_PER_CPU(int, debug_stack_usage);
-static inline void debug_stack_usage_inc(void)
+static __always_inline unsigned long local_db_save(void)
 {
-	__this_cpu_inc(debug_stack_usage);
+	unsigned long dr7;
+
+	if (static_cpu_has(X86_FEATURE_HYPERVISOR) && !hw_breakpoint_active())
+		return 0;
+
+	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 inline void debug_stack_usage_dec(void)
+
+static __always_inline void local_db_restore(unsigned long dr7)
 {
-	__this_cpu_dec(debug_stack_usage);
+	/*
+	 * 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);
 }
-void debug_stack_set_zero(void);
-void debug_stack_reset(void);
-#else /* !X86_64 */
-static inline void debug_stack_set_zero(void) { }
-static inline void debug_stack_reset(void) { }
-static inline void debug_stack_usage_inc(void) { }
-static inline void debug_stack_usage_dec(void) { }
-#endif /* X86_64 */
 
 #ifdef CONFIG_CPU_SUP_AMD
 extern void set_dr_addr_mask(unsigned long mask, int dr);