diff --git a/arch/x86/include/asm/debugreg.h b/arch/x86/include/asm/debugreg.h index fdbbbfec745a..719d95f1ab5e 100644 --- a/arch/x86/include/asm/debugreg.h +++ b/arch/x86/include/asm/debugreg.h @@ -23,7 +23,7 @@ DECLARE_PER_CPU(unsigned long, cpu_dr7); static __always_inline unsigned long native_get_debugreg(int regno) { - unsigned long val = 0; /* Damn you, gcc! */ + unsigned long val; switch (regno) { case 0: @@ -43,7 +43,7 @@ static __always_inline unsigned long native_get_debugreg(int regno) break; case 7: /* - * Apply __FORCE_ORDER to DR7 reads to forbid re-ordering them + * Use "asm volatile" for DR7 reads to forbid re-ordering them * with other code. * * This is needed because a DR7 access can cause a #VC exception @@ -55,7 +55,7 @@ static __always_inline unsigned long native_get_debugreg(int regno) * re-ordered to happen before the call to sev_es_ist_enter(), * causing stack recursion. */ - asm volatile("mov %%db7, %0" : "=r" (val) : __FORCE_ORDER); + asm volatile("mov %%db7, %0" : "=r" (val)); break; default: BUG(); @@ -83,15 +83,15 @@ static __always_inline void native_set_debugreg(int regno, unsigned long value) break; case 7: /* - * Apply __FORCE_ORDER to DR7 writes to forbid re-ordering them + * Use "asm volatile" for DR7 writes to forbid re-ordering them * with other code. * * While is didn't happen with a DR7 write (see the DR7 read * comment above which explains where it happened), add the - * __FORCE_ORDER here too to avoid similar problems in the + * "asm volatile" here too to avoid similar problems in the * future. */ - asm volatile("mov %0, %%db7" ::"r" (value), __FORCE_ORDER); + asm volatile("mov %0, %%db7" ::"r" (value)); break; default: BUG(); diff --git a/arch/x86/include/asm/special_insns.h b/arch/x86/include/asm/special_insns.h index 6266d6b9e0b8..ecda17efa042 100644 --- a/arch/x86/include/asm/special_insns.h +++ b/arch/x86/include/asm/special_insns.h @@ -10,30 +10,19 @@ #include #include -/* - * The compiler should not reorder volatile asm statements with respect to each - * other: they should execute in program order. However GCC 4.9.x and 5.x have - * a bug (which was fixed in 8.1, 7.3 and 6.5) where they might reorder - * volatile asm. The write functions are not affected since they have memory - * clobbers preventing reordering. To prevent reads from being reordered with - * respect to writes, use a dummy memory operand. - */ - -#define __FORCE_ORDER "m"(*(unsigned int *)0x1000UL) - void native_write_cr0(unsigned long val); static inline unsigned long native_read_cr0(void) { unsigned long val; - asm volatile("mov %%cr0,%0\n\t" : "=r" (val) : __FORCE_ORDER); + asm volatile("mov %%cr0,%0" : "=r" (val)); return val; } static __always_inline unsigned long native_read_cr2(void) { unsigned long val; - asm volatile("mov %%cr2,%0\n\t" : "=r" (val) : __FORCE_ORDER); + asm volatile("mov %%cr2,%0" : "=r" (val)); return val; } @@ -45,7 +34,7 @@ static __always_inline void native_write_cr2(unsigned long val) static __always_inline unsigned long __native_read_cr3(void) { unsigned long val; - asm volatile("mov %%cr3,%0\n\t" : "=r" (val) : __FORCE_ORDER); + asm volatile("mov %%cr3,%0" : "=r" (val)); return val; } @@ -66,10 +55,10 @@ static inline unsigned long native_read_cr4(void) asm volatile("1: mov %%cr4, %0\n" "2:\n" _ASM_EXTABLE(1b, 2b) - : "=r" (val) : "0" (0), __FORCE_ORDER); + : "=r" (val) : "0" (0)); #else /* CR4 always exists on x86_64. */ - asm volatile("mov %%cr4,%0\n\t" : "=r" (val) : __FORCE_ORDER); + asm volatile("mov %%cr4,%0" : "=r" (val)); #endif return val; }