diff options
Diffstat (limited to 'arch/x86/include/asm/debugreg.h')
| -rw-r--r-- | arch/x86/include/asm/debugreg.h | 131 |
1 files changed, 102 insertions, 29 deletions
diff --git a/arch/x86/include/asm/debugreg.h b/arch/x86/include/asm/debugreg.h index 9e5ca30738e5..a2c1f2d24b64 100644 --- a/arch/x86/include/asm/debugreg.h +++ b/arch/x86/include/asm/debugreg.h @@ -2,10 +2,21 @@ #ifndef _ASM_X86_DEBUGREG_H #define _ASM_X86_DEBUGREG_H - #include <linux/bug.h> +#include <linux/percpu.h> #include <uapi/asm/debugreg.h> +#include <asm/cpufeature.h> +#include <asm/msr.h> + +/* + * Define bits that are always set to 1 in DR7, only bit 10 is + * architecturally reserved to '1'. + * + * This is also the init/reset value for DR7. + */ +#define DR7_FIXED_1 0x00000400 + DECLARE_PER_CPU(unsigned long, cpu_dr7); #ifndef CONFIG_PARAVIRT_XXL @@ -18,9 +29,9 @@ 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! */ + unsigned long val; switch (regno) { case 0: @@ -39,7 +50,20 @@ static inline unsigned long native_get_debugreg(int regno) asm("mov %%db6, %0" :"=r" (val)); break; case 7: - asm("mov %%db7, %0" :"=r" (val)); + /* + * 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 + * when running under SEV-ES. Taking a #VC exception is not a + * safe thing to do just anywhere in the entry code and + * re-ordering might place the access into an unsafe location. + * + * This happened in the NMI handler, where the DR7 read was + * re-ordered to happen before the call to sev_es_ist_enter(), + * causing stack recursion. + */ + asm volatile("mov %%db7, %0" : "=r" (val)); break; default: BUG(); @@ -47,7 +71,7 @@ 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: @@ -66,7 +90,16 @@ static inline void native_set_debugreg(int regno, unsigned long value) asm("mov %0, %%db6" ::"r" (value)); break; case 7: - asm("mov %0, %%db7" ::"r" (value)); + /* + * 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 + * "asm volatile" here too to avoid similar problems in the + * future. + */ + asm volatile("mov %0, %%db7" ::"r" (value)); break; default: BUG(); @@ -75,8 +108,8 @@ static inline void native_set_debugreg(int regno, unsigned long value) static inline void hw_breakpoint_disable(void) { - /* Zero the control register for HW Breakpoint */ - set_debugreg(0UL, 7); + /* Reset the control register for HW Breakpoint */ + set_debugreg(DR7_FIXED_1, 7); /* Zero-out the individual HW breakpoint address registers */ set_debugreg(0UL, 0); @@ -85,40 +118,80 @@ 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; } -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); + + /* Architecturally set bit */ + dr7 &= ~DR7_FIXED_1; + if (dr7) + set_debugreg(DR7_FIXED_1, 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); } -int is_debug_stack(unsigned long addr); -void debug_stack_set_zero(void); -void debug_stack_reset(void); -#else /* !X86_64 */ -static inline int is_debug_stack(unsigned long addr) { return 0; } -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); +extern void amd_set_dr_addr_mask(unsigned long mask, unsigned int dr); +extern unsigned long amd_get_dr_addr_mask(unsigned int dr); #else -static inline void set_dr_addr_mask(unsigned long mask, int dr) { } +static inline void amd_set_dr_addr_mask(unsigned long mask, unsigned int dr) { } +static inline unsigned long amd_get_dr_addr_mask(unsigned int dr) +{ + return 0; +} +#endif + +static inline unsigned long get_debugctlmsr(void) +{ + unsigned long debugctlmsr = 0; + +#ifndef CONFIG_X86_DEBUGCTLMSR + if (boot_cpu_data.x86 < 6) + return 0; #endif + rdmsrq(MSR_IA32_DEBUGCTLMSR, debugctlmsr); + + return debugctlmsr; +} + +static inline void update_debugctlmsr(unsigned long debugctlmsr) +{ +#ifndef CONFIG_X86_DEBUGCTLMSR + if (boot_cpu_data.x86 < 6) + return; +#endif + wrmsrq(MSR_IA32_DEBUGCTLMSR, debugctlmsr); +} #endif /* _ASM_X86_DEBUGREG_H */ |