diff options
| -rw-r--r-- | arch/x86/include/asm/processor.h | 9 | ||||
| -rw-r--r-- | arch/x86/kernel/process.c | 7 | ||||
| -rw-r--r-- | arch/x86/kernel/process_64.c | 25 |
3 files changed, 41 insertions, 0 deletions
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 556b2b17c3e2..91946fc3c006 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -518,6 +518,15 @@ struct thread_struct { unsigned int sig_on_uaccess_err:1; + /* + * Protection Keys Register for Userspace. Loaded immediately on + * context switch. Store it in thread_struct to avoid a lookup in + * the tasks's FPU xstate buffer. This value is only valid when a + * task is scheduled out. For 'current' the authoritative source of + * PKRU is the hardware itself. + */ + u32 pkru; + /* Floating point and extended processor state */ struct fpu fpu; /* diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index de942b038815..fa6c8fa0f778 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -156,11 +156,18 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg, /* Kernel thread ? */ if (unlikely(p->flags & PF_KTHREAD)) { + p->thread.pkru = pkru_get_init_value(); memset(childregs, 0, sizeof(struct pt_regs)); kthread_frame_init(frame, sp, arg); return 0; } + /* + * Clone current's PKRU value from hardware. tsk->thread.pkru + * is only valid when scheduled out. + */ + p->thread.pkru = read_pkru(); + frame->bx = 0; *childregs = *current_pt_regs(); childregs->ax = 0; diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 40a963809203..ec0d836a13b1 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -340,6 +340,29 @@ static __always_inline void load_seg_legacy(unsigned short prev_index, } } +/* + * Store prev's PKRU value and load next's PKRU value if they differ. PKRU + * is not XSTATE managed on context switch because that would require a + * lookup in the task's FPU xsave buffer and require to keep that updated + * in various places. + */ +static __always_inline void x86_pkru_load(struct thread_struct *prev, + struct thread_struct *next) +{ + if (!cpu_feature_enabled(X86_FEATURE_OSPKE)) + return; + + /* Stash the prev task's value: */ + prev->pkru = rdpkru(); + + /* + * PKRU writes are slightly expensive. Avoid them when not + * strictly necessary: + */ + if (prev->pkru != next->pkru) + wrpkru(next->pkru); +} + static __always_inline void x86_fsgsbase_load(struct thread_struct *prev, struct thread_struct *next) { @@ -589,6 +612,8 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) x86_fsgsbase_load(prev, next); + x86_pkru_load(prev, next); + /* * Switch the PDA and FPU contexts. */ |