From 0560281266b313400b622c5ddfafb0ee8e59c702 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Wed, 27 May 2015 12:22:29 +0200 Subject: [PATCH] x86/fpu: Split out the fpu__activate_fpstate_read() method Currently fpu__activate_fpstate() is used for two distinct purposes: - read access by ptrace and core dumping, where in the core dumping case the current task's FPU state may be examined as well. - write access by ptrace, which modifies FPU registers and expects the modified registers to be reloaded on the next context switch. Split out the reading side into fpu__activate_fpstate_read(). ( Note that this is just a pure duplication of fpu__activate_fpstate() for the time being, we'll optimize the new function in the next patch. ) Cc: Andy Lutomirski Cc: Bobby Powers Cc: Borislav Petkov Cc: Dave Hansen Cc: Fenghua Yu Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Thomas Gleixner Signed-off-by: Ingo Molnar --- arch/x86/include/asm/fpu/internal.h | 1 + arch/x86/kernel/fpu/core.c | 29 +++++++++++++++++++++++++++++ arch/x86/kernel/fpu/regset.c | 6 +++--- 3 files changed, 33 insertions(+), 3 deletions(-) diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h index 62d13d515f95..3cc2086b97f8 100644 --- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -22,6 +22,7 @@ * High level FPU state handling functions: */ extern void fpu__activate_curr(struct fpu *fpu); +extern void fpu__activate_fpstate_read(struct fpu *fpu); extern void fpu__activate_fpstate(struct fpu *fpu); extern void fpu__save(struct fpu *fpu); extern void fpu__restore(struct fpu *fpu); diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index b41049247cfa..174add372bb8 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -295,6 +295,35 @@ void fpu__activate_curr(struct fpu *fpu) } EXPORT_SYMBOL_GPL(fpu__activate_curr); +/* + * This function must be called before we read a task's fpstate. + * + * If the task has not used the FPU before then initialize its + * fpstate. + * + * If the task has used the FPU before then save it. + */ +void fpu__activate_fpstate_read(struct fpu *fpu) +{ + /* + * If fpregs are active (in the current CPU), then + * copy them to the fpstate: + */ + if (fpu->fpregs_active) { + fpu__save(fpu); + } else { + if (fpu->fpstate_active) { + /* Invalidate any lazy state: */ + fpu->last_cpu = -1; + } else { + fpstate_init(&fpu->state); + + /* Safe to do for current and for stopped child tasks: */ + fpu->fpstate_active = 1; + } + } +} + /* * This function must be called before we read or write a task's fpstate. * diff --git a/arch/x86/kernel/fpu/regset.c b/arch/x86/kernel/fpu/regset.c index a1f97d9d6a45..4e40585a9c8f 100644 --- a/arch/x86/kernel/fpu/regset.c +++ b/arch/x86/kernel/fpu/regset.c @@ -33,7 +33,7 @@ int xfpregs_get(struct task_struct *target, const struct user_regset *regset, if (!cpu_has_fxsr) return -ENODEV; - fpu__activate_fpstate(fpu); + fpu__activate_fpstate_read(fpu); fpstate_sanitize_xstate(fpu); return user_regset_copyout(&pos, &count, &kbuf, &ubuf, @@ -82,7 +82,7 @@ int xstateregs_get(struct task_struct *target, const struct user_regset *regset, if (!cpu_has_xsave) return -ENODEV; - fpu__activate_fpstate(fpu); + fpu__activate_fpstate_read(fpu); xsave = &fpu->state.xsave; @@ -273,7 +273,7 @@ int fpregs_get(struct task_struct *target, const struct user_regset *regset, struct fpu *fpu = &target->thread.fpu; struct user_i387_ia32_struct env; - fpu__activate_fpstate(fpu); + fpu__activate_fpstate_read(fpu); if (!static_cpu_has(X86_FEATURE_FPU)) return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf); -- 2.39.5