The following commit has been merged into the x86/fpu branch of tip: Commit-ID: dbb60ac764581e62f2116c5a6b8926ba3a872dd4 Gitweb: https://git.kernel.org/tip/dbb60ac764581e62f2116c5a6b8926ba3a872dd4 Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx> AuthorDate: Wed, 23 Jun 2021 14:01:47 +02:00 Committer: Borislav Petkov <bp@xxxxxxx> CommitterDate: Wed, 23 Jun 2021 17:49:47 +02:00 x86/fpu: Move fpu__write_begin() to regset The only usecase for fpu__write_begin is the set() callback of regset, so the function is pointlessly global. Move it to the regset code and rename it to fpu_force_restore() which is exactly decribing what the function does. Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Reviewed-by: Borislav Petkov <bp@xxxxxxx> Link: https://lkml.kernel.org/r/20210623121453.328652975@xxxxxxxxxxxxx --- arch/x86/include/asm/fpu/internal.h | 1 - arch/x86/kernel/fpu/core.c | 24 ------------------------ arch/x86/kernel/fpu/regset.c | 25 ++++++++++++++++++++++--- 3 files changed, 22 insertions(+), 28 deletions(-) diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h index 4c669f3..854bfb0 100644 --- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -26,7 +26,6 @@ /* * High level FPU state handling functions: */ -extern void fpu__prepare_write(struct fpu *fpu); extern void fpu__save(struct fpu *fpu); extern int fpu__restore_sig(void __user *buf, int ia32_frame); extern void fpu__drop(struct fpu *fpu); diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index d390644..2243701 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -282,30 +282,6 @@ static void fpu__initialize(struct fpu *fpu) } /* - * This function must be called before we write a task's fpstate. - * - * Invalidate any cached FPU registers. - * - * After this function call, after registers in the fpstate are - * modified and the child task has woken up, the child task will - * restore the modified FPU state from the modified context. If we - * didn't clear its cached status here then the cached in-registers - * state pending on its former CPU could be restored, corrupting - * the modifications. - */ -void fpu__prepare_write(struct fpu *fpu) -{ - /* - * Only stopped child tasks can be used to modify the FPU - * state in the fpstate buffer: - */ - WARN_ON_FPU(fpu == ¤t->thread.fpu); - - /* Invalidate any cached state: */ - __fpu_invalidate_fpregs_state(fpu); -} - -/* * Drops current FPU state: deactivates the fpregs and * the fpstate. NOTE: it still leaves previous contents * in the fpregs in the eager-FPU case. diff --git a/arch/x86/kernel/fpu/regset.c b/arch/x86/kernel/fpu/regset.c index 937adf7..ddc290d 100644 --- a/arch/x86/kernel/fpu/regset.c +++ b/arch/x86/kernel/fpu/regset.c @@ -44,6 +44,25 @@ static void sync_fpstate(struct fpu *fpu) fpu__save(fpu); } +/* + * Invalidate cached FPU registers before modifying the stopped target + * task's fpstate. + * + * This forces the target task on resume to restore the FPU registers from + * modified fpstate. Otherwise the task might skip the restore and operate + * with the cached FPU registers which discards the modifications. + */ +static void fpu_force_restore(struct fpu *fpu) +{ + /* + * Only stopped child tasks can be used to modify the FPU + * state in the fpstate buffer: + */ + WARN_ON_FPU(fpu == ¤t->thread.fpu); + + __fpu_invalidate_fpregs_state(fpu); +} + int xfpregs_get(struct task_struct *target, const struct user_regset *regset, struct membuf to) { @@ -88,7 +107,7 @@ int xfpregs_set(struct task_struct *target, const struct user_regset *regset, if (newstate.mxcsr & ~mxcsr_feature_mask) return -EINVAL; - fpu__prepare_write(fpu); + fpu_force_restore(fpu); /* Copy the state */ memcpy(&fpu->state.fxsave, &newstate, sizeof(newstate)); @@ -146,7 +165,7 @@ int xstateregs_set(struct task_struct *target, const struct user_regset *regset, } } - fpu__prepare_write(fpu); + fpu_force_restore(fpu); ret = copy_kernel_to_xstate(&fpu->state.xsave, kbuf ?: tmpbuf); out: @@ -346,7 +365,7 @@ int fpregs_set(struct task_struct *target, const struct user_regset *regset, if (ret) return ret; - fpu__prepare_write(fpu); + fpu_force_restore(fpu); if (cpu_feature_enabled(X86_FEATURE_FXSR)) convert_to_fxsr(&fpu->state.fxsave, &env);
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