Commit dbb60ac7 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Borislav Petkov
Browse files

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: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Reviewed-by: default avatarBorislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121453.328652975@linutronix.de
parent 5a32fac8

arch/x86/include/asm/fpu/internal.h

+0 −1
Original line number Diff line number Diff line
@@ -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);

arch/x86/kernel/fpu/core.c

+0 −24
Original line number Diff line number Diff line
@@ -281,30 +281,6 @@ static void fpu__initialize(struct fpu *fpu) 
	trace_x86_fpu_init_state(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 == &current->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

arch/x86/kernel/fpu/regset.c

+22 −3
Original line number Diff line number Diff line
@@ -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 == &current->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);