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x86/fpu: Move fpu__write_begin() to regset

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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@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121453.328652975@linutronix.de
This commit is contained in:
Thomas Gleixner 2021-06-23 14:01:47 +02:00 committed by Borislav Petkov
parent 5a32fac8db
commit dbb60ac764
3 changed files with 22 additions and 28 deletions
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1
arch/x86/include/asm/fpu/internal.h
View File

@ -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);

24
arch/x86/kernel/fpu/core.c
View File

@ -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

25
arch/x86/kernel/fpu/regset.c
View File

@ -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);