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x86/fpu: Move FXSAVE_LEAK quirk info __copy_kernel_to_fpregs() 

copy_kernel_to_fpregs() restores all xfeatures but it is also the place
where the AMD FXSAVE_LEAK bug is handled.

That prevents fpregs_restore_userregs() to limit the restored features,
which is required to untangle PKRU and XSTATE handling and also for the
upcoming supervisor state management.

Move the FXSAVE_LEAK quirk into __copy_kernel_to_fpregs() and deinline that
function which has become rather fat.

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/20210623121456.114271278@linutronix.de
This commit is contained in:
Thomas Gleixner 2021-06-23 14:02:15 +02:00 committed by Borislav Petkov
parent 727d01100e
commit 1d9bffab11
2 changed files with 28 additions and 24 deletions
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25
arch/x86/include/asm/fpu/internal.h
View File

@ -379,33 +379,10 @@ static inline int os_xrstor_safe(struct xregs_state *xstate, u64 mask)
return err;
}
static inline void __restore_fpregs_from_fpstate(union fpregs_state *fpstate, u64 mask)
{
if (use_xsave()) {
os_xrstor(&fpstate->xsave, mask);
} else {
if (use_fxsr())
fxrstor(&fpstate->fxsave);
else
frstor(&fpstate->fsave);
}
}
extern void __restore_fpregs_from_fpstate(union fpregs_state *fpstate, u64 mask);
static inline void restore_fpregs_from_fpstate(union fpregs_state *fpstate)
{
/*
* AMD K7/K8 CPUs don't save/restore FDP/FIP/FOP unless an exception is
* pending. Clear the x87 state here by setting it to fixed values.
* "m" is a random variable that should be in L1.
*/
if (unlikely(static_cpu_has_bug(X86_BUG_FXSAVE_LEAK))) {
asm volatile(
"fnclex\n\t"
"emms\n\t"
"fildl %P[addr]" /* set F?P to defined value */
: : [addr] "m" (fpstate));
}
__restore_fpregs_from_fpstate(fpstate, -1);
}

27
arch/x86/kernel/fpu/core.c
View File

@ -124,6 +124,33 @@ void save_fpregs_to_fpstate(struct fpu *fpu)
}
EXPORT_SYMBOL(save_fpregs_to_fpstate);
void __restore_fpregs_from_fpstate(union fpregs_state *fpstate, u64 mask)
{
/*
* AMD K7/K8 and later CPUs up to Zen don't save/restore
* FDP/FIP/FOP unless an exception is pending. Clear the x87 state
* here by setting it to fixed values. "m" is a random variable
* that should be in L1.
*/
if (unlikely(static_cpu_has_bug(X86_BUG_FXSAVE_LEAK))) {
asm volatile(
"fnclex\n\t"
"emms\n\t"
"fildl %P[addr]" /* set F?P to defined value */
: : [addr] "m" (fpstate));
}
if (use_xsave()) {
os_xrstor(&fpstate->xsave, mask);
} else {
if (use_fxsr())
fxrstor(&fpstate->fxsave);
else
frstor(&fpstate->fsave);
}
}
EXPORT_SYMBOL_GPL(__restore_fpregs_from_fpstate);
void kernel_fpu_begin_mask(unsigned int kfpu_mask)
{
preempt_disable();