[tip: x86/fpu] x86/fpu: Use copy_xstate_to_uabi_buf() in xfpregs_get()

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/fpu branch of tip:

Commit-ID:     adc997b3d66d1cfa8c15a7dbafdaef239a51b5db
Gitweb:        https://git.kernel.org/tip/adc997b3d66d1cfa8c15a7dbafdaef239a51b5db
Author:        Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate:    Wed, 23 Jun 2021 14:01:43 +02:00
Committer:     Borislav Petkov <bp@xxxxxxx>
CommitterDate: Wed, 23 Jun 2021 17:49:47 +02:00

x86/fpu: Use copy_xstate_to_uabi_buf() in xfpregs_get()

Use the new functionality of copy_xstate_to_uabi_buf() to retrieve the
FX state when XSAVE* is in use. This avoids overwriting the FPU state
buffer with fpstate_sanitize_xstate() which is error prone and duplicated
code.

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/20210623121452.901736860@xxxxxxxxxxxxx
---
 arch/x86/kernel/fpu/regset.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/fpu/regset.c b/arch/x86/kernel/fpu/regset.c
index 783f84d..ccbe25f 100644
--- a/arch/x86/kernel/fpu/regset.c
+++ b/arch/x86/kernel/fpu/regset.c
@@ -33,13 +33,18 @@ int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
 {
 	struct fpu *fpu = &target->thread.fpu;
 
-	if (!boot_cpu_has(X86_FEATURE_FXSR))
+	if (!cpu_feature_enabled(X86_FEATURE_FXSR))
 		return -ENODEV;
 
 	fpu__prepare_read(fpu);
-	fpstate_sanitize_xstate(fpu);
 
-	return membuf_write(&to, &fpu->state.fxsave, sizeof(struct fxregs_state));
+	if (!use_xsave()) {
+		return membuf_write(&to, &fpu->state.fxsave,
+				    sizeof(fpu->state.fxsave));
+	}
+
+	copy_xstate_to_uabi_buf(to, &fpu->state.xsave, XSTATE_COPY_FX);
+	return 0;
 }
 
 int xfpregs_set(struct task_struct *target, const struct user_regset *regset,