x86/fpu: Use fpstate in __copy_xstate_to_uabi_buf()

With dynamically enabled features the copy function must know the features
and the size which is valid for the task. Retrieve them from fpstate.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211013145323.181495492@linutronix.de

arch/x86/kernel/fpu/core.c

@@ -187,15 +187,15 @@ EXPORT_SYMBOL_GPL(fpu_swap_kvm_fpu);
 void fpu_copy_fpstate_to_kvm_uabi(struct fpu *fpu, void *buf,
 			       unsigned int size, u32 pkru)
 {
-	union fpregs_state *kstate = &fpu->fpstate->regs;
+	struct fpstate *kstate = fpu->fpstate;
 	union fpregs_state *ustate = buf;
 	struct membuf mb = { .p = buf, .left = size };
 
 	if (cpu_feature_enabled(X86_FEATURE_XSAVE)) {
-		__copy_xstate_to_uabi_buf(mb, &kstate->xsave, pkru,
-					  XSTATE_COPY_XSAVE);
+		__copy_xstate_to_uabi_buf(mb, kstate, pkru, XSTATE_COPY_XSAVE);
 	} else {
-		memcpy(&ustate->fxsave, &kstate->fxsave, sizeof(ustate->fxsave));
+		memcpy(&ustate->fxsave, &kstate->regs.fxsave,
+		       sizeof(ustate->fxsave));
 		/* Make it restorable on a XSAVE enabled host */
 		ustate->xsave.header.xfeatures = XFEATURE_MASK_FPSSE;
 	}

arch/x86/kernel/fpu/xstate.c

@@ -969,7 +969,7 @@ static void copy_feature(bool from_xstate, struct membuf *to, void *xstate,
 /**
  * __copy_xstate_to_uabi_buf - Copy kernel saved xstate to a UABI buffer
  * @to:		membuf descriptor
- * @xsave:	The xsave from which to copy
+ * @fpstate:	The fpstate buffer from which to copy
  * @pkru_val:	The PKRU value to store in the PKRU component
  * @copy_mode:	The requested copy mode
  *
@@ -979,11 +979,12 @@ static void copy_feature(bool from_xstate, struct membuf *to, void *xstate,
  *
  * It supports partial copy but @to.pos always starts from zero.
  */
-void __copy_xstate_to_uabi_buf(struct membuf to, struct xregs_state *xsave,
+void __copy_xstate_to_uabi_buf(struct membuf to, struct fpstate *fpstate,
 			       u32 pkru_val, enum xstate_copy_mode copy_mode)
 {
 	const unsigned int off_mxcsr = offsetof(struct fxregs_state, mxcsr);
 	struct xregs_state *xinit = &init_fpstate.regs.xsave;
+	struct xregs_state *xsave = &fpstate->regs.xsave;
 	struct xstate_header header;
 	unsigned int zerofrom;
 	u64 mask;
@@ -1003,7 +1004,7 @@ void __copy_xstate_to_uabi_buf(struct membuf to, struct xregs_state *xsave,
 		break;
 
 	case XSTATE_COPY_XSAVE:
-		header.xfeatures &= xfeatures_mask_uabi();
+		header.xfeatures &= fpstate->user_xfeatures;
 		break;
 	}
 
@@ -1046,7 +1047,7 @@ void __copy_xstate_to_uabi_buf(struct membuf to, struct xregs_state *xsave,
 	 * but there is no state to copy from in the compacted
 	 * init_fpstate. The gap tracking will zero these states.
 	 */
-	mask = xfeatures_mask_uabi();
+	mask = fpstate->user_xfeatures;
 
 	for_each_extended_xfeature(i, mask) {
 		/*
@@ -1097,7 +1098,7 @@ void __copy_xstate_to_uabi_buf(struct membuf to, struct xregs_state *xsave,
 void copy_xstate_to_uabi_buf(struct membuf to, struct task_struct *tsk,
 			     enum xstate_copy_mode copy_mode)
 {
-	__copy_xstate_to_uabi_buf(to, &tsk->thread.fpu.fpstate->regs.xsave,
+	__copy_xstate_to_uabi_buf(to, tsk->thread.fpu.fpstate,
 				  tsk->thread.pkru, copy_mode);
 }
 

arch/x86/kernel/fpu/xstate.h

@@ -15,7 +15,7 @@ static inline void xstate_init_xcomp_bv(struct xregs_state *xsave, u64 mask)
 		xsave->header.xcomp_bv = mask | XCOMP_BV_COMPACTED_FORMAT;
 }
 
-extern void __copy_xstate_to_uabi_buf(struct membuf to, struct xregs_state *xsave,
+extern void __copy_xstate_to_uabi_buf(struct membuf to, struct fpstate *fpstate,
 				      u32 pkru_val, enum xstate_copy_mode copy_mode);
 
 extern void fpu__init_cpu_xstate(void);