1 files changed, 304 insertions, 241 deletions

diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 400a05e1c1c5..91d4b6de58ab 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -7,37 +7,40 @@
 #include <linux/cpu.h>
 #include <linux/pagemap.h>
 
-#include <asm/fpu/internal.h>
 #include <asm/fpu/signal.h>
 #include <asm/fpu/regset.h>
 #include <asm/fpu/xstate.h>
 
 #include <asm/sigframe.h>
+#include <asm/trapnr.h>
 #include <asm/trace/fpu.h>
 
-static struct _fpx_sw_bytes fx_sw_reserved, fx_sw_reserved_ia32;
+#include "context.h"
+#include "internal.h"
+#include "legacy.h"
+#include "xstate.h"
 
 /*
  * Check for the presence of extended state information in the
  * user fpstate pointer in the sigcontext.
  */
-static inline int check_for_xstate(struct fxregs_state __user *buf,
-				   void __user *fpstate,
-				   struct _fpx_sw_bytes *fx_sw)
+static inline bool check_xstate_in_sigframe(struct fxregs_state __user *fxbuf,
+					    struct _fpx_sw_bytes *fx_sw)
 {
 	int min_xstate_size = sizeof(struct fxregs_state) +
 			      sizeof(struct xstate_header);
+	void __user *fpstate = fxbuf;
 	unsigned int magic2;
 
-	if (__copy_from_user(fx_sw, &buf->sw_reserved[0], sizeof(*fx_sw)))
-		return -1;
+	if (__copy_from_user(fx_sw, &fxbuf->sw_reserved[0], sizeof(*fx_sw)))
+		return false;
 
 	/* Check for the first magic field and other error scenarios. */
 	if (fx_sw->magic1 != FP_XSTATE_MAGIC1 ||
 	    fx_sw->xstate_size < min_xstate_size ||
-	    fx_sw->xstate_size > fpu_user_xstate_size ||
+	    fx_sw->xstate_size > current->thread.fpu.fpstate->user_size ||
 	    fx_sw->xstate_size > fx_sw->extended_size)
-		return -1;
+		goto setfx;
 
 	/*
 	 * Check for the presence of second magic word at the end of memory
@@ -45,26 +48,34 @@ static inline int check_for_xstate(struct fxregs_state __user *buf,
 	 * fpstate layout with out copying the extended state information
 	 * in the memory layout.
 	 */
-	if (__get_user(magic2, (__u32 __user *)(fpstate + fx_sw->xstate_size))
-	    || magic2 != FP_XSTATE_MAGIC2)
-		return -1;
-
-	return 0;
+	if (__get_user(magic2, (__u32 __user *)(fpstate + fx_sw->xstate_size)))
+		return false;
+
+	if (likely(magic2 == FP_XSTATE_MAGIC2))
+		return true;
+setfx:
+	trace_x86_fpu_xstate_check_failed(&current->thread.fpu);
+
+	/* Set the parameters for fx only state */
+	fx_sw->magic1 = 0;
+	fx_sw->xstate_size = sizeof(struct fxregs_state);
+	fx_sw->xfeatures = XFEATURE_MASK_FPSSE;
+	return true;
 }
 
 /*
  * Signal frame handlers.
  */
-static inline int save_fsave_header(struct task_struct *tsk, void __user *buf)
+static inline bool save_fsave_header(struct task_struct *tsk, void __user *buf)
 {
 	if (use_fxsr()) {
-		struct xregs_state *xsave = &tsk->thread.fpu.state.xsave;
+		struct xregs_state *xsave = &tsk->thread.fpu.fpstate->regs.xsave;
 		struct user_i387_ia32_struct env;
 		struct _fpstate_32 __user *fp = buf;
 
 		fpregs_lock();
 		if (!test_thread_flag(TIF_NEED_FPU_LOAD))
-			copy_fxregs_to_kernel(&tsk->thread.fpu);
+			fxsave(&tsk->thread.fpu.fpstate->regs.fxsave);
 		fpregs_unlock();
 
 		convert_from_fxsr(&env, tsk);
@@ -72,33 +83,54 @@ static inline int save_fsave_header(struct task_struct *tsk, void __user *buf)
 		if (__copy_to_user(buf, &env, sizeof(env)) ||
 		    __put_user(xsave->i387.swd, &fp->status) ||
 		    __put_user(X86_FXSR_MAGIC, &fp->magic))
-			return -1;
+			return false;
 	} else {
 		struct fregs_state __user *fp = buf;
 		u32 swd;
+
 		if (__get_user(swd, &fp->swd) || __put_user(swd, &fp->status))
-			return -1;
+			return false;
 	}
 
-	return 0;
+	return true;
+}
+
+/*
+ * Prepare the SW reserved portion of the fxsave memory layout, indicating
+ * the presence of the extended state information in the memory layout
+ * pointed to by the fpstate pointer in the sigcontext.
+ * This is saved when ever the FP and extended state context is
+ * saved on the user stack during the signal handler delivery to the user.
+ */
+static inline void save_sw_bytes(struct _fpx_sw_bytes *sw_bytes, bool ia32_frame,
+				 struct fpstate *fpstate)
+{
+	sw_bytes->magic1 = FP_XSTATE_MAGIC1;
+	sw_bytes->extended_size = fpstate->user_size + FP_XSTATE_MAGIC2_SIZE;
+	sw_bytes->xfeatures = fpstate->user_xfeatures;
+	sw_bytes->xstate_size = fpstate->user_size;
+
+	if (ia32_frame)
+		sw_bytes->extended_size += sizeof(struct fregs_state);
 }
 
-static inline int save_xstate_epilog(void __user *buf, int ia32_frame)
+static inline bool save_xstate_epilog(void __user *buf, int ia32_frame,
+				      struct fpstate *fpstate)
 {
 	struct xregs_state __user *x = buf;
-	struct _fpx_sw_bytes *sw_bytes;
+	struct _fpx_sw_bytes sw_bytes = {};
 	u32 xfeatures;
 	int err;
 
 	/* Setup the bytes not touched by the [f]xsave and reserved for SW. */
-	sw_bytes = ia32_frame ? &fx_sw_reserved_ia32 : &fx_sw_reserved;
-	err = __copy_to_user(&x->i387.sw_reserved, sw_bytes, sizeof(*sw_bytes));
+	save_sw_bytes(&sw_bytes, ia32_frame, fpstate);
+	err = __copy_to_user(&x->i387.sw_reserved, &sw_bytes, sizeof(sw_bytes));
 
 	if (!use_xsave())
-		return err;
+		return !err;
 
 	err |= __put_user(FP_XSTATE_MAGIC2,
-			  (__u32 __user *)(buf + fpu_user_xstate_size));
+			  (__u32 __user *)(buf + fpstate->user_size));
 
 	/*
 	 * Read the xfeatures which we copied (directly from the cpu or
@@ -121,23 +153,17 @@ static inline int save_xstate_epilog(void __user *buf, int ia32_frame)
 
 	err |= __put_user(xfeatures, (__u32 __user *)&x->header.xfeatures);
 
-	return err;
+	return !err;
 }
 
 static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf)
 {
-	int err;
-
 	if (use_xsave())
-		err = copy_xregs_to_user(buf);
-	else if (use_fxsr())
-		err = copy_fxregs_to_user((struct fxregs_state __user *) buf);
+		return xsave_to_user_sigframe(buf);
+	if (use_fxsr())
+		return fxsave_to_user_sigframe((struct fxregs_state __user *) buf);
 	else
-		err = copy_fregs_to_user((struct fregs_state __user *) buf);
-
-	if (unlikely(err) && __clear_user(buf, fpu_user_xstate_size))
-		err = -EFAULT;
-	return err;
+		return fnsave_to_user_sigframe((struct fregs_state __user *) buf);
 }
 
 /*
@@ -150,10 +176,8 @@ static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf)
  *	buf == buf_fx for 64-bit frames and 32-bit fsave frame.
  *	buf != buf_fx for 32-bit frames with fxstate.
  *
- * Try to save it directly to the user frame with disabled page fault handler.
- * If this fails then do the slow path where the FPU state is first saved to
- * task's fpu->state and then copy it to the user frame pointed to by the
- * aligned pointer 'buf_fx'.
+ * Save it directly to the user frame with disabled page fault handler. If
+ * that faults, try to clear the frame which handles the page fault.
  *
  * If this is a 32-bit frame with fxstate, put a fsave header before
  * the aligned state at 'buf_fx'.
@@ -161,23 +185,37 @@ static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf)
  * For [f]xsave state, update the SW reserved fields in the [f]xsave frame
  * indicating the absence/presence of the extended state to the user.
  */
-int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
+bool copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
 {
 	struct task_struct *tsk = current;
-	int ia32_fxstate = (buf != buf_fx);
+	struct fpstate *fpstate = tsk->thread.fpu.fpstate;
+	bool ia32_fxstate = (buf != buf_fx);
 	int ret;
 
 	ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
 			 IS_ENABLED(CONFIG_IA32_EMULATION));
 
+	if (!static_cpu_has(X86_FEATURE_FPU)) {
+		struct user_i387_ia32_struct fp;
+
+		fpregs_soft_get(current, NULL, (struct membuf){.p = &fp,
+						.left = sizeof(fp)});
+		return !copy_to_user(buf, &fp, sizeof(fp));
+	}
+
 	if (!access_ok(buf, size))
-		return -EACCES;
+		return false;
 
-	if (!static_cpu_has(X86_FEATURE_FPU))
-		return fpregs_soft_get(current, NULL, 0,
-			sizeof(struct user_i387_ia32_struct), NULL,
-			(struct _fpstate_32 __user *) buf) ? -1 : 1;
+	if (use_xsave()) {
+		struct xregs_state __user *xbuf = buf_fx;
 
+		/*
+		 * Clear the xsave header first, so that reserved fields are
+		 * initialized to zero.
+		 */
+		if (__clear_user(&xbuf->header, sizeof(xbuf->header)))
+			return false;
+	}
 retry:
 	/*
 	 * Load the FPU registers if they are not valid for the current task.
@@ -187,7 +225,7 @@ retry:
 	 */
 	fpregs_lock();
 	if (test_thread_flag(TIF_NEED_FPU_LOAD))
-		__fpregs_load_activate();
+		fpregs_restore_userregs();
 
 	pagefault_disable();
 	ret = copy_fpregs_to_sigframe(buf_fx);
@@ -195,252 +233,280 @@ retry:
 	fpregs_unlock();
 
 	if (ret) {
-		if (!fault_in_pages_writeable(buf_fx, fpu_user_xstate_size))
+		if (!__clear_user(buf_fx, fpstate->user_size))
 			goto retry;
-		return -EFAULT;
+		return false;
 	}
 
 	/* Save the fsave header for the 32-bit frames. */
-	if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf))
-		return -1;
+	if ((ia32_fxstate || !use_fxsr()) && !save_fsave_header(tsk, buf))
+		return false;
 
-	if (use_fxsr() && save_xstate_epilog(buf_fx, ia32_fxstate))
-		return -1;
+	if (use_fxsr() && !save_xstate_epilog(buf_fx, ia32_fxstate, fpstate))
+		return false;
 
-	return 0;
+	return true;
 }
 
-static inline void
-sanitize_restored_xstate(union fpregs_state *state,
-			 struct user_i387_ia32_struct *ia32_env,
-			 u64 xfeatures, int fx_only)
+static int __restore_fpregs_from_user(void __user *buf, u64 ufeatures,
+				      u64 xrestore, bool fx_only)
 {
-	struct xregs_state *xsave = &state->xsave;
-	struct xstate_header *header = &xsave->header;
-
 	if (use_xsave()) {
-		/*
-		 * Note: we don't need to zero the reserved bits in the
-		 * xstate_header here because we either didn't copy them at all,
-		 * or we checked earlier that they aren't set.
-		 */
+		u64 init_bv = ufeatures & ~xrestore;
+		int ret;
 
-		/*
-		 * Init the state that is not present in the memory
-		 * layout and not enabled by the OS.
-		 */
-		if (fx_only)
-			header->xfeatures = XFEATURE_MASK_FPSSE;
+		if (likely(!fx_only))
+			ret = xrstor_from_user_sigframe(buf, xrestore);
 		else
-			header->xfeatures &= xfeatures;
-	}
-
-	if (use_fxsr()) {
-		/*
-		 * mscsr reserved bits must be masked to zero for security
-		 * reasons.
-		 */
-		xsave->i387.mxcsr &= mxcsr_feature_mask;
+			ret = fxrstor_from_user_sigframe(buf);
 
-		if (ia32_env)
-			convert_to_fxsr(&state->fxsave, ia32_env);
+		if (!ret && unlikely(init_bv))
+			os_xrstor(&init_fpstate, init_bv);
+		return ret;
+	} else if (use_fxsr()) {
+		return fxrstor_from_user_sigframe(buf);
+	} else {
+		return frstor_from_user_sigframe(buf);
 	}
 }
 
 /*
- * Restore the extended state if present. Otherwise, restore the FP/SSE state.
+ * Attempt to restore the FPU registers directly from user memory.
+ * Pagefaults are handled and any errors returned are fatal.
  */
-static int copy_user_to_fpregs_zeroing(void __user *buf, u64 xbv, int fx_only)
+static bool restore_fpregs_from_user(void __user *buf, u64 xrestore,
+				     bool fx_only, unsigned int size)
 {
-	if (use_xsave()) {
-		if (fx_only) {
-			u64 init_bv = xfeatures_mask & ~XFEATURE_MASK_FPSSE;
-			copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
-			return copy_user_to_fxregs(buf);
-		} else {
-			u64 init_bv = xfeatures_mask & ~xbv;
-			if (unlikely(init_bv))
-				copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
-			return copy_user_to_xregs(buf, xbv);
-		}
-	} else if (use_fxsr()) {
-		return copy_user_to_fxregs(buf);
-	} else
-		return copy_user_to_fregs(buf);
+	struct fpu *fpu = &current->thread.fpu;
+	int ret;
+
+retry:
+	fpregs_lock();
+	/* Ensure that XFD is up to date */
+	xfd_update_state(fpu->fpstate);
+	pagefault_disable();
+	ret = __restore_fpregs_from_user(buf, fpu->fpstate->user_xfeatures,
+					 xrestore, fx_only);
+	pagefault_enable();
+
+	if (unlikely(ret)) {
+		/*
+		 * The above did an FPU restore operation, restricted to
+		 * the user portion of the registers, and failed, but the
+		 * microcode might have modified the FPU registers
+		 * nevertheless.
+		 *
+		 * If the FPU registers do not belong to current, then
+		 * invalidate the FPU register state otherwise the task
+		 * might preempt current and return to user space with
+		 * corrupted FPU registers.
+		 */
+		if (test_thread_flag(TIF_NEED_FPU_LOAD))
+			__cpu_invalidate_fpregs_state();
+		fpregs_unlock();
+
+		/* Try to handle #PF, but anything else is fatal. */
+		if (ret != X86_TRAP_PF)
+			return false;
+
+		if (!fault_in_readable(buf, size))
+			goto retry;
+		return false;
+	}
+
+	/*
+	 * Restore supervisor states: previous context switch etc has done
+	 * XSAVES and saved the supervisor states in the kernel buffer from
+	 * which they can be restored now.
+	 *
+	 * It would be optimal to handle this with a single XRSTORS, but
+	 * this does not work because the rest of the FPU registers have
+	 * been restored from a user buffer directly.
+	 */
+	if (test_thread_flag(TIF_NEED_FPU_LOAD) && xfeatures_mask_supervisor())
+		os_xrstor_supervisor(fpu->fpstate);
+
+	fpregs_mark_activate();
+	fpregs_unlock();
+	return true;
 }
 
-static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
+static bool __fpu_restore_sig(void __user *buf, void __user *buf_fx,
+			      bool ia32_fxstate)
 {
-	struct user_i387_ia32_struct *envp = NULL;
-	int state_size = fpu_kernel_xstate_size;
-	int ia32_fxstate = (buf != buf_fx);
 	struct task_struct *tsk = current;
 	struct fpu *fpu = &tsk->thread.fpu;
 	struct user_i387_ia32_struct env;
-	u64 xfeatures = 0;
-	int fx_only = 0;
-	int ret = 0;
-
-	ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
-			 IS_ENABLED(CONFIG_IA32_EMULATION));
+	bool success, fx_only = false;
+	union fpregs_state *fpregs;
+	unsigned int state_size;
+	u64 user_xfeatures = 0;
 
-	if (!buf) {
-		fpu__clear(fpu);
-		return 0;
-	}
+	if (use_xsave()) {
+		struct _fpx_sw_bytes fx_sw_user;
 
-	if (!access_ok(buf, size))
-		return -EACCES;
+		if (!check_xstate_in_sigframe(buf_fx, &fx_sw_user))
+			return false;
 
-	if (!static_cpu_has(X86_FEATURE_FPU))
-		return fpregs_soft_set(current, NULL,
-				       0, sizeof(struct user_i387_ia32_struct),
-				       NULL, buf) != 0;
+		fx_only = !fx_sw_user.magic1;
+		state_size = fx_sw_user.xstate_size;
+		user_xfeatures = fx_sw_user.xfeatures;
+	} else {
+		user_xfeatures = XFEATURE_MASK_FPSSE;
+		state_size = fpu->fpstate->user_size;
+	}
 
-	if (use_xsave()) {
-		struct _fpx_sw_bytes fx_sw_user;
-		if (unlikely(check_for_xstate(buf_fx, buf_fx, &fx_sw_user))) {
-			/*
-			 * Couldn't find the extended state information in the
-			 * memory layout. Restore just the FP/SSE and init all
-			 * the other extended state.
-			 */
-			state_size = sizeof(struct fxregs_state);
-			fx_only = 1;
-			trace_x86_fpu_xstate_check_failed(fpu);
-		} else {
-			state_size = fx_sw_user.xstate_size;
-			xfeatures = fx_sw_user.xfeatures;
-		}
+	if (likely(!ia32_fxstate)) {
+		/* Restore the FPU registers directly from user memory. */
+		return restore_fpregs_from_user(buf_fx, user_xfeatures, fx_only,
+						state_size);
 	}
 
 	/*
-	 * The current state of the FPU registers does not matter. By setting
-	 * TIF_NEED_FPU_LOAD unconditionally it is ensured that the our xstate
-	 * is not modified on context switch and that the xstate is considered
-	 * to be loaded again on return to userland (overriding last_cpu avoids
-	 * the optimisation).
+	 * Copy the legacy state because the FP portion of the FX frame has
+	 * to be ignored for histerical raisins. The legacy state is folded
+	 * in once the larger state has been copied.
 	 */
-	set_thread_flag(TIF_NEED_FPU_LOAD);
-	__fpu_invalidate_fpregs_state(fpu);
+	if (__copy_from_user(&env, buf, sizeof(env)))
+		return false;
 
-	if ((unsigned long)buf_fx % 64)
-		fx_only = 1;
 	/*
-	 * For 32-bit frames with fxstate, copy the fxstate so it can be
-	 * reconstructed later.
+	 * By setting TIF_NEED_FPU_LOAD it is ensured that our xstate is
+	 * not modified on context switch and that the xstate is considered
+	 * to be loaded again on return to userland (overriding last_cpu avoids
+	 * the optimisation).
 	 */
-	if (ia32_fxstate) {
-		ret = __copy_from_user(&env, buf, sizeof(env));
-		if (ret)
-			goto err_out;
-		envp = &env;
-	} else {
+	fpregs_lock();
+	if (!test_thread_flag(TIF_NEED_FPU_LOAD)) {
 		/*
-		 * Attempt to restore the FPU registers directly from user
-		 * memory. For that to succeed, the user access cannot cause
-		 * page faults. If it does, fall back to the slow path below,
-		 * going through the kernel buffer with the enabled pagefault
-		 * handler.
+		 * If supervisor states are available then save the
+		 * hardware state in current's fpstate so that the
+		 * supervisor state is preserved. Save the full state for
+		 * simplicity. There is no point in optimizing this by only
+		 * saving the supervisor states and then shuffle them to
+		 * the right place in memory. It's ia32 mode. Shrug.
 		 */
-		fpregs_lock();
-		pagefault_disable();
-		ret = copy_user_to_fpregs_zeroing(buf_fx, xfeatures, fx_only);
-		pagefault_enable();
-		if (!ret) {
-			fpregs_mark_activate();
-			fpregs_unlock();
-			return 0;
-		}
-		fpregs_deactivate(fpu);
-		fpregs_unlock();
+		if (xfeatures_mask_supervisor())
+			os_xsave(fpu->fpstate);
+		set_thread_flag(TIF_NEED_FPU_LOAD);
 	}
+	__fpu_invalidate_fpregs_state(fpu);
+	__cpu_invalidate_fpregs_state();
+	fpregs_unlock();
 
-
+	fpregs = &fpu->fpstate->regs;
 	if (use_xsave() && !fx_only) {
-		u64 init_bv = xfeatures_mask & ~xfeatures;
-
-		if (using_compacted_format()) {
-			ret = copy_user_to_xstate(&fpu->state.xsave, buf_fx);
+		if (copy_sigframe_from_user_to_xstate(fpu->fpstate, buf_fx))
+			return false;
+	} else {
+		if (__copy_from_user(&fpregs->fxsave, buf_fx,
+				     sizeof(fpregs->fxsave)))
+			return false;
+
+		if (IS_ENABLED(CONFIG_X86_64)) {
+			/* Reject invalid MXCSR values. */
+			if (fpregs->fxsave.mxcsr & ~mxcsr_feature_mask)
+				return false;
 		} else {
-			ret = __copy_from_user(&fpu->state.xsave, buf_fx, state_size);
-
-			if (!ret && state_size > offsetof(struct xregs_state, header))
-				ret = validate_xstate_header(&fpu->state.xsave.header);
+			/* Mask invalid bits out for historical reasons (broken hardware). */
+			fpregs->fxsave.mxcsr &= mxcsr_feature_mask;
 		}
-		if (ret)
-			goto err_out;
-
-		sanitize_restored_xstate(&fpu->state, envp, xfeatures, fx_only);
-
-		fpregs_lock();
-		if (unlikely(init_bv))
-			copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
-		ret = copy_kernel_to_xregs_err(&fpu->state.xsave, xfeatures);
 
-	} else if (use_fxsr()) {
-		ret = __copy_from_user(&fpu->state.fxsave, buf_fx, state_size);
-		if (ret) {
-			ret = -EFAULT;
-			goto err_out;
-		}
+		/* Enforce XFEATURE_MASK_FPSSE when XSAVE is enabled */
+		if (use_xsave())
+			fpregs->xsave.header.xfeatures |= XFEATURE_MASK_FPSSE;
+	}
 
-		sanitize_restored_xstate(&fpu->state, envp, xfeatures, fx_only);
+	/* Fold the legacy FP storage */
+	convert_to_fxsr(&fpregs->fxsave, &env);
 
-		fpregs_lock();
-		if (use_xsave()) {
-			u64 init_bv = xfeatures_mask & ~XFEATURE_MASK_FPSSE;
-			copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
-		}
+	fpregs_lock();
+	if (use_xsave()) {
+		/*
+		 * Remove all UABI feature bits not set in user_xfeatures
+		 * from the memory xstate header which makes the full
+		 * restore below bring them into init state. This works for
+		 * fx_only mode as well because that has only FP and SSE
+		 * set in user_xfeatures.
+		 *
+		 * Preserve supervisor states!
+		 */
+		u64 mask = user_xfeatures | xfeatures_mask_supervisor();
 
-		ret = copy_kernel_to_fxregs_err(&fpu->state.fxsave);
+		fpregs->xsave.header.xfeatures &= mask;
+		success = !os_xrstor_safe(fpu->fpstate,
+					  fpu_kernel_cfg.max_features);
 	} else {
-		ret = __copy_from_user(&fpu->state.fsave, buf_fx, state_size);
-		if (ret)
-			goto err_out;
-
-		fpregs_lock();
-		ret = copy_kernel_to_fregs_err(&fpu->state.fsave);
+		success = !fxrstor_safe(&fpregs->fxsave);
 	}
-	if (!ret)
+
+	if (likely(success))
 		fpregs_mark_activate();
-	else
-		fpregs_deactivate(fpu);
-	fpregs_unlock();
 
-err_out:
-	if (ret)
-		fpu__clear(fpu);
-	return ret;
+	fpregs_unlock();
+	return success;
 }
 
-static inline int xstate_sigframe_size(void)
+static inline unsigned int xstate_sigframe_size(struct fpstate *fpstate)
 {
-	return use_xsave() ? fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE :
-			fpu_user_xstate_size;
+	unsigned int size = fpstate->user_size;
+
+	return use_xsave() ? size + FP_XSTATE_MAGIC2_SIZE : size;
 }
 
 /*
  * Restore FPU state from a sigframe:
  */
-int fpu__restore_sig(void __user *buf, int ia32_frame)
+bool fpu__restore_sig(void __user *buf, int ia32_frame)
 {
+	struct fpu *fpu = &current->thread.fpu;
 	void __user *buf_fx = buf;
-	int size = xstate_sigframe_size();
+	bool ia32_fxstate = false;
+	bool success = false;
+	unsigned int size;
+
+	if (unlikely(!buf)) {
+		fpu__clear_user_states(fpu);
+		return true;
+	}
 
+	size = xstate_sigframe_size(fpu->fpstate);
+
+	ia32_frame &= (IS_ENABLED(CONFIG_X86_32) ||
+		       IS_ENABLED(CONFIG_IA32_EMULATION));
+
+	/*
+	 * Only FXSR enabled systems need the FX state quirk.
+	 * FRSTOR does not need it and can use the fast path.
+	 */
 	if (ia32_frame && use_fxsr()) {
 		buf_fx = buf + sizeof(struct fregs_state);
 		size += sizeof(struct fregs_state);
+		ia32_fxstate = true;
 	}
 
-	return __fpu__restore_sig(buf, buf_fx, size);
+	if (!access_ok(buf, size))
+		goto out;
+
+	if (!IS_ENABLED(CONFIG_X86_64) && !cpu_feature_enabled(X86_FEATURE_FPU)) {
+		success = !fpregs_soft_set(current, NULL, 0,
+					   sizeof(struct user_i387_ia32_struct),
+					   NULL, buf);
+	} else {
+		success = __fpu_restore_sig(buf, buf_fx, ia32_fxstate);
+	}
+
+out:
+	if (unlikely(!success))
+		fpu__clear_user_states(fpu);
+	return success;
 }
 
 unsigned long
 fpu__alloc_mathframe(unsigned long sp, int ia32_frame,
 		     unsigned long *buf_fx, unsigned long *size)
 {
-	unsigned long frame_size = xstate_sigframe_size();
+	unsigned long frame_size = xstate_sigframe_size(current->thread.fpu.fpstate);
 
 	*buf_fx = sp = round_down(sp - frame_size, 64);
 	if (ia32_frame && use_fxsr()) {
@@ -452,28 +518,25 @@ fpu__alloc_mathframe(unsigned long sp, int ia32_frame,
 
 	return sp;
 }
-/*
- * Prepare the SW reserved portion of the fxsave memory layout, indicating
- * the presence of the extended state information in the memory layout
- * pointed by the fpstate pointer in the sigcontext.
- * This will be saved when ever the FP and extended state context is
- * saved on the user stack during the signal handler delivery to the user.
- */
-void fpu__init_prepare_fx_sw_frame(void)
+
+unsigned long __init fpu__get_fpstate_size(void)
 {
-	int size = fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE;
+	unsigned long ret = fpu_user_cfg.max_size;
 
-	fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
-	fx_sw_reserved.extended_size = size;
-	fx_sw_reserved.xfeatures = xfeatures_mask;
-	fx_sw_reserved.xstate_size = fpu_user_xstate_size;
+	if (use_xsave())
+		ret += FP_XSTATE_MAGIC2_SIZE;
 
-	if (IS_ENABLED(CONFIG_IA32_EMULATION) ||
-	    IS_ENABLED(CONFIG_X86_32)) {
-		int fsave_header_size = sizeof(struct fregs_state);
+	/*
+	 * This space is needed on (most) 32-bit kernels, or when a 32-bit
+	 * app is running on a 64-bit kernel. To keep things simple, just
+	 * assume the worst case and always include space for 'freg_state',
+	 * even for 64-bit apps on 64-bit kernels. This wastes a bit of
+	 * space, but keeps the code simple.
+	 */
+	if ((IS_ENABLED(CONFIG_IA32_EMULATION) ||
+	     IS_ENABLED(CONFIG_X86_32)) && use_fxsr())
+		ret += sizeof(struct fregs_state);
 
-		fx_sw_reserved_ia32 = fx_sw_reserved;
-		fx_sw_reserved_ia32.extended_size = size + fsave_header_size;
-	}
+	return ret;
 }