1 files changed, 248 insertions, 396 deletions

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 1cadb2faf740..c8def1b7f8fb 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -59,19 +59,24 @@ static short xsave_cpuid_features[] __initdata = {
  * This represents the full set of bits that should ever be set in a kernel
  * XSAVE buffer, both supervisor and user xstates.
  */
-u64 xfeatures_mask_all __read_mostly;
-
-static unsigned int xstate_offsets[XFEATURE_MAX] = { [ 0 ... XFEATURE_MAX - 1] = -1};
-static unsigned int xstate_sizes[XFEATURE_MAX]   = { [ 0 ... XFEATURE_MAX - 1] = -1};
-static unsigned int xstate_comp_offsets[XFEATURE_MAX] = { [ 0 ... XFEATURE_MAX - 1] = -1};
-static unsigned int xstate_supervisor_only_offsets[XFEATURE_MAX] = { [ 0 ... XFEATURE_MAX - 1] = -1};
+u64 xfeatures_mask_all __ro_after_init;
+EXPORT_SYMBOL_GPL(xfeatures_mask_all);
+
+static unsigned int xstate_offsets[XFEATURE_MAX] __ro_after_init =
+	{ [ 0 ... XFEATURE_MAX - 1] = -1};
+static unsigned int xstate_sizes[XFEATURE_MAX] __ro_after_init =
+	{ [ 0 ... XFEATURE_MAX - 1] = -1};
+static unsigned int xstate_comp_offsets[XFEATURE_MAX] __ro_after_init =
+	{ [ 0 ... XFEATURE_MAX - 1] = -1};
+static unsigned int xstate_supervisor_only_offsets[XFEATURE_MAX] __ro_after_init =
+	{ [ 0 ... XFEATURE_MAX - 1] = -1};
 
 /*
  * The XSAVE area of kernel can be in standard or compacted format;
  * it is always in standard format for user mode. This is the user
  * mode standard format size used for signal and ptrace frames.
  */
-unsigned int fpu_user_xstate_size;
+unsigned int fpu_user_xstate_size __ro_after_init;
 
 /*
  * Return whether the system supports a given xfeature.
@@ -125,103 +130,13 @@ static bool xfeature_is_supervisor(int xfeature_nr)
 }
 
 /*
- * When executing XSAVEOPT (or other optimized XSAVE instructions), if
- * a processor implementation detects that an FPU state component is still
- * (or is again) in its initialized state, it may clear the corresponding
- * bit in the header.xfeatures field, and can skip the writeout of registers
- * to the corresponding memory layout.
- *
- * This means that when the bit is zero, the state component might still contain
- * some previous - non-initialized register state.
- *
- * Before writing xstate information to user-space we sanitize those components,
- * to always ensure that the memory layout of a feature will be in the init state
- * if the corresponding header bit is zero. This is to ensure that user-space doesn't
- * see some stale state in the memory layout during signal handling, debugging etc.
- */
-void fpstate_sanitize_xstate(struct fpu *fpu)
-{
-	struct fxregs_state *fx = &fpu->state.fxsave;
-	int feature_bit;
-	u64 xfeatures;
-
-	if (!use_xsaveopt())
-		return;
-
-	xfeatures = fpu->state.xsave.header.xfeatures;
-
-	/*
-	 * None of the feature bits are in init state. So nothing else
-	 * to do for us, as the memory layout is up to date.
-	 */
-	if ((xfeatures & xfeatures_mask_all) == xfeatures_mask_all)
-		return;
-
-	/*
-	 * FP is in init state
-	 */
-	if (!(xfeatures & XFEATURE_MASK_FP)) {
-		fx->cwd = 0x37f;
-		fx->swd = 0;
-		fx->twd = 0;
-		fx->fop = 0;
-		fx->rip = 0;
-		fx->rdp = 0;
-		memset(fx->st_space, 0, sizeof(fx->st_space));
-	}
-
-	/*
-	 * SSE is in init state
-	 */
-	if (!(xfeatures & XFEATURE_MASK_SSE))
-		memset(fx->xmm_space, 0, sizeof(fx->xmm_space));
-
-	/*
-	 * First two features are FPU and SSE, which above we handled
-	 * in a special way already:
-	 */
-	feature_bit = 0x2;
-	xfeatures = (xfeatures_mask_user() & ~xfeatures) >> 2;
-
-	/*
-	 * Update all the remaining memory layouts according to their
-	 * standard xstate layout, if their header bit is in the init
-	 * state:
-	 */
-	while (xfeatures) {
-		if (xfeatures & 0x1) {
-			int offset = xstate_comp_offsets[feature_bit];
-			int size = xstate_sizes[feature_bit];
-
-			memcpy((void *)fx + offset,
-			       (void *)&init_fpstate.xsave + offset,
-			       size);
-		}
-
-		xfeatures >>= 1;
-		feature_bit++;
-	}
-}
-
-/*
  * Enable the extended processor state save/restore feature.
  * Called once per CPU onlining.
  */
 void fpu__init_cpu_xstate(void)
 {
-	u64 unsup_bits;
-
 	if (!boot_cpu_has(X86_FEATURE_XSAVE) || !xfeatures_mask_all)
 		return;
-	/*
-	 * Unsupported supervisor xstates should not be found in
-	 * the xfeatures mask.
-	 */
-	unsup_bits = xfeatures_mask_all & XFEATURE_MASK_SUPERVISOR_UNSUPPORTED;
-	WARN_ONCE(unsup_bits, "x86/fpu: Found unsupported supervisor xstates: 0x%llx\n",
-		  unsup_bits);
-
-	xfeatures_mask_all &= ~XFEATURE_MASK_SUPERVISOR_UNSUPPORTED;
 
 	cr4_set_bits(X86_CR4_OSXSAVE);
 
@@ -230,14 +145,14 @@ void fpu__init_cpu_xstate(void)
 	 * managed by XSAVE{C, OPT, S} and XRSTOR{S}.  Only XSAVE user
 	 * states can be set here.
 	 */
-	xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask_user());
+	xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask_uabi());
 
 	/*
 	 * MSR_IA32_XSS sets supervisor states managed by XSAVES.
 	 */
 	if (boot_cpu_has(X86_FEATURE_XSAVES)) {
 		wrmsrl(MSR_IA32_XSS, xfeatures_mask_supervisor() |
-				     xfeatures_mask_dynamic());
+				     xfeatures_mask_independent());
 	}
 }
 
@@ -486,7 +401,7 @@ static void __init setup_init_fpu_buf(void)
 	/*
 	 * Init all the features state with header.xfeatures being 0x0
 	 */
-	copy_kernel_to_xregs_booting(&init_fpstate.xsave);
+	os_xrstor_booting(&init_fpstate.xsave);
 
 	/*
 	 * All components are now in init state. Read the state back so
@@ -535,25 +450,11 @@ int xfeature_size(int xfeature_nr)
 	return eax;
 }
 
-/*
- * 'XSAVES' implies two different things:
- * 1. saving of supervisor/system state
- * 2. using the compacted format
- *
- * Use this function when dealing with the compacted format so
- * that it is obvious which aspect of 'XSAVES' is being handled
- * by the calling code.
- */
-int using_compacted_format(void)
-{
-	return boot_cpu_has(X86_FEATURE_XSAVES);
-}
-
 /* Validate an xstate header supplied by userspace (ptrace or sigreturn) */
-int validate_user_xstate_header(const struct xstate_header *hdr)
+static int validate_user_xstate_header(const struct xstate_header *hdr)
 {
 	/* No unknown or supervisor features may be set */
-	if (hdr->xfeatures & ~xfeatures_mask_user())
+	if (hdr->xfeatures & ~xfeatures_mask_uabi())
 		return -EINVAL;
 
 	/* Userspace must use the uncompacted format */
@@ -651,7 +552,7 @@ static void check_xstate_against_struct(int nr)
  * how large the XSAVE buffer needs to be.  We are recalculating
  * it to be safe.
  *
- * Dynamic XSAVE features allocate their own buffers and are not
+ * Independent XSAVE features allocate their own buffers and are not
  * covered by these checks. Only the size of the buffer for task->fpu
  * is checked here.
  */
@@ -667,9 +568,9 @@ static void do_extra_xstate_size_checks(void)
 		check_xstate_against_struct(i);
 		/*
 		 * Supervisor state components can be managed only by
-		 * XSAVES, which is compacted-format only.
+		 * XSAVES.
 		 */
-		if (!using_compacted_format())
+		if (!cpu_feature_enabled(X86_FEATURE_XSAVES))
 			XSTATE_WARN_ON(xfeature_is_supervisor(i));
 
 		/* Align from the end of the previous feature */
@@ -679,9 +580,9 @@ static void do_extra_xstate_size_checks(void)
 		 * The offset of a given state in the non-compacted
 		 * format is given to us in a CPUID leaf.  We check
 		 * them for being ordered (increasing offsets) in
-		 * setup_xstate_features().
+		 * setup_xstate_features(). XSAVES uses compacted format.
 		 */
-		if (!using_compacted_format())
+		if (!cpu_feature_enabled(X86_FEATURE_XSAVES))
 			paranoid_xstate_size = xfeature_uncompacted_offset(i);
 		/*
 		 * The compacted-format offset always depends on where
@@ -717,18 +618,18 @@ static unsigned int __init get_xsaves_size(void)
 }
 
 /*
- * Get the total size of the enabled xstates without the dynamic supervisor
+ * Get the total size of the enabled xstates without the independent supervisor
  * features.
  */
-static unsigned int __init get_xsaves_size_no_dynamic(void)
+static unsigned int __init get_xsaves_size_no_independent(void)
 {
-	u64 mask = xfeatures_mask_dynamic();
+	u64 mask = xfeatures_mask_independent();
 	unsigned int size;
 
 	if (!mask)
 		return get_xsaves_size();
 
-	/* Disable dynamic features. */
+	/* Disable independent features. */
 	wrmsrl(MSR_IA32_XSS, xfeatures_mask_supervisor());
 
 	/*
@@ -737,7 +638,7 @@ static unsigned int __init get_xsaves_size_no_dynamic(void)
 	 */
 	size = get_xsaves_size();
 
-	/* Re-enable dynamic features so XSAVES will work on them again. */
+	/* Re-enable independent features so XSAVES will work on them again. */
 	wrmsrl(MSR_IA32_XSS, xfeatures_mask_supervisor() | mask);
 
 	return size;
@@ -780,7 +681,7 @@ static int __init init_xstate_size(void)
 	xsave_size = get_xsave_size();
 
 	if (boot_cpu_has(X86_FEATURE_XSAVES))
-		possible_xstate_size = get_xsaves_size_no_dynamic();
+		possible_xstate_size = get_xsaves_size_no_independent();
 	else
 		possible_xstate_size = xsave_size;
 
@@ -821,6 +722,7 @@ void __init fpu__init_system_xstate(void)
 {
 	unsigned int eax, ebx, ecx, edx;
 	static int on_boot_cpu __initdata = 1;
+	u64 xfeatures;
 	int err;
 	int i;
 
@@ -855,7 +757,7 @@ void __init fpu__init_system_xstate(void)
 	cpuid_count(XSTATE_CPUID, 1, &eax, &ebx, &ecx, &edx);
 	xfeatures_mask_all |= ecx + ((u64)edx << 32);
 
-	if ((xfeatures_mask_user() & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) {
+	if ((xfeatures_mask_uabi() & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) {
 		/*
 		 * This indicates that something really unexpected happened
 		 * with the enumeration.  Disable XSAVE and try to continue
@@ -874,7 +776,11 @@ void __init fpu__init_system_xstate(void)
 			xfeatures_mask_all &= ~BIT_ULL(i);
 	}
 
-	xfeatures_mask_all &= fpu__get_supported_xfeatures_mask();
+	xfeatures_mask_all &= XFEATURE_MASK_USER_SUPPORTED |
+			      XFEATURE_MASK_SUPERVISOR_SUPPORTED;
+
+	/* Store it for paranoia check at the end */
+	xfeatures = xfeatures_mask_all;
 
 	/* Enable xstate instructions to be able to continue with initialization: */
 	fpu__init_cpu_xstate();
@@ -886,14 +792,24 @@ void __init fpu__init_system_xstate(void)
 	 * Update info used for ptrace frames; use standard-format size and no
 	 * supervisor xstates:
 	 */
-	update_regset_xstate_info(fpu_user_xstate_size, xfeatures_mask_user());
+	update_regset_xstate_info(fpu_user_xstate_size, xfeatures_mask_uabi());
 
 	fpu__init_prepare_fx_sw_frame();
 	setup_init_fpu_buf();
 	setup_xstate_comp_offsets();
 	setup_supervisor_only_offsets();
-	print_xstate_offset_size();
 
+	/*
+	 * Paranoia check whether something in the setup modified the
+	 * xfeatures mask.
+	 */
+	if (xfeatures != xfeatures_mask_all) {
+		pr_err("x86/fpu: xfeatures modified from 0x%016llx to 0x%016llx during init, disabling XSAVE\n",
+		       xfeatures, xfeatures_mask_all);
+		goto out_disable;
+	}
+
+	print_xstate_offset_size();
 	pr_info("x86/fpu: Enabled xstate features 0x%llx, context size is %d bytes, using '%s' format.\n",
 		xfeatures_mask_all,
 		fpu_kernel_xstate_size,
@@ -913,16 +829,16 @@ void fpu__resume_cpu(void)
 	/*
 	 * Restore XCR0 on xsave capable CPUs:
 	 */
-	if (boot_cpu_has(X86_FEATURE_XSAVE))
-		xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask_user());
+	if (cpu_feature_enabled(X86_FEATURE_XSAVE))
+		xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask_uabi());
 
 	/*
 	 * Restore IA32_XSS. The same CPUID bit enumerates support
 	 * of XSAVES and MSR_IA32_XSS.
 	 */
-	if (boot_cpu_has(X86_FEATURE_XSAVES)) {
+	if (cpu_feature_enabled(X86_FEATURE_XSAVES)) {
 		wrmsrl(MSR_IA32_XSS, xfeatures_mask_supervisor()  |
-				     xfeatures_mask_dynamic());
+				     xfeatures_mask_independent());
 	}
 }
 
@@ -990,36 +906,6 @@ void *get_xsave_addr(struct xregs_state *xsave, int xfeature_nr)
 }
 EXPORT_SYMBOL_GPL(get_xsave_addr);
 
-/*
- * This wraps up the common operations that need to occur when retrieving
- * data from xsave state.  It first ensures that the current task was
- * using the FPU and retrieves the data in to a buffer.  It then calculates
- * the offset of the requested field in the buffer.
- *
- * This function is safe to call whether the FPU is in use or not.
- *
- * Note that this only works on the current task.
- *
- * Inputs:
- *	@xfeature_nr: state which is defined in xsave.h (e.g. XFEATURE_FP,
- *	XFEATURE_SSE, etc...)
- * Output:
- *	address of the state in the xsave area or NULL if the state
- *	is not present or is in its 'init state'.
- */
-const void *get_xsave_field_ptr(int xfeature_nr)
-{
-	struct fpu *fpu = &current->thread.fpu;
-
-	/*
-	 * fpu__save() takes the CPU's xstate registers
-	 * and saves them off to the 'fpu memory buffer.
-	 */
-	fpu__save(fpu);
-
-	return get_xsave_addr(&fpu->state.xsave, xfeature_nr);
-}
-
 #ifdef CONFIG_ARCH_HAS_PKEYS
 
 /*
@@ -1027,17 +913,16 @@ const void *get_xsave_field_ptr(int xfeature_nr)
  * rights for @pkey to @init_val.
  */
 int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
-		unsigned long init_val)
+			      unsigned long init_val)
 {
-	u32 old_pkru;
-	int pkey_shift = (pkey * PKRU_BITS_PER_PKEY);
-	u32 new_pkru_bits = 0;
+	u32 old_pkru, new_pkru_bits = 0;
+	int pkey_shift;
 
 	/*
 	 * This check implies XSAVE support.  OSPKE only gets
 	 * set if we enable XSAVE and we enable PKU in XCR0.
 	 */
-	if (!boot_cpu_has(X86_FEATURE_OSPKE))
+	if (!cpu_feature_enabled(X86_FEATURE_OSPKE))
 		return -EINVAL;
 
 	/*
@@ -1045,7 +930,8 @@ int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
 	 * values originating from in-kernel users.  Complain
 	 * if a bad value is observed.
 	 */
-	WARN_ON_ONCE(pkey >= arch_max_pkey());
+	if (WARN_ON_ONCE(pkey >= arch_max_pkey()))
+		return -EINVAL;
 
 	/* Set the bits we need in PKRU:  */
 	if (init_val & PKEY_DISABLE_ACCESS)
@@ -1054,6 +940,7 @@ int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
 		new_pkru_bits |= PKRU_WD_BIT;
 
 	/* Shift the bits in to the correct place in PKRU for pkey: */
+	pkey_shift = pkey * PKRU_BITS_PER_PKEY;
 	new_pkru_bits <<= pkey_shift;
 
 	/* Get old PKRU and mask off any old bits in place: */
@@ -1067,170 +954,178 @@ int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
 }
 #endif /* ! CONFIG_ARCH_HAS_PKEYS */
 
-/*
- * Weird legacy quirk: SSE and YMM states store information in the
- * MXCSR and MXCSR_FLAGS fields of the FP area. That means if the FP
- * area is marked as unused in the xfeatures header, we need to copy
- * MXCSR and MXCSR_FLAGS if either SSE or YMM are in use.
- */
-static inline bool xfeatures_mxcsr_quirk(u64 xfeatures)
+static void copy_feature(bool from_xstate, struct membuf *to, void *xstate,
+			 void *init_xstate, unsigned int size)
 {
-	if (!(xfeatures & (XFEATURE_MASK_SSE|XFEATURE_MASK_YMM)))
-		return false;
-
-	if (xfeatures & XFEATURE_MASK_FP)
-		return false;
-
-	return true;
-}
-
-static void fill_gap(struct membuf *to, unsigned *last, unsigned offset)
-{
-	if (*last >= offset)
-		return;
-	membuf_write(to, (void *)&init_fpstate.xsave + *last, offset - *last);
-	*last = offset;
-}
-
-static void copy_part(struct membuf *to, unsigned *last, unsigned offset,
-		      unsigned size, void *from)
-{
-	fill_gap(to, last, offset);
-	membuf_write(to, from, size);
-	*last = offset + size;
+	membuf_write(to, from_xstate ? xstate : init_xstate, size);
 }
 
-/*
- * Convert from kernel XSAVES compacted format to standard format and copy
- * to a kernel-space ptrace buffer.
+/**
+ * copy_xstate_to_uabi_buf - Copy kernel saved xstate to a UABI buffer
+ * @to:		membuf descriptor
+ * @tsk:	The task from which to copy the saved xstate
+ * @copy_mode:	The requested copy mode
+ *
+ * Converts from kernel XSAVE or XSAVES compacted format to UABI conforming
+ * format, i.e. from the kernel internal hardware dependent storage format
+ * to the requested @mode. UABI XSTATE is always uncompacted!
  *
- * It supports partial copy but pos always starts from zero. This is called
- * from xstateregs_get() and there we check the CPU has XSAVES.
+ * It supports partial copy but @to.pos always starts from zero.
  */
-void copy_xstate_to_kernel(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)
 {
+	const unsigned int off_mxcsr = offsetof(struct fxregs_state, mxcsr);
+	struct xregs_state *xsave = &tsk->thread.fpu.state.xsave;
+	struct xregs_state *xinit = &init_fpstate.xsave;
 	struct xstate_header header;
-	const unsigned off_mxcsr = offsetof(struct fxregs_state, mxcsr);
-	unsigned size = to.left;
-	unsigned last = 0;
+	unsigned int zerofrom;
 	int i;
 
-	/*
-	 * The destination is a ptrace buffer; we put in only user xstates:
-	 */
 	memset(&header, 0, sizeof(header));
 	header.xfeatures = xsave->header.xfeatures;
-	header.xfeatures &= xfeatures_mask_user();
-
-	if (header.xfeatures & XFEATURE_MASK_FP)
-		copy_part(&to, &last, 0, off_mxcsr, &xsave->i387);
-	if (header.xfeatures & (XFEATURE_MASK_SSE | XFEATURE_MASK_YMM))
-		copy_part(&to, &last, off_mxcsr,
-			  MXCSR_AND_FLAGS_SIZE, &xsave->i387.mxcsr);
-	if (header.xfeatures & XFEATURE_MASK_FP)
-		copy_part(&to, &last, offsetof(struct fxregs_state, st_space),
-			  128, &xsave->i387.st_space);
-	if (header.xfeatures & XFEATURE_MASK_SSE)
-		copy_part(&to, &last, xstate_offsets[XFEATURE_SSE],
-			  256, &xsave->i387.xmm_space);
-	/*
-	 * Fill xsave->i387.sw_reserved value for ptrace frame:
-	 */
-	copy_part(&to, &last, offsetof(struct fxregs_state, sw_reserved),
-		  48, xstate_fx_sw_bytes);
-	/*
-	 * Copy xregs_state->header:
-	 */
-	copy_part(&to, &last, offsetof(struct xregs_state, header),
-		  sizeof(header), &header);
 
-	for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
-		/*
-		 * Copy only in-use xstates:
-		 */
-		if ((header.xfeatures >> i) & 1) {
-			void *src = __raw_xsave_addr(xsave, i);
+	/* Mask out the feature bits depending on copy mode */
+	switch (copy_mode) {
+	case XSTATE_COPY_FP:
+		header.xfeatures &= XFEATURE_MASK_FP;
+		break;
 
-			copy_part(&to, &last, xstate_offsets[i],
-				  xstate_sizes[i], src);
-		}
+	case XSTATE_COPY_FX:
+		header.xfeatures &= XFEATURE_MASK_FP | XFEATURE_MASK_SSE;
+		break;
 
+	case XSTATE_COPY_XSAVE:
+		header.xfeatures &= xfeatures_mask_uabi();
+		break;
 	}
-	fill_gap(&to, &last, size);
-}
 
-/*
- * Convert from a ptrace standard-format kernel buffer to kernel XSAVES format
- * and copy to the target thread. This is called from xstateregs_set().
- */
-int copy_kernel_to_xstate(struct xregs_state *xsave, const void *kbuf)
-{
-	unsigned int offset, size;
-	int i;
-	struct xstate_header hdr;
+	/* Copy FP state up to MXCSR */
+	copy_feature(header.xfeatures & XFEATURE_MASK_FP, &to, &xsave->i387,
+		     &xinit->i387, off_mxcsr);
 
-	offset = offsetof(struct xregs_state, header);
-	size = sizeof(hdr);
+	/* Copy MXCSR when SSE or YMM are set in the feature mask */
+	copy_feature(header.xfeatures & (XFEATURE_MASK_SSE | XFEATURE_MASK_YMM),
+		     &to, &xsave->i387.mxcsr, &xinit->i387.mxcsr,
+		     MXCSR_AND_FLAGS_SIZE);
 
-	memcpy(&hdr, kbuf + offset, size);
+	/* Copy the remaining FP state */
+	copy_feature(header.xfeatures & XFEATURE_MASK_FP,
+		     &to, &xsave->i387.st_space, &xinit->i387.st_space,
+		     sizeof(xsave->i387.st_space));
 
-	if (validate_user_xstate_header(&hdr))
-		return -EINVAL;
+	/* Copy the SSE state - shared with YMM, but independently managed */
+	copy_feature(header.xfeatures & XFEATURE_MASK_SSE,
+		     &to, &xsave->i387.xmm_space, &xinit->i387.xmm_space,
+		     sizeof(xsave->i387.xmm_space));
 
-	for (i = 0; i < XFEATURE_MAX; i++) {
-		u64 mask = ((u64)1 << i);
+	if (copy_mode != XSTATE_COPY_XSAVE)
+		goto out;
 
-		if (hdr.xfeatures & mask) {
-			void *dst = __raw_xsave_addr(xsave, i);
+	/* Zero the padding area */
+	membuf_zero(&to, sizeof(xsave->i387.padding));
 
-			offset = xstate_offsets[i];
-			size = xstate_sizes[i];
+	/* Copy xsave->i387.sw_reserved */
+	membuf_write(&to, xstate_fx_sw_bytes, sizeof(xsave->i387.sw_reserved));
 
-			memcpy(dst, kbuf + offset, size);
-		}
-	}
+	/* Copy the user space relevant state of @xsave->header */
+	membuf_write(&to, &header, sizeof(header));
 
-	if (xfeatures_mxcsr_quirk(hdr.xfeatures)) {
-		offset = offsetof(struct fxregs_state, mxcsr);
-		size = MXCSR_AND_FLAGS_SIZE;
-		memcpy(&xsave->i387.mxcsr, kbuf + offset, size);
-	}
+	zerofrom = offsetof(struct xregs_state, extended_state_area);
 
-	/*
-	 * The state that came in from userspace was user-state only.
-	 * Mask all the user states out of 'xfeatures':
-	 */
-	xsave->header.xfeatures &= XFEATURE_MASK_SUPERVISOR_ALL;
+	for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
+		/*
+		 * The ptrace buffer is in non-compacted XSAVE format.
+		 * In non-compacted format disabled features still occupy
+		 * state space, but there is no state to copy from in the
+		 * compacted init_fpstate. The gap tracking will zero this
+		 * later.
+		 */
+		if (!(xfeatures_mask_uabi() & BIT_ULL(i)))
+			continue;
 
-	/*
-	 * Add back in the features that came in from userspace:
-	 */
-	xsave->header.xfeatures |= hdr.xfeatures;
+		/*
+		 * If there was a feature or alignment gap, zero the space
+		 * in the destination buffer.
+		 */
+		if (zerofrom < xstate_offsets[i])
+			membuf_zero(&to, xstate_offsets[i] - zerofrom);
+
+		if (i == XFEATURE_PKRU) {
+			struct pkru_state pkru = {0};
+			/*
+			 * PKRU is not necessarily up to date in the
+			 * thread's XSAVE buffer.  Fill this part from the
+			 * per-thread storage.
+			 */
+			pkru.pkru = tsk->thread.pkru;
+			membuf_write(&to, &pkru, sizeof(pkru));
+		} else {
+			copy_feature(header.xfeatures & BIT_ULL(i), &to,
+				     __raw_xsave_addr(xsave, i),
+				     __raw_xsave_addr(xinit, i),
+				     xstate_sizes[i]);
+		}
+		/*
+		 * Keep track of the last copied state in the non-compacted
+		 * target buffer for gap zeroing.
+		 */
+		zerofrom = xstate_offsets[i] + xstate_sizes[i];
+	}
+
+out:
+	if (to.left)
+		membuf_zero(&to, to.left);
+}
 
+static int copy_from_buffer(void *dst, unsigned int offset, unsigned int size,
+			    const void *kbuf, const void __user *ubuf)
+{
+	if (kbuf) {
+		memcpy(dst, kbuf + offset, size);
+	} else {
+		if (copy_from_user(dst, ubuf + offset, size))
+			return -EFAULT;
+	}
 	return 0;
 }
 
-/*
- * Convert from a ptrace or sigreturn standard-format user-space buffer to
- * kernel XSAVES format and copy to the target thread. This is called from
- * xstateregs_set(), as well as potentially from the sigreturn() and
- * rt_sigreturn() system calls.
- */
-int copy_user_to_xstate(struct xregs_state *xsave, const void __user *ubuf)
+
+static int copy_uabi_to_xstate(struct xregs_state *xsave, const void *kbuf,
+			       const void __user *ubuf)
 {
 	unsigned int offset, size;
-	int i;
 	struct xstate_header hdr;
+	u64 mask;
+	int i;
 
 	offset = offsetof(struct xregs_state, header);
-	size = sizeof(hdr);
-
-	if (__copy_from_user(&hdr, ubuf + offset, size))
+	if (copy_from_buffer(&hdr, offset, sizeof(hdr), kbuf, ubuf))
 		return -EFAULT;
 
 	if (validate_user_xstate_header(&hdr))
 		return -EINVAL;
 
+	/* Validate MXCSR when any of the related features is in use */
+	mask = XFEATURE_MASK_FP | XFEATURE_MASK_SSE | XFEATURE_MASK_YMM;
+	if (hdr.xfeatures & mask) {
+		u32 mxcsr[2];
+
+		offset = offsetof(struct fxregs_state, mxcsr);
+		if (copy_from_buffer(mxcsr, offset, sizeof(mxcsr), kbuf, ubuf))
+			return -EFAULT;
+
+		/* Reserved bits in MXCSR must be zero. */
+		if (mxcsr[0] & ~mxcsr_feature_mask)
+			return -EINVAL;
+
+		/* SSE and YMM require MXCSR even when FP is not in use. */
+		if (!(hdr.xfeatures & XFEATURE_MASK_FP)) {
+			xsave->i387.mxcsr = mxcsr[0];
+			xsave->i387.mxcsr_mask = mxcsr[1];
+		}
+	}
+
 	for (i = 0; i < XFEATURE_MAX; i++) {
 		u64 mask = ((u64)1 << i);
 
@@ -1240,18 +1135,11 @@ int copy_user_to_xstate(struct xregs_state *xsave, const void __user *ubuf)
 			offset = xstate_offsets[i];
 			size = xstate_sizes[i];
 
-			if (__copy_from_user(dst, ubuf + offset, size))
+			if (copy_from_buffer(dst, offset, size, kbuf, ubuf))
 				return -EFAULT;
 		}
 	}
 
-	if (xfeatures_mxcsr_quirk(hdr.xfeatures)) {
-		offset = offsetof(struct fxregs_state, mxcsr);
-		size = MXCSR_AND_FLAGS_SIZE;
-		if (__copy_from_user(&xsave->i387.mxcsr, ubuf + offset, size))
-			return -EFAULT;
-	}
-
 	/*
 	 * The state that came in from userspace was user-state only.
 	 * Mask all the user states out of 'xfeatures':
@@ -1267,130 +1155,94 @@ int copy_user_to_xstate(struct xregs_state *xsave, const void __user *ubuf)
 }
 
 /*
- * Save only supervisor states to the kernel buffer.  This blows away all
- * old states, and is intended to be used only in __fpu__restore_sig(), where
- * user states are restored from the user buffer.
+ * Convert from a ptrace standard-format kernel buffer to kernel XSAVE[S]
+ * format and copy to the target thread. This is called from
+ * xstateregs_set().
  */
-void copy_supervisor_to_kernel(struct xregs_state *xstate)
+int copy_uabi_from_kernel_to_xstate(struct xregs_state *xsave, const void *kbuf)
 {
-	struct xstate_header *header;
-	u64 max_bit, min_bit;
-	u32 lmask, hmask;
-	int err, i;
-
-	if (WARN_ON(!boot_cpu_has(X86_FEATURE_XSAVES)))
-		return;
-
-	if (!xfeatures_mask_supervisor())
-		return;
-
-	max_bit = __fls(xfeatures_mask_supervisor());
-	min_bit = __ffs(xfeatures_mask_supervisor());
-
-	lmask = xfeatures_mask_supervisor();
-	hmask = xfeatures_mask_supervisor() >> 32;
-	XSTATE_OP(XSAVES, xstate, lmask, hmask, err);
+	return copy_uabi_to_xstate(xsave, kbuf, NULL);
+}
 
-	/* We should never fault when copying to a kernel buffer: */
-	if (WARN_ON_FPU(err))
-		return;
+/*
+ * Convert from a sigreturn standard-format user-space buffer to kernel
+ * XSAVE[S] format and copy to the target thread. This is called from the
+ * sigreturn() and rt_sigreturn() system calls.
+ */
+int copy_sigframe_from_user_to_xstate(struct xregs_state *xsave,
+				      const void __user *ubuf)
+{
+	return copy_uabi_to_xstate(xsave, NULL, ubuf);
+}
 
-	/*
-	 * At this point, the buffer has only supervisor states and must be
-	 * converted back to normal kernel format.
-	 */
-	header = &xstate->header;
-	header->xcomp_bv |= xfeatures_mask_all;
+static bool validate_xsaves_xrstors(u64 mask)
+{
+	u64 xchk;
 
+	if (WARN_ON_FPU(!cpu_feature_enabled(X86_FEATURE_XSAVES)))
+		return false;
 	/*
-	 * This only moves states up in the buffer.  Start with
-	 * the last state and move backwards so that states are
-	 * not overwritten until after they are moved.  Note:
-	 * memmove() allows overlapping src/dst buffers.
+	 * Validate that this is either a task->fpstate related component
+	 * subset or an independent one.
 	 */
-	for (i = max_bit; i >= min_bit; i--) {
-		u8 *xbuf = (u8 *)xstate;
+	if (mask & xfeatures_mask_independent())
+		xchk = ~xfeatures_mask_independent();
+	else
+		xchk = ~xfeatures_mask_all;
 
-		if (!((header->xfeatures >> i) & 1))
-			continue;
+	if (WARN_ON_ONCE(!mask || mask & xchk))
+		return false;
 
-		/* Move xfeature 'i' into its normal location */
-		memmove(xbuf + xstate_comp_offsets[i],
-			xbuf + xstate_supervisor_only_offsets[i],
-			xstate_sizes[i]);
-	}
+	return true;
 }
 
 /**
- * copy_dynamic_supervisor_to_kernel() - Save dynamic supervisor states to
- *                                       an xsave area
- * @xstate: A pointer to an xsave area
- * @mask: Represent the dynamic supervisor features saved into the xsave area
+ * xsaves - Save selected components to a kernel xstate buffer
+ * @xstate:	Pointer to the buffer
+ * @mask:	Feature mask to select the components to save
  *
- * Only the dynamic supervisor states sets in the mask are saved into the xsave
- * area (See the comment in XFEATURE_MASK_DYNAMIC for the details of dynamic
- * supervisor feature). Besides the dynamic supervisor states, the legacy
- * region and XSAVE header are also saved into the xsave area. The supervisor
- * features in the XFEATURE_MASK_SUPERVISOR_SUPPORTED and
- * XFEATURE_MASK_SUPERVISOR_UNSUPPORTED are not saved.
+ * The @xstate buffer must be 64 byte aligned and correctly initialized as
+ * XSAVES does not write the full xstate header. Before first use the
+ * buffer should be zeroed otherwise a consecutive XRSTORS from that buffer
+ * can #GP.
  *
- * The xsave area must be 64-bytes aligned.
+ * The feature mask must either be a subset of the independent features or
+ * a subset of the task->fpstate related features.
  */
-void copy_dynamic_supervisor_to_kernel(struct xregs_state *xstate, u64 mask)
+void xsaves(struct xregs_state *xstate, u64 mask)
 {
-	u64 dynamic_mask = xfeatures_mask_dynamic() & mask;
-	u32 lmask, hmask;
 	int err;
 
-	if (WARN_ON_FPU(!boot_cpu_has(X86_FEATURE_XSAVES)))
-		return;
-
-	if (WARN_ON_FPU(!dynamic_mask))
+	if (!validate_xsaves_xrstors(mask))
 		return;
 
-	lmask = dynamic_mask;
-	hmask = dynamic_mask >> 32;
-
-	XSTATE_OP(XSAVES, xstate, lmask, hmask, err);
-
-	/* Should never fault when copying to a kernel buffer */
-	WARN_ON_FPU(err);
+	XSTATE_OP(XSAVES, xstate, (u32)mask, (u32)(mask >> 32), err);
+	WARN_ON_ONCE(err);
 }
 
 /**
- * copy_kernel_to_dynamic_supervisor() - Restore dynamic supervisor states from
- *                                       an xsave area
- * @xstate: A pointer to an xsave area
- * @mask: Represent the dynamic supervisor features restored from the xsave area
+ * xrstors - Restore selected components from a kernel xstate buffer
+ * @xstate:	Pointer to the buffer
+ * @mask:	Feature mask to select the components to restore
  *
- * Only the dynamic supervisor states sets in the mask are restored from the
- * xsave area (See the comment in XFEATURE_MASK_DYNAMIC for the details of
- * dynamic supervisor feature). Besides the dynamic supervisor states, the
- * legacy region and XSAVE header are also restored from the xsave area. The
- * supervisor features in the XFEATURE_MASK_SUPERVISOR_SUPPORTED and
- * XFEATURE_MASK_SUPERVISOR_UNSUPPORTED are not restored.
+ * The @xstate buffer must be 64 byte aligned and correctly initialized
+ * otherwise XRSTORS from that buffer can #GP.
  *
- * The xsave area must be 64-bytes aligned.
+ * Proper usage is to restore the state which was saved with
+ * xsaves() into @xstate.
+ *
+ * The feature mask must either be a subset of the independent features or
+ * a subset of the task->fpstate related features.
  */
-void copy_kernel_to_dynamic_supervisor(struct xregs_state *xstate, u64 mask)
+void xrstors(struct xregs_state *xstate, u64 mask)
 {
-	u64 dynamic_mask = xfeatures_mask_dynamic() & mask;
-	u32 lmask, hmask;
 	int err;
 
-	if (WARN_ON_FPU(!boot_cpu_has(X86_FEATURE_XSAVES)))
-		return;
-
-	if (WARN_ON_FPU(!dynamic_mask))
+	if (!validate_xsaves_xrstors(mask))
 		return;
 
-	lmask = dynamic_mask;
-	hmask = dynamic_mask >> 32;
-
-	XSTATE_OP(XRSTORS, xstate, lmask, hmask, err);
-
-	/* Should never fault when copying from a kernel buffer */
-	WARN_ON_FPU(err);
+	XSTATE_OP(XRSTORS, xstate, (u32)mask, (u32)(mask >> 32), err);
+	WARN_ON_ONCE(err);
 }
 
 #ifdef CONFIG_PROC_PID_ARCH_STATUS