arch/x86/kernel/fpu/regset.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * FPU register's regset abstraction, for ptrace, core dumps, etc.
  */
 #include <asm/fpu/internal.h>
 #include <asm/fpu/signal.h>
 #include <asm/fpu/regset.h>
 #include <asm/fpu/xstate.h>
 #include <linux/sched/task_stack.h>

 /*
  * The xstateregs_active() routine is the same as the regset_fpregs_active() routine,
  * as the "regset->n" for the xstate regset will be updated based on the feature
  * capabilities supported by the xsave.
  */
 int regset_fpregs_active(struct task_struct *target, const struct user_regset *regset)
 {
 	return regset->n;
 }

 int regset_xregset_fpregs_active(struct task_struct *target, const struct user_regset *regset)
 {
 	if (boot_cpu_has(X86_FEATURE_FXSR))
 		return regset->n;
 	else
 		return 0;
 }

 int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
 		unsigned int pos, unsigned int count,
 		void *kbuf, void __user *ubuf)
 {
 	struct fpu *fpu = &target->thread.fpu;

 	if (!boot_cpu_has(X86_FEATURE_FXSR))
 		return -ENODEV;

 	fpu__prepare_read(fpu);
 	fpstate_sanitize_xstate(fpu);

 	return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
 				   &fpu->state.fxsave, 0, -1);
 }

 int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
 		unsigned int pos, unsigned int count,
 		const void *kbuf, const void __user *ubuf)
 {
 	struct fpu *fpu = &target->thread.fpu;
 	int ret;

 	if (!boot_cpu_has(X86_FEATURE_FXSR))
 		return -ENODEV;

 	fpu__prepare_write(fpu);
 	fpstate_sanitize_xstate(fpu);

 	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
 				 &fpu->state.fxsave, 0, -1);

 	/*
 	 * mxcsr reserved bits must be masked to zero for security reasons.
 	 */
 	fpu->state.fxsave.mxcsr &= mxcsr_feature_mask;

 	/*
 	 * update the header bits in the xsave header, indicating the
 	 * presence of FP and SSE state.
 	 */
 	if (boot_cpu_has(X86_FEATURE_XSAVE))
 		fpu->state.xsave.header.xfeatures |= XFEATURE_MASK_FPSSE;

 	return ret;
 }

 int xstateregs_get(struct task_struct *target, const struct user_regset *regset,
 		unsigned int pos, unsigned int count,
 		void *kbuf, void __user *ubuf)
 {
 	struct fpu *fpu = &target->thread.fpu;
 	struct xregs_state *xsave;
 	int ret;

 	if (!boot_cpu_has(X86_FEATURE_XSAVE))
 		return -ENODEV;

 	xsave = &fpu->state.xsave;

 	fpu__prepare_read(fpu);

 	if (using_compacted_format()) {
 		if (kbuf)
 			ret = copy_xstate_to_kernel(kbuf, xsave, pos, count);
 		else
 			ret = copy_xstate_to_user(ubuf, xsave, pos, count);
 	} else {
 		fpstate_sanitize_xstate(fpu);
 		/*
 		 * Copy the 48 bytes defined by the software into the xsave
 		 * area in the thread struct, so that we can copy the whole
 		 * area to user using one user_regset_copyout().
 		 */
 		memcpy(&xsave->i387.sw_reserved, xstate_fx_sw_bytes, sizeof(xstate_fx_sw_bytes));

 		/*
 		 * Copy the xstate memory layout.
 		 */
 		ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, xsave, 0, -1);
 	}
 	return ret;
 }

 int xstateregs_set(struct task_struct *target, const struct user_regset *regset,
 		  unsigned int pos, unsigned int count,
 		  const void *kbuf, const void __user *ubuf)
 {
 	struct fpu *fpu = &target->thread.fpu;
 	struct xregs_state *xsave;
 	int ret;

 	if (!boot_cpu_has(X86_FEATURE_XSAVE))
 		return -ENODEV;

 	/*
 	 * A whole standard-format XSAVE buffer is needed:
 	 */
 	if ((pos != 0) || (count < fpu_user_xstate_size))
 		return -EFAULT;

 	xsave = &fpu->state.xsave;

 	fpu__prepare_write(fpu);

 	if (using_compacted_format()) {
 		if (kbuf)
 			ret = copy_kernel_to_xstate(xsave, kbuf);
 		else
 			ret = copy_user_to_xstate(xsave, ubuf);
 	} else {
 		ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, xsave, 0, -1);
 		if (!ret)
 			ret = validate_user_xstate_header(&xsave->header);
 	}

 	/*
 	 * mxcsr reserved bits must be masked to zero for security reasons.
 	 */
 	xsave->i387.mxcsr &= mxcsr_feature_mask;

 	/*
 	 * In case of failure, mark all states as init:
 	 */
 	if (ret)
 		fpstate_init(&fpu->state);

 	return ret;
 }

 #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION

 /*
  * FPU tag word conversions.
  */

 static inline unsigned short twd_i387_to_fxsr(unsigned short twd)
 {
 	unsigned int tmp; /* to avoid 16 bit prefixes in the code */

 	/* Transform each pair of bits into 01 (valid) or 00 (empty) */
 	tmp = ~twd;
 	tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
 	/* and move the valid bits to the lower byte. */
 	tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
 	tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
 	tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */

 	return tmp;
 }

 #define FPREG_ADDR(f, n)	((void *)&(f)->st_space + (n) * 16)
 #define FP_EXP_TAG_VALID	0
 #define FP_EXP_TAG_ZERO		1
 #define FP_EXP_TAG_SPECIAL	2
 #define FP_EXP_TAG_EMPTY	3

 static inline u32 twd_fxsr_to_i387(struct fxregs_state *fxsave)
 {
 	struct _fpxreg *st;
 	u32 tos = (fxsave->swd >> 11) & 7;
 	u32 twd = (unsigned long) fxsave->twd;
 	u32 tag;
 	u32 ret = 0xffff0000u;
 	int i;

 	for (i = 0; i < 8; i++, twd >>= 1) {
 		if (twd & 0x1) {
 			st = FPREG_ADDR(fxsave, (i - tos) & 7);

 			switch (st->exponent & 0x7fff) {
 			case 0x7fff:
 				tag = FP_EXP_TAG_SPECIAL;
 				break;
 			case 0x0000:
 				if (!st->significand[0] &&
 				    !st->significand[1] &&
 				    !st->significand[2] &&
 				    !st->significand[3])
 					tag = FP_EXP_TAG_ZERO;
 				else
 					tag = FP_EXP_TAG_SPECIAL;
 				break;
 			default:
 				if (st->significand[3] & 0x8000)
 					tag = FP_EXP_TAG_VALID;
 				else
 					tag = FP_EXP_TAG_SPECIAL;
 				break;
 			}
 		} else {
 			tag = FP_EXP_TAG_EMPTY;
 		}
 		ret |= tag << (2 * i);
 	}
 	return ret;
 }

 /*
  * FXSR floating point environment conversions.
  */

 void
 convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk)
 {
 	struct fxregs_state *fxsave = &tsk->thread.fpu.state.fxsave;
 	struct _fpreg *to = (struct _fpreg *) &env->st_space[0];
 	struct _fpxreg *from = (struct _fpxreg *) &fxsave->st_space[0];
 	int i;

 	env->cwd = fxsave->cwd | 0xffff0000u;
 	env->swd = fxsave->swd | 0xffff0000u;
 	env->twd = twd_fxsr_to_i387(fxsave);

 #ifdef CONFIG_X86_64
 	env->fip = fxsave->rip;
 	env->foo = fxsave->rdp;
 	/*
 	 * should be actually ds/cs at fpu exception time, but
 	 * that information is not available in 64bit mode.
 	 */
 	env->fcs = task_pt_regs(tsk)->cs;
 	if (tsk == current) {
 		savesegment(ds, env->fos);
 	} else {
 		env->fos = tsk->thread.ds;
 	}
 	env->fos |= 0xffff0000;
 #else
 	env->fip = fxsave->fip;
 	env->fcs = (u16) fxsave->fcs | ((u32) fxsave->fop << 16);
 	env->foo = fxsave->foo;
 	env->fos = fxsave->fos;
 #endif

 	for (i = 0; i < 8; ++i)
 		memcpy(&to[i], &from[i], sizeof(to[0]));
 }

 void convert_to_fxsr(struct fxregs_state *fxsave,
 		     const struct user_i387_ia32_struct *env)

 {
 	struct _fpreg *from = (struct _fpreg *) &env->st_space[0];
 	struct _fpxreg *to = (struct _fpxreg *) &fxsave->st_space[0];
 	int i;

 	fxsave->cwd = env->cwd;
 	fxsave->swd = env->swd;
 	fxsave->twd = twd_i387_to_fxsr(env->twd);
 	fxsave->fop = (u16) ((u32) env->fcs >> 16);
 #ifdef CONFIG_X86_64
 	fxsave->rip = env->fip;
 	fxsave->rdp = env->foo;
 	/* cs and ds ignored */
 #else
 	fxsave->fip = env->fip;
 	fxsave->fcs = (env->fcs & 0xffff);
 	fxsave->foo = env->foo;
 	fxsave->fos = env->fos;
 #endif

 	for (i = 0; i < 8; ++i)
 		memcpy(&to[i], &from[i], sizeof(from[0]));
 }

 int fpregs_get(struct task_struct *target, const struct user_regset *regset,
 	       unsigned int pos, unsigned int count,
 	       void *kbuf, void __user *ubuf)
 {
 	struct fpu *fpu = &target->thread.fpu;
 	struct user_i387_ia32_struct env;

 	fpu__prepare_read(fpu);

 	if (!boot_cpu_has(X86_FEATURE_FPU))
 		return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf);

 	if (!boot_cpu_has(X86_FEATURE_FXSR))
 		return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
 					   &fpu->state.fsave, 0,
 					   -1);

 	fpstate_sanitize_xstate(fpu);

 	if (kbuf && pos == 0 && count == sizeof(env)) {
 		convert_from_fxsr(kbuf, target);
 		return 0;
 	}

 	convert_from_fxsr(&env, target);

 	return user_regset_copyout(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
 }

 int fpregs_set(struct task_struct *target, const struct user_regset *regset,
 	       unsigned int pos, unsigned int count,
 	       const void *kbuf, const void __user *ubuf)
 {
 	struct fpu *fpu = &target->thread.fpu;
 	struct user_i387_ia32_struct env;
 	int ret;

 	fpu__prepare_write(fpu);
 	fpstate_sanitize_xstate(fpu);

 	if (!boot_cpu_has(X86_FEATURE_FPU))
 		return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf);

 	if (!boot_cpu_has(X86_FEATURE_FXSR))
 		return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
 					  &fpu->state.fsave, 0,
 					  -1);

 	if (pos > 0 || count < sizeof(env))
 		convert_from_fxsr(&env, target);

 	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
 	if (!ret)
 		convert_to_fxsr(&target->thread.fpu.state.fxsave, &env);

 	/*
 	 * update the header bit in the xsave header, indicating the
 	 * presence of FP.
 	 */
 	if (boot_cpu_has(X86_FEATURE_XSAVE))
 		fpu->state.xsave.header.xfeatures |= XFEATURE_MASK_FP;
 	return ret;
 }

 /*
  * FPU state for core dumps.
  * This is only used for a.out dumps now.
  * It is declared generically using elf_fpregset_t (which is
  * struct user_i387_struct) but is in fact only used for 32-bit
  * dumps, so on 64-bit it is really struct user_i387_ia32_struct.
  */
 int dump_fpu(struct pt_regs *regs, struct user_i387_struct *ufpu)
 {
 	struct task_struct *tsk = current;

 	return !fpregs_get(tsk, NULL, 0, sizeof(struct user_i387_ia32_struct),
 			   ufpu, NULL);
 }
 EXPORT_SYMBOL(dump_fpu);

 #endif	/* CONFIG_X86_32 || CONFIG_IA32_EMULATION */
	// SPDX-License-Identifier: GPL-2.0
	/*
	* FPU register's regset abstraction, for ptrace, core dumps, etc.
	*/
	#include <asm/fpu/internal.h>
	#include <asm/fpu/signal.h>
	#include <asm/fpu/regset.h>
	#include <asm/fpu/xstate.h>
	#include <linux/sched/task_stack.h>

	/*
	* The xstateregs_active() routine is the same as the regset_fpregs_active() routine,
	* as the "regset->n" for the xstate regset will be updated based on the feature
	* capabilities supported by the xsave.
	*/
	int regset_fpregs_active(struct task_struct target, const struct user_regset regset)
	{
	return regset->n;
	}

	int regset_xregset_fpregs_active(struct task_struct target, const struct user_regset regset)
	{
	if (boot_cpu_has(X86_FEATURE_FXSR))
	return regset->n;
	else
	return 0;
	}

	int xfpregs_get(struct task_struct target, const struct user_regset regset,
	unsigned int pos, unsigned int count,
	void kbuf, void __user ubuf)
	{
	struct fpu *fpu = &target->thread.fpu;

	if (!boot_cpu_has(X86_FEATURE_FXSR))
	return -ENODEV;

	fpu__prepare_read(fpu);
	fpstate_sanitize_xstate(fpu);

	return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
	&fpu->state.fxsave, 0, -1);
	}

	int xfpregs_set(struct task_struct target, const struct user_regset regset,
	unsigned int pos, unsigned int count,
	const void kbuf, const void __user ubuf)
	{
	struct fpu *fpu = &target->thread.fpu;
	int ret;

	if (!boot_cpu_has(X86_FEATURE_FXSR))
	return -ENODEV;

	fpu__prepare_write(fpu);
	fpstate_sanitize_xstate(fpu);

	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
	&fpu->state.fxsave, 0, -1);

	/*
	* mxcsr reserved bits must be masked to zero for security reasons.
	*/
	fpu->state.fxsave.mxcsr &= mxcsr_feature_mask;

	/*
	* update the header bits in the xsave header, indicating the
	* presence of FP and SSE state.
	*/
	if (boot_cpu_has(X86_FEATURE_XSAVE))
	fpu->state.xsave.header.xfeatures \|= XFEATURE_MASK_FPSSE;

	return ret;
	}

	int xstateregs_get(struct task_struct target, const struct user_regset regset,
	unsigned int pos, unsigned int count,
	void kbuf, void __user ubuf)
	{
	struct fpu *fpu = &target->thread.fpu;
	struct xregs_state *xsave;
	int ret;

	if (!boot_cpu_has(X86_FEATURE_XSAVE))
	return -ENODEV;

	xsave = &fpu->state.xsave;

	fpu__prepare_read(fpu);

	if (using_compacted_format()) {
	if (kbuf)
	ret = copy_xstate_to_kernel(kbuf, xsave, pos, count);
	else
	ret = copy_xstate_to_user(ubuf, xsave, pos, count);
	} else {
	fpstate_sanitize_xstate(fpu);
	/*
	* Copy the 48 bytes defined by the software into the xsave
	* area in the thread struct, so that we can copy the whole
	* area to user using one user_regset_copyout().
	*/
	memcpy(&xsave->i387.sw_reserved, xstate_fx_sw_bytes, sizeof(xstate_fx_sw_bytes));

	/*
	* Copy the xstate memory layout.
	*/
	ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, xsave, 0, -1);
	}
	return ret;
	}

	int xstateregs_set(struct task_struct target, const struct user_regset regset,
	unsigned int pos, unsigned int count,
	const void kbuf, const void __user ubuf)
	{
	struct fpu *fpu = &target->thread.fpu;
	struct xregs_state *xsave;
	int ret;

	if (!boot_cpu_has(X86_FEATURE_XSAVE))
	return -ENODEV;

	/*
	* A whole standard-format XSAVE buffer is needed:
	*/
	if ((pos != 0) \|\| (count < fpu_user_xstate_size))
	return -EFAULT;

	xsave = &fpu->state.xsave;

	fpu__prepare_write(fpu);

	if (using_compacted_format()) {
	if (kbuf)
	ret = copy_kernel_to_xstate(xsave, kbuf);
	else
	ret = copy_user_to_xstate(xsave, ubuf);
	} else {
	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, xsave, 0, -1);
	if (!ret)
	ret = validate_user_xstate_header(&xsave->header);
	}

	/*
	* mxcsr reserved bits must be masked to zero for security reasons.
	*/
	xsave->i387.mxcsr &= mxcsr_feature_mask;

	/*
	* In case of failure, mark all states as init:
	*/
	if (ret)
	fpstate_init(&fpu->state);

	return ret;
	}

	#if defined CONFIG_X86_32 \|\| defined CONFIG_IA32_EMULATION

	/*
	* FPU tag word conversions.
	*/

	static inline unsigned short twd_i387_to_fxsr(unsigned short twd)
	{
	unsigned int tmp; /* to avoid 16 bit prefixes in the code */

	/* Transform each pair of bits into 01 (valid) or 00 (empty) */
	tmp = ~twd;
	tmp = (tmp \| (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
	/* and move the valid bits to the lower byte. */
	tmp = (tmp \| (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
	tmp = (tmp \| (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
	tmp = (tmp \| (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */

	return tmp;
	}

	#define FPREG_ADDR(f, n) ((void )&(f)->st_space + (n) 16)
	#define FP_EXP_TAG_VALID 0
	#define FP_EXP_TAG_ZERO 1
	#define FP_EXP_TAG_SPECIAL 2
	#define FP_EXP_TAG_EMPTY 3

	static inline u32 twd_fxsr_to_i387(struct fxregs_state *fxsave)
	{
	struct _fpxreg *st;
	u32 tos = (fxsave->swd >> 11) & 7;
	u32 twd = (unsigned long) fxsave->twd;
	u32 tag;
	u32 ret = 0xffff0000u;
	int i;

	for (i = 0; i < 8; i++, twd >>= 1) {
	if (twd & 0x1) {
	st = FPREG_ADDR(fxsave, (i - tos) & 7);

	switch (st->exponent & 0x7fff) {
	case 0x7fff:
	tag = FP_EXP_TAG_SPECIAL;
	break;
	case 0x0000:
	if (!st->significand[0] &&
	!st->significand[1] &&
	!st->significand[2] &&
	!st->significand[3])
	tag = FP_EXP_TAG_ZERO;
	else
	tag = FP_EXP_TAG_SPECIAL;
	break;
	default:
	if (st->significand[3] & 0x8000)
	tag = FP_EXP_TAG_VALID;
	else
	tag = FP_EXP_TAG_SPECIAL;
	break;
	}
	} else {
	tag = FP_EXP_TAG_EMPTY;
	}
	ret \|= tag << (2 * i);
	}
	return ret;
	}

	/*
	* FXSR floating point environment conversions.
	*/

	void
	convert_from_fxsr(struct user_i387_ia32_struct env, struct task_struct tsk)
	{
	struct fxregs_state *fxsave = &tsk->thread.fpu.state.fxsave;
	struct _fpreg to = (struct _fpreg ) &env->st_space[0];
	struct _fpxreg from = (struct _fpxreg ) &fxsave->st_space[0];
	int i;

	env->cwd = fxsave->cwd \| 0xffff0000u;
	env->swd = fxsave->swd \| 0xffff0000u;
	env->twd = twd_fxsr_to_i387(fxsave);

	#ifdef CONFIG_X86_64
	env->fip = fxsave->rip;
	env->foo = fxsave->rdp;
	/*
	* should be actually ds/cs at fpu exception time, but
	* that information is not available in 64bit mode.
	*/
	env->fcs = task_pt_regs(tsk)->cs;
	if (tsk == current) {
	savesegment(ds, env->fos);
	} else {
	env->fos = tsk->thread.ds;
	}
	env->fos \|= 0xffff0000;
	#else
	env->fip = fxsave->fip;
	env->fcs = (u16) fxsave->fcs \| ((u32) fxsave->fop << 16);
	env->foo = fxsave->foo;
	env->fos = fxsave->fos;
	#endif

	for (i = 0; i < 8; ++i)
	memcpy(&to[i], &from[i], sizeof(to[0]));
	}

	void convert_to_fxsr(struct fxregs_state *fxsave,
	const struct user_i387_ia32_struct *env)

	{
	struct _fpreg from = (struct _fpreg ) &env->st_space[0];
	struct _fpxreg to = (struct _fpxreg ) &fxsave->st_space[0];
	int i;

	fxsave->cwd = env->cwd;
	fxsave->swd = env->swd;
	fxsave->twd = twd_i387_to_fxsr(env->twd);
	fxsave->fop = (u16) ((u32) env->fcs >> 16);
	#ifdef CONFIG_X86_64
	fxsave->rip = env->fip;
	fxsave->rdp = env->foo;
	/* cs and ds ignored */
	#else
	fxsave->fip = env->fip;
	fxsave->fcs = (env->fcs & 0xffff);
	fxsave->foo = env->foo;
	fxsave->fos = env->fos;
	#endif

	for (i = 0; i < 8; ++i)
	memcpy(&to[i], &from[i], sizeof(from[0]));
	}

	int fpregs_get(struct task_struct target, const struct user_regset regset,
	unsigned int pos, unsigned int count,
	void kbuf, void __user ubuf)
	{
	struct fpu *fpu = &target->thread.fpu;
	struct user_i387_ia32_struct env;

	fpu__prepare_read(fpu);

	if (!boot_cpu_has(X86_FEATURE_FPU))
	return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf);

	if (!boot_cpu_has(X86_FEATURE_FXSR))
	return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
	&fpu->state.fsave, 0,
	-1);

	fpstate_sanitize_xstate(fpu);

	if (kbuf && pos == 0 && count == sizeof(env)) {
	convert_from_fxsr(kbuf, target);
	return 0;
	}

	convert_from_fxsr(&env, target);

	return user_regset_copyout(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
	}

	int fpregs_set(struct task_struct target, const struct user_regset regset,
	unsigned int pos, unsigned int count,
	const void kbuf, const void __user ubuf)
	{
	struct fpu *fpu = &target->thread.fpu;
	struct user_i387_ia32_struct env;
	int ret;

	fpu__prepare_write(fpu);
	fpstate_sanitize_xstate(fpu);

	if (!boot_cpu_has(X86_FEATURE_FPU))
	return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf);

	if (!boot_cpu_has(X86_FEATURE_FXSR))
	return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
	&fpu->state.fsave, 0,
	-1);

	if (pos > 0 \|\| count < sizeof(env))
	convert_from_fxsr(&env, target);

	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
	if (!ret)
	convert_to_fxsr(&target->thread.fpu.state.fxsave, &env);

	/*
	* update the header bit in the xsave header, indicating the
	* presence of FP.
	*/
	if (boot_cpu_has(X86_FEATURE_XSAVE))
	fpu->state.xsave.header.xfeatures \|= XFEATURE_MASK_FP;
	return ret;
	}

	/*
	* FPU state for core dumps.
	* This is only used for a.out dumps now.
	* It is declared generically using elf_fpregset_t (which is
	* struct user_i387_struct) but is in fact only used for 32-bit
	* dumps, so on 64-bit it is really struct user_i387_ia32_struct.
	*/
	int dump_fpu(struct pt_regs regs, struct user_i387_struct ufpu)
	{
	struct task_struct *tsk = current;

	return !fpregs_get(tsk, NULL, 0, sizeof(struct user_i387_ia32_struct),
	ufpu, NULL);
	}
	EXPORT_SYMBOL(dump_fpu);

	#endif /* CONFIG_X86_32 \|\| CONFIG_IA32_EMULATION */