arch/x86/kernel/xsave.c - maze/linux - Git at Google

 /*
  * xsave/xrstor support.
  *
  * Author: Suresh Siddha <suresh.b.siddha@intel.com>
  */
 #include <linux/bootmem.h>
 #include <linux/compat.h>
 #include <asm/i387.h>
 #ifdef CONFIG_IA32_EMULATION
 #include <asm/sigcontext32.h>
 #endif
 #include <asm/xcr.h>

 /*
  * Supported feature mask by the CPU and the kernel.
  */
 u64 pcntxt_mask;

 struct _fpx_sw_bytes fx_sw_reserved;
 #ifdef CONFIG_IA32_EMULATION
 struct _fpx_sw_bytes fx_sw_reserved_ia32;
 #endif

 /*
  * Check for the presence of extended state information in the
  * user fpstate pointer in the sigcontext.
  */
 int check_for_xstate(struct i387_fxsave_struct __user *buf,
 		     void __user *fpstate,
 		     struct _fpx_sw_bytes *fx_sw_user)
 {
 	int min_xstate_size = sizeof(struct i387_fxsave_struct) +
 			      sizeof(struct xsave_hdr_struct);
 	unsigned int magic2;
 	int err;

 	err = __copy_from_user(fx_sw_user, &buf->sw_reserved[0],
 			       sizeof(struct _fpx_sw_bytes));

 	if (err)
 		return err;

 	/*
 	 * First Magic check failed.
 	 */
 	if (fx_sw_user->magic1 != FP_XSTATE_MAGIC1)
 		return -1;

 	/*
 	 * Check for error scenarios.
 	 */
 	if (fx_sw_user->xstate_size < min_xstate_size ||
 	    fx_sw_user->xstate_size > xstate_size ||
 	    fx_sw_user->xstate_size > fx_sw_user->extended_size)
 		return -1;

 	err = __get_user(magic2, (__u32 *) (((void *)fpstate) +
 					    fx_sw_user->extended_size -
 					    FP_XSTATE_MAGIC2_SIZE));
 	/*
 	 * Check for the presence of second magic word at the end of memory
 	 * layout. This detects the case where the user just copied the legacy
 	 * fpstate layout with out copying the extended state information
 	 * in the memory layout.
 	 */
 	if (err || magic2 != FP_XSTATE_MAGIC2)
 		return -1;

 	return 0;
 }

 #ifdef CONFIG_X86_64
 /*
  * Signal frame handlers.
  */

 int save_i387_xstate(void __user *buf)
 {
 	struct task_struct *tsk = current;
 	int err = 0;

 	if (!access_ok(VERIFY_WRITE, buf, sig_xstate_size))
 		return -EACCES;

 	BUG_ON(sig_xstate_size < xstate_size);

 	if ((unsigned long)buf % 64)
 		printk("save_i387_xstate: bad fpstate %p\n", buf);

 	if (!used_math())
 		return 0;

 	if (task_thread_info(tsk)->status & TS_USEDFPU) {
 		/*
 	 	 * Start with clearing the user buffer. This will present a
 	 	 * clean context for the bytes not touched by the fxsave/xsave.
 		 */
 		err = __clear_user(buf, sig_xstate_size);
 		if (err)
 			return err;

 		if (task_thread_info(tsk)->status & TS_XSAVE)
 			err = xsave_user(buf);
 		else
 			err = fxsave_user(buf);

 		if (err)
 			return err;
 		task_thread_info(tsk)->status &= ~TS_USEDFPU;
 		stts();
 	} else {
 		if (__copy_to_user(buf, &tsk->thread.xstate->fxsave,
 				   xstate_size))
 			return -1;
 	}

 	clear_used_math(); /* trigger finit */

 	if (task_thread_info(tsk)->status & TS_XSAVE) {
 		struct _fpstate __user *fx = buf;
 		struct _xstate __user *x = buf;
 		u64 xstate_bv;

 		err = __copy_to_user(&fx->sw_reserved, &fx_sw_reserved,
 				     sizeof(struct _fpx_sw_bytes));

 		err |= __put_user(FP_XSTATE_MAGIC2,
 				  (__u32 __user *) (buf + sig_xstate_size
 						    - FP_XSTATE_MAGIC2_SIZE));

 		/*
 		 * Read the xstate_bv which we copied (directly from the cpu or
 		 * from the state in task struct) to the user buffers and
 		 * set the FP/SSE bits.
 		 */
 		err |= __get_user(xstate_bv, &x->xstate_hdr.xstate_bv);

 		/*
 		 * For legacy compatible, we always set FP/SSE bits in the bit
 		 * vector while saving the state to the user context. This will
 		 * enable us capturing any changes(during sigreturn) to
 		 * the FP/SSE bits by the legacy applications which don't touch
 		 * xstate_bv in the xsave header.
 		 *
 		 * xsave aware apps can change the xstate_bv in the xsave
 		 * header as well as change any contents in the memory layout.
 		 * xrestore as part of sigreturn will capture all the changes.
 		 */
 		xstate_bv |= XSTATE_FPSSE;

 		err |= __put_user(xstate_bv, &x->xstate_hdr.xstate_bv);

 		if (err)
 			return err;
 	}

 	return 1;
 }

 /*
  * Restore the extended state if present. Otherwise, restore the FP/SSE
  * state.
  */
 static int restore_user_xstate(void __user *buf)
 {
 	struct _fpx_sw_bytes fx_sw_user;
 	u64 mask;
 	int err;

 	if (((unsigned long)buf % 64) ||
 	     check_for_xstate(buf, buf, &fx_sw_user))
 		goto fx_only;

 	mask = fx_sw_user.xstate_bv;

 	/*
 	 * restore the state passed by the user.
 	 */
 	err = xrestore_user(buf, mask);
 	if (err)
 		return err;

 	/*
 	 * init the state skipped by the user.
 	 */
 	mask = pcntxt_mask & ~mask;

 	xrstor_state(init_xstate_buf, mask);

 	return 0;

 fx_only:
 	/*
 	 * couldn't find the extended state information in the
 	 * memory layout. Restore just the FP/SSE and init all
 	 * the other extended state.
 	 */
 	xrstor_state(init_xstate_buf, pcntxt_mask & ~XSTATE_FPSSE);
 	return fxrstor_checking((__force struct i387_fxsave_struct *)buf);
 }

 /*
  * This restores directly out of user space. Exceptions are handled.
  */
 int restore_i387_xstate(void __user *buf)
 {
 	struct task_struct *tsk = current;
 	int err = 0;

 	if (!buf) {
 		if (used_math())
 			goto clear;
 		return 0;
 	} else
 		if (!access_ok(VERIFY_READ, buf, sig_xstate_size))
 			return -EACCES;

 	if (!used_math()) {
 		err = init_fpu(tsk);
 		if (err)
 			return err;
 	}

 	if (!(task_thread_info(current)->status & TS_USEDFPU)) {
 		clts();
 		task_thread_info(current)->status |= TS_USEDFPU;
 	}
 	if (task_thread_info(tsk)->status & TS_XSAVE)
 		err = restore_user_xstate(buf);
 	else
 		err = fxrstor_checking((__force struct i387_fxsave_struct *)
 				       buf);
 	if (unlikely(err)) {
 		/*
 		 * Encountered an error while doing the restore from the
 		 * user buffer, clear the fpu state.
 		 */
 clear:
 		clear_fpu(tsk);
 		clear_used_math();
 	}
 	return err;
 }
 #endif

 /*
  * 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.
  */
 static void prepare_fx_sw_frame(void)
 {
 	int size_extended = (xstate_size - sizeof(struct i387_fxsave_struct)) +
 			     FP_XSTATE_MAGIC2_SIZE;

 	sig_xstate_size = sizeof(struct _fpstate) + size_extended;

 #ifdef CONFIG_IA32_EMULATION
 	sig_xstate_ia32_size = sizeof(struct _fpstate_ia32) + size_extended;
 #endif

 	memset(&fx_sw_reserved, 0, sizeof(fx_sw_reserved));

 	fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
 	fx_sw_reserved.extended_size = sig_xstate_size;
 	fx_sw_reserved.xstate_bv = pcntxt_mask;
 	fx_sw_reserved.xstate_size = xstate_size;
 #ifdef CONFIG_IA32_EMULATION
 	memcpy(&fx_sw_reserved_ia32, &fx_sw_reserved,
 	       sizeof(struct _fpx_sw_bytes));
 	fx_sw_reserved_ia32.extended_size = sig_xstate_ia32_size;
 #endif
 }

 /*
  * Represents init state for the supported extended state.
  */
 struct xsave_struct *init_xstate_buf;

 #ifdef CONFIG_X86_64
 unsigned int sig_xstate_size = sizeof(struct _fpstate);
 #endif

 /*
  * Enable the extended processor state save/restore feature
  */
 void __cpuinit xsave_init(void)
 {
 	if (!cpu_has_xsave)
 		return;

 	set_in_cr4(X86_CR4_OSXSAVE);

 	/*
 	 * Enable all the features that the HW is capable of
 	 * and the Linux kernel is aware of.
 	 */
 	xsetbv(XCR_XFEATURE_ENABLED_MASK, pcntxt_mask);
 }

 /*
  * setup the xstate image representing the init state
  */
 static void __init setup_xstate_init(void)
 {
 	init_xstate_buf = alloc_bootmem(xstate_size);
 	init_xstate_buf->i387.mxcsr = MXCSR_DEFAULT;
 }

 /*
  * Enable and initialize the xsave feature.
  */
 void __ref xsave_cntxt_init(void)
 {
 	unsigned int eax, ebx, ecx, edx;

 	cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx);
 	pcntxt_mask = eax + ((u64)edx << 32);

 	if ((pcntxt_mask & XSTATE_FPSSE) != XSTATE_FPSSE) {
 		printk(KERN_ERR "FP/SSE not shown under xsave features 0x%llx\n",
 		       pcntxt_mask);
 		BUG();
 	}

 	/*
 	 * Support only the state known to OS.
 	 */
 	pcntxt_mask = pcntxt_mask & XCNTXT_MASK;
 	xsave_init();

 	/*
 	 * Recompute the context size for enabled features
 	 */
 	cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx);
 	xstate_size = ebx;

 	update_regset_xstate_info(xstate_size, pcntxt_mask);
 	prepare_fx_sw_frame();

 	setup_xstate_init();

 	printk(KERN_INFO "xsave/xrstor: enabled xstate_bv 0x%llx, "
 	       "cntxt size 0x%x\n",
 	       pcntxt_mask, xstate_size);
 }
	/*
	* xsave/xrstor support.
	*
	* Author: Suresh Siddha <suresh.b.siddha@intel.com>
	*/
	#include <linux/bootmem.h>
	#include <linux/compat.h>
	#include <asm/i387.h>
	#ifdef CONFIG_IA32_EMULATION
	#include <asm/sigcontext32.h>
	#endif
	#include <asm/xcr.h>

	/*
	* Supported feature mask by the CPU and the kernel.
	*/
	u64 pcntxt_mask;

	struct _fpx_sw_bytes fx_sw_reserved;
	#ifdef CONFIG_IA32_EMULATION
	struct _fpx_sw_bytes fx_sw_reserved_ia32;
	#endif

	/*
	* Check for the presence of extended state information in the
	* user fpstate pointer in the sigcontext.
	*/
	int check_for_xstate(struct i387_fxsave_struct __user *buf,
	void __user *fpstate,
	struct _fpx_sw_bytes *fx_sw_user)
	{
	int min_xstate_size = sizeof(struct i387_fxsave_struct) +
	sizeof(struct xsave_hdr_struct);
	unsigned int magic2;
	int err;

	err = __copy_from_user(fx_sw_user, &buf->sw_reserved[0],
	sizeof(struct _fpx_sw_bytes));

	if (err)
	return err;

	/*
	* First Magic check failed.
	*/
	if (fx_sw_user->magic1 != FP_XSTATE_MAGIC1)
	return -1;

	/*
	* Check for error scenarios.
	*/
	if (fx_sw_user->xstate_size < min_xstate_size \|\|
	fx_sw_user->xstate_size > xstate_size \|\|
	fx_sw_user->xstate_size > fx_sw_user->extended_size)
	return -1;

	err = __get_user(magic2, (__u32 ) (((void )fpstate) +
	fx_sw_user->extended_size -
	FP_XSTATE_MAGIC2_SIZE));
	/*
	* Check for the presence of second magic word at the end of memory
	* layout. This detects the case where the user just copied the legacy
	* fpstate layout with out copying the extended state information
	* in the memory layout.
	*/
	if (err \|\| magic2 != FP_XSTATE_MAGIC2)
	return -1;

	return 0;
	}

	#ifdef CONFIG_X86_64
	/*
	* Signal frame handlers.
	*/

	int save_i387_xstate(void __user *buf)
	{
	struct task_struct *tsk = current;
	int err = 0;

	if (!access_ok(VERIFY_WRITE, buf, sig_xstate_size))
	return -EACCES;

	BUG_ON(sig_xstate_size < xstate_size);

	if ((unsigned long)buf % 64)
	printk("save_i387_xstate: bad fpstate %p\n", buf);

	if (!used_math())
	return 0;

	if (task_thread_info(tsk)->status & TS_USEDFPU) {
	/*
	* Start with clearing the user buffer. This will present a
	* clean context for the bytes not touched by the fxsave/xsave.
	*/
	err = __clear_user(buf, sig_xstate_size);
	if (err)
	return err;

	if (task_thread_info(tsk)->status & TS_XSAVE)
	err = xsave_user(buf);
	else
	err = fxsave_user(buf);

	if (err)
	return err;
	task_thread_info(tsk)->status &= ~TS_USEDFPU;
	stts();
	} else {
	if (__copy_to_user(buf, &tsk->thread.xstate->fxsave,
	xstate_size))
	return -1;
	}

	clear_used_math(); /* trigger finit */

	if (task_thread_info(tsk)->status & TS_XSAVE) {
	struct _fpstate __user *fx = buf;
	struct _xstate __user *x = buf;
	u64 xstate_bv;

	err = __copy_to_user(&fx->sw_reserved, &fx_sw_reserved,
	sizeof(struct _fpx_sw_bytes));

	err \|= __put_user(FP_XSTATE_MAGIC2,
	(__u32 __user *) (buf + sig_xstate_size
	- FP_XSTATE_MAGIC2_SIZE));

	/*
	* Read the xstate_bv which we copied (directly from the cpu or
	* from the state in task struct) to the user buffers and
	* set the FP/SSE bits.
	*/
	err \|= __get_user(xstate_bv, &x->xstate_hdr.xstate_bv);

	/*
	* For legacy compatible, we always set FP/SSE bits in the bit
	* vector while saving the state to the user context. This will
	* enable us capturing any changes(during sigreturn) to
	* the FP/SSE bits by the legacy applications which don't touch
	* xstate_bv in the xsave header.
	*
	* xsave aware apps can change the xstate_bv in the xsave
	* header as well as change any contents in the memory layout.
	* xrestore as part of sigreturn will capture all the changes.
	*/
	xstate_bv \|= XSTATE_FPSSE;

	err \|= __put_user(xstate_bv, &x->xstate_hdr.xstate_bv);

	if (err)
	return err;
	}

	return 1;
	}

	/*
	* Restore the extended state if present. Otherwise, restore the FP/SSE
	* state.
	*/
	static int restore_user_xstate(void __user *buf)
	{
	struct _fpx_sw_bytes fx_sw_user;
	u64 mask;
	int err;

	if (((unsigned long)buf % 64) \|\|
	check_for_xstate(buf, buf, &fx_sw_user))
	goto fx_only;

	mask = fx_sw_user.xstate_bv;

	/*
	* restore the state passed by the user.
	*/
	err = xrestore_user(buf, mask);
	if (err)
	return err;

	/*
	* init the state skipped by the user.
	*/
	mask = pcntxt_mask & ~mask;

	xrstor_state(init_xstate_buf, mask);

	return 0;

	fx_only:
	/*
	* couldn't find the extended state information in the
	* memory layout. Restore just the FP/SSE and init all
	* the other extended state.
	*/
	xrstor_state(init_xstate_buf, pcntxt_mask & ~XSTATE_FPSSE);
	return fxrstor_checking((__force struct i387_fxsave_struct *)buf);
	}

	/*
	* This restores directly out of user space. Exceptions are handled.
	*/
	int restore_i387_xstate(void __user *buf)
	{
	struct task_struct *tsk = current;
	int err = 0;

	if (!buf) {
	if (used_math())
	goto clear;
	return 0;
	} else
	if (!access_ok(VERIFY_READ, buf, sig_xstate_size))
	return -EACCES;

	if (!used_math()) {
	err = init_fpu(tsk);
	if (err)
	return err;
	}

	if (!(task_thread_info(current)->status & TS_USEDFPU)) {
	clts();
	task_thread_info(current)->status \|= TS_USEDFPU;
	}
	if (task_thread_info(tsk)->status & TS_XSAVE)
	err = restore_user_xstate(buf);
	else
	err = fxrstor_checking((__force struct i387_fxsave_struct *)
	buf);
	if (unlikely(err)) {
	/*
	* Encountered an error while doing the restore from the
	* user buffer, clear the fpu state.
	*/
	clear:
	clear_fpu(tsk);
	clear_used_math();
	}
	return err;
	}
	#endif

	/*
	* 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.
	*/
	static void prepare_fx_sw_frame(void)
	{
	int size_extended = (xstate_size - sizeof(struct i387_fxsave_struct)) +
	FP_XSTATE_MAGIC2_SIZE;

	sig_xstate_size = sizeof(struct _fpstate) + size_extended;

	#ifdef CONFIG_IA32_EMULATION
	sig_xstate_ia32_size = sizeof(struct _fpstate_ia32) + size_extended;
	#endif

	memset(&fx_sw_reserved, 0, sizeof(fx_sw_reserved));

	fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
	fx_sw_reserved.extended_size = sig_xstate_size;
	fx_sw_reserved.xstate_bv = pcntxt_mask;
	fx_sw_reserved.xstate_size = xstate_size;
	#ifdef CONFIG_IA32_EMULATION
	memcpy(&fx_sw_reserved_ia32, &fx_sw_reserved,
	sizeof(struct _fpx_sw_bytes));
	fx_sw_reserved_ia32.extended_size = sig_xstate_ia32_size;
	#endif
	}

	/*
	* Represents init state for the supported extended state.
	*/
	struct xsave_struct *init_xstate_buf;

	#ifdef CONFIG_X86_64
	unsigned int sig_xstate_size = sizeof(struct _fpstate);
	#endif

	/*
	* Enable the extended processor state save/restore feature
	*/
	void __cpuinit xsave_init(void)
	{
	if (!cpu_has_xsave)
	return;

	set_in_cr4(X86_CR4_OSXSAVE);

	/*
	* Enable all the features that the HW is capable of
	* and the Linux kernel is aware of.
	*/
	xsetbv(XCR_XFEATURE_ENABLED_MASK, pcntxt_mask);
	}

	/*
	* setup the xstate image representing the init state
	*/
	static void __init setup_xstate_init(void)
	{
	init_xstate_buf = alloc_bootmem(xstate_size);
	init_xstate_buf->i387.mxcsr = MXCSR_DEFAULT;
	}

	/*
	* Enable and initialize the xsave feature.
	*/
	void __ref xsave_cntxt_init(void)
	{
	unsigned int eax, ebx, ecx, edx;

	cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx);
	pcntxt_mask = eax + ((u64)edx << 32);

	if ((pcntxt_mask & XSTATE_FPSSE) != XSTATE_FPSSE) {
	printk(KERN_ERR "FP/SSE not shown under xsave features 0x%llx\n",
	pcntxt_mask);
	BUG();
	}

	/*
	* Support only the state known to OS.
	*/
	pcntxt_mask = pcntxt_mask & XCNTXT_MASK;
	xsave_init();

	/*
	* Recompute the context size for enabled features
	*/
	cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx);
	xstate_size = ebx;

	update_regset_xstate_info(xstate_size, pcntxt_mask);
	prepare_fx_sw_frame();

	setup_xstate_init();

	printk(KERN_INFO "xsave/xrstor: enabled xstate_bv 0x%llx, "
	"cntxt size 0x%x\n",
	pcntxt_mask, xstate_size);
	}