/*
   * 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;

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

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

  static unsigned int *xstate_offsets, *xstate_sizes, xstate_features;

  /*

   * If a processor implementation discern that a processor state component is
   * in its initialized state it may modify the corresponding bit in the
   * xsave_hdr.xstate_bv as '0', with out modifying the corresponding memory
   * layout in the case of xsaveopt. While presenting the xstate information to
   * the user, we 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 the user doesn't see some stale state in the memory layout during
   * signal handling, debugging etc.
   */
  void __sanitize_i387_state(struct task_struct *tsk)
  {
  	u64 xstate_bv;
  	int feature_bit = 0x2;
  	struct i387_fxsave_struct *fx = &tsk->thread.fpu.state->fxsave;
  
  	if (!fx)
  		return;
  
  	BUG_ON(task_thread_info(tsk)->status & TS_USEDFPU);
  
  	xstate_bv = tsk->thread.fpu.state->xsave.xsave_hdr.xstate_bv;
  
  	/*
  	 * 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 ((xstate_bv & pcntxt_mask) == pcntxt_mask)
  		return;
  
  	/*
  	 * FP is in init state
  	 */
  	if (!(xstate_bv & XSTATE_FP)) {
  		fx->cwd = 0x37f;
  		fx->swd = 0;
  		fx->twd = 0;
  		fx->fop = 0;
  		fx->rip = 0;
  		fx->rdp = 0;
  		memset(&fx->st_space[0], 0, 128);
  	}
  
  	/*
  	 * SSE is in init state
  	 */
  	if (!(xstate_bv & XSTATE_SSE))
  		memset(&fx->xmm_space[0], 0, 256);
  
  	xstate_bv = (pcntxt_mask & ~xstate_bv) >> 2;
  
  	/*
  	 * Update all the other memory layouts for which the corresponding
  	 * header bit is in the init state.
  	 */
  	while (xstate_bv) {
  		if (xstate_bv & 0x1) {
  			int offset = xstate_offsets[feature_bit];
  			int size = xstate_sizes[feature_bit];
  
  			memcpy(((void *) fx) + offset,
  			       ((void *) init_xstate_buf) + offset,
  			       size);
  		}
  
  		xstate_bv >>= 1;
  		feature_bit++;
  	}
  }

  /*
   * 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 -EFAULT;

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

  		return -EINVAL;

  
  	/*
  	 * 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 -EINVAL;

  
  	err = __get_user(magic2, (__u32 *) (((void *)fpstate) +
  					    fx_sw_user->extended_size -
  					    FP_XSTATE_MAGIC2_SIZE));

  	if (err)
  		return err;

  	/*
  	 * 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 (magic2 != FP_XSTATE_MAGIC2)
  		return -EFAULT;

  
  	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
  ", buf);
  
  	if (!used_math())
  		return 0;

  	if (task_thread_info(tsk)->status & TS_USEDFPU) {

  		if (use_xsave())

  			err = xsave_user(buf);
  		else
  			err = fxsave_user(buf);

  		if (err)
  			return err;
  		task_thread_info(tsk)->status &= ~TS_USEDFPU;
  		stts();
  	} else {

  		sanitize_i387_state(tsk);

  		if (__copy_to_user(buf, &tsk->thread.fpu.state->fxsave,

  				   xstate_size))
  			return -1;
  	}

  	clear_used_math(); /* trigger finit */

  	if (use_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;

  	if (unlikely(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 (use_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
  }

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

  /*
   * Enable the extended processor state save/restore feature
   */

  static inline void xstate_enable(void)

  {

  	set_in_cr4(X86_CR4_OSXSAVE);

  	xsetbv(XCR_XFEATURE_ENABLED_MASK, pcntxt_mask);

  }
  
  /*

   * Record the offsets and sizes of different state managed by the xsave
   * memory layout.
   */

  static void __init setup_xstate_features(void)

  {
  	int eax, ebx, ecx, edx, leaf = 0x2;
  
  	xstate_features = fls64(pcntxt_mask);
  	xstate_offsets = alloc_bootmem(xstate_features * sizeof(int));
  	xstate_sizes = alloc_bootmem(xstate_features * sizeof(int));
  
  	do {

  		cpuid_count(XSTATE_CPUID, leaf, &eax, &ebx, &ecx, &edx);

  
  		if (eax == 0)
  			break;
  
  		xstate_offsets[leaf] = ebx;
  		xstate_sizes[leaf] = eax;
  
  		leaf++;
  	} while (1);
  }
  
  /*

   * setup the xstate image representing the init state
   */

  static void __init setup_xstate_init(void)

  {

  	setup_xstate_features();
  
  	/*
  	 * Setup init_xstate_buf to represent the init state of
  	 * all the features managed by the xsave
  	 */

  	init_xstate_buf = alloc_bootmem_align(xstate_size,
  					      __alignof__(struct xsave_struct));

  	init_xstate_buf->i387.mxcsr = MXCSR_DEFAULT;

  	clts();
  	/*
  	 * Init all the features state with header_bv being 0x0
  	 */
  	xrstor_state(init_xstate_buf, -1);
  	/*
  	 * Dump the init state again. This is to identify the init state
  	 * of any feature which is not represented by all zero's.
  	 */
  	xsave_state(init_xstate_buf, -1);
  	stts();

  }
  
  /*
   * Enable and initialize the xsave feature.
   */

  static void __init xstate_enable_boot_cpu(void)

  {
  	unsigned int eax, ebx, ecx, edx;

  	if (boot_cpu_data.cpuid_level < XSTATE_CPUID) {
  		WARN(1, KERN_ERR "XSTATE_CPUID missing
  ");
  		return;
  	}
  
  	cpuid_count(XSTATE_CPUID, 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
  ",
  		       pcntxt_mask);

  		BUG();
  	}
  
  	/*

  	 * Support only the state known to OS.

  	 */

  	pcntxt_mask = pcntxt_mask & XCNTXT_MASK;

  	xstate_enable();

  
  	/*
  	 * Recompute the context size for enabled features
  	 */

  	cpuid_count(XSTATE_CPUID, 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
  ",

  	       pcntxt_mask, xstate_size);

  }

  /*
   * For the very first instance, this calls xstate_enable_boot_cpu();
   * for all subsequent instances, this calls xstate_enable().
   *
   * This is somewhat obfuscated due to the lack of powerful enough
   * overrides for the section checks.
   */

  void __cpuinit xsave_init(void)
  {

  	static __refdata void (*next_func)(void) = xstate_enable_boot_cpu;
  	void (*this_func)(void);

  	if (!cpu_has_xsave)
  		return;

  	this_func = next_func;
  	next_func = xstate_enable;
  	this_func();

  }