text: // SPDX-License-Identifier: GPL-2.0
  /*
   * FPU signal frame handling routines.
   */
  
  #include <linux/compat.h>
  #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/trace/fpu.h>
  
  static struct _fpx_sw_bytes fx_sw_reserved, fx_sw_reserved_ia32;
  
  /*
   * 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)
  {
  	int min_xstate_size = sizeof(struct fxregs_state) +
  			      sizeof(struct xstate_header);
  	unsigned int magic2;
  
  	if (__copy_from_user(fx_sw, &buf->sw_reserved[0], sizeof(*fx_sw)))
  		return -1;
  
  	/* 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 > fx_sw->extended_size)
  		return -1;
  
  	/*
  	 * 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 (__get_user(magic2, (__u32 __user *)(fpstate + fx_sw->xstate_size))
  	    || magic2 != FP_XSTATE_MAGIC2)
  		return -1;
  
  	return 0;
  }
  
  /*
   * Signal frame handlers.
   */
  static inline int save_fsave_header(struct task_struct *tsk, void __user *buf)
  {
  	if (use_fxsr()) {
  		struct xregs_state *xsave = &tsk->thread.fpu.state.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);
  		fpregs_unlock();
  
  		convert_from_fxsr(&env, tsk);
  
  		if (__copy_to_user(buf, &env, sizeof(env)) ||
  		    __put_user(xsave->i387.swd, &fp->status) ||
  		    __put_user(X86_FXSR_MAGIC, &fp->magic))
  			return -1;
  	} else {
  		struct fregs_state __user *fp = buf;
  		u32 swd;
  		if (__get_user(swd, &fp->swd) || __put_user(swd, &fp->status))
  			return -1;
  	}
  
  	return 0;
  }
  
  static inline int save_xstate_epilog(void __user *buf, int ia32_frame)
  {
  	struct xregs_state __user *x = buf;
  	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));
  
  	if (!use_xsave())
  		return err;
  
  	err |= __put_user(FP_XSTATE_MAGIC2,
  			  (__u32 __user *)(buf + fpu_user_xstate_size));
  
  	/*
  	 * Read the xfeatures which we copied (directly from the cpu or
  	 * from the state in task struct) to the user buffers.
  	 */
  	err |= __get_user(xfeatures, (__u32 __user *)&x->header.xfeatures);
  
  	/*
  	 * 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
  	 * xfeatures in the xsave header.
  	 *
  	 * xsave aware apps can change the xfeatures in the xsave
  	 * header as well as change any contents in the memory layout.
  	 * xrestore as part of sigreturn will capture all the changes.
  	 */
  	xfeatures |= XFEATURE_MASK_FPSSE;
  
  	err |= __put_user(xfeatures, (__u32 __user *)&x->header.xfeatures);
  
  	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);
  	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;
  }
  
  /*
   * Save the fpu, extended register state to the user signal frame.
   *
   * 'buf_fx' is the 64-byte aligned pointer at which the [f|fx|x]save
   *  state is copied.
   *  'buf' points to the 'buf_fx' or to the fsave header followed by 'buf_fx'.
   *
   *	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'.
   *
   * If this is a 32-bit frame with fxstate, put a fsave header before
   * the aligned state at 'buf_fx'.
   *
   * 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)
  {
  	struct task_struct *tsk = current;
  	int 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)) ? -EFAULT : 0;
  	}
  
  	if (!access_ok(buf, size))
  		return -EACCES;
  retry:
  	/*
  	 * Load the FPU registers if they are not valid for the current task.
  	 * With a valid FPU state we can attempt to save the state directly to
  	 * userland's stack frame which will likely succeed. If it does not,
  	 * resolve the fault in the user memory and try again.
  	 */
  	fpregs_lock();
  	if (test_thread_flag(TIF_NEED_FPU_LOAD))
  		__fpregs_load_activate();
  
  	pagefault_disable();
  	ret = copy_fpregs_to_sigframe(buf_fx);
  	pagefault_enable();
  	fpregs_unlock();
  
  	if (ret) {
  		if (!fault_in_pages_writeable(buf_fx, fpu_user_xstate_size))
  			goto retry;
  		return -EFAULT;
  	}
  
  	/* Save the fsave header for the 32-bit frames. */
  	if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf))
  		return -1;
  
  	if (use_fxsr() && save_xstate_epilog(buf_fx, ia32_fxstate))
  		return -1;
  
  	return 0;
  }
  
  static inline void
  sanitize_restored_user_xstate(union fpregs_state *state,
  			      struct user_i387_ia32_struct *ia32_env,
  			      u64 user_xfeatures, int fx_only)
  {
  	struct xregs_state *xsave = &state->xsave;
  	struct xstate_header *header = &xsave->header;
  
  	if (use_xsave()) {
  		/*
  		 * Clear all feature bits which are not set in
  		 * user_xfeatures and clear all extended features
  		 * for fx_only mode.
  		 */
  		u64 mask = fx_only ? XFEATURE_MASK_FPSSE : user_xfeatures;
  
  		/*
  		 * Supervisor state has to be preserved. The sigframe
  		 * restore can only modify user features, i.e. @mask
  		 * cannot contain them.
  		 */
  		header->xfeatures &= mask | xfeatures_mask_supervisor();
  	}
  
  	if (use_fxsr()) {
  		/*
  		 * mscsr reserved bits must be masked to zero for security
  		 * reasons.
  		 */
  		xsave->i387.mxcsr &= mxcsr_feature_mask;
  
  		if (ia32_env)
  			convert_to_fxsr(&state->fxsave, ia32_env);
  	}
  }
  
  /*
   * Restore the extended state if present. Otherwise, restore the FP/SSE state.
   */
  static int copy_user_to_fpregs_zeroing(void __user *buf, u64 xbv, int fx_only)
  {
  	u64 init_bv;
  	int r;
  
  	if (use_xsave()) {
  		if (fx_only) {
  			init_bv = xfeatures_mask_user() & ~XFEATURE_MASK_FPSSE;
  
  			r = copy_user_to_fxregs(buf);
  			if (!r)
  				copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
  			return r;
  		} else {
  			init_bv = xfeatures_mask_user() & ~xbv;
  
  			r = copy_user_to_xregs(buf, xbv);
  			if (!r && unlikely(init_bv))
  				copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
  			return r;
  		}
  	} else if (use_fxsr()) {
  		return copy_user_to_fxregs(buf);
  	} else
  		return copy_user_to_fregs(buf);
  }
  
  static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
  {
  	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 user_xfeatures = 0;
  	int fx_only = 0;
  	int ret = 0;
  
  	ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
  			 IS_ENABLED(CONFIG_IA32_EMULATION));
  
  	if (!buf) {
  		fpu__clear_user_states(fpu);
  		return 0;
  	}
  
  	if (!access_ok(buf, size)) {
  		ret = -EACCES;
  		goto out;
  	}
  
  	if (!static_cpu_has(X86_FEATURE_FPU)) {
  		ret = fpregs_soft_set(current, NULL, 0,
  				      sizeof(struct user_i387_ia32_struct),
  				      NULL, buf);
  		goto out;
  	}
  
  	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;
  			user_xfeatures = fx_sw_user.xfeatures;
  		}
  	}
  
  	if ((unsigned long)buf_fx % 64)
  		fx_only = 1;
  
  	if (!ia32_fxstate) {
  		/*
  		 * 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.
  		 */
  		fpregs_lock();
  		pagefault_disable();
  		ret = copy_user_to_fpregs_zeroing(buf_fx, user_xfeatures, fx_only);
  		pagefault_enable();
  		if (!ret) {
  
  			/*
  			 * 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.
  			 *
  			 * We cannot do a single XRSTORS here - which would
  			 * be nice - because the rest of the FPU registers are
  			 * being restored from a user buffer directly. The
  			 * single XRSTORS happens below, when the user buffer
  			 * has been copied to the kernel one.
  			 */
  			if (test_thread_flag(TIF_NEED_FPU_LOAD) &&
  			    xfeatures_mask_supervisor())
  				copy_kernel_to_xregs(&fpu->state.xsave,
  						     xfeatures_mask_supervisor());
  			fpregs_mark_activate();
  			fpregs_unlock();
  			return 0;
  		}
  
  		/*
  		 * 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.
  		 *
  		 * In case current owns the FPU registers then no further
  		 * action is required. The fixup below will handle it
  		 * correctly.
  		 */
  		if (test_thread_flag(TIF_NEED_FPU_LOAD))
  			__cpu_invalidate_fpregs_state();
  
  		fpregs_unlock();
  	} else {
  		/*
  		 * For 32-bit frames with fxstate, copy the fxstate so it can
  		 * be reconstructed later.
  		 */
  		ret = __copy_from_user(&env, buf, sizeof(env));
  		if (ret)
  			goto out;
  		envp = &env;
  	}
  
  	/*
  	 * 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).
  	 */
  	fpregs_lock();
  
  	if (!test_thread_flag(TIF_NEED_FPU_LOAD)) {
  
  		/*
  		 * Supervisor states are not modified by user space input.  Save
  		 * current supervisor states first and invalidate the FPU regs.
  		 */
  		if (xfeatures_mask_supervisor())
  			copy_supervisor_to_kernel(&fpu->state.xsave);
  		set_thread_flag(TIF_NEED_FPU_LOAD);
  	}
  	__fpu_invalidate_fpregs_state(fpu);
  	fpregs_unlock();
  
  	if (use_xsave() && !fx_only) {
  		u64 init_bv = xfeatures_mask_user() & ~user_xfeatures;
  
  		ret = copy_user_to_xstate(&fpu->state.xsave, buf_fx);
  		if (ret)
  			goto out;
  
  		sanitize_restored_user_xstate(&fpu->state, envp, user_xfeatures,
  					      fx_only);
  
  		fpregs_lock();
  		if (unlikely(init_bv))
  			copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
  
  		/*
  		 * Restore previously saved supervisor xstates along with
  		 * copied-in user xstates.
  		 */
  		ret = copy_kernel_to_xregs_err(&fpu->state.xsave,
  					       user_xfeatures | xfeatures_mask_supervisor());
  
  	} else if (use_fxsr()) {
  		ret = __copy_from_user(&fpu->state.fxsave, buf_fx, state_size);
  		if (ret) {
  			ret = -EFAULT;
  			goto out;
  		}
  
  		sanitize_restored_user_xstate(&fpu->state, envp, user_xfeatures,
  					      fx_only);
  
  		fpregs_lock();
  		if (use_xsave()) {
  			u64 init_bv;
  
  			init_bv = xfeatures_mask_user() & ~XFEATURE_MASK_FPSSE;
  			copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
  		}
  
  		ret = copy_kernel_to_fxregs_err(&fpu->state.fxsave);
  	} else {
  		ret = __copy_from_user(&fpu->state.fsave, buf_fx, state_size);
  		if (ret)
  			goto out;
  
  		fpregs_lock();
  		ret = copy_kernel_to_fregs_err(&fpu->state.fsave);
  	}
  	if (!ret)
  		fpregs_mark_activate();
  	else
  		fpregs_deactivate(fpu);
  	fpregs_unlock();
  
  out:
  	if (ret)
  		fpu__clear_user_states(fpu);
  	return ret;
  }
  
  static inline int xstate_sigframe_size(void)
  {
  	return use_xsave() ? fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE :
  			fpu_user_xstate_size;
  }
  
  /*
   * Restore FPU state from a sigframe:
   */
  int fpu__restore_sig(void __user *buf, int ia32_frame)
  {
  	void __user *buf_fx = buf;
  	int size = xstate_sigframe_size();
  
  	if (ia32_frame && use_fxsr()) {
  		buf_fx = buf + sizeof(struct fregs_state);
  		size += sizeof(struct fregs_state);
  	}
  
  	return __fpu__restore_sig(buf, buf_fx, size);
  }
  
  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();
  
  	*buf_fx = sp = round_down(sp - frame_size, 64);
  	if (ia32_frame && use_fxsr()) {
  		frame_size += sizeof(struct fregs_state);
  		sp -= sizeof(struct fregs_state);
  	}
  
  	*size = frame_size;
  
  	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)
  {
  	int size = fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE;
  
  	fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
  	fx_sw_reserved.extended_size = size;
  	fx_sw_reserved.xfeatures = xfeatures_mask_user();
  	fx_sw_reserved.xstate_size = fpu_user_xstate_size;
  
  	if (IS_ENABLED(CONFIG_IA32_EMULATION) ||
  	    IS_ENABLED(CONFIG_X86_32)) {
  		int fsave_header_size = sizeof(struct fregs_state);
  
  		fx_sw_reserved_ia32 = fx_sw_reserved;
  		fx_sw_reserved_ia32.extended_size = size + fsave_header_size;
  	}
  }
  
  