1 files changed, 542 insertions, 0 deletions

diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
new file mode 100644
index 000000000..558076dbd
--- /dev/null
+++ b/arch/x86/kernel/fpu/signal.c
@@ -0,0 +1,542 @@
+// 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/signal.h>
+#include <asm/fpu/regset.h>
+#include <asm/fpu/xstate.h>
+
+#include <asm/sigframe.h>
+#include <asm/trapnr.h>
+#include <asm/trace/fpu.h>
+
+#include "context.h"
+#include "internal.h"
+#include "legacy.h"
+#include "xstate.h"
+
+/*
+ * Check for the presence of extended state information in the
+ * user fpstate pointer in the sigcontext.
+ */
+static inline bool check_xstate_in_sigframe(struct fxregs_state __user *fxbuf,
+					    struct _fpx_sw_bytes *fx_sw)
+{
+	int min_xstate_size = sizeof(struct fxregs_state) +
+			      sizeof(struct xstate_header);
+	void __user *fpstate = fxbuf;
+	unsigned int magic2;
+
+	if (__copy_from_user(fx_sw, &fxbuf->sw_reserved[0], sizeof(*fx_sw)))
+		return false;
+
+	/* 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 > current->thread.fpu.fpstate->user_size ||
+	    fx_sw->xstate_size > fx_sw->extended_size)
+		goto setfx;
+
+	/*
+	 * 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)))
+		return false;
+
+	if (likely(magic2 == FP_XSTATE_MAGIC2))
+		return true;
+setfx:
+	trace_x86_fpu_xstate_check_failed(&current->thread.fpu);
+
+	/* Set the parameters for fx only state */
+	fx_sw->magic1 = 0;
+	fx_sw->xstate_size = sizeof(struct fxregs_state);
+	fx_sw->xfeatures = XFEATURE_MASK_FPSSE;
+	return true;
+}
+
+/*
+ * Signal frame handlers.
+ */
+static inline bool save_fsave_header(struct task_struct *tsk, void __user *buf)
+{
+	if (use_fxsr()) {
+		struct xregs_state *xsave = &tsk->thread.fpu.fpstate->regs.xsave;
+		struct user_i387_ia32_struct env;
+		struct _fpstate_32 __user *fp = buf;
+
+		fpregs_lock();
+		if (!test_thread_flag(TIF_NEED_FPU_LOAD))
+			fxsave(&tsk->thread.fpu.fpstate->regs.fxsave);
+		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 false;
+	} else {
+		struct fregs_state __user *fp = buf;
+		u32 swd;
+
+		if (__get_user(swd, &fp->swd) || __put_user(swd, &fp->status))
+			return false;
+	}
+
+	return true;
+}
+
+/*
+ * Prepare the SW reserved portion of the fxsave memory layout, indicating
+ * the presence of the extended state information in the memory layout
+ * pointed to by the fpstate pointer in the sigcontext.
+ * This is saved when ever the FP and extended state context is
+ * saved on the user stack during the signal handler delivery to the user.
+ */
+static inline void save_sw_bytes(struct _fpx_sw_bytes *sw_bytes, bool ia32_frame,
+				 struct fpstate *fpstate)
+{
+	sw_bytes->magic1 = FP_XSTATE_MAGIC1;
+	sw_bytes->extended_size = fpstate->user_size + FP_XSTATE_MAGIC2_SIZE;
+	sw_bytes->xfeatures = fpstate->user_xfeatures;
+	sw_bytes->xstate_size = fpstate->user_size;
+
+	if (ia32_frame)
+		sw_bytes->extended_size += sizeof(struct fregs_state);
+}
+
+static inline bool save_xstate_epilog(void __user *buf, int ia32_frame,
+				      struct fpstate *fpstate)
+{
+	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. */
+	save_sw_bytes(&sw_bytes, ia32_frame, fpstate);
+	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 + fpstate->user_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)
+{
+	if (use_xsave())
+		return xsave_to_user_sigframe(buf);
+	if (use_fxsr())
+		return fxsave_to_user_sigframe((struct fxregs_state __user *) buf);
+	else
+		return fnsave_to_user_sigframe((struct fregs_state __user *) buf);
+}
+
+/*
+ * 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.
+ *
+ * Save it directly to the user frame with disabled page fault handler. If
+ * that faults, try to clear the frame which handles the page fault.
+ *
+ * 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.
+ */
+bool copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
+{
+	struct task_struct *tsk = current;
+	struct fpstate *fpstate = tsk->thread.fpu.fpstate;
+	bool 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));
+	}
+
+	if (!access_ok(buf, size))
+		return false;
+
+	if (use_xsave()) {
+		struct xregs_state __user *xbuf = buf_fx;
+
+		/*
+		 * Clear the xsave header first, so that reserved fields are
+		 * initialized to zero.
+		 */
+		if (__clear_user(&xbuf->header, sizeof(xbuf->header)))
+			return false;
+	}
+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_restore_userregs();
+
+	pagefault_disable();
+	ret = copy_fpregs_to_sigframe(buf_fx);
+	pagefault_enable();
+	fpregs_unlock();
+
+	if (ret) {
+		if (!__clear_user(buf_fx, fpstate->user_size))
+			goto retry;
+		return false;
+	}
+
+	/* Save the fsave header for the 32-bit frames. */
+	if ((ia32_fxstate || !use_fxsr()) && !save_fsave_header(tsk, buf))
+		return false;
+
+	if (use_fxsr() && !save_xstate_epilog(buf_fx, ia32_fxstate, fpstate))
+		return false;
+
+	return true;
+}
+
+static int __restore_fpregs_from_user(void __user *buf, u64 ufeatures,
+				      u64 xrestore, bool fx_only)
+{
+	if (use_xsave()) {
+		u64 init_bv = ufeatures & ~xrestore;
+		int ret;
+
+		if (likely(!fx_only))
+			ret = xrstor_from_user_sigframe(buf, xrestore);
+		else
+			ret = fxrstor_from_user_sigframe(buf);
+
+		if (!ret && unlikely(init_bv))
+			os_xrstor(&init_fpstate, init_bv);
+		return ret;
+	} else if (use_fxsr()) {
+		return fxrstor_from_user_sigframe(buf);
+	} else {
+		return frstor_from_user_sigframe(buf);
+	}
+}
+
+/*
+ * Attempt to restore the FPU registers directly from user memory.
+ * Pagefaults are handled and any errors returned are fatal.
+ */
+static bool restore_fpregs_from_user(void __user *buf, u64 xrestore,
+				     bool fx_only, unsigned int size)
+{
+	struct fpu *fpu = &current->thread.fpu;
+	int ret;
+
+retry:
+	fpregs_lock();
+	/* Ensure that XFD is up to date */
+	xfd_update_state(fpu->fpstate);
+	pagefault_disable();
+	ret = __restore_fpregs_from_user(buf, fpu->fpstate->user_xfeatures,
+					 xrestore, fx_only);
+	pagefault_enable();
+
+	if (unlikely(ret)) {
+		/*
+		 * 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.
+		 */
+		if (test_thread_flag(TIF_NEED_FPU_LOAD))
+			__cpu_invalidate_fpregs_state();
+		fpregs_unlock();
+
+		/* Try to handle #PF, but anything else is fatal. */
+		if (ret != X86_TRAP_PF)
+			return false;
+
+		if (!fault_in_readable(buf, size))
+			goto retry;
+		return false;
+	}
+
+	/*
+	 * 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.
+	 *
+	 * It would be optimal to handle this with a single XRSTORS, but
+	 * this does not work because the rest of the FPU registers have
+	 * been restored from a user buffer directly.
+	 */
+	if (test_thread_flag(TIF_NEED_FPU_LOAD) && xfeatures_mask_supervisor())
+		os_xrstor_supervisor(fpu->fpstate);
+
+	fpregs_mark_activate();
+	fpregs_unlock();
+	return true;
+}
+
+static bool __fpu_restore_sig(void __user *buf, void __user *buf_fx,
+			      bool ia32_fxstate)
+{
+	struct task_struct *tsk = current;
+	struct fpu *fpu = &tsk->thread.fpu;
+	struct user_i387_ia32_struct env;
+	bool success, fx_only = false;
+	union fpregs_state *fpregs;
+	unsigned int state_size;
+	u64 user_xfeatures = 0;
+
+	if (use_xsave()) {
+		struct _fpx_sw_bytes fx_sw_user;
+
+		if (!check_xstate_in_sigframe(buf_fx, &fx_sw_user))
+			return false;
+
+		fx_only = !fx_sw_user.magic1;
+		state_size = fx_sw_user.xstate_size;
+		user_xfeatures = fx_sw_user.xfeatures;
+	} else {
+		user_xfeatures = XFEATURE_MASK_FPSSE;
+		state_size = fpu->fpstate->user_size;
+	}
+
+	if (likely(!ia32_fxstate)) {
+		/* Restore the FPU registers directly from user memory. */
+		return restore_fpregs_from_user(buf_fx, user_xfeatures, fx_only,
+						state_size);
+	}
+
+	/*
+	 * Copy the legacy state because the FP portion of the FX frame has
+	 * to be ignored for histerical raisins. The legacy state is folded
+	 * in once the larger state has been copied.
+	 */
+	if (__copy_from_user(&env, buf, sizeof(env)))
+		return false;
+
+	/*
+	 * 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)) {
+		/*
+		 * If supervisor states are available then save the
+		 * hardware state in current's fpstate so that the
+		 * supervisor state is preserved. Save the full state for
+		 * simplicity. There is no point in optimizing this by only
+		 * saving the supervisor states and then shuffle them to
+		 * the right place in memory. It's ia32 mode. Shrug.
+		 */
+		if (xfeatures_mask_supervisor())
+			os_xsave(fpu->fpstate);
+		set_thread_flag(TIF_NEED_FPU_LOAD);
+	}
+	__fpu_invalidate_fpregs_state(fpu);
+	__cpu_invalidate_fpregs_state();
+	fpregs_unlock();
+
+	fpregs = &fpu->fpstate->regs;
+	if (use_xsave() && !fx_only) {
+		if (copy_sigframe_from_user_to_xstate(tsk, buf_fx))
+			return false;
+	} else {
+		if (__copy_from_user(&fpregs->fxsave, buf_fx,
+				     sizeof(fpregs->fxsave)))
+			return false;
+
+		if (IS_ENABLED(CONFIG_X86_64)) {
+			/* Reject invalid MXCSR values. */
+			if (fpregs->fxsave.mxcsr & ~mxcsr_feature_mask)
+				return false;
+		} else {
+			/* Mask invalid bits out for historical reasons (broken hardware). */
+			fpregs->fxsave.mxcsr &= mxcsr_feature_mask;
+		}
+
+		/* Enforce XFEATURE_MASK_FPSSE when XSAVE is enabled */
+		if (use_xsave())
+			fpregs->xsave.header.xfeatures |= XFEATURE_MASK_FPSSE;
+	}
+
+	/* Fold the legacy FP storage */
+	convert_to_fxsr(&fpregs->fxsave, &env);
+
+	fpregs_lock();
+	if (use_xsave()) {
+		/*
+		 * Remove all UABI feature bits not set in user_xfeatures
+		 * from the memory xstate header which makes the full
+		 * restore below bring them into init state. This works for
+		 * fx_only mode as well because that has only FP and SSE
+		 * set in user_xfeatures.
+		 *
+		 * Preserve supervisor states!
+		 */
+		u64 mask = user_xfeatures | xfeatures_mask_supervisor();
+
+		fpregs->xsave.header.xfeatures &= mask;
+		success = !os_xrstor_safe(fpu->fpstate,
+					  fpu_kernel_cfg.max_features);
+	} else {
+		success = !fxrstor_safe(&fpregs->fxsave);
+	}
+
+	if (likely(success))
+		fpregs_mark_activate();
+
+	fpregs_unlock();
+	return success;
+}
+
+static inline unsigned int xstate_sigframe_size(struct fpstate *fpstate)
+{
+	unsigned int size = fpstate->user_size;
+
+	return use_xsave() ? size + FP_XSTATE_MAGIC2_SIZE : size;
+}
+
+/*
+ * Restore FPU state from a sigframe:
+ */
+bool fpu__restore_sig(void __user *buf, int ia32_frame)
+{
+	struct fpu *fpu = &current->thread.fpu;
+	void __user *buf_fx = buf;
+	bool ia32_fxstate = false;
+	bool success = false;
+	unsigned int size;
+
+	if (unlikely(!buf)) {
+		fpu__clear_user_states(fpu);
+		return true;
+	}
+
+	size = xstate_sigframe_size(fpu->fpstate);
+
+	ia32_frame &= (IS_ENABLED(CONFIG_X86_32) ||
+		       IS_ENABLED(CONFIG_IA32_EMULATION));
+
+	/*
+	 * Only FXSR enabled systems need the FX state quirk.
+	 * FRSTOR does not need it and can use the fast path.
+	 */
+	if (ia32_frame && use_fxsr()) {
+		buf_fx = buf + sizeof(struct fregs_state);
+		size += sizeof(struct fregs_state);
+		ia32_fxstate = true;
+	}
+
+	if (!access_ok(buf, size))
+		goto out;
+
+	if (!IS_ENABLED(CONFIG_X86_64) && !cpu_feature_enabled(X86_FEATURE_FPU)) {
+		success = !fpregs_soft_set(current, NULL, 0,
+					   sizeof(struct user_i387_ia32_struct),
+					   NULL, buf);
+	} else {
+		success = __fpu_restore_sig(buf, buf_fx, ia32_fxstate);
+	}
+
+out:
+	if (unlikely(!success))
+		fpu__clear_user_states(fpu);
+	return success;
+}
+
+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(current->thread.fpu.fpstate);
+
+	*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;
+}
+
+unsigned long __init fpu__get_fpstate_size(void)
+{
+	unsigned long ret = fpu_user_cfg.max_size;
+
+	if (use_xsave())
+		ret += FP_XSTATE_MAGIC2_SIZE;
+
+	/*
+	 * This space is needed on (most) 32-bit kernels, or when a 32-bit
+	 * app is running on a 64-bit kernel. To keep things simple, just
+	 * assume the worst case and always include space for 'freg_state',
+	 * even for 64-bit apps on 64-bit kernels. This wastes a bit of
+	 * space, but keeps the code simple.
+	 */
+	if ((IS_ENABLED(CONFIG_IA32_EMULATION) ||
+	     IS_ENABLED(CONFIG_X86_32)) && use_fxsr())
+		ret += sizeof(struct fregs_state);
+
+	return ret;
+}
+