1 files changed, 429 insertions, 122 deletions

diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index 4a77f4976e11..417140cd399b 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -19,12 +19,14 @@
 #include <linux/ratelimit.h>
 #include <linux/rseq.h>
 #include <linux/syscalls.h>
+#include <linux/pkeys.h>
 
 #include <asm/daifflags.h>
 #include <asm/debug-monitors.h>
 #include <asm/elf.h>
 #include <asm/exception.h>
 #include <asm/cacheflush.h>
+#include <asm/gcs.h>
 #include <asm/ucontext.h>
 #include <asm/unistd.h>
 #include <asm/fpsimd.h>
@@ -34,6 +36,8 @@
 #include <asm/traps.h>
 #include <asm/vdso.h>
 
+#define GCS_SIGNAL_CAP(addr) (((unsigned long)addr) & GCS_CAP_ADDR_MASK)
+
 /*
  * Do a signal return; undo the signal stack. These are aligned to 128-bit.
  */
@@ -42,11 +46,6 @@ struct rt_sigframe {
 	struct ucontext uc;
 };
 
-struct frame_record {
-	u64 fp;
-	u64 lr;
-};
-
 struct rt_sigframe_user_layout {
 	struct rt_sigframe __user *sigframe;
 	struct frame_record __user *next_frame;
@@ -56,19 +55,73 @@ struct rt_sigframe_user_layout {
 
 	unsigned long fpsimd_offset;
 	unsigned long esr_offset;
+	unsigned long gcs_offset;
 	unsigned long sve_offset;
 	unsigned long tpidr2_offset;
 	unsigned long za_offset;
 	unsigned long zt_offset;
 	unsigned long fpmr_offset;
+	unsigned long poe_offset;
 	unsigned long extra_offset;
 	unsigned long end_offset;
 };
 
-#define BASE_SIGFRAME_SIZE round_up(sizeof(struct rt_sigframe), 16)
+/*
+ * Holds any EL0-controlled state that influences unprivileged memory accesses.
+ * This includes both accesses done in userspace and uaccess done in the kernel.
+ *
+ * This state needs to be carefully managed to ensure that it doesn't cause
+ * uaccess to fail when setting up the signal frame, and the signal handler
+ * itself also expects a well-defined state when entered.
+ */
+struct user_access_state {
+	u64 por_el0;
+};
+
 #define TERMINATOR_SIZE round_up(sizeof(struct _aarch64_ctx), 16)
 #define EXTRA_CONTEXT_SIZE round_up(sizeof(struct extra_context), 16)
 
+/*
+ * Save the user access state into ua_state and reset it to disable any
+ * restrictions.
+ */
+static void save_reset_user_access_state(struct user_access_state *ua_state)
+{
+	if (system_supports_poe()) {
+		u64 por_enable_all = 0;
+
+		for (int pkey = 0; pkey < arch_max_pkey(); pkey++)
+			por_enable_all |= POR_ELx_PERM_PREP(pkey, POE_RWX);
+
+		ua_state->por_el0 = read_sysreg_s(SYS_POR_EL0);
+		write_sysreg_s(por_enable_all, SYS_POR_EL0);
+		/* Ensure that any subsequent uaccess observes the updated value */
+		isb();
+	}
+}
+
+/*
+ * Set the user access state for invoking the signal handler.
+ *
+ * No uaccess should be done after that function is called.
+ */
+static void set_handler_user_access_state(void)
+{
+	if (system_supports_poe())
+		write_sysreg_s(POR_EL0_INIT, SYS_POR_EL0);
+}
+
+/*
+ * Restore the user access state to the values saved in ua_state.
+ *
+ * No uaccess should be done after that function is called.
+ */
+static void restore_user_access_state(const struct user_access_state *ua_state)
+{
+	if (system_supports_poe())
+		write_sysreg_s(ua_state->por_el0, SYS_POR_EL0);
+}
+
 static void init_user_layout(struct rt_sigframe_user_layout *user)
 {
 	const size_t reserved_size =
@@ -185,6 +238,10 @@ struct user_ctxs {
 	u32 zt_size;
 	struct fpmr_context __user *fpmr;
 	u32 fpmr_size;
+	struct poe_context __user *poe;
+	u32 poe_size;
+	struct gcs_context __user *gcs;
+	u32 gcs_size;
 };
 
 static int preserve_fpsimd_context(struct fpsimd_context __user *ctx)
@@ -193,6 +250,8 @@ static int preserve_fpsimd_context(struct fpsimd_context __user *ctx)
 		&current->thread.uw.fpsimd_state;
 	int err;
 
+	fpsimd_sync_from_effective_state(current);
+
 	/* copy the FP and status/control registers */
 	err = __copy_to_user(ctx->vregs, fpsimd->vregs, sizeof(fpsimd->vregs));
 	__put_user_error(fpsimd->fpsr, &ctx->fpsr, err);
@@ -205,37 +264,46 @@ static int preserve_fpsimd_context(struct fpsimd_context __user *ctx)
 	return err ? -EFAULT : 0;
 }
 
-static int restore_fpsimd_context(struct user_ctxs *user)
+static int read_fpsimd_context(struct user_fpsimd_state *fpsimd,
+			       struct user_ctxs *user)
 {
-	struct user_fpsimd_state fpsimd;
-	int err = 0;
+	int err;
 
 	/* check the size information */
 	if (user->fpsimd_size != sizeof(struct fpsimd_context))
 		return -EINVAL;
 
 	/* copy the FP and status/control registers */
-	err = __copy_from_user(fpsimd.vregs, &(user->fpsimd->vregs),
-			       sizeof(fpsimd.vregs));
-	__get_user_error(fpsimd.fpsr, &(user->fpsimd->fpsr), err);
-	__get_user_error(fpsimd.fpcr, &(user->fpsimd->fpcr), err);
+	err = __copy_from_user(fpsimd->vregs, &(user->fpsimd->vregs),
+			       sizeof(fpsimd->vregs));
+	__get_user_error(fpsimd->fpsr, &(user->fpsimd->fpsr), err);
+	__get_user_error(fpsimd->fpcr, &(user->fpsimd->fpcr), err);
+
+	return err ? -EFAULT : 0;
+}
+
+static int restore_fpsimd_context(struct user_ctxs *user)
+{
+	struct user_fpsimd_state fpsimd;
+	int err;
+
+	err = read_fpsimd_context(&fpsimd, user);
+	if (err)
+		return err;
 
 	clear_thread_flag(TIF_SVE);
+	current->thread.svcr &= ~SVCR_SM_MASK;
 	current->thread.fp_type = FP_STATE_FPSIMD;
 
 	/* load the hardware registers from the fpsimd_state structure */
-	if (!err)
-		fpsimd_update_current_state(&fpsimd);
-
-	return err ? -EFAULT : 0;
+	fpsimd_update_current_state(&fpsimd);
+	return 0;
 }
 
 static int preserve_fpmr_context(struct fpmr_context __user *ctx)
 {
 	int err = 0;
 
-	current->thread.uw.fpmr = read_sysreg_s(SYS_FPMR);
-
 	__put_user_error(FPMR_MAGIC, &ctx->head.magic, err);
 	__put_user_error(sizeof(*ctx), &ctx->head.size, err);
 	__put_user_error(current->thread.uw.fpmr, &ctx->fpmr, err);
@@ -253,7 +321,35 @@ static int restore_fpmr_context(struct user_ctxs *user)
 
 	__get_user_error(fpmr, &user->fpmr->fpmr, err);
 	if (!err)
-		write_sysreg_s(fpmr, SYS_FPMR);
+		current->thread.uw.fpmr = fpmr;
+
+	return err;
+}
+
+static int preserve_poe_context(struct poe_context __user *ctx,
+				const struct user_access_state *ua_state)
+{
+	int err = 0;
+
+	__put_user_error(POE_MAGIC, &ctx->head.magic, err);
+	__put_user_error(sizeof(*ctx), &ctx->head.size, err);
+	__put_user_error(ua_state->por_el0, &ctx->por_el0, err);
+
+	return err;
+}
+
+static int restore_poe_context(struct user_ctxs *user,
+			       struct user_access_state *ua_state)
+{
+	u64 por_el0;
+	int err = 0;
+
+	if (user->poe_size != sizeof(*user->poe))
+		return -EINVAL;
+
+	__get_user_error(por_el0, &(user->poe->por_el0), err);
+	if (!err)
+		ua_state->por_el0 = por_el0;
 
 	return err;
 }
@@ -287,11 +383,6 @@ static int preserve_sve_context(struct sve_context __user *ctx)
 	err |= __copy_to_user(&ctx->__reserved, reserved, sizeof(reserved));
 
 	if (vq) {
-		/*
-		 * This assumes that the SVE state has already been saved to
-		 * the task struct by calling the function
-		 * fpsimd_signal_preserve_current_state().
-		 */
 		err |= __copy_to_user((char __user *)ctx + SVE_SIG_REGS_OFFSET,
 				      current->thread.sve_state,
 				      SVE_SIG_REGS_SIZE(vq));
@@ -306,6 +397,7 @@ static int restore_sve_fpsimd_context(struct user_ctxs *user)
 	unsigned int vl, vq;
 	struct user_fpsimd_state fpsimd;
 	u16 user_vl, flags;
+	bool sm;
 
 	if (user->sve_size < sizeof(*user->sve))
 		return -EINVAL;
@@ -315,7 +407,8 @@ static int restore_sve_fpsimd_context(struct user_ctxs *user)
 	if (err)
 		return err;
 
-	if (flags & SVE_SIG_FLAG_SM) {
+	sm = flags & SVE_SIG_FLAG_SM;
+	if (sm) {
 		if (!system_supports_sme())
 			return -EINVAL;
 
@@ -335,28 +428,23 @@ static int restore_sve_fpsimd_context(struct user_ctxs *user)
 	if (user_vl != vl)
 		return -EINVAL;
 
-	if (user->sve_size == sizeof(*user->sve)) {
-		clear_thread_flag(TIF_SVE);
-		current->thread.svcr &= ~SVCR_SM_MASK;
-		current->thread.fp_type = FP_STATE_FPSIMD;
-		goto fpsimd_only;
-	}
+	/*
+	 * Non-streaming SVE state may be preserved without an SVE payload, in
+	 * which case the SVE context only has a header with VL==0, and all
+	 * state can be restored from the FPSIMD context.
+	 *
+	 * Streaming SVE state is always preserved with an SVE payload. For
+	 * consistency and robustness, reject restoring streaming SVE state
+	 * without an SVE payload.
+	 */
+	if (!sm && user->sve_size == sizeof(*user->sve))
+		return restore_fpsimd_context(user);
 
 	vq = sve_vq_from_vl(vl);
 
 	if (user->sve_size < SVE_SIG_CONTEXT_SIZE(vq))
 		return -EINVAL;
 
-	/*
-	 * Careful: we are about __copy_from_user() directly into
-	 * thread.sve_state with preemption enabled, so protection is
-	 * needed to prevent a racing context switch from writing stale
-	 * registers back over the new data.
-	 */
-
-	fpsimd_flush_task_state(current);
-	/* From now, fpsimd_thread_switch() won't touch thread.sve_state */
-
 	sve_alloc(current, true);
 	if (!current->thread.sve_state) {
 		clear_thread_flag(TIF_SVE);
@@ -376,19 +464,14 @@ static int restore_sve_fpsimd_context(struct user_ctxs *user)
 		set_thread_flag(TIF_SVE);
 	current->thread.fp_type = FP_STATE_SVE;
 
-fpsimd_only:
-	/* copy the FP and status/control registers */
-	/* restore_sigframe() already checked that user->fpsimd != NULL. */
-	err = __copy_from_user(fpsimd.vregs, user->fpsimd->vregs,
-			       sizeof(fpsimd.vregs));
-	__get_user_error(fpsimd.fpsr, &user->fpsimd->fpsr, err);
-	__get_user_error(fpsimd.fpcr, &user->fpsimd->fpcr, err);
+	err = read_fpsimd_context(&fpsimd, user);
+	if (err)
+		return err;
 
-	/* load the hardware registers from the fpsimd_state structure */
-	if (!err)
-		fpsimd_update_current_state(&fpsimd);
+	/* Merge the FPSIMD registers into the SVE state */
+	fpsimd_update_current_state(&fpsimd);
 
-	return err ? -EFAULT : 0;
+	return 0;
 }
 
 #else /* ! CONFIG_ARM64_SVE */
@@ -408,13 +491,12 @@ extern int preserve_sve_context(void __user *ctx);
 
 static int preserve_tpidr2_context(struct tpidr2_context __user *ctx)
 {
+	u64 tpidr2_el0 = read_sysreg_s(SYS_TPIDR2_EL0);
 	int err = 0;
 
-	current->thread.tpidr2_el0 = read_sysreg_s(SYS_TPIDR2_EL0);
-
 	__put_user_error(TPIDR2_MAGIC, &ctx->head.magic, err);
 	__put_user_error(sizeof(*ctx), &ctx->head.size, err);
-	__put_user_error(current->thread.tpidr2_el0, &ctx->tpidr2, err);
+	__put_user_error(tpidr2_el0, &ctx->tpidr2, err);
 
 	return err;
 }
@@ -456,11 +538,6 @@ static int preserve_za_context(struct za_context __user *ctx)
 	err |= __copy_to_user(&ctx->__reserved, reserved, sizeof(reserved));
 
 	if (vq) {
-		/*
-		 * This assumes that the ZA state has already been saved to
-		 * the task struct by calling the function
-		 * fpsimd_signal_preserve_current_state().
-		 */
 		err |= __copy_to_user((char __user *)ctx + ZA_SIG_REGS_OFFSET,
 				      current->thread.sme_state,
 				      ZA_SIG_REGS_SIZE(vq));
@@ -495,16 +572,6 @@ static int restore_za_context(struct user_ctxs *user)
 	if (user->za_size < ZA_SIG_CONTEXT_SIZE(vq))
 		return -EINVAL;
 
-	/*
-	 * Careful: we are about __copy_from_user() directly into
-	 * thread.sme_state with preemption enabled, so protection is
-	 * needed to prevent a racing context switch from writing stale
-	 * registers back over the new data.
-	 */
-
-	fpsimd_flush_task_state(current);
-	/* From now, fpsimd_thread_switch() won't touch thread.sve_state */
-
 	sme_alloc(current, true);
 	if (!current->thread.sme_state) {
 		current->thread.svcr &= ~SVCR_ZA_MASK;
@@ -542,11 +609,6 @@ static int preserve_zt_context(struct zt_context __user *ctx)
 	BUILD_BUG_ON(sizeof(ctx->__reserved) != sizeof(reserved));
 	err |= __copy_to_user(&ctx->__reserved, reserved, sizeof(reserved));
 
-	/*
-	 * This assumes that the ZT state has already been saved to
-	 * the task struct by calling the function
-	 * fpsimd_signal_preserve_current_state().
-	 */
 	err |= __copy_to_user((char __user *)ctx + ZT_SIG_REGS_OFFSET,
 			      thread_zt_state(&current->thread),
 			      ZT_SIG_REGS_SIZE(1));
@@ -572,16 +634,6 @@ static int restore_zt_context(struct user_ctxs *user)
 	if (nregs != 1)
 		return -EINVAL;
 
-	/*
-	 * Careful: we are about __copy_from_user() directly into
-	 * thread.zt_state with preemption enabled, so protection is
-	 * needed to prevent a racing context switch from writing stale
-	 * registers back over the new data.
-	 */
-
-	fpsimd_flush_task_state(current);
-	/* From now, fpsimd_thread_switch() won't touch ZT in thread state */
-
 	err = __copy_from_user(thread_zt_state(&current->thread),
 			       (char __user const *)user->zt +
 					ZT_SIG_REGS_OFFSET,
@@ -604,6 +656,82 @@ extern int restore_zt_context(struct user_ctxs *user);
 
 #endif /* ! CONFIG_ARM64_SME */
 
+#ifdef CONFIG_ARM64_GCS
+
+static int preserve_gcs_context(struct gcs_context __user *ctx)
+{
+	int err = 0;
+	u64 gcspr = read_sysreg_s(SYS_GCSPR_EL0);
+
+	/*
+	 * If GCS is enabled we will add a cap token to the frame,
+	 * include it in the GCSPR_EL0 we report to support stack
+	 * switching via sigreturn if GCS is enabled.  We do not allow
+	 * enabling via sigreturn so the token is only relevant for
+	 * threads with GCS enabled.
+	 */
+	if (task_gcs_el0_enabled(current))
+		gcspr -= 8;
+
+	__put_user_error(GCS_MAGIC, &ctx->head.magic, err);
+	__put_user_error(sizeof(*ctx), &ctx->head.size, err);
+	__put_user_error(gcspr, &ctx->gcspr, err);
+	__put_user_error(0, &ctx->reserved, err);
+	__put_user_error(current->thread.gcs_el0_mode,
+			 &ctx->features_enabled, err);
+
+	return err;
+}
+
+static int restore_gcs_context(struct user_ctxs *user)
+{
+	u64 gcspr, enabled;
+	int err = 0;
+
+	if (user->gcs_size != sizeof(*user->gcs))
+		return -EINVAL;
+
+	__get_user_error(gcspr, &user->gcs->gcspr, err);
+	__get_user_error(enabled, &user->gcs->features_enabled, err);
+	if (err)
+		return err;
+
+	/* Don't allow unknown modes */
+	if (enabled & ~PR_SHADOW_STACK_SUPPORTED_STATUS_MASK)
+		return -EINVAL;
+
+	err = gcs_check_locked(current, enabled);
+	if (err != 0)
+		return err;
+
+	/* Don't allow enabling */
+	if (!task_gcs_el0_enabled(current) &&
+	    (enabled & PR_SHADOW_STACK_ENABLE))
+		return -EINVAL;
+
+	/* If we are disabling disable everything */
+	if (!(enabled & PR_SHADOW_STACK_ENABLE))
+		enabled = 0;
+
+	current->thread.gcs_el0_mode = enabled;
+
+	/*
+	 * We let userspace set GCSPR_EL0 to anything here, we will
+	 * validate later in gcs_restore_signal().
+	 */
+	write_sysreg_s(gcspr, SYS_GCSPR_EL0);
+
+	return 0;
+}
+
+#else /* ! CONFIG_ARM64_GCS */
+
+/* Turn any non-optimised out attempts to use these into a link error: */
+extern int preserve_gcs_context(void __user *ctx);
+extern int restore_gcs_context(struct user_ctxs *user);
+
+#endif /* ! CONFIG_ARM64_GCS */
+
 static int parse_user_sigframe(struct user_ctxs *user,
 			       struct rt_sigframe __user *sf)
 {
@@ -621,6 +749,8 @@ static int parse_user_sigframe(struct user_ctxs *user,
 	user->za = NULL;
 	user->zt = NULL;
 	user->fpmr = NULL;
+	user->poe = NULL;
+	user->gcs = NULL;
 
 	if (!IS_ALIGNED((unsigned long)base, 16))
 		goto invalid;
@@ -671,6 +801,17 @@ static int parse_user_sigframe(struct user_ctxs *user,
 			/* ignore */
 			break;
 
+		case POE_MAGIC:
+			if (!system_supports_poe())
+				goto invalid;
+
+			if (user->poe)
+				goto invalid;
+
+			user->poe = (struct poe_context __user *)head;
+			user->poe_size = size;
+			break;
+
 		case SVE_MAGIC:
 			if (!system_supports_sve() && !system_supports_sme())
 				goto invalid;
@@ -726,6 +867,17 @@ static int parse_user_sigframe(struct user_ctxs *user,
 			user->fpmr_size = size;
 			break;
 
+		case GCS_MAGIC:
+			if (!system_supports_gcs())
+				goto invalid;
+
+			if (user->gcs)
+				goto invalid;
+
+			user->gcs = (struct gcs_context __user *)head;
+			user->gcs_size = size;
+			break;
+
 		case EXTRA_MAGIC:
 			if (have_extra_context)
 				goto invalid;
@@ -809,7 +961,8 @@ invalid:
 }
 
 static int restore_sigframe(struct pt_regs *regs,
-			    struct rt_sigframe __user *sf)
+			    struct rt_sigframe __user *sf,
+			    struct user_access_state *ua_state)
 {
 	sigset_t set;
 	int i, err;
@@ -831,6 +984,8 @@ static int restore_sigframe(struct pt_regs *regs,
 	 */
 	forget_syscall(regs);
 
+	fpsimd_save_and_flush_current_state();
+
 	err |= !valid_user_regs(&regs->user_regs, current);
 	if (err == 0)
 		err = parse_user_sigframe(&user, sf);
@@ -845,6 +1000,9 @@ static int restore_sigframe(struct pt_regs *regs,
 			err = restore_fpsimd_context(&user);
 	}
 
+	if (err == 0 && system_supports_gcs() && user.gcs)
+		err = restore_gcs_context(&user);
+
 	if (err == 0 && system_supports_tpidr2() && user.tpidr2)
 		err = restore_tpidr2_context(&user);
 
@@ -857,13 +1015,69 @@ static int restore_sigframe(struct pt_regs *regs,
 	if (err == 0 && system_supports_sme2() && user.zt)
 		err = restore_zt_context(&user);
 
+	if (err == 0 && system_supports_poe() && user.poe)
+		err = restore_poe_context(&user, ua_state);
+
 	return err;
 }
 
+#ifdef CONFIG_ARM64_GCS
+static int gcs_restore_signal(void)
+{
+	u64 gcspr_el0, cap;
+	int ret;
+
+	if (!system_supports_gcs())
+		return 0;
+
+	if (!(current->thread.gcs_el0_mode & PR_SHADOW_STACK_ENABLE))
+		return 0;
+
+	gcspr_el0 = read_sysreg_s(SYS_GCSPR_EL0);
+
+	/*
+	 * Ensure that any changes to the GCS done via GCS operations
+	 * are visible to the normal reads we do to validate the
+	 * token.
+	 */
+	gcsb_dsync();
+
+	/*
+	 * GCSPR_EL0 should be pointing at a capped GCS, read the cap.
+	 * We don't enforce that this is in a GCS page, if it is not
+	 * then faults will be generated on GCS operations - the main
+	 * concern is to protect GCS pages.
+	 */
+	ret = copy_from_user(&cap, (unsigned long __user *)gcspr_el0,
+			     sizeof(cap));
+	if (ret)
+		return -EFAULT;
+
+	/*
+	 * Check that the cap is the actual GCS before replacing it.
+	 */
+	if (cap != GCS_SIGNAL_CAP(gcspr_el0))
+		return -EINVAL;
+
+	/* Invalidate the token to prevent reuse */
+	put_user_gcs(0, (unsigned long __user *)gcspr_el0, &ret);
+	if (ret != 0)
+		return -EFAULT;
+
+	write_sysreg_s(gcspr_el0 + 8, SYS_GCSPR_EL0);
+
+	return 0;
+}
+
+#else
+static int gcs_restore_signal(void) { return 0; }
+#endif
+
 SYSCALL_DEFINE0(rt_sigreturn)
 {
 	struct pt_regs *regs = current_pt_regs();
 	struct rt_sigframe __user *frame;
+	struct user_access_state ua_state;
 
 	/* Always make any pending restarted system calls return -EINTR */
 	current->restart_block.fn = do_no_restart_syscall;
@@ -880,12 +1094,17 @@ SYSCALL_DEFINE0(rt_sigreturn)
 	if (!access_ok(frame, sizeof (*frame)))
 		goto badframe;
 
-	if (restore_sigframe(regs, frame))
+	if (restore_sigframe(regs, frame, &ua_state))
+		goto badframe;
+
+	if (gcs_restore_signal())
 		goto badframe;
 
 	if (restore_altstack(&frame->uc.uc_stack))
 		goto badframe;
 
+	restore_user_access_state(&ua_state);
+
 	return regs->regs[0];
 
 badframe:
@@ -920,6 +1139,15 @@ static int setup_sigframe_layout(struct rt_sigframe_user_layout *user,
 			return err;
 	}
 
+#ifdef CONFIG_ARM64_GCS
+	if (system_supports_gcs() && (add_all || current->thread.gcspr_el0)) {
+		err = sigframe_alloc(user, &user->gcs_offset,
+				     sizeof(struct gcs_context));
+		if (err)
+			return err;
+	}
+#endif
+
 	if (system_supports_sve() || system_supports_sme()) {
 		unsigned int vq = 0;
 
@@ -980,11 +1208,19 @@ static int setup_sigframe_layout(struct rt_sigframe_user_layout *user,
 			return err;
 	}
 
+	if (system_supports_poe()) {
+		err = sigframe_alloc(user, &user->poe_offset,
+				     sizeof(struct poe_context));
+		if (err)
+			return err;
+	}
+
 	return sigframe_alloc_end(user);
 }
 
 static int setup_sigframe(struct rt_sigframe_user_layout *user,
-			  struct pt_regs *regs, sigset_t *set)
+			  struct pt_regs *regs, sigset_t *set,
+			  const struct user_access_state *ua_state)
 {
 	int i, err = 0;
 	struct rt_sigframe __user *sf = user->sigframe;
@@ -1020,6 +1256,12 @@ static int setup_sigframe(struct rt_sigframe_user_layout *user,
 		__put_user_error(current->thread.fault_code, &esr_ctx->esr, err);
 	}
 
+	if (system_supports_gcs() && err == 0 && user->gcs_offset) {
+		struct gcs_context __user *gcs_ctx =
+			apply_user_offset(user, user->gcs_offset);
+		err |= preserve_gcs_context(gcs_ctx);
+	}
+
 	/* Scalable Vector Extension state (including streaming), if present */
 	if ((system_supports_sve() || system_supports_sme()) &&
 	    err == 0 && user->sve_offset) {
@@ -1042,6 +1284,13 @@ static int setup_sigframe(struct rt_sigframe_user_layout *user,
 		err |= preserve_fpmr_context(fpmr_ctx);
 	}
 
+	if (system_supports_poe() && err == 0) {
+		struct poe_context __user *poe_ctx =
+			apply_user_offset(user, user->poe_offset);
+
+		err |= preserve_poe_context(poe_ctx, ua_state);
+	}
+
 	/* ZA state if present */
 	if (system_supports_sme() && err == 0 && user->za_offset) {
 		struct za_context __user *za_ctx =
@@ -1130,15 +1379,81 @@ static int get_sigframe(struct rt_sigframe_user_layout *user,
 	return 0;
 }
 
-static void setup_return(struct pt_regs *regs, struct k_sigaction *ka,
+#ifdef CONFIG_ARM64_GCS
+
+static int gcs_signal_entry(__sigrestore_t sigtramp, struct ksignal *ksig)
+{
+	u64 gcspr_el0;
+	int ret = 0;
+
+	if (!system_supports_gcs())
+		return 0;
+
+	if (!task_gcs_el0_enabled(current))
+		return 0;
+
+	/*
+	 * We are entering a signal handler, current register state is
+	 * active.
+	 */
+	gcspr_el0 = read_sysreg_s(SYS_GCSPR_EL0);
+
+	/*
+	 * Push a cap and the GCS entry for the trampoline onto the GCS.
+	 */
+	put_user_gcs((unsigned long)sigtramp,
+		     (unsigned long __user *)(gcspr_el0 - 16), &ret);
+	put_user_gcs(GCS_SIGNAL_CAP(gcspr_el0 - 8),
+		     (unsigned long __user *)(gcspr_el0 - 8), &ret);
+	if (ret != 0)
+		return ret;
+
+	gcspr_el0 -= 16;
+	write_sysreg_s(gcspr_el0, SYS_GCSPR_EL0);
+
+	return 0;
+}
+#else
+
+static int gcs_signal_entry(__sigrestore_t sigtramp, struct ksignal *ksig)
+{
+	return 0;
+}
+
+#endif
+
+static int setup_return(struct pt_regs *regs, struct ksignal *ksig,
 			 struct rt_sigframe_user_layout *user, int usig)
 {
 	__sigrestore_t sigtramp;
+	int err;
+
+	if (ksig->ka.sa.sa_flags & SA_RESTORER)
+		sigtramp = ksig->ka.sa.sa_restorer;
+	else
+		sigtramp = VDSO_SYMBOL(current->mm->context.vdso, sigtramp);
+
+	err = gcs_signal_entry(sigtramp, ksig);
+	if (err)
+		return err;
+
+	/*
+	 * We must not fail from this point onwards. We are going to update
+	 * registers, including SP, in order to invoke the signal handler. If
+	 * we failed and attempted to deliver a nested SIGSEGV to a handler
+	 * after that point, the subsequent sigreturn would end up restoring
+	 * the (partial) state for the original signal handler.
+	 */
 
 	regs->regs[0] = usig;
+	if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
+		regs->regs[1] = (unsigned long)&user->sigframe->info;
+		regs->regs[2] = (unsigned long)&user->sigframe->uc;
+	}
 	regs->sp = (unsigned long)user->sigframe;
 	regs->regs[29] = (unsigned long)&user->next_frame->fp;
-	regs->pc = (unsigned long)ka->sa.sa_handler;
+	regs->regs[30] = (unsigned long)sigtramp;
+	regs->pc = (unsigned long)ksig->ka.sa.sa_handler;
 
 	/*
 	 * Signal delivery is a (wacky) indirect function call in
@@ -1161,29 +1476,12 @@ static void setup_return(struct pt_regs *regs, struct k_sigaction *ka,
 
 	/* Signal handlers are invoked with ZA and streaming mode disabled */
 	if (system_supports_sme()) {
-		/*
-		 * If we were in streaming mode the saved register
-		 * state was SVE but we will exit SM and use the
-		 * FPSIMD register state - flush the saved FPSIMD
-		 * register state in case it gets loaded.
-		 */
-		if (current->thread.svcr & SVCR_SM_MASK) {
-			memset(&current->thread.uw.fpsimd_state, 0,
-			       sizeof(current->thread.uw.fpsimd_state));
-			current->thread.fp_type = FP_STATE_FPSIMD;
-		}
-
-		current->thread.svcr &= ~(SVCR_ZA_MASK |
-					  SVCR_SM_MASK);
-		sme_smstop();
+		task_smstop_sm(current);
+		current->thread.svcr &= ~SVCR_ZA_MASK;
+		write_sysreg_s(0, SYS_TPIDR2_EL0);
 	}
 
-	if (ka->sa.sa_flags & SA_RESTORER)
-		sigtramp = ka->sa.sa_restorer;
-	else
-		sigtramp = VDSO_SYMBOL(current->mm->context.vdso, sigtramp);
-
-	regs->regs[30] = (unsigned long)sigtramp;
+	return 0;
 }
 
 static int setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set,
@@ -1191,28 +1489,37 @@ static int setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set,
 {
 	struct rt_sigframe_user_layout user;
 	struct rt_sigframe __user *frame;
+	struct user_access_state ua_state;
 	int err = 0;
 
-	fpsimd_signal_preserve_current_state();
+	fpsimd_save_and_flush_current_state();
 
 	if (get_sigframe(&user, ksig, regs))
 		return 1;
 
+	save_reset_user_access_state(&ua_state);
 	frame = user.sigframe;
 
 	__put_user_error(0, &frame->uc.uc_flags, err);
 	__put_user_error(NULL, &frame->uc.uc_link, err);
 
 	err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
-	err |= setup_sigframe(&user, regs, set);
-	if (err == 0) {
-		setup_return(regs, &ksig->ka, &user, usig);
-		if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
-			err |= copy_siginfo_to_user(&frame->info, &ksig->info);
-			regs->regs[1] = (unsigned long)&frame->info;
-			regs->regs[2] = (unsigned long)&frame->uc;
-		}
-	}
+	err |= setup_sigframe(&user, regs, set, &ua_state);
+	if (ksig->ka.sa.sa_flags & SA_SIGINFO)
+		err |= copy_siginfo_to_user(&frame->info, &ksig->info);
+
+	if (err == 0)
+		err = setup_return(regs, ksig, &user, usig);
+
+	/*
+	 * We must not fail if setup_return() succeeded - see comment at the
+	 * beginning of setup_return().
+	 */
+
+	if (err == 0)
+		set_handler_user_access_state();
+	else
+		restore_user_access_state(&ua_state);
 
 	return err;
 }