1 files changed, 35 insertions, 1 deletions

diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
index f418ebc65f95..78b3e0f8e997 100644
--- a/arch/arm64/kernel/mte.c
+++ b/arch/arm64/kernel/mte.c
@@ -186,6 +186,11 @@ void mte_check_tfsr_el1(void)
 }
 #endif
 
+/*
+ * This is where we actually resolve the system and process MTE mode
+ * configuration into an actual value in SCTLR_EL1 that affects
+ * userspace.
+ */
 static void mte_update_sctlr_user(struct task_struct *task)
 {
 	/*
@@ -199,9 +204,20 @@ static void mte_update_sctlr_user(struct task_struct *task)
 	unsigned long pref, resolved_mte_tcf;
 
 	pref = __this_cpu_read(mte_tcf_preferred);
+	/*
+	 * If there is no overlap between the system preferred and
+	 * program requested values go with what was requested.
+	 */
 	resolved_mte_tcf = (mte_ctrl & pref) ? pref : mte_ctrl;
 	sctlr &= ~SCTLR_EL1_TCF0_MASK;
-	if (resolved_mte_tcf & MTE_CTRL_TCF_ASYNC)
+	/*
+	 * Pick an actual setting. The order in which we check for
+	 * set bits and map into register values determines our
+	 * default order.
+	 */
+	if (resolved_mte_tcf & MTE_CTRL_TCF_ASYMM)
+		sctlr |= SCTLR_EL1_TCF0_ASYMM;
+	else if (resolved_mte_tcf & MTE_CTRL_TCF_ASYNC)
 		sctlr |= SCTLR_EL1_TCF0_ASYNC;
 	else if (resolved_mte_tcf & MTE_CTRL_TCF_SYNC)
 		sctlr |= SCTLR_EL1_TCF0_SYNC;
@@ -253,6 +269,9 @@ void mte_thread_switch(struct task_struct *next)
 	mte_update_sctlr_user(next);
 	mte_update_gcr_excl(next);
 
+	/* TCO may not have been disabled on exception entry for the current task. */
+	mte_disable_tco_entry(next);
+
 	/*
 	 * Check if an async tag exception occurred at EL1.
 	 *
@@ -293,6 +312,17 @@ long set_mte_ctrl(struct task_struct *task, unsigned long arg)
 	if (arg & PR_MTE_TCF_SYNC)
 		mte_ctrl |= MTE_CTRL_TCF_SYNC;
 
+	/*
+	 * If the system supports it and both sync and async modes are
+	 * specified then implicitly enable asymmetric mode.
+	 * Userspace could see a mix of both sync and async anyway due
+	 * to differing or changing defaults on CPUs.
+	 */
+	if (cpus_have_cap(ARM64_MTE_ASYMM) &&
+	    (arg & PR_MTE_TCF_ASYNC) &&
+	    (arg & PR_MTE_TCF_SYNC))
+		mte_ctrl |= MTE_CTRL_TCF_ASYMM;
+
 	task->thread.mte_ctrl = mte_ctrl;
 	if (task == current) {
 		preempt_disable();
@@ -467,6 +497,8 @@ static ssize_t mte_tcf_preferred_show(struct device *dev,
 		return sysfs_emit(buf, "async\n");
 	case MTE_CTRL_TCF_SYNC:
 		return sysfs_emit(buf, "sync\n");
+	case MTE_CTRL_TCF_ASYMM:
+		return sysfs_emit(buf, "asymm\n");
 	default:
 		return sysfs_emit(buf, "???\n");
 	}
@@ -482,6 +514,8 @@ static ssize_t mte_tcf_preferred_store(struct device *dev,
 		tcf = MTE_CTRL_TCF_ASYNC;
 	else if (sysfs_streq(buf, "sync"))
 		tcf = MTE_CTRL_TCF_SYNC;
+	else if (cpus_have_cap(ARM64_MTE_ASYMM) && sysfs_streq(buf, "asymm"))
+		tcf = MTE_CTRL_TCF_ASYMM;
 	else
 		return -EINVAL;