arm64/boot: Disable trapping of PMZR_EL0 writes to EL2grafted

__init_el2_fgt2() writes one mask to both HDFGRTR2_EL2 and HDFGWTR2_EL2.
PMZR_EL0 is write-only, so its trap bit, nPMZR_EL0, exists only in
HDFGWTR2_EL2 and is therefore never set: a PMZR_EL0 write from the host
traps to EL2, where the nVHE hypervisor has no handler and BUG()s. The
kernel never writes PMZR_EL0, but kernel.perf_user_access=1 has the PMU
driver set PMUSERENR_EL0.UEN for a task with a user-read event, so a
write from EL0 reaches the trap and takes the host down without a panic
message.

Accumulate the HDFGWTR2_EL2 bits separately, as __init_el2_fgt() already
does for HDFGWTR_EL2, and set nPMZR_EL0 with the other FEAT_PMUv3p9
bits.

Fixes: 858c7bfcb35e1 ("arm64/boot: Enable EL2 requirements for FEAT_PMUv3p9")
Cc: stable@vger.kernel.org
Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Oliver Upton <oupton@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>

1 files changed, 55 insertions, 0 deletions

diff --git a/drivers/tty/tty_mutex.c b/drivers/tty/tty_mutex.c
new file mode 100644
index 000000000..784e46a0a
--- /dev/null
+++ b/drivers/tty/tty_mutex.c
@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/tty.h>
+#include <linux/module.h>
+#include <linux/kallsyms.h>
+#include <linux/semaphore.h>
+#include <linux/sched.h>
+#include "tty.h"
+
+/* Legacy tty mutex glue */
+
+/*
+ * Getting the big tty mutex.
+ */
+
+void tty_lock(struct tty_struct *tty)
+{
+	tty_kref_get(tty);
+	mutex_lock(&tty->legacy_mutex);
+}
+EXPORT_SYMBOL(tty_lock);
+
+int tty_lock_interruptible(struct tty_struct *tty)
+{
+	int ret;
+
+	tty_kref_get(tty);
+	ret = mutex_lock_interruptible(&tty->legacy_mutex);
+	if (ret)
+		tty_kref_put(tty);
+	return ret;
+}
+
+void tty_unlock(struct tty_struct *tty)
+{
+	mutex_unlock(&tty->legacy_mutex);
+	tty_kref_put(tty);
+}
+EXPORT_SYMBOL(tty_unlock);
+
+void tty_lock_slave(struct tty_struct *tty)
+{
+	if (tty && tty != tty->link)
+		tty_lock(tty);
+}
+
+void tty_unlock_slave(struct tty_struct *tty)
+{
+	if (tty && tty != tty->link)
+		tty_unlock(tty);
+}
+
+void tty_set_lock_subclass(struct tty_struct *tty)
+{
+	lockdep_set_subclass(&tty->legacy_mutex, TTY_LOCK_SLAVE);
+}