On 7/25/25 04:22, Peter Maydell wrote:
FEAT_SME adds the TPIDR2 userspace-accessible system register, which
is used as part of the procedure calling standard's lazy saving
scheme for the ZA registers:
https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst#66the-za-lazy-saving-scheme
The Linux kernel has a signal frame record for saving
and restoring this value when calling signal handlers, but
we forgot to implement this. The result is that code which
tries to unwind an exception out of a signal handler will
not work correctly.
Add support for the missing record.
Cc: [email protected]
Fixes: 78011586b90d1 ("target/arm: Enable SME for user-only")
Signed-off-by: Peter Maydell <[email protected]>
---
linux-user/aarch64/signal.c | 46 +++++++++++++++++++++++++++++++++++--
1 file changed, 44 insertions(+), 2 deletions(-)
Oh my. I spent yesterday working on this and other signal handling fixes. Though from a
FEAT_GCS starting point, so I still hadn't seen the clear tpidr2 on signal delivery change.
+static void target_setup_tpidr2_record(struct target_tpidr2_context *tpidr2,
+ CPUARMState *env, int size)
+{
+ __put_user(TARGET_TPIDR2_MAGIC, &tpidr2->head.magic);
+ __put_user(sizeof(struct target_tpidr2_context), &tpidr2->head.size);
+ __put_user(env->cp15.tpidr2_el0, &tpidr2->tpidr2);
+}
Drop the unused size argument.
+static bool target_restore_tpidr2_record(CPUARMState *env,
+ struct target_tpidr2_context *tpidr2)
+{
+ if (!cpu_isar_feature(aa64_sme, env_archcpu(env))) {
+ return false;
+ }
+ __get_user(env->cp15.tpidr2_el0, &tpidr2->tpidr2);
+ return true;
+}
The sme check is better placed in target_restore_sigframe ...
+ case TARGET_TPIDR2_MAGIC:
+ if (tpidr2 || size != sizeof(struct target_tpidr2_context)) {
+ goto err;
+ }
... here. Then target_restore_tpidr2_record has no failure modes and can
return void ...
@@ -497,6 +530,9 @@ static int target_restore_sigframe(CPUARMState *env,
if (za && !target_restore_za_record(env, za, za_size, &svcr)) {
goto err;
}
+ if (tpidr2 && !target_restore_tpidr2_record(env, tpidr2)) {
+ goto err;
+ }
... which simplifies this.
r~
