When exec'ing a 32-bit task on a system with mismatched support for
32-bit EL0, try to ensure that it starts life on a CPU that can actually
run it.
Reviewed-by: Quentin Perret <qperret@xxxxxxxxxx>
Signed-off-by: Will Deacon <will@xxxxxxxxxx>
---
arch/arm64/kernel/process.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 9a2532d848f0..da313b738c7c 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -633,8 +633,20 @@ void arch_setup_new_exec(void)
if (is_compat_task()) {
mmflags = MMCF_AARCH32;
- if (static_branch_unlikely(&arm64_mismatched_32bit_el0))
+
+ /*
+ * Restrict the CPU affinity mask for a 32-bit task so that
+ * it contains only 32-bit-capable CPUs.
+ *
+ * From the perspective of the task, this looks similar to
+ * what would happen if the 64-bit-only CPUs were hot-unplugged
+ * at the point of execve(), although we try a bit harder to
+ * honour the cpuset hierarchy.
+ */
+ if (static_branch_unlikely(&arm64_mismatched_32bit_el0)) {
+ force_compatible_cpus_allowed_ptr(current);
set_tsk_thread_flag(current, TIF_NOTIFY_RESUME);
+ }
}
current->mm->context.flags = mmflags;
--
2.29.2.576.ga3fc446d84-goog
