[PATCH v5 12/15] arm64: exec: Adjust affinity for compat tasks with mismatched 32-bit EL0
From: Will Deacon <will@kernel.org>
Date: 2020-12-08 13:30:44
Also in:
linux-arch, lkml
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
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 <redacted> Signed-off-by: Will Deacon <will@kernel.org> --- 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
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