The generic THREAD_INFO_IN_TASK definition of thread_info::flags is a u32, matching x86 prior to the introduction of THREAD_INFO_IN_TASK.
However, common helpers like test_ti_thread_flag() implicitly assume that thread_info::flags has at least the size and alignment of unsigned long, and relying on padding and alignment provided by other elements of task_struct is somewhat fragile. Additionally, some architectures use more that 32 bits for thread_info::flags, and others may need to in future. With THREAD_INFO_IN_TASK, task struct follows thread_info with a long field, and thus we no longer save any space as we did back in commit affa219b60a11b32 ("x86: change thread_info's flag field back to 32 bits"). Given all this, it makes more sense for the generic thread_info::flags to be an unsigned long. Make it so. Signed-off-by: Mark Rutland <mark.rutl...@arm.com> Cc: Andrew Morton <a...@linux-foundation.org> Cc: Andy Lutomirski <l...@kernel.org> Cc: Kees Cook <keesc...@chromium.org> Cc: linux-kernel@vger.kernel.org --- include/linux/thread_info.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) As discussed in the arm64 RFC. Andy, I'm assuming that as with affa219b60a11b32 no x86 assembly fixups are required. An x86_64 defconfig built fine for me. I've based this on your x86/vmap_stack branch. I'm not sure what the plan is for merging that. If I should be using a different branch to base the arm64 work atop of, please let me know! Thanks, Mark. diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h index f3837c7..a2c2f88 100644 --- a/include/linux/thread_info.h +++ b/include/linux/thread_info.h @@ -13,7 +13,7 @@ #ifdef CONFIG_THREAD_INFO_IN_TASK struct thread_info { - u32 flags; /* low level flags */ + unsigned long flags; /* low level flags */ }; #define INIT_THREAD_INFO(tsk) \ -- 1.9.1