[PATCH] arm64: fix bug for reloading FPSIMD state after execve on cpu 0.

From: Chunyan Zhang
Date: Tue Aug 25 2015 - 22:45:19 EST

From: Janet Liu <janet.liu@xxxxxxxxxxxxxx>

If process A is running on CPU 0 and do execve syscall and after sched_exec,
dest_cpu is 0, fpsimd_state.cpu is 0. If at the time Process A get scheduled
out and after some kernel threads running on CPU 0, process A is back in CPU 0,
A's fpsimd_state.cpu is current cpu id "0", and per_cpu(fpsimd_last_state)
points A's fpsimd_state, TIF_FOREIGN_FPSTATE will be clear, kernel will not
reload the context during it return to userspace. so set the cpu's
fpsimd_last_state to NULL to avoid this.

Signed-off-by: Janet Liu <janet.liu@xxxxxxxxxxxxxx>
Signed-off-by: Chunyan Zhang <chunyan.zhang@xxxxxxxxxxxxxx>
arch/arm64/kernel/fpsimd.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 44d6f75..ec58d94 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -159,6 +159,7 @@ void fpsimd_flush_thread(void)
memset(&current->thread.fpsimd_state, 0, sizeof(struct fpsimd_state));
+ this_cpu_write(fpsimd_last_state, NULL);


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/