@@ -26,9 +26,19 @@ struct ucontext {
struct ucontext *uc_link;
stack_t uc_stack;
sigset_t uc_sigmask;
- /* glibc uses a 1024-bit sigset_t */
+ /* There's some padding here to allow sigset_t to be expanded in the
+ * future. Though this is unlikely, other architectures put uc_sigmask
+ * at the end of this structure and explicitly state it can be
+ * expanded, so we didn't want to box ourselves in here. */
__u8 __unused[1024 / 8 - sizeof(sigset_t)];
- /* last for future expansion */
+ /* We can't put uc_sigmask at the end of this structure because we need
+ * to be able to expand sigcontext in the future. For example, the
+ * vector ISA extension will almost certainly add ISA state. We want
+ * to ensure all user-visible ISA state can be saved and restored via a
+ * ucontext, so we're putting this at the end in order to allow for
+ * infinite extensibility. Since we know this will be extended and we
+ * assume sigset_t won't be extended an extreme amount, we're
+ * prioritizing this. */
struct sigcontext uc_mcontext;
};
> If that layout is indeed better, maybe we should change asm-generic
> to use that, and fall back to the old layout for the architectures that
> already use it.
That cropped up during glibc as well, and I think it might be the right answer.
Should I submit another patch that fixes up the other ISAs?
> If one is as good as the other, could you change kernel and glibc
> to use the normal one instead?
>
>> + */
>> +VERSION
>> +{
>> + LINUX_2.6 {
>> + global:
>> + __vdso_rt_sigreturn;
>> + __vdso_cmpxchg32;
>> + __vdso_cmpxchg64;
>> + local: *;
>> + };
>
> The last vdso that got added was for arm64, and it was still
> during linux-2.6 times.
>
> Should this instead use the version that you are targetting for
> the merge, i.e. 4.15?
That sounds right to me
@@ -67,7 +67,7 @@ PHDRS
*/
VERSION
{
- LINUX_2.6 {
+ LINUX_4.15 {
global:
__vdso_rt_sigreturn;
__vdso_cmpxchg32;