Re: [PATCH v3 0/3] MR4987: ntdll: Support generic xstate (part 1).

[Alexandre Julliard (＠julliard)]

Alexandre Julliard (@julliard) commented about dlls/ntdll/unix/signal_x86_64.c:
>                 "movl 0xb0(%rcx),%r14d\n\t"     /* frame->syscall_flags */
>                 "testl $3,%r14d\n\t"            /* SYSCALL_HAVE_XSAVE | SYSCALL_HAVE_XSAVEC */
>                 "jz 2f\n\t"
> -
>               "movl $7,%eax\n\t"
> -
>               "xorl %edx,%edx\n\t"
> -
>               "movq %rdx,0x2c0(%rcx)\n\t"
> -
>               "movq %rdx,0x2c8(%rcx)\n\t"
> -
>               "movq %rdx,0x2d0(%rcx)\n\t"
> -
>               "movl %gs:0x340,%eax\n\t"       /* amd64_thread_data()->xstate_features_mask */
> -
>               "movl %gs:0x344,%edx\n\t"       /* amd64_thread_data()->xstate_features_mask high dword */

macOS needs an extra indirection for TEB accesses.