Florian Weimer, le dim. 12 févr. 2023 17:40:58 +0100, a ecrit: > * Samuel Thibault via Libc-alpha: > > > Sergey Bugaev, le dim. 12 févr. 2023 19:25:11 +0300, a ecrit: > >> On Sun, Feb 12, 2023 at 7:11 PM Samuel Thibault <samuel.thiba...@gnu.org> > >> wrote: > >> > Sergey Bugaev, le dim. 12 févr. 2023 14:10:42 +0300, a ecrit: > >> > > We should not need a getter routine, because one can simply inspect > >> > > the target > >> > > thread's state (unless, again, I misunderstand things horribly). > >> > > >> > For 16bit fs/gs values we could read them from userland yes. But for > >> > fs/gs base, the FSGSBASE instruction is not available on all 64bit > >> > processors. And ATM in THREAD_TCB we want to be able to get the base of > >> > another thread. > >> > >> What I've meant is: > >> > >> __thread_get_state (whatever_thread, &state); > >> uintptr_t its_fs_base = state->fs_base; > >> > >> You can't really do the same to *write* [fg]s_base, because doing > >> thread_set_state on your own thread is bound to end badly. > > > > ? Well, sure, just like setting fs/gs through thread state was not done > > for i386. > > > > I don't see where you're aiming. Getting fs/gs from __thread_get_state > > won't actually give you the base, you'll just read something like 0. > > The convention is that the FSBASE address is at %fs:0.
Yes, but that works only for reading your own base, not the base of another thread. Samuel
