From: Samuel Thibault <samuel.thibault@gnu.org>
To: Florian Weimer <fw@deneb.enyo.de>
Cc: "Sergey Bugaev" <bugaevc@gmail.com>,
bug-hurd@gnu.org, libc-alpha@sourceware.org,
"Flávio Cruz" <flaviocruz@gmail.com>
Subject: Re: [RFC PATCH glibc 11/12] hurd, htl: Add some x86_64-specific code
Date: Sun, 12 Feb 2023 20:37:33 +0100 [thread overview]
Message-ID: <20230212193733.p7jeei25lo2fwr67@begin> (raw)
In-Reply-To: <87lel2n0m0.fsf@mid.deneb.enyo.de>
Florian Weimer, le dim. 12 févr. 2023 20:29:43 +0100, a ecrit:
> * Samuel Thibault:
>
> > 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.thibault@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.
>
> Well, yes, but how do you identify the other thread? Usually by the
> address of its TCB.
Yes, but that's not (yet) the case in htl.
Samuel
next prev parent reply other threads:[~2023-02-12 19:37 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-12 11:10 [RFC PATCH 0/12] Towards glibc on x86_64-gnu Sergey Bugaev
2023-02-12 11:10 ` [RFC PATCH glibc 1/12] hurd: Refactor readlinkat() Sergey Bugaev
2023-02-12 14:49 ` Samuel Thibault
2023-02-12 11:10 ` [RFC PATCH glibc 2/12] hurd: Use mach_msg_type_number_t where appropriate Sergey Bugaev
2023-02-12 14:52 ` Samuel Thibault
2023-02-12 11:10 ` [RFC PATCH glibc 3/12] mach, hurd: Cast through uintptr_t Sergey Bugaev
2023-02-12 14:55 ` Samuel Thibault
2023-02-12 11:10 ` [RFC PATCH glibc 4/12] hurd: Fix xattr error value Sergey Bugaev
2023-02-12 14:56 ` Samuel Thibault
2023-02-12 11:10 ` [RFC PATCH glibc 5/12] htl: Fix semaphore reference Sergey Bugaev
2023-02-12 14:57 ` Samuel Thibault
2023-02-12 11:10 ` [RFC PATCH hurd 6/12] hurd: Fix modes_t and speeds_t types on 64-bit Sergey Bugaev
2023-02-12 15:00 ` Samuel Thibault
2023-02-12 15:15 ` Sergey Bugaev
2023-02-12 15:22 ` Samuel Thibault
2023-02-12 16:13 ` Sergey Bugaev
2023-02-12 16:30 ` Samuel Thibault
2023-02-12 19:03 ` Samuel Thibault
2023-02-12 11:10 ` [RFC PATCH mig 7/12] Drop -undef -ansi from cpp flags Sergey Bugaev
2023-02-12 15:01 ` Samuel Thibault
2023-02-12 18:43 ` Flávio Cruz
2023-02-12 18:44 ` Samuel Thibault
2023-02-12 11:10 ` [RFC PATCH mig 8/12] Set max type alignment to sizeof(long) Sergey Bugaev
2023-02-12 11:10 ` [RFC PATCH glibc 9/12] mach: Look for mach_i386.defs on x86_64 too Sergey Bugaev
2023-02-12 15:07 ` Samuel Thibault
2023-02-12 15:38 ` Sergey Bugaev
2023-02-12 15:46 ` Samuel Thibault
2023-02-12 16:01 ` Sergey Bugaev
2023-02-16 20:22 ` Joseph Myers
2023-02-12 11:10 ` [RFC PATCH glibc 10/12] hurd: Set up the basic tree for x86_64-gnu Sergey Bugaev
2023-02-12 15:15 ` Samuel Thibault
2023-02-12 11:10 ` [RFC PATCH glibc 11/12] hurd, htl: Add some x86_64-specific code Sergey Bugaev
2023-02-12 16:11 ` Samuel Thibault
2023-02-12 16:25 ` Sergey Bugaev
2023-02-12 16:36 ` Samuel Thibault
2023-02-12 16:40 ` Florian Weimer
2023-02-12 16:46 ` Samuel Thibault
2023-02-12 19:29 ` Florian Weimer
2023-02-12 19:37 ` Samuel Thibault [this message]
2023-02-12 16:51 ` Sergey Bugaev
2023-02-12 17:02 ` Samuel Thibault
2023-02-12 17:06 ` Sergey Bugaev
2023-02-12 11:10 ` [RFC PATCH glibc 12/12] C11 thrd: Downgrade the default alignment of mtx_t Sergey Bugaev
2023-02-12 15:18 ` Samuel Thibault
2023-02-12 15:52 ` Sergey Bugaev
2023-02-12 16:29 ` Samuel Thibault
2023-02-12 16:12 ` [RFC PATCH 0/12] Towards glibc on x86_64-gnu Samuel Thibault
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