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Re: [PATCH 07/10] hurd: Fix x86_64 _hurd_tls_fork
From: |
Samuel Thibault |
Subject: |
Re: [PATCH 07/10] hurd: Fix x86_64 _hurd_tls_fork |
Date: |
Wed, 17 May 2023 23:01:10 +0200 |
User-agent: |
NeoMutt/20170609 (1.8.3) |
Applied, thanks!
Sergey Bugaev via Libc-alpha, le mer. 17 mai 2023 22:14:33 +0300, a ecrit:
> It is illegal to call thread_get_state () on mach_thread_self (), so
> this codepath cannot be used as-is to fork the calling thread's TLS.
> Fortunately we can use THREAD_SELF (aka %fs:0x0) to find out the value
> of our fs_base without calling into the kernel.
>
> Fixes: f6cf701efc61c9ad910372bda14b9a235db310a8
> "hurd: Implement TLS for x86_64"
>
> Checked on x86_64-gnu: fork () now works!
>
> Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
> ---
> It would be nice if GNU Mach allowed
>
> thread_get_state (mach_thread_self (), i386_FSGS_BASE_STATE)
>
> like it already allows thread_set_state for this case. But even if
> gnumach adds suppport for this, doing it in userspace without an extra
> RPC is still better.
>
> sysdeps/mach/hurd/x86_64/tls.h | 25 +++++++++++++++++++------
> 1 file changed, 19 insertions(+), 6 deletions(-)
>
> diff --git a/sysdeps/mach/hurd/x86_64/tls.h b/sysdeps/mach/hurd/x86_64/tls.h
> index 35dcef44..6487ed35 100644
> --- a/sysdeps/mach/hurd/x86_64/tls.h
> +++ b/sysdeps/mach/hurd/x86_64/tls.h
> @@ -140,12 +140,25 @@ _hurd_tls_fork (thread_t child, thread_t orig,
> error_t err;
> struct i386_fsgs_base_state state;
> mach_msg_type_number_t state_count = i386_FSGS_BASE_STATE_COUNT;
> - err = __thread_get_state (orig, i386_FSGS_BASE_STATE,
> - (thread_state_t) &state,
> - &state_count);
> - if (err)
> - return err;
> - assert (state_count == i386_FSGS_BASE_STATE_COUNT);
> +
> + extern thread_t hurd_thread_self (void);
> + if (orig != hurd_thread_self ())
> + {
> + err = __thread_get_state (orig, i386_FSGS_BASE_STATE,
> + (thread_state_t) &state,
> + &state_count);
> + if (err)
> + return err;
> + assert (state_count == i386_FSGS_BASE_STATE_COUNT);
> + }
> + else
> + {
> + /* It is illegal to call thread_get_state () on mach_thread_self ().
> + But we're only interested in the value of fs_base, and since we're
> + this thread, we know it points to our TCB. */
> + state.fs_base = (unsigned long) THREAD_SELF;
> + state.gs_base = 0;
> + }
>
> return __thread_set_state (child, i386_FSGS_BASE_STATE,
> (thread_state_t) &state,
> --
> 2.40.1
>
--
Samuel
---
Pour une évaluation indépendante, transparente et rigoureuse !
Je soutiens la Commission d'Évaluation de l'Inria.
- Re: [RFC PATCH 06/10] hurd: Make sure to not use tcb->self, (continued)
- Re: [RFC PATCH 06/10] hurd: Make sure to not use tcb->self, Joseph Myers, 2023/05/18
- Re: [RFC PATCH 06/10] hurd: Make sure to not use tcb->self, Sergey Bugaev, 2023/05/18
- Re: [RFC PATCH 06/10] hurd: Make sure to not use tcb->self, Joseph Myers, 2023/05/18
- Re: [RFC PATCH 06/10] hurd: Make sure to not use tcb->self, Samuel Thibault, 2023/05/18
- Re: [RFC PATCH 06/10] hurd: Make sure to not use tcb->self, Sergey Bugaev, 2023/05/19
- Re: [RFC PATCH 06/10] hurd: Make sure to not use tcb->self, Florian Weimer, 2023/05/19
- Re: [RFC PATCH 06/10] hurd: Make sure to not use tcb->self, Joseph Myers, 2023/05/19
- [PATCH] hurd: Fix using interposable hurd_thread_self, Sergey Bugaev, 2023/05/19
- Re: [PATCH] hurd: Fix using interposable hurd_thread_self, Samuel Thibault, 2023/05/19
[PATCH 07/10] hurd: Fix x86_64 _hurd_tls_fork, Sergey Bugaev, 2023/05/17
- Re: [PATCH 07/10] hurd: Fix x86_64 _hurd_tls_fork,
Samuel Thibault <=
[PATCH 08/10] hurd: Fix setting up pthreads, Sergey Bugaev, 2023/05/17
[PATCH 09/10] hurd: Also make it possible to call strlen very early, Sergey Bugaev, 2023/05/17
[RFC PATCH 10/10] hurd: Regenerate errno.h, Sergey Bugaev, 2023/05/17