From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from eggs.gnu.org (eggs.gnu.org [IPv6:2001:470:142:3::10]) by sourceware.org (Postfix) with ESMTPS id 2706B3858D20 for ; Fri, 14 Apr 2023 17:34:30 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 2706B3858D20 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=gnu.org Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=gnu.org Received: from fencepost.gnu.org ([2001:470:142:3::e]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pnNJc-00046S-P6; Fri, 14 Apr 2023 13:34:28 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=gnu.org; s=fencepost-gnu-org; h=In-Reply-To:MIME-Version:References:Subject:To:From: Date; bh=S8eUautEFQwXz+cTvKE1Pq4X0/GBs3zAYfRrOLHIlhQ=; b=QKXKh1Alrpa/+vEyOXfB yhYv3uKJY0SsHN53tTCDLZPNhb1pA+8Pv0BZToaFfd6lVzyXINtxJMfDW91Hh36Le1rEKO4XnC4V5 pJBZOtmebjmF9HkTzltfFIWGMA/S72weHIL2FKbOhv7YBe68AmMY8mbwlUAeKuRslRILITRrsAUkC 4iDhyUVAkTgIOC10d+rQ++aY10nQAj44sJy0Lxd8wZP4Ik53biQ5xHYihtX/M6xvvfXZgMC64WO3a EA+iE/hp7AJTBuTWn3VsJwZ1Nx9DPg9AAUlas3RlQ9vO2Vbs1TUd0TBgRnN8sBgaraAYX5jsDbs5b b0az+1DZHB7Nnw==; Received: from [2a01:cb19:4a:a400:de41:a9ff:fe47:ec49] (helo=begin) by fencepost.gnu.org with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pnNJb-0004jU-UA; Fri, 14 Apr 2023 13:34:28 -0400 Received: from samy by begin with local (Exim 4.96) (envelope-from ) id 1pnNJa-00AKnF-2r; Fri, 14 Apr 2023 19:34:26 +0200 Date: Fri, 14 Apr 2023 19:34:26 +0200 From: Samuel Thibault To: Sergey Bugaev Cc: libc-alpha@sourceware.org, bug-hurd@gnu.org Subject: Re: [RFC PATCH glibc 24/34] hurd: Only check for TLS initialization inside rtld or in static builds Message-ID: <20230414173426.ecq3dz57po2csniv@begin> Mail-Followup-To: Sergey Bugaev , libc-alpha@sourceware.org, bug-hurd@gnu.org References: <20230319151017.531737-1-bugaevc@gmail.com> <20230319151017.531737-25-bugaevc@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20230319151017.531737-25-bugaevc@gmail.com> Organization: I am not organized User-Agent: NeoMutt/20170609 (1.8.3) X-Spam-Status: No, score=-11.4 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,GIT_PATCH_0,KAM_SHORT,SPF_HELO_PASS,SPF_PASS,TXREP,T_SCC_BODY_TEXT_LINE,URIBL_BLACK autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: Reapplied on top of "Remove __hurd_local_reply_port", thanks! Sergey Bugaev, le dim. 19 mars 2023 18:10:07 +0300, a ecrit: > When glibc is built as a shared library, TLS is always initialized by > the call of TLS_INIT_TP () macro made inside the dynamic loader, prior > to running the main program (see dl-call_tls_init_tp.h). We can take > advantage of this: we know for sure that __LIBC_NO_TLS () will evaluate > to 0 in all other cases, so let the compiler know that explicitly too. > > Also, only define _hurd_tls_init () and TLS_INIT_TP () under the same > conditions (either !SHARED or inside rtld), to statically assert that > this is the case. > > Other than a microoptimization, this also helps with avoiding awkward > sharing of the __libc_tls_initialized variable between ld.so and libc.so > that we would have to do otherwise -- we know for sure that no sharing > is required, simply because __libc_tls_initialized would always be set > to true inside libc.so. > > Signed-off-by: Sergey Bugaev > --- > sysdeps/mach/hurd/Makefile | 4 ++ > sysdeps/mach/hurd/i386/dl-tls-initialized.c | 21 +++++++++ > sysdeps/mach/hurd/i386/tls.h | 43 +++++++++++-------- > sysdeps/mach/hurd/x86/init-first.c | 11 +---- > sysdeps/mach/hurd/x86_64/dl-tls-initialized.c | 21 +++++++++ > sysdeps/mach/hurd/x86_64/tls.h | 19 +++++--- > 6 files changed, 85 insertions(+), 34 deletions(-) > create mode 100644 sysdeps/mach/hurd/i386/dl-tls-initialized.c > create mode 100644 sysdeps/mach/hurd/x86_64/dl-tls-initialized.c > > diff --git a/sysdeps/mach/hurd/Makefile b/sysdeps/mach/hurd/Makefile > index d5584930..f43e92ba 100644 > --- a/sysdeps/mach/hurd/Makefile > +++ b/sysdeps/mach/hurd/Makefile > @@ -197,6 +197,10 @@ ifeq (hurd, $(subdir)) > sysdep_routines += cthreads > endif > > +ifeq (elf, $(subdir)) > +sysdep-dl-routines += dl-tls-initialized > +endif > + > ifeq (io, $(subdir)) > sysdep_routines += f_setlk close_nocancel close_nocancel_nostatus \ > fcntl_nocancel open_nocancel openat_nocancel read_nocancel \ > diff --git a/sysdeps/mach/hurd/i386/dl-tls-initialized.c b/sysdeps/mach/hurd/i386/dl-tls-initialized.c > new file mode 100644 > index 00000000..493ec239 > --- /dev/null > +++ b/sysdeps/mach/hurd/i386/dl-tls-initialized.c > @@ -0,0 +1,21 @@ > +/* Determine whether TLS is initialized, for i386/Hurd. > + Copyright (C) 1995-2023 Free Software Foundation, Inc. > + This file is part of the GNU C Library. > + > + The GNU C Library is free software; you can redistribute it and/or > + modify it under the terms of the GNU Lesser General Public > + License as published by the Free Software Foundation; either > + version 2.1 of the License, or (at your option) any later version. > + > + The GNU C Library is distributed in the hope that it will be useful, > + but WITHOUT ANY WARRANTY; without even the implied warranty of > + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU > + Lesser General Public License for more details. > + > + You should have received a copy of the GNU Lesser General Public > + License along with the GNU C Library; if not, see > + . */ > + > +#ifndef SHARED > +unsigned short __init1_desc; > +#endif > diff --git a/sysdeps/mach/hurd/i386/tls.h b/sysdeps/mach/hurd/i386/tls.h > index 0f8dd241..ee7b8004 100644 > --- a/sysdeps/mach/hurd/i386/tls.h > +++ b/sysdeps/mach/hurd/i386/tls.h > @@ -69,18 +69,6 @@ _Static_assert (offsetof (tcbhead_t, __private_ss) == 0x30, > | (desc->high_word & 0xff000000)); \ > }) > > -/* Return 1 if TLS is not initialized yet. */ > -#ifndef SHARED > -extern unsigned short __init1_desc; > -#define __HURD_DESC_INITIAL(gs, ds) ((gs) == (ds) || (gs) == __init1_desc) > -#else > -#define __HURD_DESC_INITIAL(gs, ds) ((gs) == (ds)) > -#endif > - > -#define __LIBC_NO_TLS() \ > - ({ unsigned short ds, gs; \ > - asm ("movw %%ds,%w0; movw %%gs,%w1" : "=q" (ds), "=q" (gs)); \ > - __builtin_expect(__HURD_DESC_INITIAL(gs, ds), 0); }) > #endif > > /* The TCB can have any size and the memory following the address the > @@ -125,6 +113,28 @@ extern unsigned short __init1_desc; > > # define HURD_SEL_LDT(sel) (__builtin_expect ((sel) & 4, 0)) > > +#ifndef SHARED > +extern unsigned short __init1_desc; > +# define __HURD_DESC_INITIAL(gs, ds) ((gs) == (ds) || (gs) == __init1_desc) > +#else > +# define __HURD_DESC_INITIAL(gs, ds) ((gs) == (ds)) > +#endif > + > +#if !defined (SHARED) || IS_IN (rtld) > +/* Return 1 if TLS is not initialized yet. */ > +extern inline bool __attribute__ ((unused)) > +__LIBC_NO_TLS (void) > +{ > + unsigned short ds, gs; > + asm ("movw %%ds, %w0\n" > + "movw %%gs, %w1" > + : "=q" (ds), "=q" (gs)); > + return __glibc_unlikely (__HURD_DESC_INITIAL (gs, ds)); > +} > + > +/* Code to initially initialize the thread pointer. This might need > + special attention since 'errno' is not yet available and if the > + operation can cause a failure 'errno' must not be touched. */ > static inline bool __attribute__ ((unused)) > _hurd_tls_init (tcbhead_t *tcb) > { > @@ -168,11 +178,10 @@ out: > return success; > } > > -/* Code to initially initialize the thread pointer. This might need > - special attention since 'errno' is not yet available and if the > - operation can cause a failure 'errno' must not be touched. */ > -# define TLS_INIT_TP(descr) \ > - _hurd_tls_init ((tcbhead_t *) (descr)) > +# define TLS_INIT_TP(descr) _hurd_tls_init ((tcbhead_t *) (descr)) > +#else /* defined (SHARED) && !IS_IN (rtld) */ > +# define __LIBC_NO_TLS() 0 > +#endif > > # if __GNUC_PREREQ (6, 0) > > diff --git a/sysdeps/mach/hurd/x86/init-first.c b/sysdeps/mach/hurd/x86/init-first.c > index 48c330ec..89a5f44c 100644 > --- a/sysdeps/mach/hurd/x86/init-first.c > +++ b/sysdeps/mach/hurd/x86/init-first.c > @@ -40,13 +40,6 @@ extern char **_dl_argv; > > #ifndef SHARED > static tcbhead_t __init1_tcbhead; > -# ifndef __x86_64__ > -unsigned short __init1_desc; > -# endif > -#endif > - > -#ifdef __x86_64__ > -unsigned char __libc_tls_initialized; > #endif > > /* Things that want to be run before _hurd_init or much anything else. > @@ -166,9 +159,7 @@ first_init (void) > _hurd_tls_init (&__init1_tcbhead); > > /* Make sure __LIBC_NO_TLS () keeps evaluating to 1. */ > -# ifdef __x86_64__ > - __libc_tls_initialized = 0; > -# else > +# ifndef __x86_64__ > asm ("movw %%gs,%w0" : "=m" (__init1_desc)); > # endif > #endif > diff --git a/sysdeps/mach/hurd/x86_64/dl-tls-initialized.c b/sysdeps/mach/hurd/x86_64/dl-tls-initialized.c > new file mode 100644 > index 00000000..d0766f95 > --- /dev/null > +++ b/sysdeps/mach/hurd/x86_64/dl-tls-initialized.c > @@ -0,0 +1,21 @@ > +/* Determine whether TLS is initialized, for x86_64/Hurd. > + Copyright (C) 1995-2023 Free Software Foundation, Inc. > + This file is part of the GNU C Library. > + > + The GNU C Library is free software; you can redistribute it and/or > + modify it under the terms of the GNU Lesser General Public > + License as published by the Free Software Foundation; either > + version 2.1 of the License, or (at your option) any later version. > + > + The GNU C Library is distributed in the hope that it will be useful, > + but WITHOUT ANY WARRANTY; without even the implied warranty of > + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU > + Lesser General Public License for more details. > + > + You should have received a copy of the GNU Lesser General Public > + License along with the GNU C Library; if not, see > + . */ > + > +#if !defined (SHARED) || IS_IN (rtld) > +unsigned short __libc_tls_initialized; > +#endif > diff --git a/sysdeps/mach/hurd/x86_64/tls.h b/sysdeps/mach/hurd/x86_64/tls.h > index cf74e1f4..da504d9c 100644 > --- a/sysdeps/mach/hurd/x86_64/tls.h > +++ b/sysdeps/mach/hurd/x86_64/tls.h > @@ -68,10 +68,6 @@ _Static_assert (offsetof (tcbhead_t, stack_guard) == 0x28, > _Static_assert (offsetof (tcbhead_t, __private_ss) == 0x70, > "split stack pointer offset"); > > -extern unsigned char __libc_tls_initialized; > - > -# define __LIBC_NO_TLS() __builtin_expect (!__libc_tls_initialized, 0) > - > /* The TCB can have any size and the memory following the address the > thread pointer points to is unspecified. Allocate the TCB there. */ > # define TLS_TCB_AT_TP 1 > @@ -87,8 +83,6 @@ extern unsigned char __libc_tls_initialized; > # define TCB_ALIGNMENT 64 > > > -# define TLS_INIT_TP(descr) _hurd_tls_init ((tcbhead_t *) (descr)) > - > # define THREAD_SELF \ > (*(tcbhead_t * __seg_fs *) offsetof (tcbhead_t, tcb)) > /* Read member of the thread descriptor directly. */ > @@ -174,6 +168,10 @@ _hurd_tls_new (thread_t child, tcbhead_t *tcb) > i386_FSGS_BASE_STATE_COUNT); > } > > +# if !defined (SHARED) || IS_IN (rtld) > +extern unsigned char __libc_tls_initialized; > +# define __LIBC_NO_TLS() __builtin_expect (!__libc_tls_initialized, 0) > + > static inline bool __attribute__ ((unused)) > _hurd_tls_init (tcbhead_t *tcb) > { > @@ -184,11 +182,18 @@ _hurd_tls_init (tcbhead_t *tcb) > tcb->multiple_threads = 1; > > err = _hurd_tls_new (self, tcb); > + if (err == 0) > + __libc_tls_initialized = 1; > __mach_port_deallocate (__mach_task_self (), self); > - __libc_tls_initialized = 1; > return err == 0; > } > > +# define TLS_INIT_TP(descr) _hurd_tls_init ((tcbhead_t *) (descr)) > +# else /* defined (SHARED) && !IS_IN (rtld) */ > +# define __LIBC_NO_TLS() 0 > +# endif > + > + > > /* Global scope switch support. */ > # define THREAD_GSCOPE_FLAG_UNUSED 0 > -- > 2.39.2 > -- Samuel --- Pour une évaluation indépendante, transparente et rigoureuse ! Je soutiens la Commission d'Évaluation de l'Inria.