From e2756903329365134089d23548e9083d23bc3dd9 Mon Sep 17 00:00:00 2001 From: Sergey Bugaev Date: Sun, 19 Mar 2023 18:10:07 +0300 Subject: hurd: Only check for TLS initialization inside rtld or in static builds 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 Message-Id: <20230319151017.531737-25-bugaevc@gmail.com> --- 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 | 16 ++++++---- 6 files changed, 83 insertions(+), 33 deletions(-) create mode 100644 sysdeps/mach/hurd/i386/dl-tls-initialized.c create mode 100644 sysdeps/mach/hurd/x86_64/dl-tls-initialized.c (limited to 'sysdeps/mach/hurd') diff --git a/sysdeps/mach/hurd/Makefile b/sysdeps/mach/hurd/Makefile index 0e880755ca..8fb6baf09e 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 0000000000..493ec2396c --- /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 694be9fd64..0ac8917a95 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) { @@ -173,11 +183,10 @@ 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 48c330ec06..89a5f44cdd 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 0000000000..d0766f955d --- /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 e5c6f82acd..2b7135f635 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) { @@ -197,6 +195,12 @@ _hurd_tls_init (tcbhead_t *tcb) 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 -- cgit v1.2.3