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086df229ee
On Linux/i386, there are 3 ways to make a system call: 1. call *%gs:SYSINFO_OFFSET. This requires TLS initialization. 2. call *_dl_sysinfo. This requires relocation of _dl_sysinfo. 3. int $0x80. This is slower than #2 and #3, but works everywhere. When an object file is compiled with PIC, #1 is prefered since it is faster than #3 and doesn't require relocation of _dl_sysinfo. For dynamic executables, ld.so initializes TLS. However, for static executables, before TLS is initialized by __libc_setup_tls, #3 should be used for system calls. This patch adds <startup.h> which defines _startup_fatal and defaults it to __libc_fatal. It replaces __libc_fatal with _startup_fatal in static executables where it is called before __libc_setup_tls is called. This header file is included in all files containing functions which are called before __libc_setup_tls is called. On Linux/i386, when PIE is enabled by default, _startup_fatal is turned into ABORT_INSTRUCTION and I386_USE_SYSENTER is defined to 0 so that "int $0x80" is used for system calls before __libc_setup_tls is called. Tested on i686 and x86-64. Without this patch, all statically-linked tests will fail on i686 when the compiler defaults to -fPIE. [BZ #21913] * csu/libc-tls.c: Include <startup.h> first. (__libc_setup_tls): Call _startup_fatal instead of __libc_fatal. * elf/dl-tunables.c: Include <startup.h> first. * include/libc-symbols.h (BUILD_PIE_DEFAULT): New. * sysdeps/generic/startup.h: New file. * sysdeps/unix/sysv/linux/i386/startup.h: Likewise. * sysdeps/unix/sysv/linux/i386/brk.c [BUILD_PIE_DEFAULT != 0] (I386_USE_SYSENTER): New. Defined to 0.
37 lines
1.3 KiB
C
37 lines
1.3 KiB
C
/* Linux/i386 definitions of functions used by static libc main startup.
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Copyright (C) 2017 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#if BUILD_PIE_DEFAULT
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# include <abort-instr.h>
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/* Can't use "call *%gs:SYSINFO_OFFSET" during statup in static PIE. */
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# define I386_USE_SYSENTER 0
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__attribute__ ((__noreturn__))
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static inline void
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_startup_fatal (const char *message __attribute__ ((unused)))
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{
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/* This is only called very early during startup in static PIE.
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FIXME: How can it be improved? */
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ABORT_INSTRUCTION;
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__builtin_unreachable ();
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}
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#else
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# include_next <startup.h>
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#endif
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