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47618209d0
Extern symbol access in position independent code usually involves GOT indirection which needs RELATIVE reloc in a static linked PIE. (On some targets this is avoided e.g. because the linker can relax a GOT access to a pc-relative access, but this is not generally true.) Code that runs before static PIE self relocation must avoid relying on dynamic relocations which can be ensured by using hidden visibility. However we cannot just make all symbols hidden: On i386, all calls to IFUNC functions must go through PLT and calls to hidden functions CANNOT go through PLT in PIE since EBX used in PIE PLT may not be set up for local calls to hidden IFUNC functions. This patch aims to make symbol references hidden in code that is used before and by _dl_relocate_static_pie when building a static PIE libc. Note: for an object that is used in the startup code, its references and definition may not have consistent visibility: it is only forced hidden in the startup code. This is needed for fixing bug 27072. Co-authored-by: H.J. Lu <hjl.tools@gmail.com> Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
41 lines
1.5 KiB
C
41 lines
1.5 KiB
C
/* Define and initialize the `__libc_enable_secure' flag. Generic version.
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Copyright (C) 1996-2021 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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<https://www.gnu.org/licenses/>. */
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/* This file is used in the static libc. For the shared library,
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dl-sysdep.c defines and initializes __libc_enable_secure. */
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/* Mark symbols hidden in static PIE for early self relocation to work. */
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#if BUILD_PIE_DEFAULT
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# pragma GCC visibility push(hidden)
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#endif
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#include <startup.h>
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#include <libc-internal.h>
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/* If nonzero __libc_enable_secure is already set. */
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int __libc_enable_secure_decided;
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/* Safest assumption, if somehow the initializer isn't run. */
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int __libc_enable_secure = 1;
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void
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__libc_init_secure (void)
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{
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if (__libc_enable_secure_decided == 0)
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__libc_enable_secure = (startup_geteuid () != startup_getuid ()
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|| startup_getegid () != startup_getgid ());
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}
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