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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>
71 lines
2.4 KiB
C
71 lines
2.4 KiB
C
/* Support for relocating static PIE.
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Copyright (C) 2017-2021 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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#if ENABLE_STATIC_PIE
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/* Mark symbols hidden in static PIE for early self relocation to work. */
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# pragma GCC visibility push(hidden)
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#include <unistd.h>
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#include <ldsodefs.h>
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#include "dynamic-link.h"
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/* Relocate static executable with PIE. */
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void
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_dl_relocate_static_pie (void)
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{
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struct link_map *main_map = _dl_get_dl_main_map ();
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# define STATIC_PIE_BOOTSTRAP
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# define BOOTSTRAP_MAP (main_map)
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# define RESOLVE_MAP(sym, version, flags) BOOTSTRAP_MAP
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# include "dynamic-link.h"
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/* Figure out the run-time load address of static PIE. */
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main_map->l_addr = elf_machine_load_address ();
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/* Read our own dynamic section and fill in the info array. */
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main_map->l_ld = ((void *) main_map->l_addr + elf_machine_dynamic ());
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elf_get_dynamic_info (main_map, NULL);
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# ifdef ELF_MACHINE_BEFORE_RTLD_RELOC
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ELF_MACHINE_BEFORE_RTLD_RELOC (main_map->l_info);
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# endif
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/* Relocate ourselves so we can do normal function calls and
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data access using the global offset table. */
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ELF_DYNAMIC_RELOCATE (main_map, 0, 0, 0);
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main_map->l_relocated = 1;
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/* Initialize _r_debug. */
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struct r_debug *r = _dl_debug_initialize (0, LM_ID_BASE);
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r->r_state = RT_CONSISTENT;
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/* Set up debugging before the debugger is notified for the first
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time. */
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# ifdef ELF_MACHINE_DEBUG_SETUP
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/* Some machines (e.g. MIPS) don't use DT_DEBUG in this way. */
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ELF_MACHINE_DEBUG_SETUP (main_map, r);
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# else
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if (main_map->l_info[DT_DEBUG] != NULL)
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/* There is a DT_DEBUG entry in the dynamic section. Fill it in
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with the run-time address of the r_debug structure */
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main_map->l_info[DT_DEBUG]->d_un.d_ptr = (ElfW(Addr)) r;
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# endif
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}
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#endif
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