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035c012e32
It turns out the startup code in csu/elf-init.c has a perfect pair of ROP gadgets (see Marco-Gisbert and Ripoll-Ripoll, "return-to-csu: A New Method to Bypass 64-bit Linux ASLR"). These functions are not needed in dynamically-linked binaries because DT_INIT/DT_INIT_ARRAY are already processed by the dynamic linker. However, the dynamic linker skipped the main program for some reason. For maximum backwards compatibility, this is not changed, and instead, the main map is consulted from __libc_start_main if the init function argument is a NULL pointer. For statically linked binaries, the old approach based on linker symbols is still used because there is nothing else available. A new symbol version __libc_start_main@@GLIBC_2.34 is introduced because new binaries running on an old libc would not run their ELF constructors, leading to difficult-to-debug issues.
83 lines
2.8 KiB
C
83 lines
2.8 KiB
C
/* Configuration of lookup functions.
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Copyright (C) 2000-2021 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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#define ELF_FUNCTION_PTR_IS_SPECIAL
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#define DL_UNMAP_IS_SPECIAL
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#include <dl-fptr.h>
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/* Forward declaration. */
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struct link_map;
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void *_dl_symbol_address (struct link_map *map, const ElfW(Sym) *ref);
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rtld_hidden_proto (_dl_symbol_address)
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#define DL_SYMBOL_ADDRESS(map, ref) _dl_symbol_address(map, ref)
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Elf32_Addr _dl_lookup_address (const void *address);
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#define DL_LOOKUP_ADDRESS(addr) _dl_lookup_address ((const void *) addr)
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void attribute_hidden _dl_unmap (struct link_map *map);
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#define DL_UNMAP(map) _dl_unmap (map)
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#define DL_DT_FUNCTION_ADDRESS(map, start, attr, addr) \
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attr volatile unsigned int fptr[2]; \
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/* The test for "start & 2" below is to accommodate old binaries which \
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violated the ELF ABI by pointing DT_INIT and DT_FINI at a function \
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descriptor. */ \
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if ((ElfW(Addr)) (start) & 2) \
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addr = (ElfW(Addr)) start; \
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else \
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{ \
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fptr[0] = (unsigned int) (start); \
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fptr[1] = (map)->l_info[DT_PLTGOT]->d_un.d_ptr; \
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/* Set bit 30 to indicate to $$dyncall that this is a PLABEL. */ \
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addr = (ElfW(Addr))((unsigned int)fptr | 2); \
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} \
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#define DL_CALL_DT_INIT(map, start, argc, argv, env) \
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{ \
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ElfW(Addr) addr; \
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DL_DT_FUNCTION_ADDRESS(map, start, , addr) \
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dl_init_t init = (dl_init_t) addr; \
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init (argc, argv, env); \
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}
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#define DL_CALL_DT_FINI(map, start) \
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{ \
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ElfW(Addr) addr; \
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DL_DT_FUNCTION_ADDRESS(map, start, , addr) \
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fini_t fini = (fini_t) addr; \
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fini (); \
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}
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/* The type of the return value of fixup/profile_fixup */
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#define DL_FIXUP_VALUE_TYPE struct fdesc
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/* Construct a fixup value from the address and linkmap */
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#define DL_FIXUP_MAKE_VALUE(map, addr) \
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(map) ? ((struct fdesc) { (addr), (map)->l_info[DT_PLTGOT]->d_un.d_ptr }) \
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: ((struct fdesc) { 0, 0 })
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/* Extract the code address from a fixup value */
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#define DL_FIXUP_VALUE_CODE_ADDR(value) ((value).ip)
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#define DL_FIXUP_VALUE_ADDR(value) ((uintptr_t) &(value))
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#define DL_FIXUP_ADDR_VALUE(addr) (*(struct fdesc *) (addr))
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