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- /* Copyright (C) 2014 Stony Brook University
- This file is part of Graphene Library OS.
- Graphene Library OS 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 3 of the
- License, or (at your option) any later version.
- Graphene Library OS 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 this program. If not, see <http://www.gnu.org/licenses/>. */
- /*
- * dl-machine-x86_64.c
- *
- * This file contains x64-specific codes for relocating ELF binaries.
- * Most of the source codes are imported from GNU C library.
- */
- #ifndef __DL_MACHINE_H__
- #define __DL_MACHINE_H__
- #define ELF_MACHINE_NAME "x86_64"
- #include "ldsodefs.h"
- /* Return nonzero iff ELF header is compatible with the running host. */
- static inline int __attribute__((unused)) elf_machine_matches_host(const Elf64_Ehdr* ehdr) {
- return ehdr->e_machine == EM_X86_64;
- }
- /* ELF_RTYPE_CLASS_PLT iff TYPE describes relocation of a PLT entry or
- TLS variable, so undefined references should not be allowed to
- define the value.
- ELF_RTYPE_CLASS_NOCOPY iff TYPE should not be allowed to resolve to one
- of the main executable's symbols, as for a COPY reloc. */
- #define elf_machine_type_class(type) \
- ((((type) == R_X86_64_JUMP_SLOT \
- || (type) == R_X86_64_DTPMOD64 \
- || (type) == R_X86_64_DTPOFF64 \
- || (type) == R_X86_64_TPOFF64 \
- || (type) == R_X86_64_TLSDESC) \
- * ELF_RTYPE_CLASS_PLT) \
- | (((type) == R_X86_64_COPY) * ELF_RTYPE_CLASS_COPY))
- /* The x86-64 never uses Elf64_Rel relocations. */
- #define ELF_MACHINE_NO_REL 1
- /* Perform the relocation specified by RELOC and SYM (which is fully resolved).
- MAP is the object containing the reloc. */
- //#define DEBUG_RELOC
- static bool elf_machine_rela(struct link_map* l, ElfW(Rela) * reloc, Elf64_Sym* sym,
- void* const reloc_addr_arg) {
- Elf64_Addr* const reloc_addr = reloc_addr_arg;
- const unsigned long int r_type = ELF64_R_TYPE(reloc->r_info);
- const char* __attribute__((unused)) strtab = (const void*)D_PTR(l->l_info[DT_STRTAB]);
- #ifdef DEBUG_RELOC
- #define debug_reloc(r_type, sym, value) \
- ({ \
- if (strtab && (sym) && (sym)->st_name) \
- debug(#r_type ": %s\n", strtab + (sym)->st_name); \
- else if (value) \
- debug(#r_type ": %p\n", (value)); \
- else \
- debug(#r_type "\n", (value)); \
- })
- #else
- #define debug_reloc(...) ({})
- #endif
- if (r_type == R_X86_64_RELATIVE || r_type == R_X86_64_NONE)
- return false;
- Elf64_Sym* refsym = sym;
- Elf64_Addr value;
- Elf64_Addr sym_map = RESOLVE_MAP(&strtab, &sym);
- if (!sym_map || !sym || refsym == sym)
- return false;
- value = sym_map + sym->st_value;
- /* We do a very special relocation for loaded libraries */
- PROTECT_PAGE(l, refsym, sizeof(*refsym));
- PROTECT_PAGE(l, reloc_addr, sizeof(*reloc_addr));
- refsym->st_info = sym->st_info;
- refsym->st_size = sym->st_size;
- if (__builtin_expect(ELFW(ST_TYPE)(sym->st_info) == STT_GNU_IFUNC, 0) &&
- __builtin_expect(sym->st_shndx != SHN_UNDEF, 1)) {
- value = ((Elf64_Addr(*)(void))value)();
- refsym->st_info ^= ELFW(ST_TYPE)(sym->st_info);
- refsym->st_info |= STT_FUNC;
- }
- debug_reloc("shim symbol", sym, value);
- refsym->st_value = value - l->l_addr;
- *reloc_addr = value + ((r_type == R_X86_64_GLOB_DAT || r_type == R_X86_64_JUMP_SLOT ||
- r_type == R_X86_64_64)
- ? reloc->r_addend
- : 0);
- /* We have relocated the symbol, we don't want the
- interpreter to relocate it again. */
- if (r_type != R_X86_64_NONE) {
- PROTECT_PAGE(l, reloc, sizeof(*reloc));
- reloc->r_info = (reloc->r_info ^ ELF64_R_TYPE(reloc->r_info)) | R_X86_64_NONE;
- }
- return true;
- }
- #endif /* !DL_MACHINE_H */
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