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Diffstat (limited to 'sysdeps/unix/sysv/linux/dl-machine.h')
| -rw-r--r-- | sysdeps/unix/sysv/linux/dl-machine.h | 214 |
1 files changed, 214 insertions, 0 deletions
diff --git a/sysdeps/unix/sysv/linux/dl-machine.h b/sysdeps/unix/sysv/linux/dl-machine.h new file mode 100644 index 0000000000..2ed6c670e5 --- /dev/null +++ b/sysdeps/unix/sysv/linux/dl-machine.h @@ -0,0 +1,214 @@ +/* Machine-dependent ELF dynamic relocation inline functions. + i386/Linux version. +Copyright (C) 1995 Free Software Foundation, Inc. +This file is part of the GNU C Library. + +The GNU C Library is free software; you can redistribute it and/or +modify it under the terms of the GNU Library General Public License as +published by the Free Software Foundation; either version 2 of the +License, or (at your option) any later version. + +The GNU C Library 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 +Library General Public License for more details. + +You should have received a copy of the GNU Library General Public +License along with the GNU C Library; see the file COPYING.LIB. If +not, write to the Free Software Foundation, Inc., 675 Mass Ave, +Cambridge, MA 02139, USA. */ + +#define ELF_MACHINE_NAME "i386" + +#include <assert.h> +#include <string.h> +#include <link.h> +#include <syscall.h> +#include <sys/mman.h> + +/* Return nonzero iff E_MACHINE is compatible with the running host. */ +static inline int +elf_machine_matches_host (Elf32_Half e_machine) +{ + switch (e_machine) + { + case EM_386: + case EM_486: + return 1; + default: + return 0; + } +} + + +/* Return the run-time address of the _GLOBAL_OFFSET_TABLE_. + Must be inlined in a function which uses global data. */ +static inline Elf32_Addr * +elf_machine_got (void) +{ + register Elf32_Addr *got asm ("%ebx"); + return got; +} + + +/* Return the run-time load address of the shared object. */ +static inline Elf32_Addr +elf_machine_load_address (void) +{ + Elf32_Addr addr; + asm (" call here\n" + "here: popl %0\n" + " subl $here, %0" + : "=r" (addr)); + return addr; +} +/* The `subl' insn above will contain an R_386_32 relocation entry + intended to insert the run-time address of the label `here'. + This will be the first relocation in the text of the dynamic linker; + we skip it to avoid trying to modify read-only text in this early stage. */ +#define ELF_MACHINE_BEFORE_RTLD_RELOC(dynamic_info) \ + ++(const Elf32_Rel *) (dynamic_info)[DT_REL]->d_un.d_ptr; \ + (dynamic_info)[DT_RELSZ]->d_un.d_val -= sizeof (Elf32_Rel) + +/* Perform the relocation specified by RELOC and SYM (which is fully resolved). + MAP is the object containing the reloc. */ + +static inline void +elf_machine_rel (struct link_map *map, + const Elf32_Rel *reloc, + Elf32_Addr sym_loadaddr, const Elf32_Sym *sym) +{ + Elf32_Addr *const reloc_addr = (void *) (map->l_addr + reloc->r_offset); + const Elf32_Addr sym_value = sym_loadaddr + sym->st_value; + + switch (ELF32_R_TYPE (reloc->r_info)) + { + case R_386_COPY: + memcpy (reloc_addr, (void *) sym_value, sym->st_size); + break; + case R_386_GLOB_DAT: + case R_386_JMP_SLOT: + *reloc_addr = sym_value; + break; + case R_386_32: + if (map->l_type == lt_interpreter) + { + /* Undo the relocation done here during bootstrapping. Now we will + relocate it anew, possibly using a binding found in the user + program or a loaded library rather than the dynamic linker's + built-in definitions used while loading those libraries. */ + const Elf32_Sym *const dlsymtab + = (void *) (map->l_addr + map->l_info[DT_SYMTAB]->d_un.d_ptr); + *reloc_addr -= (map->l_addr + + dlsymtab[ELF32_R_SYM (reloc->r_info)].st_value); + } + *reloc_addr += sym_value; + break; + case R_386_RELATIVE: + if (map->l_type != lt_interpreter) /* Already done in dynamic linker. */ + *reloc_addr += map->l_addr; + break; + case R_386_PC32: + *reloc_addr = sym_value - (Elf32_Addr) reloc_addr; + break; + default: + assert (! "unexpected dynamic reloc type"); + break; + } +} + +static inline void +elf_machine_lazy_rel (struct link_map *map, const Elf32_Rel *reloc) +{ + Elf32_Addr *const reloc_addr = (void *) (map->l_addr + reloc->r_offset); + switch (ELF32_R_TYPE (reloc->r_info)) + { + case R_386_JMP_SLOT: + *reloc_addr += map->l_addr; + break; + default: + assert (! "unexpected PLT reloc type"); + break; + } +} + +/* The i386 never uses Elf32_Rela relocations. */ +#define ELF_MACHINE_NO_RELA 1 + + +/* Set up the loaded object described by L so its unrelocated PLT + entries will jump to the on-demand fixup code in dl-runtime.c. */ + +static inline void +elf_machine_runtime_setup (struct link_map *l) +{ + Elf32_Addr *got; + extern void _dl_runtime_resolve (Elf32_Word); + + /* The GOT entries for functions in the PLT have not yet been filled + in. Their initial contents will arrange when called to push an + offset into the .rel.plt section, push _GLOBAL_OFFSET_TABLE_[1], + and then jump to _GLOBAL_OFFSET_TABLE[2]. */ + got = (Elf32_Addr *) (l->l_addr + l->l_info[DT_PLTGOT]->d_un.d_ptr); + got[1] = (Elf32_Addr) l; /* Identify this shared object. */ + /* This function will get called to fix up the GOT entry indicated by + the offset on the stack, and then jump to the resolved address. */ + got[2] = (Elf32_Addr) &_dl_runtime_resolve; +} + + +/* Mask identifying addresses reserved for the user program, + where the dynamic linker should not map anything. */ +#define ELF_MACHINE_USER_ADDRESS_MASK 0xf8000000UL + + + +/* Initial entry point code for the dynamic linker. + The C function `_dl_start' is the real entry point; + its return value is the user program's entry point. */ + +#define RTLD_START asm ("\ +.text\n\ +.globl _start\n\ +.globl _dl_start_user\n\ +_start:\n\ + call _dl_start\n\ +_dl_start_user:\n\ + # Save the user entry point address in %edi.\n\ + movl %eax, %edi\n\ + # Point %ebx at the GOT. + call 0f\n\ +0: popl %ebx\n\ + addl $_GLOBAL_OFFSET_TABLE_+[.-0b], %ebx\n\ + # See if we were run as a command with the executable file\n\ + # name as an extra leading argument.\n\ + movl rtld_command@GOT(%ebx), %eax\n\ + movl (%eax),%eax\n\ + testl %eax,%eax\n\ + jz 0f\n\ + # Pop the original argument count, decrement it, and replace\n\ + # the original first argument pointer with the new count.\n\ + popl %eax\n\ + decl %eax\n\ + movl %eax,(%esp)\n\ + # Call _dl_init_next to return the address of an initializer\n\ + # function to run.\n\ +0: call _dl_init_next@PLT\n\ + # Check for zero return, when out of initializers.\n\ + testl %eax,%eax\n\ + jz 1f\n\ + # Call the shared object initializer function.\n\ + # NOTE: We depend only on the registers (%ebx and %edi)\n\ + # and the return address pushed by this call;\n\ + # the initializer is called with the stack just\n\ + # as it appears on entry, and it is free to move\n\ + # the stack around, as long as it winds up jumping to\n\ + # the return address on the top of the stack.\n\ + call *%eax\n\ + # Loop to call _dl_init_next for the next initializer.\n\ + jmp 0b\n\ +1: # Pass our finalizer function to the user in %edx, as per ELF ABI.\n\ + movl _dl_fini@GOT(%ebx), %edx\n\ + # Jump to the user's entry point.\n\ + jmp *%edi\n\ +"); |