diff options
Diffstat (limited to 'elf/rtld.c')
| -rw-r--r-- | elf/rtld.c | 267 |
1 files changed, 267 insertions, 0 deletions
diff --git a/elf/rtld.c b/elf/rtld.c new file mode 100644 index 0000000000..fd75779a01 --- /dev/null +++ b/elf/rtld.c @@ -0,0 +1,267 @@ +/* Run time dynamic linker. +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. */ + +#include <link.h> +#include "dynamic-link.h" +#include <stddef.h> +#include <stdlib.h> +#include <unistd.h> + + +#ifdef RTLD_START +RTLD_START +#else +#error "sysdeps/MACHINE/dl-machine.h fails to define RTLD_START" +#endif + +/* System-specific function to do initial startup for the dynamic linker. + After this, file access calls and getenv must work. This is responsible + for setting _dl_secure if we need to be secure (e.g. setuid), + and for setting _dl_argc and _dl_argv, and then calling _dl_main. */ +extern Elf32_Addr _dl_sysdep_start (void **start_argptr, + void (*dl_main) (const Elf32_Phdr *phdr, + Elf32_Word phent, + Elf32_Addr *user_entry)); + +int _dl_secure; +int _dl_argc; +char **_dl_argv; + +struct r_debug dl_r_debug; + +static void dl_main (const Elf32_Phdr *phdr, + Elf32_Word phent, + Elf32_Addr *user_entry); + +Elf32_Addr +_dl_start (void *arg) +{ + Elf32_Addr rtld_loadaddr; + Elf32_Dyn *dynamic_section; + Elf32_Dyn *dynamic_info[DT_NUM]; + + /* Figure out the run-time load address of the dynamic linker itself. */ + rtld_loadaddr = elf_machine_load_address (); + + /* Read our own dynamic section and fill in the info array. + Conveniently, the first element of the GOT contains the + offset of _DYNAMIC relative to the run-time load address. */ + dynamic_section = (void *) rtld_loadaddr + *elf_machine_got (); + elf_get_dynamic_info (dynamic_section, dynamic_info); + +#ifdef ELF_MACHINE_BEFORE_RTLD_RELOC + ELF_MACHINE_BEFORE_RTLD_RELOC (dynamic_info); +#endif + + /* Relocate ourselves so we can do normal function calls and + data access using the global offset table. */ + { + Elf32_Addr resolve (const Elf32_Sym **ref) + { + assert ((*ref)->st_shndx != SHN_UNDEF); + return rtld_loadaddr; + } + elf_dynamic_relocate (dynamic_info, rtld_loadaddr, 0, resolve); + } + + /* Now life is sane; we can call functions and access global data. + Set up to use the operating system facilities, and find out from + the operating system's program loader where to find the program + header table in core. */ + + dl_r_debug.r_ldbase = rtld_loadaddr; /* Record our load address. */ + + /* Call the OS-dependent function to set up life so we can do things like + file access. It will call `dl_main' (below) to do all the real work + of the dynamic linker, and then unwind our frame and run the user + entry point on the same stack we entered on. */ + return _dl_sysdep_start (&arg, &dl_main); +} + + +/* Now life is peachy; we can do all normal operations. + On to the real work. */ + +void _start (void); + +static void +dl_main (const Elf32_Phdr *phdr, + Elf32_Word phent, + Elf32_Addr *user_entry) +{ + void doit (void) + { + const Elf32_Phdr *ph; + struct link_map *l; + const char *interpreter_name; + int lazy; + + if (*user_entry == (Elf32_Addr) &_start) + { + /* Ho ho. We are not the program interpreter! We are the program + itself! This means someone ran ld.so as a command. Well, that + might be convenient to do sometimes. We support it by + interpreting the args like this: + + ld.so PROGRAM ARGS... + + The first argument is the name of a file containing an ELF + executable we will load and run with the following arguments. To + simplify life here, PROGRAM is searched for using the normal rules + for shared objects, rather than $PATH or anything like that. We + just load it and use its entry point; we don't pay attention to + its PT_INTERP command (we are the interpreter ourselves). This is + an easy way to test a new ld.so before installing it. */ + if (_dl_argc < 2) + _dl_sysdep_fatal ("\ +Usage: ld.so EXECUTABLE-FILE [ARGS-FOR-PROGRAM...]\n\ +You have invoked `ld.so', the helper program for shared library executables.\n\ +This program usually lives in the file `/lib/ld.so', and special directives\n\ +in executable files using ELF shared libraries tell the system's program\n\ +loader to load the helper program from this file. This helper program loads\n\ +the shared libraries needed by the program executable, prepares the program\n\ +to run, and runs it. You may invoke this helper program directly from the\n\ +command line to load and run an ELF executable file; this is like executing\n\ +that file itself, but always uses this helper program from the file you\n\ +specified, instead of the helper program file specified in the executable\n\ +file you run. This is mostly of use for maintainers to test new versions\n\ +of this helper program; chances are you did not intend to run this program.\n" + ); + + interpreter_name = _dl_argv[0]; + --_dl_argc; + ++_dl_argv; + l = _dl_map_object (NULL, _dl_argv[0], user_entry); + phdr = l->l_phdr; + phent = l->l_phnum; + l->l_type = lt_executable; + l->l_libname = (char *) ""; + } + else + { + /* Create a link_map for the executable itself. + This will be what dlopen on "" returns. */ + l = _dl_new_object ((char *) "", "", lt_executable); + l->l_phdr = phdr; + l->l_phnum = phent; + interpreter_name = 0; + } + + /* Scan the program header table for the dynamic section. */ + for (ph = phdr; ph < &phdr[phent]; ++ph) + switch (ph->p_type) + { + case PT_DYNAMIC: + /* This tells us where to find the dynamic section, + which tells us everything we need to do. */ + l->l_ld = (void *) ph->p_vaddr; + break; + case PT_INTERP: + /* This "interpreter segment" was used by the program loader to + find the program interpreter, which is this program itself, the + dynamic linker. We note what name finds us, so that a future + dlopen call or DT_NEEDED entry, for something that wants to link + against the dynamic linker as a shared library, will know that + the shared object is already loaded. */ + interpreter_name = (void *) ph->p_vaddr; + break; + } + assert (interpreter_name); /* How else did we get here? */ + + /* Extract the contents of the dynamic section for easy access. */ + elf_get_dynamic_info (l->l_ld, l->l_info); + /* Set up our cache of pointers into the hash table. */ + _dl_setup_hash (l); + + if (l->l_info[DT_DEBUG]) + /* There is a DT_DEBUG entry in the dynamic section. Fill it in + with the run-time address of the r_debug structure, which we + will set up later to communicate with the debugger. */ + l->l_info[DT_DEBUG]->d_un.d_ptr = (Elf32_Addr) &dl_r_debug; + + l = _dl_new_object ((char *) interpreter_name, interpreter_name, + lt_interpreter); + + /* Now process all the DT_NEEDED entries and map in the objects. + Each new link_map will go on the end of the chain, so we will + come across it later in the loop to map in its dependencies. */ + for (l = _dl_loaded; l; l = l->l_next) + { + if (l->l_info[DT_NEEDED]) + { + const char *strtab + = (void *) l->l_addr + l->l_info[DT_STRTAB]->d_un.d_ptr; + const Elf32_Dyn *d; + for (d = l->l_ld; d->d_tag != DT_NULL; ++d) + if (d->d_tag == DT_NEEDED) + _dl_map_object (l, strtab + d->d_un.d_val, NULL); + } + l->l_deps_loaded = 1; + } + + l = _dl_loaded->l_next; + assert (l->l_type == lt_interpreter); + if (l->l_opencount == 0) + { + /* No DT_NEEDED entry referred to the interpreter object itself. + Remove it from the maps we will use for symbol resolution. */ + l->l_prev->l_next = l->l_next; + if (l->l_next) + l->l_next->l_prev = l->l_prev; + } + + lazy = _dl_secure || *(getenv ("LD_BIND_NOW") ?: ""); + + /* Now we have all the objects loaded. Relocate them all. + We do this in reverse order so that copy relocs of earlier + objects overwrite the data written by later objects. */ + l = _dl_loaded; + while (l->l_next) + l = l->l_next; + do + { + _dl_relocate_object (l, lazy); + l = l->l_prev; + } while (l); + + /* Tell the debugger where to find the map of loaded objects. */ + dl_r_debug.r_version = 1 /* R_DEBUG_VERSION XXX */; + dl_r_debug.r_map = _dl_loaded; + dl_r_debug.r_brk = (Elf32_Addr) &_dl_r_debug_state; +} + const char *errstring; + int err; + + err = _dl_catch_error (&errstring, &doit); + if (errstring) + _dl_sysdep_fatal (_dl_argv[0] ?: "<program name unknown>", + ": error in loading shared libraries\n", + errstring, err ? ": " : NULL, + err ? strerror (err) : NULL, NULL); + + /* Once we return, _dl_sysdep_start will invoke + the DT_INIT functions and then *USER_ENTRY. */ +} + +/* This function exists solely to have a breakpoint set on it by the + debugger. */ +void +_dl_r_debug_state (void) +{ +} |