diff options
| -rw-r--r-- | ChangeLog | 5 | ||||
| -rw-r--r-- | elf/dl-runtime.c (renamed from sysdeps/i386/dl-runtime.c) | 78 | ||||
| -rw-r--r-- | elf/dynamic-link.h | 4 | ||||
| -rw-r--r-- | sysdeps/i386/dl-machine.h | 14 | ||||
| -rw-r--r-- | sysdeps/stub/dl-runtime.c | 64 |
5 files changed, 62 insertions, 103 deletions
@@ -1,5 +1,10 @@ Tue Feb 13 00:12:12 1996 Roland McGrath <roland@charlie-brown.gnu.ai.mit.edu> + * sysdeps/i386/dl-machine.h (ELF_MACHINE_RUNTIME_TRAMPOLINE, + elf_machine_relplt): New macros. + * elf/dl-runtime.c: New file. + * sysdeps/i386/dl-runtime.c, sysdeps/stub/dl-runtime.c: Files removed. + * gmon/Makefile (headers): Remove machine-gmon.h. * sysdeps/stub/machine-gmon.h, sysdeps/i386/machine-gmon.h: Removed. * gmon/mcount.c [! NO_UNDERSCORES] (_mcount): Specify "mcount" as diff --git a/sysdeps/i386/dl-runtime.c b/elf/dl-runtime.c index 5e4a289..7e554bc 100644 --- a/sysdeps/i386/dl-runtime.c +++ b/elf/dl-runtime.c @@ -1,5 +1,5 @@ -/* On-demand PLT fixup for shared objects. i386 version. -Copyright (C) 1995 Free Software Foundation, Inc. +/* On-demand PLT fixup for shared objects. +Copyright (C) 1995, 1996 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 @@ -20,28 +20,42 @@ Cambridge, MA 02139, USA. */ #include <link.h> #include "dynamic-link.h" -/* This function is not called in the normal way. The PLT jumps here, not - using a call. The stack looks like this: - --->8(%esp) address to return to the caller of the function in the PLT - 4(%esp) relocation offset for this PLT entry - 0(%esp) identifier for this shared object (struct link_map *) - - The user expects the real function the PLT refers to to be entered - with 8(%esp) as the top of stack. */ - -void -_dl_runtime_resolve (Elf32_Word reloc_offset) +/* Figure out the right type, Rel or Rela. */ +#define elf_machine_rel 1 +#define elf_machine_rela 2 +#if elf_machine_relplt == elf_machine_rel +#define PLTREL Elf32_Rel +#elif elf_machine_relplt == elf_machine_rela +#define PLTREL Elf32_Rela +#else +#error "dl-machine.h bug: elf_machine_relplt not rel or rela" +#endif +#undef elf_machine_rel +#undef elf_machine_rela + +/* We need to define the function as a local symbol so that the reference + in the trampoline code will be a local PC-relative call. Tell the + compiler not to worry that the function appears not to be called. */ + +static Elf32_Addr fixup (struct link_map *l, Elf32_Word reloc_offset) + __attribute__ ((unused)); + +/* This function is called through a special trampoline from the PLT the + first time each PLT entry is called. We must perform the relocation + specified in the PLT of the given shared object, and return the resolved + function address to the trampoline, which will restart the original call + to that address. Future calls will bounce directly from the PLT to the + function. */ + +static Elf32_Addr +fixup (struct link_map *l, Elf32_Word reloc_offset) { - __label__ return_insn; - struct link_map *l = (void *) (&reloc_offset)[-1]; - const Elf32_Sym *const symtab = (const Elf32_Sym *) (l->l_addr + l->l_info[DT_SYMTAB]->d_un.d_ptr); const char *strtab = (const char *) (l->l_addr + l->l_info[DT_STRTAB]->d_un.d_ptr); - const Elf32_Rel *const reloc + const PLTREL *const reloc = (const void *) (l->l_addr + l->l_info[DT_JMPREL]->d_un.d_ptr + reloc_offset); @@ -61,34 +75,26 @@ _dl_runtime_resolve (Elf32_Word reloc_offset) } else scope = _dl_loaded; - + definer = &symtab[ELF32_R_SYM (reloc->r_info)]; loadbase = _dl_lookup_symbol (strtab + definer->st_name, &definer, scope, l->l_name, 0); - + /* Restore list frobnication done above for DT_SYMBOLIC. */ l->l_next = real_next; if (l->l_prev) l->l_prev->l_next = l; /* Apply the relocation with that value. */ - elf_machine_rel (l, reloc, loadbase, definer); + elf_machine_relplt (l, reloc, loadbase, definer); - /* The top of the stack is the word we set L from; but this location - holds the address we will return to. Store there the address of a - "ret" instruction, which will pop the stack and run the code at the - address in the next stack word. */ - (&reloc_offset)[-1] = (Elf32_Word) &&return_insn; + return *(Elf32_Addr *) (l->l_addr + reloc->r_offset); +} - /* The next stack word is our argument RELOC_OFFSET; but that "ret" will - pop and jump to this location, and the next stack word is the user's - return address. So store here the resolved address of the function - referred to by this PLT entry; once "ret" pops this address, the - function in the shared object will run with the stack arranged just as - when the user entered the PLT. */ - (&reloc_offset)[0] = *(Elf32_Word *) (l->l_addr + reloc->r_offset); - return; +/* This macro is defined in dl-machine.h to define the entry point called + by the PLT. The `fixup' function above does the real work, but a little + more twiddling is needed to get the stack right and jump to the address + finally resolved. */ - return_insn: asm volatile ("ret"); -} +ELF_MACHINE_RUNTIME_TRAMPOLINE diff --git a/elf/dynamic-link.h b/elf/dynamic-link.h index ed8d24c..38236ba 100644 --- a/elf/dynamic-link.h +++ b/elf/dynamic-link.h @@ -1,5 +1,5 @@ /* Inline functions for dynamic linking. -Copyright (C) 1995 Free Software Foundation, Inc. +Copyright (C) 1995, 1996 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 @@ -43,7 +43,7 @@ elf_get_dynamic_info (Elf32_Dyn *dyn, Elf32_Dyn *info[DT_NUM + DT_PROCNUM]) dyn->d_tag < DT_LOPROC + DT_PROCNUM) info[dyn->d_tag - DT_LOPROC + DT_NUM] = dyn; else - assert (! "bad dynamic tag"); + assert (! "bad dynamic tag"); dyn++; } diff --git a/sysdeps/i386/dl-machine.h b/sysdeps/i386/dl-machine.h index 4ce4d4b..8f72073 100644 --- a/sysdeps/i386/dl-machine.h +++ b/sysdeps/i386/dl-machine.h @@ -157,8 +157,20 @@ elf_machine_runtime_setup (struct link_map *l, int lazy) the offset on the stack, and then jump to the resolved address. */ got[2] = (Elf32_Addr) &_dl_runtime_resolve; } -} + /* This code is used in dl-runtime.c to call the `fixup' function + and then redirect to the address it returns. */ +#define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\ + .globl _dl_runtime_resolve + .type _dl_runtime_resolve, @function +_dl_runtime_resolve: + call fixup # Args pushed by PLT. + addl $8, %esp # Pop args. + jmp *%eax # Jump to function address. +"); +/* The PLT uses Elf32_Rel relocs. */ +#define elf_machine_relplt elf_machine_rel +} /* Mask identifying addresses reserved for the user program, where the dynamic linker should not map anything. */ diff --git a/sysdeps/stub/dl-runtime.c b/sysdeps/stub/dl-runtime.c deleted file mode 100644 index f660ef2..0000000 --- a/sysdeps/stub/dl-runtime.c +++ /dev/null @@ -1,64 +0,0 @@ -/* On-demand PLT fixup for shared objects. Stub 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. */ - -#include <link.h> -#include "dynamic-link.h" - -/* This function is not called in the normal way. The PLT jumps here, not - using a call. */ -void -_dl_runtime_resolve () -{ - struct link_map *l = ???; - Elf32_Word reloc_offset = ???; - - const Elf32_Sym *const symtab - = (const Elf32_Sym *) l->l_info[DT_SYMTAB]->d_un.d_ptr; - const char *strtab - = ((void *) l->l_addr + l->l_info[DT_STRTAB]->d_un.d_ptr); - - const Elf32_Rel *const reloc = (void *) (l->l_info[DT_JMPREL]->d_un.d_ptr - + reloc_offset); - - const Elf32_Sym *definer; - Elf32_Addr loadbase; - struct link_map *scope, *real_next; - - /* Look up the symbol's run-time value. */ - - real_next = l->l_next; - if (l->l_info[DT_SYMBOLIC]) - { - l->l_prev->l_next = real_next; - l->l_next = _dl_loaded; - scope = l; - } - else - scope = _dl_loaded; - - definer = &symtab[ELF32_R_SYM (reloc->r_info)]; - loadbase = _dl_lookup_symbol (strtab + definer->st_name, &definer, scope); - - /* Restore list frobnication done above for DT_SYMBOLIC. */ - l->l_next = real_next; - l->l_prev->l_next = l; - - /* Apply the relocation with that value. */ - elf_machine_rel (l->l_addr, l->l_info, reloc, loadbase, definer); -} |