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Tue Feb 13 00:12:12 1996 Roland McGrath <roland@charlie-brown.gnu.ai.mit.edu>

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* 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.
	* 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.
This commit is contained in:
Roland McGrath 1996-02-13 07:05:16 +00:00
parent dbdb6189d5
commit 38334018ff
5 changed files with 61 additions and 102 deletions
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5
ChangeLog
View File

@ -1,5 +1,10 @@
Tue Feb 13 00:12:12 1996 Roland McGrath <roland@charlie-brown.gnu.ai.mit.edu> 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. * gmon/Makefile (headers): Remove machine-gmon.h.
* sysdeps/stub/machine-gmon.h, sysdeps/i386/machine-gmon.h: Removed. * sysdeps/stub/machine-gmon.h, sysdeps/i386/machine-gmon.h: Removed.
* gmon/mcount.c [! NO_UNDERSCORES] (_mcount): Specify "mcount" as * gmon/mcount.c [! NO_UNDERSCORES] (_mcount): Specify "mcount" as

76
sysdeps/i386/dl-runtime.c → elf/dl-runtime.c
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@ -1,5 +1,5 @@
/* On-demand PLT fixup for shared objects. i386 version. /* On-demand PLT fixup for shared objects.
Copyright (C) 1995 Free Software Foundation, Inc. Copyright (C) 1995, 1996 Free Software Foundation, Inc.
This file is part of the GNU C Library. This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or 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 <link.h>
#include "dynamic-link.h" #include "dynamic-link.h"
/* This function is not called in the normal way. The PLT jumps here, not /* Figure out the right type, Rel or Rela. */
using a call. The stack looks like this: #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
-->8(%esp) address to return to the caller of the function in the PLT /* We need to define the function as a local symbol so that the reference
4(%esp) relocation offset for this PLT entry in the trampoline code will be a local PC-relative call. Tell the
0(%esp) identifier for this shared object (struct link_map *) compiler not to worry that the function appears not to be called. */
The user expects the real function the PLT refers to to be entered static Elf32_Addr fixup (struct link_map *l, Elf32_Word reloc_offset)
with 8(%esp) as the top of stack. */ __attribute__ ((unused));
void /* This function is called through a special trampoline from the PLT the
_dl_runtime_resolve (Elf32_Word reloc_offset) 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 *const symtab
= (const Elf32_Sym *) (l->l_addr + l->l_info[DT_SYMTAB]->d_un.d_ptr); = (const Elf32_Sym *) (l->l_addr + l->l_info[DT_SYMTAB]->d_un.d_ptr);
const char *strtab = const char *strtab =
(const char *) (l->l_addr + l->l_info[DT_STRTAB]->d_un.d_ptr); (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 + = (const void *) (l->l_addr + l->l_info[DT_JMPREL]->d_un.d_ptr +
reloc_offset); reloc_offset);
@ -61,34 +75,26 @@ _dl_runtime_resolve (Elf32_Word reloc_offset)
} }
else else
scope = _dl_loaded; scope = _dl_loaded;
definer = &symtab[ELF32_R_SYM (reloc->r_info)]; definer = &symtab[ELF32_R_SYM (reloc->r_info)];
loadbase = _dl_lookup_symbol (strtab + definer->st_name, &definer, loadbase = _dl_lookup_symbol (strtab + definer->st_name, &definer,
scope, l->l_name, 0); scope, l->l_name, 0);
/* Restore list frobnication done above for DT_SYMBOLIC. */ /* Restore list frobnication done above for DT_SYMBOLIC. */
l->l_next = real_next; l->l_next = real_next;
if (l->l_prev) if (l->l_prev)
l->l_prev->l_next = l; l->l_prev->l_next = l;
/* Apply the relocation with that value. */ /* 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 return *(Elf32_Addr *) (l->l_addr + reloc->r_offset);
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;
/* 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;
return_insn: asm volatile ("ret");
} }
/* 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. */
ELF_MACHINE_RUNTIME_TRAMPOLINE

4
elf/dynamic-link.h
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@ -1,5 +1,5 @@
/* Inline functions for dynamic linking. /* 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. This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or 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) dyn->d_tag < DT_LOPROC + DT_PROCNUM)
info[dyn->d_tag - DT_LOPROC + DT_NUM] = dyn; info[dyn->d_tag - DT_LOPROC + DT_NUM] = dyn;
else else
assert (! "bad dynamic tag"); assert (! "bad dynamic tag");
dyn++; dyn++;
} }

14
sysdeps/i386/dl-machine.h
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@ -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. */ the offset on the stack, and then jump to the resolved address. */
got[2] = (Elf32_Addr) &_dl_runtime_resolve; 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, /* Mask identifying addresses reserved for the user program,
where the dynamic linker should not map anything. */ where the dynamic linker should not map anything. */

64
sysdeps/stub/dl-runtime.c
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@ -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);
}