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authorRoland McGrath <roland@gnu.org>1995-05-02 06:35:55 +0000
committerRoland McGrath <roland@gnu.org>1995-05-02 06:35:55 +0000
commitd66e34cd423425c348bcc83df127dd19711b0b9a (patch)
tree97058e776d3b4fe06ef54bc4951596991652183f /sysdeps/i386
parent08162fa888913a5153d2fcdc4e1a816b57b1fe56 (diff)
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* sysdeps/mach/i386/sysdep.h (SNARF_ARGS, CALL_WITH_SP): Rewritten.
* sysdeps/i386/dl-machine.h: New file. * sysdeps/stub/dl-machine.h: New file. * sysdeps/i386/dl-runtime.c: New file. * sysdeps/stub/dl-runtime.c: New file. * sysdeps/i386/elf/start.S: New file. * sysdeps/generic/dl-sysdep.c: New file. * sysdeps/mach/hurd/dl-sysdep.c: New file.
Diffstat (limited to 'sysdeps/i386')
-rw-r--r--sysdeps/i386/dl-machine.h169
-rw-r--r--sysdeps/i386/dl-runtime.c92
-rw-r--r--sysdeps/i386/elf/start.S86
3 files changed, 347 insertions, 0 deletions
diff --git a/sysdeps/i386/dl-machine.h b/sysdeps/i386/dl-machine.h
new file mode 100644
index 0000000..5e1ee2a
--- /dev/null
+++ b/sysdeps/i386/dl-machine.h
@@ -0,0 +1,169 @@
+/* Machine-dependent ELF dynamic relocation inline functions. i386 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>
+
+
+/* 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;
+
+/* Perform the relocation specified by RELOC and SYM (which is fully resolved).
+ LOADADDR is the load address of the object; INFO is an array indexed
+ by DT_* of the .dynamic section info. */
+
+static inline void
+elf_machine_rel (Elf32_Addr loadaddr, Elf32_Dyn *info[DT_NUM],
+ const Elf32_Rel *reloc,
+ Elf32_Addr sym_loadaddr, const Elf32_Sym *sym)
+{
+ Elf32_Addr *const reloc_addr = (Elf32_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:
+ *reloc_addr += sym_value;
+ break;
+ case R_386_RELATIVE:
+ *reloc_addr += loadaddr;
+ break;
+ case R_386_PC32:
+ *reloc_addr = sym_value - (Elf32_Addr) reloc_addr;
+ break;
+ default:
+ assert (! "unexpected dynamic reloc type");
+ break;
+ }
+}
+
+
+/* The i386 never uses Elf32_Rela relocations. */
+static inline void
+elf_machine_rela (Elf32_Addr loadaddr, Elf32_Dyn *info[DT_NUM],
+ const Elf32_Rela *reloc,
+ Elf32_Addr sym_loadaddr, const Elf32_Sym *sym)
+{
+ _dl_signal_error (0, "Elf32_Rela relocation requested -- unused on i386");
+}
+
+
+/* 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)
+{
+ 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]. */
+ Elf32_Addr *got = (Elf32_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;
+}
+
+
+/* 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\
+_start: call _dl_start\n\
+ # Save the user entry point address in %ebx.\n\
+ movl %eax, %ebx\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)\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\
+ # Pass our finalizer function to the user in %edx, as per ELF ABI.\n\
+1: call 2f\n\
+2: popl %eax\n\
+ addl $_GLOBAL_OFFSET_TABLE_+[.-2b], %eax\n\
+ leal _dl_fini@GOT(%eax), %edx\n\
+ # Jump to the user entry point.\n\
+ jmp *%ebx\n\
+");
diff --git a/sysdeps/i386/dl-runtime.c b/sysdeps/i386/dl-runtime.c
new file mode 100644
index 0000000..897524f
--- /dev/null
+++ b/sysdeps/i386/dl-runtime.c
@@ -0,0 +1,92 @@
+/* On-demand PLT fixup for shared objects. i386 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. */
+
+register void *sp asm ("%esp");
+
+#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
+ 8(%esp) as the top of stack. */
+
+void
+_dl_runtime_resolve (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_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);
+
+ /* 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;
+
+ /* 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 *) reloc->r_offset;
+
+ return;
+
+ return_insn: asm volatile ("ret");
+}
diff --git a/sysdeps/i386/elf/start.S b/sysdeps/i386/elf/start.S
new file mode 100644
index 0000000..5c29ce4
--- /dev/null
+++ b/sysdeps/i386/elf/start.S
@@ -0,0 +1,86 @@
+/* Startup code compliant to the ELF i386 ABI.
+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. */
+
+/* This is the canonical entry point, usually the first thing in the text
+ segment. The SVR4/i386 ABI (pages 3-31, 3-32) says that when the entry
+ point runs, most registers' values are unspecified, except for:
+
+ %edx Contains a function pointer to be registered with `atexit'.
+ This is how the dynamic linker arranges to have DT_FINI
+ functions called for shared libraries that have been loaded
+ before this code runs.
+
+ %esp The stack contains the arguments and environment:
+ 0(%esp) argc
+ 4(%esp) argv[0]
+ ...
+ (4*argc)(%esp) NULL
+ (4*(argc+1))(%esp) envp[0]
+ ...
+ NULL
+*/
+
+ .text
+ .globl _start
+_start:
+ /* Clear the frame pointer. The ABI suggests this be done, to mark
+ the outermost frame obviously. */
+ movl $0, %ebp
+
+ /* %edx contains the address of the shared library termination
+ function, which we will register with `atexit' to be called by
+ `exit'. I suspect that on some systems, and when statically
+ linked, this will not be set by anything to any function
+ pointer; hopefully it will be zero so we don't try to call
+ random pointers. */
+ testl %edx
+ jeq nofini
+ pushl %edx
+ call atexit
+ addl $4, %esp
+nofini:
+
+ /* Do essential libc initialization. In statically linked
+ programs under the GNU Hurd, this is what sets up the
+ arguments on the stack for the code below. */
+ call __libc_init_first
+
+ /* Extract the arguments and environment as encoded on the stack
+ and set up the arguments for `main': argc, argv, envp. */
+ popl %esi /* Pop the argument count. */
+ leal 4(%esp,%esi,4), %eax /* envp = &argv[argc + 1] */
+ movl %eax, _environ /* Store it in the global variable. */
+ pushl %eax /* Push third argument: envp. */
+ leal 4(%esp), %eax /* argv starts just above that word. */
+ pushl %eax /* Push second argument: argv. */
+ pushl %esi /* Push first argument: argc. */
+
+ /* Call `_init', which is the entry point to our own `.init'
+ section; and register with `atexit' to have `exit' call
+ `_fini', which is the entry point to our own `.fini' section. */
+ call _init
+ pushl $_fini
+ call atexit
+ addl $4, %esp
+
+ /* Call the user's main function, and exit with its value. */
+ call main
+ pushl %eax
+ call exit /* This should never return. */
+ hlt /* Crash if somehow it does return. */