4.4BSD/usr/src/contrib/emacs-18.57/src/unexelf.c
/* Copyright (C) 1985, 1986, 1987, 1988 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 1, or (at your option)
any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
In other words, you are welcome to use, share and improve this program.
You are forbidden to forbid anyone else to use, share and improve
what you give them. Help stamp out software-hoarding! */
/*
* unexec.c - Convert a running program into an a.out file.
*
* Author: Spencer W. Thomas
* Computer Science Dept.
* University of Utah
* Date: Tue Mar 2 1982
* Modified heavily since then.
*
* Synopsis:
* unexec (new_name, a_name, data_start, bss_start, entry_address)
* char *new_name, *a_name;
* unsigned data_start, bss_start, entry_address;
*
* Takes a snapshot of the program and makes an a.out format file in the
* file named by the string argument new_name.
* If a_name is non-NULL, the symbol table will be taken from the given file.
* On some machines, an existing a_name file is required.
*
* The boundaries within the a.out file may be adjusted with the data_start
* and bss_start arguments. Either or both may be given as 0 for defaults.
*
* Data_start gives the boundary between the text segment and the data
* segment of the program. The text segment can contain shared, read-only
* program code and literal data, while the data segment is always unshared
* and unprotected. Data_start gives the lowest unprotected address.
* The value you specify may be rounded down to a suitable boundary
* as required by the machine you are using.
*
* Specifying zero for data_start means the boundary between text and data
* should not be the same as when the program was loaded.
* If NO_REMAP is defined, the argument data_start is ignored and the
* segment boundaries are never changed.
*
* Bss_start indicates how much of the data segment is to be saved in the
* a.out file and restored when the program is executed. It gives the lowest
* unsaved address, and is rounded up to a page boundary. The default when 0
* is given assumes that the entire data segment is to be stored, including
* the previous data and bss as well as any additional storage allocated with
* break (2).
*
* The new file is set up to start at entry_address.
*
* If you make improvements I'd like to get them too.
* harpo!utah-cs!thomas, thomas@Utah-20
*
*/
/* Even more heavily modified by james@bigtex.cactus.org of Dell Computer Co.
* ELF support added.
*
* Basic theory: the data space of the running process needs to be
* dumped to the output file. Normally we would just enlarge the size
* of .data, scooting everything down. But we can't do that in ELF,
* because there is often something between the .data space and the
* .bss space.
*
* In the temacs dump below, notice that the Global Offset Table
* (.got) and the Dynamic link data (.dynamic) come between .data1 and
* .bss. It does not work to overlap .data with these fields.
*
* The solution is to create a new .data segment. This segment is
* filled with data from the current process. Since the contents of
* various sections refer to sections by index, the new .data segment
* is made the last in the table to avoid changing any existing index.
* This is an example of how the section headers are changed. "Addr"
* is a process virtual address. "Offset" is a file offset.
raid:/nfs/raid/src/dist-18.56/src> dump -h temacs
temacs:
**** SECTION HEADER TABLE ****
[No] Type Flags Addr Offset Size Name
Link Info Adralgn Entsize
[1] 1 2 0x80480d4 0xd4 0x13 .interp
0 0 0x1 0
[2] 5 2 0x80480e8 0xe8 0x388 .hash
3 0 0x4 0x4
[3] 11 2 0x8048470 0x470 0x7f0 .dynsym
4 1 0x4 0x10
[4] 3 2 0x8048c60 0xc60 0x3ad .dynstr
0 0 0x1 0
[5] 9 2 0x8049010 0x1010 0x338 .rel.plt
3 7 0x4 0x8
[6] 1 6 0x8049348 0x1348 0x3 .init
0 0 0x4 0
[7] 1 6 0x804934c 0x134c 0x680 .plt
0 0 0x4 0x4
[8] 1 6 0x80499cc 0x19cc 0x3c56f .text
0 0 0x4 0
[9] 1 6 0x8085f3c 0x3df3c 0x3 .fini
0 0 0x4 0
[10] 1 2 0x8085f40 0x3df40 0x69c .rodata
0 0 0x4 0
[11] 1 2 0x80865dc 0x3e5dc 0xd51 .rodata1
0 0 0x4 0
[12] 1 3 0x8088330 0x3f330 0x20afc .data
0 0 0x4 0
[13] 1 3 0x80a8e2c 0x5fe2c 0x89d .data1
0 0 0x4 0
[14] 1 3 0x80a96cc 0x606cc 0x1a8 .got
0 0 0x4 0x4
[15] 6 3 0x80a9874 0x60874 0x80 .dynamic
4 0 0x4 0x8
[16] 8 3 0x80a98f4 0x608f4 0x449c .bss
0 0 0x4 0
[17] 2 0 0 0x608f4 0x9b90 .symtab
18 371 0x4 0x10
[18] 3 0 0 0x6a484 0x8526 .strtab
0 0 0x1 0
[19] 3 0 0 0x729aa 0x93 .shstrtab
0 0 0x1 0
[20] 1 0 0 0x72a3d 0x68b7 .comment
0 0 0x1 0
raid:/nfs/raid/src/dist-18.56/src> dump -h xemacs
xemacs:
**** SECTION HEADER TABLE ****
[No] Type Flags Addr Offset Size Name
Link Info Adralgn Entsize
[1] 1 2 0x80480d4 0xd4 0x13 .interp
0 0 0x1 0
[2] 5 2 0x80480e8 0xe8 0x388 .hash
3 0 0x4 0x4
[3] 11 2 0x8048470 0x470 0x7f0 .dynsym
4 1 0x4 0x10
[4] 3 2 0x8048c60 0xc60 0x3ad .dynstr
0 0 0x1 0
[5] 9 2 0x8049010 0x1010 0x338 .rel.plt
3 7 0x4 0x8
[6] 1 6 0x8049348 0x1348 0x3 .init
0 0 0x4 0
[7] 1 6 0x804934c 0x134c 0x680 .plt
0 0 0x4 0x4
[8] 1 6 0x80499cc 0x19cc 0x3c56f .text
0 0 0x4 0
[9] 1 6 0x8085f3c 0x3df3c 0x3 .fini
0 0 0x4 0
[10] 1 2 0x8085f40 0x3df40 0x69c .rodata
0 0 0x4 0
[11] 1 2 0x80865dc 0x3e5dc 0xd51 .rodata1
0 0 0x4 0
[12] 1 3 0x8088330 0x3f330 0x20afc .data
0 0 0x4 0
[13] 1 3 0x80a8e2c 0x5fe2c 0x89d .data1
0 0 0x4 0
[14] 1 3 0x80a96cc 0x606cc 0x1a8 .got
0 0 0x4 0x4
[15] 6 3 0x80a9874 0x60874 0x80 .dynamic
4 0 0x4 0x8
[16] 8 3 0x80c6800 0x7d800 0 .bss
0 0 0x4 0
[17] 2 0 0 0x7d800 0x9b90 .symtab
18 371 0x4 0x10
[18] 3 0 0 0x87390 0x8526 .strtab
0 0 0x1 0
[19] 3 0 0 0x8f8b6 0x93 .shstrtab
0 0 0x1 0
[20] 1 0 0 0x8f949 0x68b7 .comment
0 0 0x1 0
[21] 1 3 0x80a98f4 0x608f4 0x1cf0c .data
0 0 0x4 0
* This is an example of how the file header is changed. "Shoff" is
* the section header offset within the file. Since that table is
* after the new .data section, it is moved. "Shnum" is the number of
* sections, which we increment.
*
* "Phoff" is the file offset to the program header. "Phentsize" and
* "Shentsz" are the program and section header entries sizes respectively.
* These can be larger than the apparent struct sizes.
raid:/nfs/raid/src/dist-18.56/src> dump -f temacs
temacs:
**** ELF HEADER ****
Class Data Type Machine Version
Entry Phoff Shoff Flags Ehsize
Phentsize Phnum Shentsz Shnum Shstrndx
1 1 2 3 1
0x80499cc 0x34 0x792f4 0 0x34
0x20 5 0x28 21 19
raid:/nfs/raid/src/dist-18.56/src> dump -f xemacs
xemacs:
**** ELF HEADER ****
Class Data Type Machine Version
Entry Phoff Shoff Flags Ehsize
Phentsize Phnum Shentsz Shnum Shstrndx
1 1 2 3 1
0x80499cc 0x34 0x96200 0 0x34
0x20 5 0x28 22 19
* These are the program headers. "Offset" is the file offset to the
* segment. "Vaddr" is the memory load address. "Filesz" is the
* segment size as it appears in the file, and "Memsz" is the size in
* memory. Below, the third segment is the code and the fourth is the
* data: the difference between Filesz and Memsz is .bss
raid:/nfs/raid/src/dist-18.56/src> dump -o temacs
temacs:
***** PROGRAM EXECUTION HEADER *****
Type Offset Vaddr Paddr
Filesz Memsz Flags Align
6 0x34 0x8048034 0
0xa0 0xa0 5 0
3 0xd4 0 0
0x13 0 4 0
1 0x34 0x8048034 0
0x3f2f9 0x3f2f9 5 0x1000
1 0x3f330 0x8088330 0
0x215c4 0x25a60 7 0x1000
2 0x60874 0x80a9874 0
0x80 0 7 0
raid:/nfs/raid/src/dist-18.56/src> dump -o xemacs
xemacs:
***** PROGRAM EXECUTION HEADER *****
Type Offset Vaddr Paddr
Filesz Memsz Flags Align
6 0x34 0x8048034 0
0xa0 0xa0 5 0
3 0xd4 0 0
0x13 0 4 0
1 0x34 0x8048034 0
0x3f2f9 0x3f2f9 5 0x1000
1 0x3f330 0x8088330 0
0x3e4d0 0x3e4d0 7 0x1000
2 0x60874 0x80a9874 0
0x80 0 7 0
*/
#include <sys/types.h>
#include <stdio.h>
#include <sys/stat.h>
#include <memory.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
#include <elf.h>
#include <sys/mman.h>
#ifndef emacs
#define fatal(a, b, c) fprintf(stderr, a, b, c), exit(1)
#else
extern void fatal(char *, ...);
#endif
/* Get the address of a particular section or program header entry,
* accounting for the size of the entries.
*/
#define OLD_SECTION_H(n) \
(*(Elf32_Shdr *) ((byte *) old_section_h + old_file_h->e_shentsize * (n)))
#define NEW_SECTION_H(n) \
(*(Elf32_Shdr *) ((byte *) new_section_h + new_file_h->e_shentsize * (n)))
#define OLD_PROGRAM_H(n) \
(*(Elf32_Phdr *) ((byte *) old_program_h + old_file_h->e_phentsize * (n)))
#define NEW_PROGRAM_H(n) \
(*(Elf32_Phdr *) ((byte *) new_program_h + new_file_h->e_phentsize * (n)))
typedef unsigned char byte;
/* ****************************************************************
* unexec
*
* driving logic.
*
* In ELF, this works by replacing the old .bss section with a new
* .data section, and inserting an empty .bss immediately afterwards.
*
*/
void
unexec (new_name, old_name, data_start, bss_start, entry_address)
char *new_name, *old_name;
unsigned data_start, bss_start, entry_address;
{
extern unsigned int bss_end;
int new_file, old_file, new_file_size;
/* Pointers to the base of the image of the two files. */
caddr_t old_base, new_base;
/* Pointers to the file, program and section headers for the old and new
* files.
*/
Elf32_Ehdr *old_file_h, *new_file_h;
Elf32_Phdr *old_program_h, *new_program_h;
Elf32_Shdr *old_section_h, *new_section_h;
/* Point to the section name table in the old file */
char *old_section_names;
Elf32_Addr old_bss_addr, new_bss_addr;
Elf32_Word old_bss_size, new_data2_size;
Elf32_Off new_data2_offset;
Elf32_Addr new_data2_addr;
int n, old_bss_index, old_data_index, new_data2_index;
struct stat stat_buf;
/* Open the old file & map it into the address space. */
old_file = open (old_name, O_RDONLY);
if (old_file < 0)
fatal ("Can't open %s for reading: errno %d\n", old_name, errno);
if (fstat (old_file, &stat_buf) == -1)
fatal ("Can't fstat(%s): errno %d\n", old_name, errno);
old_base = mmap (0, stat_buf.st_size, PROT_READ, MAP_SHARED, old_file, 0);
if (old_base == (caddr_t) -1)
fatal ("Can't mmap(%s): errno %d\n", old_name, errno);
#ifdef DEBUG
fprintf (stderr, "mmap(%s, %x) -> %x\n", old_name, stat_buf.st_size,
old_base);
#endif
/* Get pointers to headers & section names */
old_file_h = (Elf32_Ehdr *) old_base;
old_program_h = (Elf32_Phdr *) ((byte *) old_base + old_file_h->e_phoff);
old_section_h = (Elf32_Shdr *) ((byte *) old_base + old_file_h->e_shoff);
old_section_names = (char *) old_base
+ OLD_SECTION_H(old_file_h->e_shstrndx).sh_offset;
/* Find the old .bss section. Figure out parameters of the new
* data2 and bss sections.
*/
for (old_bss_index = 1; old_bss_index < old_file_h->e_shnum; old_bss_index++)
{
#ifdef DEBUG
fprintf (stderr, "Looking for .bss - found %s\n",
old_section_names + OLD_SECTION_H(old_bss_index).sh_name);
#endif
if (!strcmp (old_section_names + OLD_SECTION_H(old_bss_index).sh_name,
".bss"))
break;
}
if (old_bss_index == old_file_h->e_shnum)
fatal ("Can't find .bss in %s.\n", old_name, 0);
old_bss_addr = OLD_SECTION_H(old_bss_index).sh_addr;
old_bss_size = OLD_SECTION_H(old_bss_index).sh_size;
#if defined(emacs) || !defined(DEBUG)
bss_end = (unsigned int) sbrk (0);
new_bss_addr = (Elf32_Addr) bss_end;
#else
new_bss_addr = old_bss_addr + old_bss_size + 0x1234;
#endif
new_data2_addr = old_bss_addr;
new_data2_size = new_bss_addr - old_bss_addr;
new_data2_offset = OLD_SECTION_H(old_bss_index).sh_offset;
#ifdef DEBUG
fprintf (stderr, "old_bss_index %d\n", old_bss_index);
fprintf (stderr, "old_bss_addr %x\n", old_bss_addr);
fprintf (stderr, "old_bss_size %x\n", old_bss_size);
fprintf (stderr, "new_bss_addr %x\n", new_bss_addr);
fprintf (stderr, "new_data2_addr %x\n", new_data2_addr);
fprintf (stderr, "new_data2_size %x\n", new_data2_size);
fprintf (stderr, "new_data2_offset %x\n", new_data2_offset);
#endif
if ((unsigned) new_bss_addr < (unsigned) old_bss_addr + old_bss_size)
fatal (".bss shrank when undumping???\n", 0, 0);
/* Set the output file to the right size and mmap(2) it. Set
* pointers to various interesting objects. stat_buf still has
* old_file data.
*/
new_file = open (new_name, O_RDWR | O_CREAT, 0666);
if (new_file < 0)
fatal ("Can't creat(%s): errno %d\n", new_name, errno);
new_file_size = stat_buf.st_size + old_file_h->e_shentsize + new_data2_size;
if (ftruncate (new_file, new_file_size))
fatal ("Can't ftruncate(%s): errno %d\n", new_name, errno);
new_base = mmap (0, new_file_size, PROT_READ | PROT_WRITE, MAP_SHARED,
new_file, 0);
if (new_base == (caddr_t) -1)
fatal ("Can't mmap(%s): errno %d\n", new_name, errno);
new_file_h = (Elf32_Ehdr *) new_base;
new_program_h = (Elf32_Phdr *) ((byte *) new_base + old_file_h->e_phoff);
new_section_h = (Elf32_Shdr *)
((byte *) new_base + old_file_h->e_shoff + new_data2_size);
/* Make our new file, program and section headers as copies of the
* originals.
*/
memcpy (new_file_h, old_file_h, old_file_h->e_ehsize);
memcpy (new_program_h, old_program_h,
old_file_h->e_phnum * old_file_h->e_phentsize);
memcpy (new_section_h, old_section_h,
old_file_h->e_shnum * old_file_h->e_shentsize);
/* Fix up file header. We'll add one section. Section header is
* further away now.
*/
new_file_h->e_shoff += new_data2_size;
new_file_h->e_shnum += 1;
#ifdef DEBUG
fprintf (stderr, "Old section offset %x\n", old_file_h->e_shoff);
fprintf (stderr, "Old section count %d\n", old_file_h->e_shnum);
fprintf (stderr, "New section offset %x\n", new_file_h->e_shoff);
fprintf (stderr, "New section count %d\n", new_file_h->e_shnum);
#endif
/* Fix up a new program header. Extend the writable data segment so
* that the bss area is covered too. Find that segment by looking
* for a segment that ends just before the .bss area. Make sure
* that no segments are above the new .data2. Put a loop at the end
* to adjust the offset and address of any segment that is above
* data2, just in case we decide to allow this later.
*/
for (n = new_file_h->e_phnum - 1; n >= 0; n--)
{
if (NEW_PROGRAM_H(n).p_vaddr + NEW_PROGRAM_H(n).p_filesz > old_bss_addr)
fatal ("Program segment above .bss in %s\n", old_name, 0);
if (NEW_PROGRAM_H(n).p_type == PT_LOAD
&& (NEW_PROGRAM_H(n).p_vaddr + NEW_PROGRAM_H(n).p_filesz
== old_bss_addr))
break;
}
if (n < 0)
fatal ("Couldn't find segment next to .bss in %s\n", old_name, 0);
NEW_PROGRAM_H(n).p_filesz += new_data2_size;
NEW_PROGRAM_H(n).p_memsz = NEW_PROGRAM_H(n).p_filesz;
#if 0 /* Maybe allow section after data2 - does this ever happen? */
for (n = new_file_h->e_phnum - 1; n >= 0; n--)
{
if (NEW_PROGRAM_H(n).p_vaddr
&& NEW_PROGRAM_H(n).p_vaddr >= new_data2_addr)
NEW_PROGRAM_H(n).p_vaddr += new_data2_size - old_bss_size;
if (NEW_PROGRAM_H(n).p_offset >= new_data2_offset)
NEW_PROGRAM_H(n).p_offset += new_data2_size;
}
#endif
/* Fix up section headers based on new .data2 section. Any section
* whose offset or virtual address is after the new .data2 section
* gets its value adjusted. .bss size becomes zero and new address
* is set. data2 section header gets added by copying the existing
* .data header and modifying the offset, address and size.
*/
for (n = 1; n < new_file_h->e_shnum; n++)
{
if (NEW_SECTION_H(n).sh_offset >= new_data2_offset)
NEW_SECTION_H(n).sh_offset += new_data2_size;
if (NEW_SECTION_H(n).sh_addr
&& NEW_SECTION_H(n).sh_addr >= new_data2_addr)
NEW_SECTION_H(n).sh_addr += new_data2_size - old_bss_size;
}
new_data2_index = old_file_h->e_shnum;
for (old_data_index = 1; old_data_index < old_file_h->e_shnum;
old_data_index++)
if (!strcmp (old_section_names + OLD_SECTION_H(old_data_index).sh_name,
".data"))
break;
if (old_data_index == old_file_h->e_shnum)
fatal ("Can't find .data in %s.\n", old_name, 0);
memcpy (&NEW_SECTION_H(new_data2_index), &OLD_SECTION_H(old_data_index),
new_file_h->e_shentsize);
NEW_SECTION_H(new_data2_index).sh_addr = new_data2_addr;
NEW_SECTION_H(new_data2_index).sh_offset = new_data2_offset;
NEW_SECTION_H(new_data2_index).sh_size = new_data2_size;
NEW_SECTION_H(old_bss_index).sh_size = 0;
NEW_SECTION_H(old_bss_index).sh_addr = new_data2_addr + new_data2_size;
/* Write out the sections. .data and .data1 (and data2, called
* ".data" in the strings table) get copied from the current process
* instead of the old file.
*/
for (n = new_file_h->e_shnum - 1; n; n--)
{
caddr_t src;
if (NEW_SECTION_H(n).sh_type == SHT_NULL
|| NEW_SECTION_H(n).sh_type == SHT_NOBITS)
continue;
if (!strcmp (old_section_names + NEW_SECTION_H(n).sh_name, ".data")
|| !strcmp ((old_section_names + NEW_SECTION_H(n).sh_name),
".data1"))
src = (caddr_t) NEW_SECTION_H(n).sh_addr;
else
src = old_base + OLD_SECTION_H(n).sh_offset;
memcpy (NEW_SECTION_H(n).sh_offset + new_base, src,
NEW_SECTION_H(n).sh_size);
}
/* Close the files and make the new file executable */
if (close (old_file))
fatal ("Can't close(%s): errno %d\n", old_name, errno);
if (close (new_file))
fatal ("Can't close(%s): errno %d\n", new_name, errno);
if (stat (new_name, &stat_buf) == -1)
fatal ("Can't stat(%s): errno %d\n", new_name, errno);
n = umask (777);
umask (n);
stat_buf.st_mode |= 0111 & ~n;
if (chmod (new_name, stat_buf.st_mode) == -1)
fatal ("Can't chmod(%s): errno %d\n", new_name, errno);
}