Commit f1913a26 authored by Richard M. Stallman's avatar Richard M. Stallman
Browse files

Initial revision

parent 44ef8c25
/* Unexec for Siemens machines running Sinix (modified SVR4).
Copyright (C) 1985, 1986, 1987, 1988, 1990, 1992, 1993, 1994
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 2, 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.
*/
/* Modified by wtien@urbana.mcd.mot.com of Motorola Inc.
*
* The above mechanism does not work if the unexeced ELF file is being
* re-layout by other applications (such as `strip'). All the applications
* that re-layout the internal of ELF will layout all sections in ascending
* order of their file offsets. After the re-layout, the data2 section will
* still be the LAST section in the section header vector, but its file offset
* is now being pushed far away down, and causes part of it not to be mapped
* in (ie. not covered by the load segment entry in PHDR vector), therefore
* causes the new binary to fail.
*
* The solution is to modify the unexec algorithm to insert the new data2
* section header right before the new bss section header, so their file
* offsets will be in the ascending order. Since some of the section's (all
* sections AFTER the bss section) indexes are now changed, we also need to
* modify some fields to make them point to the right sections. This is done
* by macro PATCH_INDEX. All the fields that need to be patched are:
*
* 1. ELF header e_shstrndx field.
* 2. section header sh_link and sh_info field.
* 3. symbol table entry st_shndx field.
*/
/*
* New modifications for Siemens Nixdorf's MIPS-based machines.
* Marco.Walther@mch.sni.de
*
* The problem: Before the bss segment we have a so called sbss segment
* (small bss) and maybe an sdata segment. These segments
* must also be handled correct.
*
* /home1/marco/emacs/emacs-19.22/src
* dump -hv temacs
*
* temacs:
*
* **** SECTION HEADER TABLE ****
* [No] Type Flags Addr Offset Size Name
* Link Info Adralgn Entsize
*
* [1] PBIT -A-- 0x4000f4 0xf4 0x13 .interp
* 0 0 0x1 0
*
* [2] REGI -A-- 0x400108 0x108 0x18 .reginfo
* 0 0 0x4 0x18
*
* [3] DYNM -A-- 0x400120 0x120 0xb8 .dynamic
* 6 0 0x4 0x8
*
* [4] HASH -A-- 0x4001d8 0x1d8 0x8a0 .hash
* 5 0 0x4 0x4
*
* [5] DYNS -A-- 0x400a78 0xa78 0x11f0 .dynsym
* 6 2 0x4 0x10
*
* [6] STRT -A-- 0x401c68 0x1c68 0xbf9 .dynstr
* 0 0 0x1 0
*
* [7] REL -A-- 0x402864 0x2864 0x18 .rel.dyn
* 5 14 0x4 0x8
*
* [8] PBIT -AI- 0x402880 0x2880 0x60 .init
* 0 0 0x10 0x1
*
* [9] PBIT -AI- 0x4028e0 0x28e0 0x1234 .plt
* 0 0 0x4 0x4
*
* [10] PBIT -AI- 0x403b20 0x3b20 0xee400 .text
* 0 0 0x20 0x1
*
* [11] PBIT -AI- 0x4f1f20 0xf1f20 0x60 .fini
* 0 0 0x10 0x1
*
* [12] PBIT -A-- 0x4f1f80 0xf1f80 0xd90 .rdata
* 0 0 0x10 0x1
*
* [13] PBIT -A-- 0x4f2d10 0xf2d10 0x17e0 .rodata
* 0 0 0x10 0x1
*
* [14] PBIT WA-- 0x5344f0 0xf44f0 0x4b3e4 .data <<<<<
* 0 0 0x10 0x1
*
* [15] PBIT WA-G 0x57f8d4 0x13f8d4 0x2a84 .got
* 0 0 0x4 0x4
*
* [16] PBIT WA-G 0x582360 0x142360 0x10 .sdata <<<<<
* 0 0 0x10 0x1
*
* [17] NOBI WA-G 0x582370 0x142370 0xb84 .sbss <<<<<
* 0 0 0x4 0
*
* [18] NOBI WA-- 0x582f00 0x142370 0x27ec0 .bss <<<<<
* 0 0 0x10 0x1
*
* [19] SYMT ---- 0 0x142370 0x10e40 .symtab
* 20 1108 0x4 0x10
*
* [20] STRT ---- 0 0x1531b0 0xed9e .strtab
* 0 0 0x1 0
*
* [21] STRT ---- 0 0x161f4e 0xb5 .shstrtab
* 0 0 0x1 0
*
* [22] PBIT ---- 0 0x162003 0x28e2a .comment
* 0 0 0x1 0x1
*
* [23] PBIT ---- 0 0x18ae2d 0x592 .debug
* 0 0 0x1 0
*
* [24] PBIT ---- 0 0x18b3bf 0x80 .line
* 0 0 0x1 0
*
* [25] MDBG ---- 0 0x18b440 0x60 .mdebug
* 0 0 0x4 0
*
*
* dump -hv emacs
*
* emacs:
*
* **** SECTION HEADER TABLE ****
* [No] Type Flags Addr Offset Size Name
* Link Info Adralgn Entsize
*
* [1] PBIT -A-- 0x4000f4 0xf4 0x13 .interp
* 0 0 0x1 0
*
* [2] REGI -A-- 0x400108 0x108 0x18 .reginfo
* 0 0 0x4 0x18
*
* [3] DYNM -A-- 0x400120 0x120 0xb8 .dynamic
* 6 0 0x4 0x8
*
* [4] HASH -A-- 0x4001d8 0x1d8 0x8a0 .hash
* 5 0 0x4 0x4
*
* [5] DYNS -A-- 0x400a78 0xa78 0x11f0 .dynsym
* 6 2 0x4 0x10
*
* [6] STRT -A-- 0x401c68 0x1c68 0xbf9 .dynstr
* 0 0 0x1 0
*
* [7] REL -A-- 0x402864 0x2864 0x18 .rel.dyn
* 5 14 0x4 0x8
*
* [8] PBIT -AI- 0x402880 0x2880 0x60 .init
* 0 0 0x10 0x1
*
* [9] PBIT -AI- 0x4028e0 0x28e0 0x1234 .plt
* 0 0 0x4 0x4
*
* [10] PBIT -AI- 0x403b20 0x3b20 0xee400 .text
* 0 0 0x20 0x1
*
* [11] PBIT -AI- 0x4f1f20 0xf1f20 0x60 .fini
* 0 0 0x10 0x1
*
* [12] PBIT -A-- 0x4f1f80 0xf1f80 0xd90 .rdata
* 0 0 0x10 0x1
*
* [13] PBIT -A-- 0x4f2d10 0xf2d10 0x17e0 .rodata
* 0 0 0x10 0x1
*
* [14] PBIT WA-- 0x5344f0 0xf44f0 0x4b3e4 .data <<<<<
* 0 0 0x10 0x1
*
* [15] PBIT WA-G 0x57f8d4 0x13f8d4 0x2a84 .got
* 0 0 0x4 0x4
*
* [16] PBIT WA-G 0x582360 0x142360 0xb94 .sdata <<<<<
* 0 0 0x10 0x1
*
* [17] PBIT WA-- 0x582f00 0x142f00 0x94100 .data <<<<<
* 0 0 0x10 0x1
*
* [18] NOBI WA-G 0x617000 0x1d7000 0 .sbss <<<<<
* 0 0 0x4 0
*
* [19] NOBI WA-- 0x617000 0x1d7000 0 .bss <<<<<
* 0 0 0x4 0x1
*
* [20] SYMT ---- 0 0x1d7000 0x10e40 .symtab
* 21 1109 0x4 0x10
*
* [21] STRT ---- 0 0x1e7e40 0xed9e .strtab
* 0 0 0x1 0
*
* [22] STRT ---- 0 0x1f6bde 0xb5 .shstrtab
* 0 0 0x1 0
*
* [23] PBIT ---- 0 0x1f6c93 0x28e2a .comment
* 0 0 0x1 0x1
*
* [24] PBIT ---- 0 0x21fabd 0x592 .debug
* 0 0 0x1 0
*
* [25] PBIT ---- 0 0x22004f 0x80 .line
* 0 0 0x1 0
*
* [26] MDBG ---- 0 0x2200d0 0x60 .mdebug
* 0 0 0x4 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)))
#define PATCH_INDEX(n) \
do { \
if ((n) >= old_sbss_index) \
(n) += 1 + (old_sdata_index ? 0 : 1); } while (0)
typedef unsigned char byte;
/* Round X up to a multiple of Y. */
int
round_up (x, y)
int x, y;
{
int rem = x % y;
if (rem == 0)
return x;
return x - rem + y;
}
/* ****************************************************************
* 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_Addr old_sbss_addr;
Elf32_Word old_bss_size, new_data2_size;
Elf32_Word old_sbss_size, new_data3_size;
Elf32_Off new_data2_offset;
Elf32_Off new_data3_offset;
Elf32_Addr new_data2_addr;
Elf32_Addr new_data3_addr;
Elf32_Word old_sdata_size, new_sdata_size;
int old_sdata_index = 0;
int n, nn, old_data_index, new_data2_align;
int old_bss_index;
int old_sbss_index;
int old_bss_padding;
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 .sbss section.
*/
for (old_sbss_index = 1; old_sbss_index < old_file_h->e_shnum;
old_sbss_index++)
{
#ifdef DEBUG
fprintf (stderr, "Looking for .sbss - found %s\n",
old_section_names + OLD_SECTION_H(old_sbss_index).sh_name);
#endif
if (!strcmp (old_section_names + OLD_SECTION_H(old_sbss_index).sh_name,
".sbss"))
break;
}
if (old_sbss_index == old_file_h->e_shnum)
fatal ("Can't find .sbss in %s.\n", old_name, 0);
if (!strcmp(old_section_names + OLD_SECTION_H(old_sbss_index - 1).sh_name,
".sdata"))
{
old_sdata_index = old_sbss_index - 1;
}
/* Find the old .bss section.
*/
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);
if (old_sbss_index != (old_bss_index - 1))
fatal (".sbss should come immediatly before .bss in %s.\n", old_name, 0);
/* Figure out parameters of the new data3 and data2 sections.
* Change the sbss and bss sections.
*/
old_bss_addr = OLD_SECTION_H(old_bss_index).sh_addr;
old_bss_size = OLD_SECTION_H(old_bss_index).sh_size;
old_sbss_addr = OLD_SECTION_H(old_sbss_index).sh_addr;
old_sbss_size = OLD_SECTION_H(old_sbss_index).sh_size;
if (old_sdata_index)
{
old_sdata_size = OLD_SECTION_H(old_sdata_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
if (old_sdata_index)
{
new_sdata_size = OLD_SECTION_H(old_sbss_index).sh_offset -
OLD_SECTION_H(old_sdata_index).sh_offset + old_sbss_size;
}
new_data3_addr = old_sbss_addr;
new_data3_size = old_sbss_size;
new_data3_offset = OLD_SECTION_H(old_sbss_index).sh_offset;
new_data2_addr = old_bss_addr;
new_data2_size = new_bss_addr - old_bss_addr;
new_data2_align = (new_data3_offset + old_sbss_size) %
OLD_SECTION_H(old_bss_index).sh_addralign;
new_data2_align = new_data2_align ?
OLD_SECTION_H(old_bss_index).sh_addralign - new_data2_align :
0;
new_data2_offset = new_data3_offset + old_sbss_size + new_data2_align;
old_bss_padding = OLD_SECTION_H(old_bss_index).sh_offset -
OLD_SECTION_H(old_sbss_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);
fprintf (stderr, "old_sbss_index %d\n", old_sbss_index);
fprintf (stderr, "old_sbss_addr %x\n", old_sbss_addr);
fprintf (stderr, "old_sbss_size %x\n", old_sbss_size);
if (old_sdata_index)
{
fprintf (stderr, "old_sdata_size %x\n", old_sdata_size);
fprintf (stderr, "new_sdata_size %x\n", new_sdata_size);
}
else
{
fprintf (stderr, "new_data3_addr %x\n", new_data3_addr);
fprintf (stderr, "new_data3_size %x\n", new_data3_size);
fprintf (stderr, "new_data3_offset %x\n", new_data3_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 +
((1 + (old_sdata_index ? 0 : 1)) * old_file_h->e_shentsize) +
new_data2_size + new_data3_size + new_data2_align;
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 +
new_data2_align +
new_data3_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);
/* Modify the e_shstrndx if necessary. */
PATCH_INDEX (new_file_h->e_shstrndx);
/* Fix up file header. We'll add one section. Section header is
* further away now.
*/
new_file_h->e_shoff += new_data2_size + new_data2_align + new_data3_size;
new_file_h->e_shnum += 1 + (old_sdata_index ? 0 : 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--)
{
/* Compute maximum of all requirements for alignment of section. */
int alignment = (NEW_PROGRAM_H (n)).p_align;
if ((OLD_SECTION_H (old_bss_index)).sh_addralign > alignment)
alignment = OLD_SECTION_H (old_bss_index).sh_addralign;
if ((OLD_SECTION_H (old_sbss_index)).sh_addralign > alignment)
alignment = OLD_SECTION_H (old_sbss_index).sh_addralign;
/* Supposedly this condition is okay for the SGI. */
#if 0
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);
#endif
if (NEW_PROGRAM_H(n).p_type == PT_LOAD
&& (round_up ((NEW_PROGRAM_H (n)).p_vaddr
+ (NEW_PROGRAM_H (n)).p_filesz,
alignment)
== round_up (old_bss_addr, alignment)))
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_data2_align +
new_data3_size;
NEW_PROGRAM_H(n).p_memsz = NEW_PROGRAM_H(n).p_filesz;
#if 1 /* 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_data3_addr)
NEW_PROGRAM_H(n).p_vaddr += new_data2_size - old_bss_size +
new_data3_size - old_sbss_size;
if (NEW_PROGRAM_H(n).p_offset >= new_data3_offset)
NEW_PROGRAM_H(n).p_offset += new_data2_size + new_data2_align +
new_data3_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.
*/