Commit e40c4104 authored by Richard M. Stallman's avatar Richard M. Stallman
Browse files

(unexec): Move data2 section header up so all section

headers will be in ascending order.  This will prevent the unexeced
emacs that being processed by other applications (such as strip)
to fail.

Handle rounding of section boundaries.
(round_up): New function.
parent 99e0a2e0
/* Copyright (C) 1985, 1986, 1987, 1988 Free Software Foundation, Inc.
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NO WARRANTY, TO THE EXTENT PERMITTED BY APPLICABLE STATE LAW. EXCEPT
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/* Copyright (C) 1985, 1986, 1987, 1988, 1990, 1992
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
......@@ -397,7 +315,100 @@ Filesz Memsz Flags Align
*/
/* 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.
*
* The above example now should look like:
**** 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] 1 3 0x80a98f4 0x608f4 0x1cf0c .data
0 0 0x4 0
[17] 8 3 0x80c6800 0x7d800 0 .bss
0 0 0x4 0
[18] 2 0 0 0x7d800 0x9b90 .symtab
19 371 0x4 0x10
[19] 3 0 0 0x87390 0x8526 .strtab
0 0 0x1 0
[20] 3 0 0 0x8f8b6 0x93 .shstrtab
0 0 0x1 0
[21] 1 0 0 0x8f949 0x68b7 .comment
0 0 0x1 0
*/
#include <sys/types.h>
#include <stdio.h>
#include <sys/stat.h>
......@@ -428,8 +439,24 @@ extern void fatal(char *, ...);
#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_bss_index) \
(n)++; } 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
*
......@@ -465,7 +492,7 @@ unexec (new_name, old_name, data_start, bss_start, entry_address)
Elf32_Off new_data2_offset;
Elf32_Addr new_data2_addr;
int n, old_bss_index, old_data_index, new_data2_index;
int n, nn, old_bss_index, old_data_index, new_data2_index;
struct stat stat_buf;
/* Open the old file & map it into the address space. */
......@@ -570,8 +597,9 @@ unexec (new_name, old_name, data_start, bss_start, entry_address)
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);
/* 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.
......@@ -597,12 +625,19 @@ unexec (new_name, old_name, data_start, bss_start, entry_address)
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 (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))
&& (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)
......@@ -629,19 +664,6 @@ unexec (new_name, old_name, data_start, bss_start, entry_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,
......@@ -650,38 +672,98 @@ unexec (new_name, old_name, data_start, bss_start, entry_address)
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--)
/* Walk through all section headers, insert the new data2 section right
before the new bss section. */
for (n = 1, nn = 1; n < old_file_h->e_shnum; n++, nn++)
{
caddr_t src;
if (NEW_SECTION_H(n).sh_type == SHT_NULL
|| NEW_SECTION_H(n).sh_type == SHT_NOBITS)
/* If it is bss section, insert the new data2 section before it. */
if (n == old_bss_index)
{
/* Steal the data section header for this data2 section. */
memcpy (&NEW_SECTION_H(nn), &OLD_SECTION_H(old_data_index),
new_file_h->e_shentsize);
NEW_SECTION_H(nn).sh_addr = new_data2_addr;
NEW_SECTION_H(nn).sh_offset = new_data2_offset;
NEW_SECTION_H(nn).sh_size = new_data2_size;
/* Use the bss section's alignment. This will assure that the
new data2 section always be placed in the same spot as the old
bss section by any other application. */
NEW_SECTION_H(nn).sh_addralign = OLD_SECTION_H(n).sh_addralign;
/* Now copy over what we have in the memory now. */
memcpy (NEW_SECTION_H(nn).sh_offset + new_base,
(caddr_t) OLD_SECTION_H(n).sh_addr,
new_data2_size);
nn++;
}
memcpy (&NEW_SECTION_H(nn), &OLD_SECTION_H(n),
old_file_h->e_shentsize);
/* The new bss section's size is zero, and its file offset and virtual
address should be off by NEW_DATA2_SIZE. */
if (n == old_bss_index)
{
/* NN should be `old_bss_index + 1' at this point. */
NEW_SECTION_H(nn).sh_offset += new_data2_size;
NEW_SECTION_H(nn).sh_addr += new_data2_size;
/* Let the new bss section address alignment be the same as the
section address alignment followed the old bss section, so
this section will be placed in exactly the same place. */
NEW_SECTION_H(nn).sh_addralign = OLD_SECTION_H(nn).sh_addralign;
NEW_SECTION_H(nn).sh_size = 0;
}
/* Any section that was original placed AFTER the bss section should now
be off by NEW_DATA2_SIZE. */
else if (NEW_SECTION_H(nn).sh_offset >= new_data2_offset)
NEW_SECTION_H(nn).sh_offset += new_data2_size;
/* If any section hdr refers to the section after the new .data
section, make it refer to next one because we have inserted
a new section in between. */
PATCH_INDEX(NEW_SECTION_H(nn).sh_link);
PATCH_INDEX(NEW_SECTION_H(nn).sh_info);
/* Now, start to copy the content of sections. */
if (NEW_SECTION_H(nn).sh_type == SHT_NULL
|| NEW_SECTION_H(nn).sh_type == SHT_NOBITS)
continue;
/* 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.
*/
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;
src = (caddr_t) OLD_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);
memcpy (NEW_SECTION_H(nn).sh_offset + new_base, src,
NEW_SECTION_H(nn).sh_size);
/* If it is the symbol table, its st_shndx field needs to be patched. */
if (NEW_SECTION_H(nn).sh_type == SHT_SYMTAB
|| NEW_SECTION_H(nn).sh_type == SHT_DYNSYM)
{
Elf32_Shdr *spt = &NEW_SECTION_H(nn);
unsigned int num = spt->sh_size / spt->sh_entsize;
Elf32_Sym * sym = (Elf32_Sym *) (NEW_SECTION_H(nn).sh_offset +
new_base);
for (; num--; sym++)
{
if ((sym->st_shndx == SHN_UNDEF)
|| (sym->st_shndx == SHN_ABS)
|| (sym->st_shndx == SHN_COMMON))
continue;
PATCH_INDEX(sym->st_shndx);
}
}
}
/* Close the files and make the new file executable */
......
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