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libr/src/libr-elf.c

413 lines
12 KiB

/*
*
* Copyright (c) 2008 Erich Hoover
*
* libr libelf Backend - Add resources into ELF binaries using libelf
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* To provide feedback, report bugs, or otherwise contact me:
* ehoover at mines dot edu
*
*/
/* Include compile-time parameters */
#include "config.h"
#include "libr.h"
#include <sys/stat.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
//#define MANUAL_LAYOUT true
extern void libr_set_error(libr_intstatus error);
/*
* Write the output file using libelf
*/
void write_output(libr_file *file_handle)
{
/* Update the ELF file on the disk */
if(elf_update(file_handle->elf_handle, ELF_C_NULL) < 0)
{
printf("elf_update() failed: %s.", elf_errmsg(-1));
return;
}
if(elf_update(file_handle->elf_handle, ELF_C_WRITE) < 0)
{
printf("elf_update() failed: %s.", elf_errmsg(-1));
return;
}
/* Close the handles */
elf_end(file_handle->elf_handle);
close(file_handle->fd_handle);
}
/*
* Return the size of the file represented by the file descriptor
*/
off_t file_size(int fd)
{
struct stat file_stat;
if(fstat(fd, &file_stat) == ERROR)
return ERROR;
return file_stat.st_size;
}
/*
* Open the handles for working with the file using libelf
*/
libr_intstatus open_handles(libr_file *file_handle, char *filename, libr_access_t access)
{
const int elf_access[2] = {ELF_C_READ, ELF_C_RDWR};
const int fd_access[2] = {O_RDONLY, O_RDWR};
Elf *e = NULL;
int fd = 0;
if((fd = open(filename, fd_access[access], 0)) < 0)
RETURN(LIBR_ERROR_OPENFAILED, "Failed to open input file");
if((e = elf_begin(fd, elf_access[access], NULL)) == NULL)
RETURN(LIBR_ERROR_BEGINFAILED, "Failed to open ELF file: %s.", elf_errmsg(-1));
if(elf_kind(e) != ELF_K_ELF)
RETURN(LIBR_ERROR_WRONGFORMAT, "Invalid input file format");
file_handle->access = access;
file_handle->fd_handle = fd;
file_handle->elf_handle = e;
file_handle->file_size = file_size(fd);
file_handle->version = EV_CURRENT; /* This should probably match the rest of the file */
RETURN_OK;
}
/*
* Expand a section
* (Only used when manually controlling ELF layout)
*/
#ifdef MANUAL_LAYOUT
libr_intstatus expand_section(Elf *e, Elf_Scn *scn, size_t size, int reset)
{
size_t offset = 0, delta = 0;
Elf_Scn *tmpscn = NULL;
GElf_Shdr shdr;
if(gelf_getshdr(scn, &shdr) != &shdr)
RETURN(LIBR_INTERROR_GETSHDR, "Failed to obtain ELF header: %s", elf_errmsg(-1));
if(reset)
{
delta = (size-shdr.sh_size);
shdr.sh_size = size;
}
else
{
delta = size;
shdr.sh_size += size;
}
offset = shdr.sh_offset;
if(gelf_update_shdr(scn, &shdr) < 0)
RETURN(LIBR_ERROR_UPDATE, "Failed to perform dynamic update: %s.", elf_errmsg(-1));
if(elf_update(e, ELF_C_NULL) < 0)
RETURN(LIBR_ERROR_UPDATE, "Failed to perform dynamic update: %s.", elf_errmsg(-1));
/* Update any section that follows this one data-wise */
/*
****** This does not work yet
while((tmpscn = elf_nextscn(e, tmpscn)) != NULL)
{
if(tmpscn == scn)
continue;
if(gelf_getshdr(tmpscn, &shdr) != &shdr)
return LIBR_INTERROR_GETSHDR;
if(offset < shdr.sh_offset)
{
if((name = elf_strptr(e, ehdr.e_shstrndx, shdr.sh_name)) == NULL)
RETURN(LIBR_ERROR_STRPTR, "Failed to obtain section string pointer: %s.", elf_errmsg(-1));
shdr.sh_offset += delta;
if(gelf_update_shdr(tmpscn, &shdr) < 0)
RETURN(LIBR_ERROR_UPDATE, "Failed to perform dynamic update: %s.", elf_errmsg(-1));
if(elf_update(e, ELF_C_NULL) < 0)
RETURN(LIBR_ERROR_UPDATE, "Failed to perform dynamic update: %s.", elf_errmsg(-1));
}
}
*/
return LIBR_OK;
}
#endif /* MANUAL_LAYOUT */
/*
* Obtain the data from a section using libelf
*/
libr_data *get_data(libr_file *file_handle, libr_section *scn)
{
return elf_getdata(scn, NULL);
}
/*
* Create new data for a section using libelf
*/
libr_data *new_data(libr_file *file_handle, libr_section *scn)
{
return elf_newdata(scn);
}
/*
* Set data for a section using libelf (not written yet)
*/
libr_intstatus set_data(libr_file *file_handle, libr_section *scn, libr_data *data, off_t offset, char *buffer, size_t size)
{
data->d_align = 1;
data->d_off = offset;
data->d_buf = buffer;
data->d_type = ELF_T_BYTE;
data->d_size = size;
data->d_version = file_handle->version;
#ifdef MANUAL_LAYOUT
if(expand_section(file_handle->elf_handle, scn, data->d_size, true) != LIBR_OK)
RETURN(LIBR_ERROR_EXPANDSECTION, "Failed to expand section");
#else
if(elf_update(file_handle->elf_handle, ELF_C_NULL) < 0)
RETURN(LIBR_ERROR_UPDATE, "Failed to perform dynamic update: %s.", elf_errmsg(-1));
if(elf_update(file_handle->elf_handle, ELF_C_WRITE) < 0)
RETURN(LIBR_ERROR_UPDATE, "Failed to perform dynamic update: %s.", elf_errmsg(-1));
#endif /* MANUAL_LAYOUT */
RETURN_OK;
}
/*
* Find a named section from the ELF file using libelf
*/
libr_intstatus find_section(libr_file *file_handle, char *section, libr_section **retscn)
{
Elf *e = file_handle->elf_handle;
Elf_Scn *scn = NULL;
char *name = NULL;
GElf_Ehdr ehdr;
GElf_Shdr shdr;
uintmax_t si;
if(gelf_getehdr(e, &ehdr) == NULL)
RETURN(LIBR_ERROR_GETEHDR, "Failed to obtain ELF header: %s", elf_errmsg(-1));
while((scn = elf_nextscn(e, scn)) != NULL)
{
if(gelf_getshdr(scn, &shdr) != &shdr)
RETURN(LIBR_ERROR_GETSHDR, "Failed to obtain ELF section header: %s", elf_errmsg(-1));
if((name = elf_strptr(e, ehdr.e_shstrndx, shdr.sh_name)) == NULL)
RETURN(LIBR_ERROR_STRPTR, "Failed to obtain section string pointer: %s.", elf_errmsg(-1));
si = (uintmax_t) elf_ndxscn(scn);
/*
printf("%d: %s (%d %d)\n", (long) si, name, (long) shdr.sh_offset, (long) shdr.sh_size);
*/
if(strcmp(name, section) == 0)
{
*retscn = scn;
RETURN_OK;
}
}
RETURN(LIBR_ERROR_NOSECTION, "ELF resource section not found");
}
/*
* Add a new section and create a name for it in the ELF string table using libelf
*/
libr_intstatus add_section(libr_file *file_handle, char *section, Elf_Scn **retscn)
{
Elf_Scn *scn = NULL, *strscn = NULL;
Elf *e = file_handle->elf_handle;
#ifdef MANUAL_LAYOUT
size_t tblsize = 0;
#endif /* MANUAL_LAYOUT */
Elf_Data *data;
GElf_Ehdr ehdr;
GElf_Shdr shdr;
if(gelf_getehdr(e, &ehdr) == NULL)
RETURN(LIBR_ERROR_GETEHDR, "Failed to obtain ELF header: %s", elf_errmsg(-1));
/* TODO: Support creating a string table for objects that don't have one */
if(!ehdr.e_shstrndx)
RETURN(LIBR_ERROR_NOTABLE, "No ELF string table");
strscn = elf_getscn(e, ehdr.e_shstrndx);
if(strscn == NULL)
RETURN(LIBR_ERROR_TABLE, "Failed to open string table: %s.", elf_errmsg(-1));
data = elf_newdata(strscn);
if(data == NULL)
RETURN(LIBR_ERROR_NEWDATA, "Failed to create data for section");
data->d_align = 1;
#ifdef MANUAL_LAYOUT
{
GElf_Shdr strshdr;
if(gelf_getshdr(strscn, &strshdr) != &strshdr)
RETURN(LIBR_ERROR_GETSHDR, "Failed to obtain ELF section header: %s", elf_errmsg(-1));
data->d_off = strshdr.sh_size;
#endif /* MANUAL_LAYOUT */
data->d_size = (size_t) strlen(section)+1;
data->d_type = ELF_T_BYTE;
data->d_buf = section;
data->d_version = file_handle->version;
#ifdef MANUAL_LAYOUT
if(expand_section(e, strscn, data->d_size, false) != LIBR_OK)
return false;
}
#else
/* Update the internal offset information */
if(elf_update(e, ELF_C_NULL) < 0)
RETURN(LIBR_ERROR_UPDATE, "Failed to perform dynamic update: %s.", elf_errmsg(-1));
#endif /* MANUAL_LAYOUT */
/* seek to the end of the section data */
if((scn = elf_newscn(e)) == NULL)
RETURN(LIBR_ERROR_NEWSECTION, "Failed to create new section");
if(gelf_getshdr(scn, &shdr) != &shdr)
RETURN(LIBR_ERROR_GETSHDR, "Failed to obtain ELF section header: %s", elf_errmsg(-1));
shdr.sh_addralign = 1;
#ifdef MANUAL_LAYOUT
shdr.sh_offset = file_handle->file_size;
#endif /* MANUAL_LAYOUT */
shdr.sh_size = 0;
shdr.sh_name = data->d_off;
shdr.sh_type = SHT_NOTE; /* TODO: Does "NOTE" type fit best? */
shdr.sh_flags = SHF_WRITE;
shdr.sh_entsize = 0;
if(gelf_update_shdr(scn, &shdr) < 0)
RETURN(LIBR_ERROR_UPDATE, "Failed to perform dynamic update: %s.", elf_errmsg(-1));
*retscn = scn;
RETURN_OK;
}
/*
* Remove a section and eliminate it from the ELF string table using libelf
*/
libr_intstatus remove_section(libr_file *file_handle, libr_section *scn)
{
unsigned int table_size, str_size;
char *buffer = NULL, *tmp = NULL;
Elf *e = file_handle->elf_handle;
int remaining_size;
Elf_Scn *strscn;
Elf_Data *data;
GElf_Ehdr ehdr;
GElf_Shdr shdr;
if(gelf_getehdr(e, &ehdr) == NULL)
RETURN(LIBR_ERROR_GETEHDR, "Failed to obtain ELF header: %s", elf_errmsg(-1));
/* Grab the string table */
if(!ehdr.e_shstrndx)
RETURN(LIBR_ERROR_NOTABLE, "No ELF string table");
strscn = elf_getscn(e, ehdr.e_shstrndx);
if(strscn == NULL)
RETURN(LIBR_ERROR_TABLE, "Failed to open string table: %s.", elf_errmsg(-1));
if((data = elf_getdata(strscn, NULL)) == NULL)
RETURN(LIBR_ERROR_GETDATA, "Failed to obtain data of section");
/* Find where the section name is in the string table */
if(gelf_getshdr(scn, &shdr) != &shdr)
RETURN(LIBR_ERROR_GETSHDR, "Failed to obtain ELF section header: %s", elf_errmsg(-1));
table_size = data->d_size;
buffer = (char *) data->d_buf;
/* Excise the string from the table */
str_size = strlen(&buffer[shdr.sh_name])+1;
remaining_size = table_size-(shdr.sh_name+str_size);
if(remaining_size < 0)
RETURN(LIBR_ERROR_SIZEMISMATCH, "Section's data size does not make sense");
if(remaining_size > 0)
{
/* If there is data after our icon entry in the table then it must be moved before resizing
* NOTE: Using memcpy with overlapping addresses is not allowed, use temporary buffer.
*/
tmp = (char *) malloc(remaining_size);
memcpy(tmp, &buffer[shdr.sh_name+str_size], remaining_size);
memcpy(&buffer[shdr.sh_name], tmp, remaining_size);
free(tmp);
}
data->d_size -= str_size;
/* Update the internal offset information */
if(elf_update(e, ELF_C_NULL) < 0)
RETURN(LIBR_ERROR_UPDATE, "Failed to perform dynamic update: %s.", elf_errmsg(-1));
#ifdef MANUAL_LAYOUT
{
GElf_Shdr strshdr;
if(gelf_getshdr(strscn, &strshdr) != &strshdr)
RETURN(LIBR_ERROR_GETSHDR, "Failed to obtain ELF section header: %s", elf_errmsg(-1));
strshdr.sh_size -= str_size;
if(gelf_update_shdr(strscn, &strshdr) < 0)
RETURN(LIBR_ERROR_UPDATE, "Failed to perform dynamic update: %s.", elf_errmsg(-1));
}
#endif /* MANUAL_LAYOUT */
/* Clear the section itself and update the offsets */
if(elfx_remscn(e, scn) == 0)
RETURN(LIBR_ERROR_REMOVESECTION, "Failed to remove section: %s.", elf_errmsg(-1));
RETURN_OK;
}
/*
* Return the pointer to the actual data in the section
*/
void *data_pointer(libr_section *scn, libr_data *data)
{
return data->d_buf;
}
/*
* Return the size of the data in the section
*/
size_t data_size(libr_section *scn, libr_data *data)
{
return data->d_size;
}
/*
* Return the next section in the ELF file
*/
libr_section *next_section(libr_file *file_handle, libr_section *scn)
{
return elf_nextscn(file_handle->elf_handle, scn);
}
/*
* Retrieve the name of a section
*/
char *section_name(libr_file *file_handle, libr_section *scn)
{
char *name = NULL;
GElf_Shdr shdr;
GElf_Ehdr ehdr;
if(gelf_getehdr(file_handle->elf_handle, &ehdr) == NULL)
return NULL;
if(gelf_getshdr(scn, &shdr) != &shdr)
return NULL;
if((name = elf_strptr(file_handle->elf_handle, ehdr.e_shstrndx, shdr.sh_name)) == NULL)
return NULL;
return strdup(name);
}
/*
* Initialize the libelf backend
*/
void initialize_backend(void)
{
if(elf_version(EV_CURRENT) == EV_NONE)
return; //errx(EX_SOFTWARE, "ELF library initialization failed: %s", elf_errmsg(-1));
}