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