| /* |
| * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. |
| * |
| * This code 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 |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| * |
| */ |
| |
| /* |
| * Name: fix_empty_sec_hdr_flags.c |
| * |
| * Description: Remove the SHF_ALLOC flag from "empty" section headers. |
| * An "empty" section header has sh_addr == 0 and sh_size == 0. |
| * |
| * This program is adapted from the example program shown on the |
| * elf(3elf) man page and from code from the Solaris compiler |
| * driver. |
| */ |
| |
| #include <fcntl.h> |
| #include <stdio.h> |
| #include <libelf.h> |
| #include <stdlib.h> |
| #include <string.h> |
| #include <unistd.h> |
| |
| static void failure(void); |
| |
| void |
| main(int argc, char ** argv) { |
| void * ehdr; /* ELF header */ |
| unsigned int i; /* section counter */ |
| int fd; /* descriptor for file */ |
| Elf * elf; /* ELF descriptor */ |
| char * elf_ident; /* ELF identity string */ |
| char * elf_obj; /* elf_obj file */ |
| int fix_count; /* number of flags fixed */ |
| int is_elfclass64; /* is an ELFCLASS64 file? */ |
| Elf_Scn * scn; /* ELF section descriptor */ |
| void * shdr; /* ELF section header */ |
| Elf_Data * shstrtab; /* ELF section header string table */ |
| |
| if (argc != 2) { |
| (void) fprintf(stderr, "Usage: %s elf_obj\n", argv[0]); |
| exit(2); |
| } |
| |
| /* open the elf_obj */ |
| elf_obj = argv[1]; |
| if ((fd = open(elf_obj, O_RDWR)) == -1) { |
| (void) fprintf(stderr, "%s: cannot open file.\n", elf_obj); |
| exit(3); |
| } |
| |
| (void) printf("Opening '%s' for update\n", elf_obj); |
| (void) fflush(stdout); |
| (void) elf_version(EV_CURRENT); /* coordinate ELF versions */ |
| |
| /* obtain the ELF descriptors from the input file */ |
| if ((elf = elf_begin(fd, ELF_C_RDWR, NULL)) == NULL) { |
| failure(); |
| } |
| |
| /* determine if ELFCLASS64 or not? */ |
| elf_ident = elf_getident(elf, NULL); |
| is_elfclass64 = (elf_ident[EI_CLASS] == ELFCLASS64); |
| |
| /* get the ELF header */ |
| if (is_elfclass64) { |
| ehdr = elf64_getehdr(elf); |
| } else { |
| ehdr = elf32_getehdr(elf); |
| } |
| if (ehdr == NULL) { |
| failure(); |
| } |
| |
| /* get the ELF section descriptor */ |
| if (is_elfclass64) { |
| scn = elf_getscn(elf, ((Elf64_Ehdr *) ehdr)->e_shstrndx); |
| } else { |
| scn = elf_getscn(elf, ((Elf32_Ehdr *) ehdr)->e_shstrndx); |
| } |
| if (scn == NULL) { |
| failure(); |
| } |
| |
| /* get the section header string table */ |
| shstrtab = elf_getdata(scn, NULL); |
| if (shstrtab == NULL) { |
| failure(); |
| } |
| |
| fix_count = 0; |
| |
| /* traverse the sections of the input file */ |
| for (i = 1, scn = NULL; scn = elf_nextscn(elf, scn); i++) { |
| int has_flag_set; /* is SHF_ALLOC flag set? */ |
| int is_empty; /* is section empty? */ |
| char * name; /* short hand pointer */ |
| |
| /* get the section header */ |
| if (is_elfclass64) { |
| shdr = elf64_getshdr(scn); |
| } else { |
| shdr = elf32_getshdr(scn); |
| } |
| if (shdr == NULL) { |
| failure(); |
| } |
| |
| if (is_elfclass64) { |
| name = (char *)shstrtab->d_buf + ((Elf64_Shdr *) shdr)->sh_name; |
| } else { |
| name = (char *)shstrtab->d_buf + ((Elf32_Shdr *) shdr)->sh_name; |
| } |
| |
| if (is_elfclass64) { |
| has_flag_set = ((Elf64_Shdr *) shdr)->sh_flags & SHF_ALLOC; |
| is_empty = ((Elf64_Shdr *) shdr)->sh_addr == 0 && |
| ((Elf64_Shdr *) shdr)->sh_size == 0; |
| } else { |
| has_flag_set = ((Elf32_Shdr *) shdr)->sh_flags & SHF_ALLOC; |
| is_empty = ((Elf32_Shdr *) shdr)->sh_addr == 0 && |
| ((Elf32_Shdr *) shdr)->sh_size == 0; |
| } |
| |
| if (is_empty && has_flag_set) { |
| (void) printf("section[%u] '%s' is empty, " |
| "but SHF_ALLOC flag is set.\n", i, name); |
| (void) printf("Clearing the SHF_ALLOC flag.\n"); |
| |
| if (is_elfclass64) { |
| ((Elf64_Shdr *) shdr)->sh_flags &= ~SHF_ALLOC; |
| } else { |
| ((Elf32_Shdr *) shdr)->sh_flags &= ~SHF_ALLOC; |
| } |
| fix_count++; |
| } |
| } /* end for each ELF section */ |
| |
| if (fix_count > 0) { |
| (void) printf("Saving %d updates to '%s'\n", fix_count, elf_obj); |
| (void) fflush(stdout); |
| (void) elf_update(elf, ELF_C_NULL); /* recalc ELF memory structures */ |
| (void) elf_update(elf, ELF_C_WRITE); /* write out changes to ELF obj */ |
| } else { |
| (void) printf("No SHF_ALLOC flags needed to be cleared.\n"); |
| } |
| |
| (void) elf_end(elf); /* done with ELF obj */ |
| (void) close(fd); |
| |
| (void) printf("Done %s '%s'\n", |
| (fix_count > 0) ? "updating" : "with", elf_obj); |
| (void) fflush(stdout); |
| exit(0); |
| } /* end main */ |
| |
| |
| static void |
| failure() { |
| (void) fprintf(stderr, "%s\n", elf_errmsg(elf_errno())); |
| exit(6); |
| } |