| /* |
| * Copyright (c) 2000, 2001, 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. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * 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. |
| */ |
| |
| #include <stdio.h> |
| #include <sys/mman.h> |
| #include <dlfcn.h> |
| #include <libelf.h> |
| #include <strings.h> |
| #include <fcntl.h> |
| #include <sys/param.h> |
| #include <stdlib.h> |
| #include <thread.h> |
| #include <synch.h> |
| #include <stdarg.h> |
| |
| #define TRUE 1 |
| #define FALSE 0 |
| |
| |
| static void fail(const char *err, ...) |
| { |
| va_list ap; |
| va_start(ap, err); |
| vfprintf(stderr, err, ap); |
| fflush(stderr); |
| va_end(ap); |
| exit(2); |
| } |
| |
| |
| static Elf_Scn *find_section(Elf *elf, Elf_Data *sectionStringData, |
| const char *name) |
| { |
| Elf_Scn *result = NULL; |
| Elf32_Shdr *symHeader; |
| const char *p; |
| |
| while ((result = elf_nextscn(elf, result)) != NULL) { |
| symHeader = elf32_getshdr(result); |
| p = (const char *)(sectionStringData->d_buf) + symHeader->sh_name; |
| if (strcmp(p, name) == 0) |
| break; |
| } |
| return result; |
| } |
| |
| |
| static void trash_mcount(int count, Elf_Data *data, Elf_Data *stringData) |
| { |
| int i; |
| for (i = 0; i < count; ++i) { |
| Elf32_Sym *sym = ((Elf32_Sym *)data->d_buf) + i; |
| char *name = (char *)stringData->d_buf + sym->st_name; |
| |
| if (strcmp(name, "_mcount") == 0) { |
| name[6] = 'T'; |
| break; |
| } |
| } |
| if (i < count) |
| printf("Symbol _mcount found and changed.\n"); |
| else |
| printf("Symbol _mcount not found.\n"); |
| } |
| |
| |
| /* |
| * In the executable program named as the sole command line argument, find |
| * the symbol _mcount, if present, and change its name to something |
| * different. The symbol _mcount is included in Solaris/x86 programs by |
| * the compilers, and its presence prevents preloaded modules from |
| * supplying a custom implementation of that method. |
| */ |
| |
| int main(int argc, char **argv) |
| { |
| Elf32_Ehdr *ehdr; |
| Elf_Scn *sectionStringSection; |
| Elf_Scn *stringSection; |
| Elf_Scn *dynStringSection; |
| Elf_Scn *symSection; |
| Elf_Scn *dynSymSection; |
| Elf32_Shdr *symHeader; |
| Elf32_Shdr *dynSymHeader; |
| Elf32_Shdr *dynStringHeader; |
| Elf32_Shdr *stringHeader; |
| Elf *elf; |
| const char *p; |
| int i; |
| const char *fullName; |
| int fd; |
| Elf_Data *sectionStringData; |
| Elf_Data *symData; |
| Elf_Data *dynSymData; |
| Elf_Data *symStringData; |
| Elf_Data *dynSymStringData; |
| int symCount; |
| int dynSymCount; |
| |
| |
| if (argc != 2) { |
| fprintf(stderr, "Usage:\n" |
| "\t%s <file>\n", argv[0]); |
| exit(1); |
| } |
| |
| fullName = argv[1]; |
| |
| /* Open the ELF file. Get section headers. */ |
| |
| elf_version(EV_CURRENT); |
| fd = open(fullName, O_RDWR); |
| if (fd < 0) |
| fail("Unable to open ELF file %s.\n", fullName); |
| elf = elf_begin(fd, ELF_C_RDWR, (Elf *)0); |
| if (elf == NULL) |
| fail("elf_begin failed.\n"); |
| ehdr = elf32_getehdr(elf); |
| sectionStringSection = elf_getscn(elf, ehdr->e_shstrndx); |
| sectionStringData = elf_getdata(sectionStringSection, NULL); |
| |
| /* Find the symbol table section. */ |
| |
| symSection = find_section(elf, sectionStringData, ".symtab"); |
| if (symSection != NULL) { |
| symData = elf_getdata(symSection, NULL); |
| symCount = symData->d_size / sizeof (Elf32_Sym); |
| |
| /* Find the string section, trash the _mcount symbol. */ |
| |
| stringSection = find_section(elf, sectionStringData, ".strtab"); |
| if (stringSection == NULL) |
| fail("Unable to find string table.\n"); |
| symStringData = elf_getdata(stringSection, NULL); |
| trash_mcount(symCount, symData, symStringData); |
| } else { |
| fprintf(stderr, "Unable to find symbol table.\n"); |
| } |
| |
| /* Find the dynamic symbol table section. */ |
| |
| dynSymSection = find_section(elf, sectionStringData, ".dynsym"); |
| if (dynSymSection != NULL) { |
| dynSymData = elf_getdata(dynSymSection, NULL); |
| dynSymCount = dynSymData->d_size / sizeof (Elf32_Sym); |
| |
| /* Find the dynamic string section, trash the _mcount symbol. */ |
| |
| dynStringSection = find_section(elf, sectionStringData, ".dynstr"); |
| if (dynStringSection == NULL) |
| fail("Unable to find dynamic string table.\n"); |
| dynSymStringData = elf_getdata(dynStringSection, NULL); |
| trash_mcount(dynSymCount, dynSymData, dynSymStringData); |
| } else { |
| fail("Unable to find dynamic symbol table.\n"); |
| } |
| |
| elf_update(elf, ELF_C_WRITE); |
| elf_end(elf); |
| |
| exit(0); |
| } |