1 /* 2 * Copyright (C) 2006 The Android Open Source Project 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * * Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * * Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in 12 * the documentation and/or other materials provided with the 13 * distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS 22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29 #include <elf.h> 30 #include <string.h> 31 #include <sys/auxv.h> 32 #include <sys/types.h> 33 #include <link.h> 34 35 /* ld provides this to us in the default link script */ 36 extern "C" void* __executable_start; 37 38 int dl_iterate_phdr(int (*cb)(struct dl_phdr_info* info, size_t size, void* data), void* data) { 39 ElfW(Ehdr)* ehdr = reinterpret_cast<ElfW(Ehdr)*>(&__executable_start); 40 41 if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0) { 42 return -1; 43 } 44 45 // Dynamic binaries get their dl_iterate_phdr from the dynamic linker, but 46 // static binaries get this. We don't have a list of shared objects to 47 // iterate over, since there's really only a single monolithic blob of 48 // code/data, plus optionally a VDSO. 49 50 struct dl_phdr_info exe_info; 51 exe_info.dlpi_addr = 0; 52 exe_info.dlpi_name = NULL; 53 exe_info.dlpi_phdr = reinterpret_cast<ElfW(Phdr)*>(reinterpret_cast<uintptr_t>(ehdr) + ehdr->e_phoff); 54 exe_info.dlpi_phnum = ehdr->e_phnum; 55 56 // Try the executable first. 57 int rc = cb(&exe_info, sizeof(exe_info), data); 58 if (rc != 0) { 59 return rc; 60 } 61 62 // Try the VDSO if that didn't work. 63 ElfW(Ehdr)* ehdr_vdso = reinterpret_cast<ElfW(Ehdr)*>(getauxval(AT_SYSINFO_EHDR)); 64 if (ehdr_vdso == nullptr) { 65 // There is no VDSO, so there's nowhere left to look. 66 return rc; 67 } 68 69 struct dl_phdr_info vdso_info; 70 vdso_info.dlpi_addr = 0; 71 vdso_info.dlpi_name = NULL; 72 vdso_info.dlpi_phdr = reinterpret_cast<ElfW(Phdr)*>(reinterpret_cast<char*>(ehdr_vdso) + ehdr_vdso->e_phoff); 73 vdso_info.dlpi_phnum = ehdr_vdso->e_phnum; 74 for (size_t i = 0; i < vdso_info.dlpi_phnum; ++i) { 75 if (vdso_info.dlpi_phdr[i].p_type == PT_LOAD) { 76 vdso_info.dlpi_addr = (ElfW(Addr)) ehdr_vdso - vdso_info.dlpi_phdr[i].p_vaddr; 77 break; 78 } 79 } 80 return cb(&vdso_info, sizeof(vdso_info), data); 81 } 82
