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
dl_iterate_phdr(int (* cb)(struct dl_phdr_info * info,size_t size,void * data),void * data)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 #if defined(AT_SYSINFO_EHDR)
57 // Try the executable first.
58 int rc = cb(&exe_info, sizeof(exe_info), data);
59 if (rc != 0) {
60 return rc;
61 }
62
63 // Try the VDSO if that didn't work.
64 ElfW(Ehdr)* ehdr_vdso = reinterpret_cast<ElfW(Ehdr)*>(getauxval(AT_SYSINFO_EHDR));
65 if (ehdr_vdso == nullptr) {
66 // There is no VDSO, so there's nowhere left to look.
67 return rc;
68 }
69
70 struct dl_phdr_info vdso_info;
71 vdso_info.dlpi_addr = 0;
72 vdso_info.dlpi_name = NULL;
73 vdso_info.dlpi_phdr = reinterpret_cast<ElfW(Phdr)*>(reinterpret_cast<char*>(ehdr_vdso) + ehdr_vdso->e_phoff);
74 vdso_info.dlpi_phnum = ehdr_vdso->e_phnum;
75 for (size_t i = 0; i < vdso_info.dlpi_phnum; ++i) {
76 if (vdso_info.dlpi_phdr[i].p_type == PT_LOAD) {
77 vdso_info.dlpi_addr = (ElfW(Addr)) ehdr_vdso - vdso_info.dlpi_phdr[i].p_vaddr;
78 break;
79 }
80 }
81 return cb(&vdso_info, sizeof(vdso_info), data);
82 #else
83 // There's only the executable to try.
84 return cb(&exe_info, sizeof(exe_info), data);
85 #endif
86 }
87