1/*
2 * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25#include "salibelf.h"
26#include <stdlib.h>
27#include <unistd.h>
28#include <string.h>
29
30extern void print_debug(const char*,...);
31
32// ELF file parsing helpers. Note that we do *not* use libelf here.
33int read_elf_header(int fd, ELF_EHDR* ehdr) {
34   if (pread(fd, ehdr, sizeof (ELF_EHDR), 0) != sizeof (ELF_EHDR) ||
35            memcmp(&ehdr->e_ident[EI_MAG0], ELFMAG, SELFMAG) != 0 ||
36            ehdr->e_version != EV_CURRENT) {
37        return 0;
38   }
39   return 1;
40}
41
42bool is_elf_file(int fd) {
43   ELF_EHDR ehdr;
44   return read_elf_header(fd, &ehdr);
45}
46
47// read program header table of an ELF file
48ELF_PHDR* read_program_header_table(int fd, ELF_EHDR* hdr) {
49   ELF_PHDR* phbuf = 0;
50   // allocate memory for program header table
51   size_t nbytes = hdr->e_phnum * hdr->e_phentsize;
52
53   if ((phbuf = (ELF_PHDR*) malloc(nbytes)) == NULL) {
54      print_debug("can't allocate memory for reading program header table\n");
55      return NULL;
56   }
57
58   if (pread(fd, phbuf, nbytes, hdr->e_phoff) != nbytes) {
59      print_debug("ELF file is truncated! can't read program header table\n");
60      free(phbuf);
61      return NULL;
62   }
63
64   return phbuf;
65}
66
67// read section header table of an ELF file
68ELF_SHDR* read_section_header_table(int fd, ELF_EHDR* hdr) {
69   ELF_SHDR* shbuf = 0;
70   // allocate memory for section header table
71   size_t nbytes = hdr->e_shnum * hdr->e_shentsize;
72
73   if ((shbuf = (ELF_SHDR*) malloc(nbytes)) == NULL) {
74      print_debug("can't allocate memory for reading section header table\n");
75      return NULL;
76   }
77
78   if (pread(fd, shbuf, nbytes, hdr->e_shoff) != nbytes) {
79      print_debug("ELF file is truncated! can't read section header table\n");
80      free(shbuf);
81      return NULL;
82   }
83
84   return shbuf;
85}
86
87// read a particular section's data
88void* read_section_data(int fd, ELF_EHDR* ehdr, ELF_SHDR* shdr) {
89  void *buf = NULL;
90  if (shdr->sh_type == SHT_NOBITS || shdr->sh_size == 0) {
91     return buf;
92  }
93  if ((buf = calloc(shdr->sh_size, 1)) == NULL) {
94     print_debug("can't allocate memory for reading section data\n");
95     return NULL;
96  }
97  if (pread(fd, buf, shdr->sh_size, shdr->sh_offset) != shdr->sh_size) {
98     free(buf);
99     print_debug("section data read failed\n");
100     return NULL;
101  }
102  return buf;
103}
104
105uintptr_t find_base_address(int fd, ELF_EHDR* ehdr) {
106  uintptr_t baseaddr = (uintptr_t)-1;
107  int cnt;
108  ELF_PHDR *phbuf, *phdr;
109
110  // read program header table
111  if ((phbuf = read_program_header_table(fd, ehdr)) == NULL) {
112    goto quit;
113  }
114
115  // the base address of a shared object is the lowest vaddr of
116  // its loadable segments (PT_LOAD)
117  for (phdr = phbuf, cnt = 0; cnt < ehdr->e_phnum; cnt++, phdr++) {
118    if (phdr->p_type == PT_LOAD && phdr->p_vaddr < baseaddr) {
119      baseaddr = phdr->p_vaddr;
120    }
121  }
122
123quit:
124  if (phbuf) free(phbuf);
125  return baseaddr;
126}
127