elf_object.cc revision 2620 
1/*
2 * Copyright (c) 2003-2005 The Regents of The University of Michigan
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 are
7 * met: redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer;
9 * redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution;
12 * neither the name of the copyright holders nor the names of its
13 * contributors may be used to endorse or promote products derived from
14 * this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29#include <string>
30
31// Because of the -Wundef flag we have to do this
32#define __LIBELF_INTERNAL__     0
33// counterintuitive, but the flag below causes libelf to define
34// 64-bit elf types that apparently didn't exist in some older
35// versions of Linux.  They seem to be there in 2.4.x, so don't
36// set this now (it causes things to break on 64-bit platforms).
37#define __LIBELF64_LINUX        0
38#define __LIBELF_NEED_LINK_H    0
39#define __LIBELF_SYMBOL_VERSIONS 0
40
41#include "libelf/libelf.h"
42#include "libelf/gelf.h"
43
44#include "base/loader/elf_object.hh"
45#include "base/misc.hh"
46
47#include "base/loader/symtab.hh"
48
49#include "base/trace.hh"	// for DPRINTF
50
51#include "sim/byteswap.hh"
52
53
54using namespace std;
55
56ObjectFile *
57ElfObject::tryFile(const string &fname, int fd, size_t len, uint8_t *data)
58{
59    Elf *elf;
60    GElf_Ehdr ehdr;
61    Arch arch = UnknownArch;
62    OpSys opSys = UnknownOpSys;
63
64    // check that header matches library version
65    if (elf_version(EV_CURRENT) == EV_NONE)
66        panic("wrong elf version number!");
67
68    // get a pointer to elf structure
69    elf = elf_memory((char*)data,len);
70    // will only fail if fd is invalid
71    assert(elf != NULL);
72
73    // Check that we actually have a elf file
74    if (gelf_getehdr(elf, &ehdr) ==0) {
75        DPRINTFR(Loader, "Not ELF\n");
76        elf_end(elf);
77        return NULL;
78    } else {
79        //Detect the architecture
80        //Since we don't know how to check for alpha right now, we'll
81        //just assume if it wasn't something else and it's 64 bit, that's
82        //what it must be.
83        if (ehdr.e_machine == EM_SPARC64 ||
84                ehdr.e_machine == EM_SPARC ||
85                ehdr.e_machine == EM_SPARCV9) {
86            arch = ObjectFile::SPARC;
87        } else if (ehdr.e_machine == EM_MIPS
88                && ehdr.e_ident[EI_CLASS] == ELFCLASS32) {
89            arch = ObjectFile::Mips;
90        } else if (ehdr.e_ident[EI_CLASS] == ELFCLASS64) {
91            arch = ObjectFile::Alpha;
92        } else {
93            warn("Unknown architecture: %d\n", ehdr.e_machine);
94            arch = ObjectFile::UnknownArch;
95        }
96
97        //Detect the operating system
98        switch (ehdr.e_ident[EI_OSABI])
99        {
100
101          case ELFOSABI_LINUX:
102            opSys = ObjectFile::Linux;
103            break;
104          case ELFOSABI_SOLARIS:
105            opSys = ObjectFile::Solaris;
106            break;
107          case ELFOSABI_TRU64:
108            opSys = ObjectFile::Tru64;
109            break;
110          default:
111            opSys = ObjectFile::UnknownOpSys;
112        }
113
114        //take a look at the .note.ABI section
115        //It can let us know what's what.
116        if (opSys == ObjectFile::UnknownOpSys) {
117            Elf_Scn *section;
118            GElf_Shdr shdr;
119            Elf_Data *data;
120            uint32_t osAbi;;
121            int secIdx = 1;
122
123            // Get the first section
124            section = elf_getscn(elf, secIdx);
125
126            // While there are no more sections
127            while (section != NULL && opSys == ObjectFile::UnknownOpSys) {
128                gelf_getshdr(section, &shdr);
129                if (shdr.sh_type == SHT_NOTE && !strcmp(".note.ABI-tag",
130                            elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name))) {
131                    // we have found a ABI note section
132                    // Check the 5th 32bit word for OS  0 == linux, 1 == hurd,
133                    // 2 == solaris, 3 == freebsd
134                    data = elf_rawdata(section, NULL);
135                    assert(data->d_buf);
136                    if(ehdr.e_ident[EI_DATA] == ELFDATA2LSB)
137                        osAbi = htole(((uint32_t*)data->d_buf)[4]);
138                    else
139                        osAbi = htobe(((uint32_t*)data->d_buf)[4]);
140
141                    switch(osAbi) {
142                      case 0:
143                        opSys = ObjectFile::Linux;
144                        break;
145                      case 2:
146                        opSys = ObjectFile::Solaris;
147                        break;
148                    }
149                } // if section found
150                if (!strcmp(".SUNW_version", elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name)))
151                        opSys = ObjectFile::Solaris;
152                if (!strcmp(".stab.index", elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name)))
153                        opSys = ObjectFile::Solaris;
154
155            section = elf_getscn(elf, ++secIdx);
156            } // while sections
157        }
158
159        elf_end(elf);
160        return new ElfObject(fname, fd, len, data, arch, opSys);
161    }
162}
163
164
165ElfObject::ElfObject(const string &_filename, int _fd,
166                     size_t _len, uint8_t *_data,
167                     Arch _arch, OpSys _opSys)
168    : ObjectFile(_filename, _fd, _len, _data, _arch, _opSys)
169
170{
171    Elf *elf;
172    GElf_Ehdr ehdr;
173
174    // check that header matches library version
175    if (elf_version(EV_CURRENT) == EV_NONE)
176        panic("wrong elf version number!");
177
178    // get a pointer to elf structure
179    elf = elf_memory((char*)fileData,len);
180    // will only fail if fd is invalid
181    assert(elf != NULL);
182
183    // Check that we actually have a elf file
184    if (gelf_getehdr(elf, &ehdr) ==0) {
185        panic("Not ELF, shouldn't be here");
186    }
187
188    entry = ehdr.e_entry;
189
190
191    // initialize segment sizes to 0 in case they're not present
192    text.size = data.size = bss.size = 0;
193
194    for (int i = 0; i < ehdr.e_phnum; ++i) {
195        GElf_Phdr phdr;
196        if (gelf_getphdr(elf, i, &phdr) == 0) {
197            panic("gelf_getphdr failed for section %d", i);
198        }
199
200        // for now we don't care about non-loadable segments
201        if (!(phdr.p_type & PT_LOAD))
202            continue;
203
204        // the headers don't explicitly distinguish text from data,
205        // but empirically the text segment comes first.
206        if (text.size == 0) {  // haven't seen text segment yet
207            text.baseAddr = phdr.p_vaddr;
208            text.size = phdr.p_filesz;
209            text.fileImage = fileData + phdr.p_offset;
210            // if there's any padding at the end that's not in the
211            // file, call it the bss.  This happens in the "text"
212            // segment if there's only one loadable segment (as for
213            // kernel images).
214            bss.size = phdr.p_memsz - phdr.p_filesz;
215            bss.baseAddr = phdr.p_vaddr + phdr.p_filesz;
216            bss.fileImage = NULL;
217        } else if (data.size == 0) { // have text, this must be data
218            data.baseAddr = phdr.p_vaddr;
219            data.size = phdr.p_filesz;
220            data.fileImage = fileData + phdr.p_offset;
221            // if there's any padding at the end that's not in the
222            // file, call it the bss.  Warn if this happens for both
223            // the text & data segments (should only have one bss).
224            if (phdr.p_memsz - phdr.p_filesz > 0 && bss.size != 0) {
225                warn("Two implied bss segments in file!\n");
226            }
227            bss.size = phdr.p_memsz - phdr.p_filesz;
228            bss.baseAddr = phdr.p_vaddr + phdr.p_filesz;
229            bss.fileImage = NULL;
230        } else {
231            warn("More than two loadable segments in ELF object.");
232            warn("Ignoring segment @ 0x%x length 0x%x.",
233                 phdr.p_vaddr, phdr.p_filesz);
234        }
235    }
236
237    // should have found at least one loadable segment
238    assert(text.size != 0);
239
240    DPRINTFR(Loader, "text: 0x%x %d\ndata: 0x%x %d\nbss: 0x%x %d\n",
241             text.baseAddr, text.size, data.baseAddr, data.size,
242             bss.baseAddr, bss.size);
243
244    elf_end(elf);
245
246    // We will actually read the sections when we need to load them
247}
248
249
250bool
251ElfObject::loadSomeSymbols(SymbolTable *symtab, int binding)
252{
253    Elf *elf;
254    int sec_idx = 1; // there is a 0 but it is nothing, go figure
255    Elf_Scn *section;
256    GElf_Shdr shdr;
257    Elf_Data *data;
258    int count, ii;
259    bool found = false;
260    GElf_Sym sym;
261
262    if (!symtab)
263        return false;
264
265    // check that header matches library version
266    if (elf_version(EV_CURRENT) == EV_NONE)
267        panic("wrong elf version number!");
268
269    // get a pointer to elf structure
270    elf = elf_memory((char*)fileData,len);
271
272    assert(elf != NULL);
273
274    // Get the first section
275    section = elf_getscn(elf, sec_idx);
276
277    // While there are no more sections
278    while (section != NULL) {
279        gelf_getshdr(section, &shdr);
280
281        if (shdr.sh_type == SHT_SYMTAB) {
282            found = true;
283            data = elf_getdata(section, NULL);
284            count = shdr.sh_size / shdr.sh_entsize;
285            DPRINTF(Loader, "Found Symbol Table, %d symbols present\n", count);
286
287            // loop through all the symbols, only loading global ones
288            for (ii = 0; ii < count; ++ii) {
289                gelf_getsym(data, ii, &sym);
290                if (GELF_ST_BIND(sym.st_info) == binding) {
291                   symtab->insert(sym.st_value,
292                                  elf_strptr(elf, shdr.sh_link, sym.st_name));
293                }
294            }
295        }
296        ++sec_idx;
297        section = elf_getscn(elf, sec_idx);
298    }
299
300    elf_end(elf);
301
302    return found;
303}
304
305bool
306ElfObject::loadGlobalSymbols(SymbolTable *symtab)
307{
308    return loadSomeSymbols(symtab, STB_GLOBAL);
309}
310
311bool
312ElfObject::loadLocalSymbols(SymbolTable *symtab)
313{
314    return loadSomeSymbols(symtab, STB_LOCAL);
315}
316