elf_object.cc revision 2634:db0b1133abd5 
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#define __LIBELF_NEED_LINK_H    0
34#define __LIBELF_SYMBOL_VERSIONS 0
35
36#include "gelf.h"
37
38#include "base/loader/elf_object.hh"
39#include "base/misc.hh"
40
41#include "base/loader/symtab.hh"
42
43#include "base/trace.hh"	// for DPRINTF
44
45#include "sim/byteswap.hh"
46
47
48using namespace std;
49
50ObjectFile *
51ElfObject::tryFile(const string &fname, int fd, size_t len, uint8_t *data)
52{
53    Elf *elf;
54    GElf_Ehdr ehdr;
55    Arch arch = UnknownArch;
56    OpSys opSys = UnknownOpSys;
57
58    // check that header matches library version
59    if (elf_version(EV_CURRENT) == EV_NONE)
60        panic("wrong elf version number!");
61
62    // get a pointer to elf structure
63    elf = elf_memory((char*)data,len);
64    // will only fail if fd is invalid
65    assert(elf != NULL);
66
67    // Check that we actually have a elf file
68    if (gelf_getehdr(elf, &ehdr) ==0) {
69        DPRINTFR(Loader, "Not ELF\n");
70        elf_end(elf);
71        return NULL;
72    } else {
73        //Detect the architecture
74        //Since we don't know how to check for alpha right now, we'll
75        //just assume if it wasn't something else and it's 64 bit, that's
76        //what it must be.
77        if (ehdr.e_machine == EM_SPARC64 ||
78                ehdr.e_machine == EM_SPARC ||
79                ehdr.e_machine == EM_SPARCV9) {
80            arch = ObjectFile::SPARC;
81        } else if (ehdr.e_machine == EM_MIPS
82                && ehdr.e_ident[EI_CLASS] == ELFCLASS32) {
83            arch = ObjectFile::Mips;
84        } else if (ehdr.e_ident[EI_CLASS] == ELFCLASS64) {
85            arch = ObjectFile::Alpha;
86        } else {
87            warn("Unknown architecture: %d\n", ehdr.e_machine);
88            arch = ObjectFile::UnknownArch;
89        }
90
91        //Detect the operating system
92        switch (ehdr.e_ident[EI_OSABI])
93        {
94
95          case ELFOSABI_LINUX:
96            opSys = ObjectFile::Linux;
97            break;
98          case ELFOSABI_SOLARIS:
99            opSys = ObjectFile::Solaris;
100            break;
101          case ELFOSABI_TRU64:
102            opSys = ObjectFile::Tru64;
103            break;
104          default:
105            opSys = ObjectFile::UnknownOpSys;
106        }
107
108        //take a look at the .note.ABI section
109        //It can let us know what's what.
110        if (opSys == ObjectFile::UnknownOpSys) {
111            Elf_Scn *section;
112            GElf_Shdr shdr;
113            Elf_Data *data;
114            uint32_t osAbi;;
115            int secIdx = 1;
116
117            // Get the first section
118            section = elf_getscn(elf, secIdx);
119
120            // While there are no more sections
121            while (section != NULL && opSys == ObjectFile::UnknownOpSys) {
122                gelf_getshdr(section, &shdr);
123                if (shdr.sh_type == SHT_NOTE && !strcmp(".note.ABI-tag",
124                            elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name))) {
125                    // we have found a ABI note section
126                    // Check the 5th 32bit word for OS  0 == linux, 1 == hurd,
127                    // 2 == solaris, 3 == freebsd
128                    data = elf_rawdata(section, NULL);
129                    assert(data->d_buf);
130                    if(ehdr.e_ident[EI_DATA] == ELFDATA2LSB)
131                        osAbi = htole(((uint32_t*)data->d_buf)[4]);
132                    else
133                        osAbi = htobe(((uint32_t*)data->d_buf)[4]);
134
135                    switch(osAbi) {
136                      case 0:
137                        opSys = ObjectFile::Linux;
138                        break;
139                      case 2:
140                        opSys = ObjectFile::Solaris;
141                        break;
142                    }
143                } // if section found
144                if (!strcmp(".SUNW_version", elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name)))
145                        opSys = ObjectFile::Solaris;
146                if (!strcmp(".stab.index", elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name)))
147                        opSys = ObjectFile::Solaris;
148
149            section = elf_getscn(elf, ++secIdx);
150            } // while sections
151        }
152
153        elf_end(elf);
154        return new ElfObject(fname, fd, len, data, arch, opSys);
155    }
156}
157
158
159ElfObject::ElfObject(const string &_filename, int _fd,
160                     size_t _len, uint8_t *_data,
161                     Arch _arch, OpSys _opSys)
162    : ObjectFile(_filename, _fd, _len, _data, _arch, _opSys)
163
164{
165    Elf *elf;
166    GElf_Ehdr ehdr;
167
168    // check that header matches library version
169    if (elf_version(EV_CURRENT) == EV_NONE)
170        panic("wrong elf version number!");
171
172    // get a pointer to elf structure
173    elf = elf_memory((char*)fileData,len);
174    // will only fail if fd is invalid
175    assert(elf != NULL);
176
177    // Check that we actually have a elf file
178    if (gelf_getehdr(elf, &ehdr) ==0) {
179        panic("Not ELF, shouldn't be here");
180    }
181
182    entry = ehdr.e_entry;
183
184
185    // initialize segment sizes to 0 in case they're not present
186    text.size = data.size = bss.size = 0;
187
188    for (int i = 0; i < ehdr.e_phnum; ++i) {
189        GElf_Phdr phdr;
190        if (gelf_getphdr(elf, i, &phdr) == 0) {
191            panic("gelf_getphdr failed for section %d", i);
192        }
193
194        // for now we don't care about non-loadable segments
195        if (!(phdr.p_type & PT_LOAD))
196            continue;
197
198        // the headers don't explicitly distinguish text from data,
199        // but empirically the text segment comes first.
200        if (text.size == 0) {  // haven't seen text segment yet
201            text.baseAddr = phdr.p_vaddr;
202            text.size = phdr.p_filesz;
203            text.fileImage = fileData + phdr.p_offset;
204            // if there's any padding at the end that's not in the
205            // file, call it the bss.  This happens in the "text"
206            // segment if there's only one loadable segment (as for
207            // kernel images).
208            bss.size = phdr.p_memsz - phdr.p_filesz;
209            bss.baseAddr = phdr.p_vaddr + phdr.p_filesz;
210            bss.fileImage = NULL;
211        } else if (data.size == 0) { // have text, this must be data
212            data.baseAddr = phdr.p_vaddr;
213            data.size = phdr.p_filesz;
214            data.fileImage = fileData + phdr.p_offset;
215            // if there's any padding at the end that's not in the
216            // file, call it the bss.  Warn if this happens for both
217            // the text & data segments (should only have one bss).
218            if (phdr.p_memsz - phdr.p_filesz > 0 && bss.size != 0) {
219                warn("Two implied bss segments in file!\n");
220            }
221            bss.size = phdr.p_memsz - phdr.p_filesz;
222            bss.baseAddr = phdr.p_vaddr + phdr.p_filesz;
223            bss.fileImage = NULL;
224        } else {
225            warn("More than two loadable segments in ELF object.");
226            warn("Ignoring segment @ 0x%x length 0x%x.",
227                 phdr.p_vaddr, phdr.p_filesz);
228        }
229    }
230
231    // should have found at least one loadable segment
232    assert(text.size != 0);
233
234    DPRINTFR(Loader, "text: 0x%x %d\ndata: 0x%x %d\nbss: 0x%x %d\n",
235             text.baseAddr, text.size, data.baseAddr, data.size,
236             bss.baseAddr, bss.size);
237
238    elf_end(elf);
239
240    // We will actually read the sections when we need to load them
241}
242
243
244bool
245ElfObject::loadSomeSymbols(SymbolTable *symtab, int binding)
246{
247    Elf *elf;
248    int sec_idx = 1; // there is a 0 but it is nothing, go figure
249    Elf_Scn *section;
250    GElf_Shdr shdr;
251    Elf_Data *data;
252    int count, ii;
253    bool found = false;
254    GElf_Sym sym;
255
256    if (!symtab)
257        return false;
258
259    // check that header matches library version
260    if (elf_version(EV_CURRENT) == EV_NONE)
261        panic("wrong elf version number!");
262
263    // get a pointer to elf structure
264    elf = elf_memory((char*)fileData,len);
265
266    assert(elf != NULL);
267
268    // Get the first section
269    section = elf_getscn(elf, sec_idx);
270
271    // While there are no more sections
272    while (section != NULL) {
273        gelf_getshdr(section, &shdr);
274
275        if (shdr.sh_type == SHT_SYMTAB) {
276            found = true;
277            data = elf_getdata(section, NULL);
278            count = shdr.sh_size / shdr.sh_entsize;
279            DPRINTF(Loader, "Found Symbol Table, %d symbols present\n", count);
280
281            // loop through all the symbols, only loading global ones
282            for (ii = 0; ii < count; ++ii) {
283                gelf_getsym(data, ii, &sym);
284                if (GELF_ST_BIND(sym.st_info) == binding) {
285                   symtab->insert(sym.st_value,
286                                  elf_strptr(elf, shdr.sh_link, sym.st_name));
287                }
288            }
289        }
290        ++sec_idx;
291        section = elf_getscn(elf, sec_idx);
292    }
293
294    elf_end(elf);
295
296    return found;
297}
298
299bool
300ElfObject::loadGlobalSymbols(SymbolTable *symtab)
301{
302    return loadSomeSymbols(symtab, STB_GLOBAL);
303}
304
305bool
306ElfObject::loadLocalSymbols(SymbolTable *symtab)
307{
308    return loadSomeSymbols(symtab, STB_LOCAL);
309}
310