elf_object.cc revision 2600 
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                ehdr.e_machine == EM_SPARC32PLUS) {
87            arch = ObjectFile::SPARC;
88        } else if (ehdr.e_machine == EM_MIPS
89                && ehdr.e_ident[EI_CLASS] == ELFCLASS32) {
90            arch = ObjectFile::Mips;
91        } else if (ehdr.e_ident[EI_CLASS] == ELFCLASS64) {
92            arch = ObjectFile::Alpha;
93        } else {
94            warn("Unknown architecture: %d\n", ehdr.e_machine);
95            arch = ObjectFile::UnknownArch;
96        }
97
98        //Detect the operating system
99        switch (ehdr.e_ident[EI_OSABI])
100        {
101
102          case ELFOSABI_LINUX:
103            opSys = ObjectFile::Linux;
104            break;
105          case ELFOSABI_SOLARIS:
106            opSys = ObjectFile::Solaris;
107            break;
108          case ELFOSABI_TRU64:
109            opSys = ObjectFile::Tru64;
110            break;
111          default:
112            opSys = ObjectFile::UnknownOpSys;
113        }
114
115        //take a look at the .note.ABI section
116        //It can let us know what's what.
117        if (opSys == ObjectFile::UnknownOpSys) {
118            Elf_Scn *section;
119            GElf_Shdr shdr;
120            Elf_Data *data;
121            uint32_t osAbi;;
122            int secIdx = 1;
123
124            // Get the first section
125            section = elf_getscn(elf, secIdx);
126
127            // While there are no more sections
128            while (section != NULL && opSys == ObjectFile::UnknownOpSys) {
129                gelf_getshdr(section, &shdr);
130                if (shdr.sh_type == SHT_NOTE && !strcmp(".note.ABI-tag",
131                            elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name))) {
132                    // we have found a ABI note section
133                    // Check the 5th 32bit word for OS  0 == linux, 1 == hurd,
134                    // 2 == solaris, 3 == freebsd
135                    data = elf_rawdata(section, NULL);
136                    assert(data->d_buf);
137                    if(ehdr.e_ident[EI_DATA] == ELFDATA2LSB)
138                        osAbi = htole(((uint32_t*)data->d_buf)[4]);
139                    else
140                        osAbi = htobe(((uint32_t*)data->d_buf)[4]);
141
142                    switch(osAbi) {
143                      case 0:
144                        opSys = ObjectFile::Linux;
145                        break;
146                      case 2:
147                        opSys = ObjectFile::Solaris;
148                        break;
149                    }
150                } // if section found
151                if (!strcmp(".SUNW_version", elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name)))
152                        opSys = ObjectFile::Solaris;
153                if (!strcmp(".stab.index", elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name)))
154                        opSys = ObjectFile::Solaris;
155
156            section = elf_getscn(elf, ++secIdx);
157            } // while sections
158        }
159
160        elf_end(elf);
161        return new ElfObject(fname, fd, len, data, arch, opSys);
162    }
163}
164
165
166ElfObject::ElfObject(const string &_filename, int _fd,
167                     size_t _len, uint8_t *_data,
168                     Arch _arch, OpSys _opSys)
169    : ObjectFile(_filename, _fd, _len, _data, _arch, _opSys)
170
171{
172    Elf *elf;
173    GElf_Ehdr ehdr;
174
175    // check that header matches library version
176    if (elf_version(EV_CURRENT) == EV_NONE)
177        panic("wrong elf version number!");
178
179    // get a pointer to elf structure
180    elf = elf_memory((char*)fileData,len);
181    // will only fail if fd is invalid
182    assert(elf != NULL);
183
184    // Check that we actually have a elf file
185    if (gelf_getehdr(elf, &ehdr) ==0) {
186        panic("Not ELF, shouldn't be here");
187    }
188
189    entry = ehdr.e_entry;
190
191
192    // initialize segment sizes to 0 in case they're not present
193    text.size = data.size = bss.size = 0;
194
195    for (int i = 0; i < ehdr.e_phnum; ++i) {
196        GElf_Phdr phdr;
197        if (gelf_getphdr(elf, i, &phdr) == 0) {
198            panic("gelf_getphdr failed for section %d", i);
199        }
200
201        // for now we don't care about non-loadable segments
202        if (!(phdr.p_type & PT_LOAD))
203            continue;
204
205        // the headers don't explicitly distinguish text from data,
206        // but empirically the text segment comes first.
207        if (text.size == 0) {  // haven't seen text segment yet
208            text.baseAddr = phdr.p_vaddr;
209            text.size = phdr.p_filesz;
210            text.fileImage = fileData + phdr.p_offset;
211            // if there's any padding at the end that's not in the
212            // file, call it the bss.  This happens in the "text"
213            // segment if there's only one loadable segment (as for
214            // kernel images).
215            bss.size = phdr.p_memsz - phdr.p_filesz;
216            bss.baseAddr = phdr.p_vaddr + phdr.p_filesz;
217            bss.fileImage = NULL;
218        } else if (data.size == 0) { // have text, this must be data
219            data.baseAddr = phdr.p_vaddr;
220            data.size = phdr.p_filesz;
221            data.fileImage = fileData + phdr.p_offset;
222            // if there's any padding at the end that's not in the
223            // file, call it the bss.  Warn if this happens for both
224            // the text & data segments (should only have one bss).
225            if (phdr.p_memsz - phdr.p_filesz > 0 && bss.size != 0) {
226                warn("Two implied bss segments in file!\n");
227            }
228            bss.size = phdr.p_memsz - phdr.p_filesz;
229            bss.baseAddr = phdr.p_vaddr + phdr.p_filesz;
230            bss.fileImage = NULL;
231        } else {
232            warn("More than two loadable segments in ELF object.");
233            warn("Ignoring segment @ 0x%x length 0x%x.",
234                 phdr.p_vaddr, phdr.p_filesz);
235        }
236    }
237
238    // should have found at least one loadable segment
239    assert(text.size != 0);
240
241    DPRINTFR(Loader, "text: 0x%x %d\ndata: 0x%x %d\nbss: 0x%x %d\n",
242             text.baseAddr, text.size, data.baseAddr, data.size,
243             bss.baseAddr, bss.size);
244
245    elf_end(elf);
246
247    // We will actually read the sections when we need to load them
248}
249
250
251bool
252ElfObject::loadSomeSymbols(SymbolTable *symtab, int binding)
253{
254    Elf *elf;
255    int sec_idx = 1; // there is a 0 but it is nothing, go figure
256    Elf_Scn *section;
257    GElf_Shdr shdr;
258    Elf_Data *data;
259    int count, ii;
260    bool found = false;
261    GElf_Sym sym;
262
263    if (!symtab)
264        return false;
265
266    // check that header matches library version
267    if (elf_version(EV_CURRENT) == EV_NONE)
268        panic("wrong elf version number!");
269
270    // get a pointer to elf structure
271    elf = elf_memory((char*)fileData,len);
272
273    assert(elf != NULL);
274
275    // Get the first section
276    section = elf_getscn(elf, sec_idx);
277
278    // While there are no more sections
279    while (section != NULL) {
280        gelf_getshdr(section, &shdr);
281
282        if (shdr.sh_type == SHT_SYMTAB) {
283            found = true;
284            data = elf_getdata(section, NULL);
285            count = shdr.sh_size / shdr.sh_entsize;
286            DPRINTF(Loader, "Found Symbol Table, %d symbols present\n", count);
287
288            // loop through all the symbols, only loading global ones
289            for (ii = 0; ii < count; ++ii) {
290                gelf_getsym(data, ii, &sym);
291                if (GELF_ST_BIND(sym.st_info) == binding) {
292                   symtab->insert(sym.st_value,
293                                  elf_strptr(elf, shdr.sh_link, sym.st_name));
294                }
295            }
296        }
297        ++sec_idx;
298        section = elf_getscn(elf, sec_idx);
299    }
300
301    elf_end(elf);
302
303    return found;
304}
305
306bool
307ElfObject::loadGlobalSymbols(SymbolTable *symtab)
308{
309    return loadSomeSymbols(symtab, STB_GLOBAL);
310}
311
312bool
313ElfObject::loadLocalSymbols(SymbolTable *symtab)
314{
315    return loadSomeSymbols(symtab, STB_LOCAL);
316}
317