elf_object.cc revision 4111:65fffcb4fae9 
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 * Authors: Steve Reinhardt
29 *          Ali Saidi
30 */
31
32#include <string>
33
34// Because of the -Wundef flag we have to do this
35#define __LIBELF_INTERNAL__     0
36#define __LIBELF_NEED_LINK_H    0
37#define __LIBELF_SYMBOL_VERSIONS 0
38
39#include "gelf.h"
40
41#include "base/loader/elf_object.hh"
42#include "base/misc.hh"
43
44#include "base/loader/symtab.hh"
45
46#include "base/trace.hh"	// for DPRINTF
47
48#include "sim/byteswap.hh"
49
50
51using namespace std;
52
53ObjectFile *
54ElfObject::tryFile(const string &fname, int fd, size_t len, uint8_t *data)
55{
56    Elf *elf;
57    GElf_Ehdr ehdr;
58    Arch arch = UnknownArch;
59    OpSys opSys = UnknownOpSys;
60
61    // check that header matches library version
62    if (elf_version(EV_CURRENT) == EV_NONE)
63        panic("wrong elf version number!");
64
65    // get a pointer to elf structure
66    elf = elf_memory((char*)data,len);
67    // will only fail if fd is invalid
68    assert(elf != NULL);
69
70    // Check that we actually have a elf file
71    if (gelf_getehdr(elf, &ehdr) ==0) {
72        DPRINTFR(Loader, "Not ELF\n");
73        elf_end(elf);
74        return NULL;
75    } else {
76        //Detect the architecture
77        //Since we don't know how to check for alpha right now, we'll
78        //just assume if it wasn't something else and it's 64 bit, that's
79        //what it must be.
80        if (ehdr.e_machine == EM_SPARC64 ||
81                (ehdr.e_machine == EM_SPARC &&
82                 ehdr.e_ident[EI_CLASS] == ELFCLASS64)||
83                ehdr.e_machine == EM_SPARCV9) {
84            arch = ObjectFile::SPARC64;
85        } else if (ehdr.e_machine == EM_SPARC32PLUS ||
86                        (ehdr.e_machine == EM_SPARC &&
87                         ehdr.e_ident[EI_CLASS] == ELFCLASS32)) {
88            arch = ObjectFile::SPARC32;
89        } else if (ehdr.e_machine == EM_MIPS
90                && ehdr.e_ident[EI_CLASS] == ELFCLASS32) {
91            arch = ObjectFile::Mips;
92        } else if (ehdr.e_ident[EI_CLASS] == ELFCLASS64) {
93            arch = ObjectFile::Alpha;
94        } else {
95            warn("Unknown architecture: %d\n", ehdr.e_machine);
96            arch = ObjectFile::UnknownArch;
97        }
98
99        //Detect the operating system
100        switch (ehdr.e_ident[EI_OSABI])
101        {
102
103          case ELFOSABI_LINUX:
104            opSys = ObjectFile::Linux;
105            break;
106          case ELFOSABI_SOLARIS:
107            opSys = ObjectFile::Solaris;
108            break;
109          case ELFOSABI_TRU64:
110            opSys = ObjectFile::Tru64;
111            break;
112          default:
113            opSys = ObjectFile::UnknownOpSys;
114        }
115
116        //take a look at the .note.ABI section
117        //It can let us know what's what.
118        if (opSys == ObjectFile::UnknownOpSys) {
119            Elf_Scn *section;
120            GElf_Shdr shdr;
121            Elf_Data *data;
122            uint32_t osAbi;;
123            int secIdx = 1;
124
125            // Get the first section
126            section = elf_getscn(elf, secIdx);
127
128            // While there are no more sections
129            while (section != NULL && opSys == ObjectFile::UnknownOpSys) {
130                gelf_getshdr(section, &shdr);
131                if (shdr.sh_type == SHT_NOTE && !strcmp(".note.ABI-tag",
132                            elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name))) {
133                    // we have found a ABI note section
134                    // Check the 5th 32bit word for OS  0 == linux, 1 == hurd,
135                    // 2 == solaris, 3 == freebsd
136                    data = elf_rawdata(section, NULL);
137                    assert(data->d_buf);
138                    if(ehdr.e_ident[EI_DATA] == ELFDATA2LSB)
139                        osAbi = htole(((uint32_t*)data->d_buf)[4]);
140                    else
141                        osAbi = htobe(((uint32_t*)data->d_buf)[4]);
142
143                    switch(osAbi) {
144                      case 0:
145                        opSys = ObjectFile::Linux;
146                        break;
147                      case 2:
148                        opSys = ObjectFile::Solaris;
149                        break;
150                    }
151                } // if section found
152                if (!strcmp(".SUNW_version", elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name)))
153                        opSys = ObjectFile::Solaris;
154                if (!strcmp(".stab.index", elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name)))
155                        opSys = ObjectFile::Solaris;
156
157            section = elf_getscn(elf, ++secIdx);
158            } // while sections
159        }
160
161        ElfObject * result = new ElfObject(fname, fd, len, data, arch, opSys);
162
163        //The number of headers in the file
164        result->_programHeaderCount = ehdr.e_phnum;
165        //Record the size of each entry
166        result->_programHeaderSize = ehdr.e_phentsize;
167        if(result->_programHeaderCount) //If there is a program header table
168        {
169            //Figure out the virtual address of the header table in the
170            //final memory image. We use the program headers themselves
171            //to translate from a file offset to the address in the image.
172            GElf_Phdr phdr;
173            uint64_t e_phoff = ehdr.e_phoff;
174            result->_programHeaderTable = 0;
175            for(int hdrnum = 0; hdrnum < result->_programHeaderCount; hdrnum++)
176            {
177                gelf_getphdr(elf, hdrnum, &phdr);
178                //Check if we've found the segment with the headers in it
179                if(phdr.p_offset <= e_phoff &&
180                        phdr.p_offset + phdr.p_filesz > e_phoff)
181                {
182                    result->_programHeaderTable = phdr.p_vaddr + e_phoff;
183                    break;
184                }
185            }
186        }
187        else
188            result->_programHeaderTable = 0;
189
190
191        elf_end(elf);
192        return result;
193    }
194}
195
196
197ElfObject::ElfObject(const string &_filename, int _fd,
198                     size_t _len, uint8_t *_data,
199                     Arch _arch, OpSys _opSys)
200    : ObjectFile(_filename, _fd, _len, _data, _arch, _opSys)
201
202{
203    Elf *elf;
204    GElf_Ehdr ehdr;
205
206    // check that header matches library version
207    if (elf_version(EV_CURRENT) == EV_NONE)
208        panic("wrong elf version number!");
209
210    // get a pointer to elf structure
211    elf = elf_memory((char*)fileData,len);
212    // will only fail if fd is invalid
213    assert(elf != NULL);
214
215    // Check that we actually have a elf file
216    if (gelf_getehdr(elf, &ehdr) ==0) {
217        panic("Not ELF, shouldn't be here");
218    }
219
220    entry = ehdr.e_entry;
221
222
223    // initialize segment sizes to 0 in case they're not present
224    text.size = data.size = bss.size = 0;
225
226    for (int i = 0; i < ehdr.e_phnum; ++i) {
227        GElf_Phdr phdr;
228        if (gelf_getphdr(elf, i, &phdr) == 0) {
229            panic("gelf_getphdr failed for section %d", i);
230        }
231
232        // for now we don't care about non-loadable segments
233        if (!(phdr.p_type & PT_LOAD))
234            continue;
235
236        // the headers don't explicitly distinguish text from data,
237        // but empirically the text segment comes first.
238        if (text.size == 0) {  // haven't seen text segment yet
239            text.baseAddr = phdr.p_vaddr;
240            text.size = phdr.p_filesz;
241            text.fileImage = fileData + phdr.p_offset;
242            // if there's any padding at the end that's not in the
243            // file, call it the bss.  This happens in the "text"
244            // segment if there's only one loadable segment (as for
245            // kernel images).
246            bss.size = phdr.p_memsz - phdr.p_filesz;
247            bss.baseAddr = phdr.p_vaddr + phdr.p_filesz;
248            bss.fileImage = NULL;
249        } else if (data.size == 0) { // have text, this must be data
250            data.baseAddr = phdr.p_vaddr;
251            data.size = phdr.p_filesz;
252            data.fileImage = fileData + phdr.p_offset;
253            // if there's any padding at the end that's not in the
254            // file, call it the bss.  Warn if this happens for both
255            // the text & data segments (should only have one bss).
256            if (phdr.p_memsz - phdr.p_filesz > 0 && bss.size != 0) {
257                warn("Two implied bss segments in file!\n");
258            }
259            bss.size = phdr.p_memsz - phdr.p_filesz;
260            bss.baseAddr = phdr.p_vaddr + phdr.p_filesz;
261            bss.fileImage = NULL;
262        } else {
263            warn("More than two loadable segments in ELF object.");
264            warn("Ignoring segment @ 0x%x length 0x%x.",
265                 phdr.p_vaddr, phdr.p_filesz);
266        }
267    }
268
269    // should have found at least one loadable segment
270    assert(text.size != 0);
271
272    DPRINTFR(Loader, "text: 0x%x %d\ndata: 0x%x %d\nbss: 0x%x %d\n",
273             text.baseAddr, text.size, data.baseAddr, data.size,
274             bss.baseAddr, bss.size);
275
276    elf_end(elf);
277
278    // We will actually read the sections when we need to load them
279}
280
281
282bool
283ElfObject::loadSomeSymbols(SymbolTable *symtab, int binding)
284{
285    Elf *elf;
286    int sec_idx = 1; // there is a 0 but it is nothing, go figure
287    Elf_Scn *section;
288    GElf_Shdr shdr;
289    Elf_Data *data;
290    int count, ii;
291    bool found = false;
292    GElf_Sym sym;
293
294    if (!symtab)
295        return false;
296
297    // check that header matches library version
298    if (elf_version(EV_CURRENT) == EV_NONE)
299        panic("wrong elf version number!");
300
301    // get a pointer to elf structure
302    elf = elf_memory((char*)fileData,len);
303
304    assert(elf != NULL);
305
306    // Get the first section
307    section = elf_getscn(elf, sec_idx);
308
309    // While there are no more sections
310    while (section != NULL) {
311        gelf_getshdr(section, &shdr);
312
313        if (shdr.sh_type == SHT_SYMTAB) {
314            found = true;
315            data = elf_getdata(section, NULL);
316            count = shdr.sh_size / shdr.sh_entsize;
317            DPRINTF(Loader, "Found Symbol Table, %d symbols present\n", count);
318
319            // loop through all the symbols, only loading global ones
320            for (ii = 0; ii < count; ++ii) {
321                gelf_getsym(data, ii, &sym);
322                if (GELF_ST_BIND(sym.st_info) == binding) {
323                   symtab->insert(sym.st_value,
324                                  elf_strptr(elf, shdr.sh_link, sym.st_name));
325                }
326            }
327        }
328        ++sec_idx;
329        section = elf_getscn(elf, sec_idx);
330    }
331
332    elf_end(elf);
333
334    return found;
335}
336
337bool
338ElfObject::loadGlobalSymbols(SymbolTable *symtab, Addr addrMask)
339{
340    return loadSomeSymbols(symtab, STB_GLOBAL);
341}
342
343bool
344ElfObject::loadLocalSymbols(SymbolTable *symtab, Addr addrMask)
345{
346    return loadSomeSymbols(symtab, STB_LOCAL);
347}
348
349bool
350ElfObject::isDynamic()
351{
352    Elf *elf;
353    int sec_idx = 1; // there is a 0 but it is nothing, go figure
354    Elf_Scn *section;
355    GElf_Shdr shdr;
356
357    GElf_Ehdr ehdr;
358
359    // check that header matches library version
360    if (elf_version(EV_CURRENT) == EV_NONE)
361        panic("wrong elf version number!");
362
363    // get a pointer to elf structure
364    elf = elf_memory((char*)fileData,len);
365    assert(elf != NULL);
366
367    // Check that we actually have a elf file
368    if (gelf_getehdr(elf, &ehdr) ==0) {
369        panic("Not ELF, shouldn't be here");
370    }
371
372    // Get the first section
373    section = elf_getscn(elf, sec_idx);
374
375    // While there are no more sections
376    while (section != NULL) {
377        gelf_getshdr(section, &shdr);
378        if (!strcmp(".interp", elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name)))
379            return true;
380        section = elf_getscn(elf, ++sec_idx);
381    } // while sections
382    return false;
383}
384
385
386