elf_object.cc revision 5090 
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#include "gelf.h"
35
36#include "base/loader/elf_object.hh"
37#include "base/loader/symtab.hh"
38#include "base/misc.hh"
39#include "base/trace.hh"	// for DPRINTF
40#include "sim/byteswap.hh"
41
42using namespace std;
43
44ObjectFile *
45ElfObject::tryFile(const string &fname, int fd, size_t len, uint8_t *data)
46{
47    Elf *elf;
48    GElf_Ehdr ehdr;
49    Arch arch = UnknownArch;
50    OpSys opSys = UnknownOpSys;
51
52    // check that header matches library version
53    if (elf_version(EV_CURRENT) == EV_NONE)
54        panic("wrong elf version number!");
55
56    // get a pointer to elf structure
57    elf = elf_memory((char*)data,len);
58    // will only fail if fd is invalid
59    assert(elf != NULL);
60
61    // Check that we actually have a elf file
62    if (gelf_getehdr(elf, &ehdr) ==0) {
63        DPRINTFR(Loader, "Not ELF\n");
64        elf_end(elf);
65        return NULL;
66    } else {
67        //Detect the architecture
68        //Since we don't know how to check for alpha right now, we'll
69        //just assume if it wasn't something else and it's 64 bit, that's
70        //what it must be.
71        if (ehdr.e_machine == EM_SPARC64 ||
72                (ehdr.e_machine == EM_SPARC &&
73                 ehdr.e_ident[EI_CLASS] == ELFCLASS64)||
74                ehdr.e_machine == EM_SPARCV9) {
75            arch = ObjectFile::SPARC64;
76        } else if (ehdr.e_machine == EM_SPARC32PLUS ||
77                        (ehdr.e_machine == EM_SPARC &&
78                         ehdr.e_ident[EI_CLASS] == ELFCLASS32)) {
79            arch = ObjectFile::SPARC32;
80        } else if (ehdr.e_machine == EM_MIPS
81                && ehdr.e_ident[EI_CLASS] == ELFCLASS32) {
82            arch = ObjectFile::Mips;
83        } else if (ehdr.e_machine == EM_X86_64 &&
84                ehdr.e_ident[EI_CLASS] == ELFCLASS64) {
85            //In the future, we might want to differentiate between 32 bit
86            //and 64 bit x86 processes in case there are differences in their
87            //initial stack frame.
88            arch = ObjectFile::X86;
89        } else if (ehdr.e_ident[EI_CLASS] == ELFCLASS64) {
90            arch = ObjectFile::Alpha;
91        } else {
92            warn("Unknown architecture: %d\n", ehdr.e_machine);
93            arch = ObjectFile::UnknownArch;
94        }
95
96        //Detect the operating system
97        switch (ehdr.e_ident[EI_OSABI])
98        {
99
100          case ELFOSABI_LINUX:
101            opSys = ObjectFile::Linux;
102            break;
103          case ELFOSABI_SOLARIS:
104            opSys = ObjectFile::Solaris;
105            break;
106          case ELFOSABI_TRU64:
107            opSys = ObjectFile::Tru64;
108            break;
109          default:
110            opSys = ObjectFile::UnknownOpSys;
111        }
112
113        //take a look at the .note.ABI section
114        //It can let us know what's what.
115        if (opSys == ObjectFile::UnknownOpSys) {
116            Elf_Scn *section;
117            GElf_Shdr shdr;
118            Elf_Data *data;
119            uint32_t osAbi;;
120            int secIdx = 1;
121
122            // Get the first section
123            section = elf_getscn(elf, secIdx);
124
125            // While there are no more sections
126            while (section != NULL && opSys == ObjectFile::UnknownOpSys) {
127                gelf_getshdr(section, &shdr);
128                if (shdr.sh_type == SHT_NOTE && !strcmp(".note.ABI-tag",
129                            elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name))) {
130                    // we have found a ABI note section
131                    // Check the 5th 32bit word for OS  0 == linux, 1 == hurd,
132                    // 2 == solaris, 3 == freebsd
133                    data = elf_rawdata(section, NULL);
134                    assert(data->d_buf);
135                    if(ehdr.e_ident[EI_DATA] == ELFDATA2LSB)
136                        osAbi = htole(((uint32_t*)data->d_buf)[4]);
137                    else
138                        osAbi = htobe(((uint32_t*)data->d_buf)[4]);
139
140                    switch(osAbi) {
141                      case 0:
142                        opSys = ObjectFile::Linux;
143                        break;
144                      case 2:
145                        opSys = ObjectFile::Solaris;
146                        break;
147                    }
148                } // if section found
149                if (!strcmp(".SUNW_version", elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name)))
150                        opSys = ObjectFile::Solaris;
151                if (!strcmp(".stab.index", elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name)))
152                        opSys = ObjectFile::Solaris;
153
154            section = elf_getscn(elf, ++secIdx);
155            } // while sections
156        }
157
158        ElfObject * result = new ElfObject(fname, fd, len, data, arch, opSys);
159
160        //The number of headers in the file
161        result->_programHeaderCount = ehdr.e_phnum;
162        //Record the size of each entry
163        result->_programHeaderSize = ehdr.e_phentsize;
164        if(result->_programHeaderCount) //If there is a program header table
165        {
166            //Figure out the virtual address of the header table in the
167            //final memory image. We use the program headers themselves
168            //to translate from a file offset to the address in the image.
169            GElf_Phdr phdr;
170            uint64_t e_phoff = ehdr.e_phoff;
171            result->_programHeaderTable = 0;
172            for(int hdrnum = 0; hdrnum < result->_programHeaderCount; hdrnum++)
173            {
174                gelf_getphdr(elf, hdrnum, &phdr);
175                //Check if we've found the segment with the headers in it
176                if(phdr.p_offset <= e_phoff &&
177                        phdr.p_offset + phdr.p_filesz > e_phoff)
178                {
179                    result->_programHeaderTable = phdr.p_vaddr + e_phoff;
180                    break;
181                }
182            }
183        }
184        else
185            result->_programHeaderTable = 0;
186
187
188        elf_end(elf);
189        return result;
190    }
191}
192
193
194ElfObject::ElfObject(const string &_filename, int _fd,
195                     size_t _len, uint8_t *_data,
196                     Arch _arch, OpSys _opSys)
197    : ObjectFile(_filename, _fd, _len, _data, _arch, _opSys)
198
199{
200    Elf *elf;
201    GElf_Ehdr ehdr;
202
203    // check that header matches library version
204    if (elf_version(EV_CURRENT) == EV_NONE)
205        panic("wrong elf version number!");
206
207    // get a pointer to elf structure
208    elf = elf_memory((char*)fileData,len);
209    // will only fail if fd is invalid
210    assert(elf != NULL);
211
212    // Check that we actually have a elf file
213    if (gelf_getehdr(elf, &ehdr) ==0) {
214        panic("Not ELF, shouldn't be here");
215    }
216
217    entry = ehdr.e_entry;
218
219    // initialize segment sizes to 0 in case they're not present
220    text.size = data.size = bss.size = 0;
221
222    int secIdx = 1;
223    Elf_Scn *section;
224    GElf_Shdr shdr;
225
226    // The first address of some important sections.
227    Addr textSecStart = 0;
228    Addr dataSecStart = 0;
229    Addr bssSecStart = 0;
230
231    // Get the first section
232    section = elf_getscn(elf, secIdx);
233
234    // Find the beginning of the most interesting sections.
235    while (section != NULL) {
236        gelf_getshdr(section, &shdr);
237        char * secName = elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name);
238
239        if (!strcmp(".text", secName)) {
240            textSecStart = shdr.sh_addr;
241        } else if (!strcmp(".data", secName)) {
242            dataSecStart = shdr.sh_addr;
243        } else if (!strcmp(".bss", secName)) {
244            bssSecStart = shdr.sh_addr;
245        }
246
247        section = elf_getscn(elf, ++secIdx);
248    }
249
250    // Go through all the segments in the program, record them, and scrape
251    // out information about the text, data, and bss areas needed by other
252    // code.
253    for (int i = 0; i < ehdr.e_phnum; ++i) {
254        GElf_Phdr phdr;
255        if (gelf_getphdr(elf, i, &phdr) == 0) {
256            panic("gelf_getphdr failed for segment %d.", i);
257        }
258
259        // for now we don't care about non-loadable segments
260        if (!(phdr.p_type & PT_LOAD))
261            continue;
262
263        // Check to see if this segment contains the bss section.
264        if (phdr.p_vaddr <= bssSecStart &&
265                phdr.p_vaddr + phdr.p_memsz > bssSecStart &&
266                phdr.p_memsz - phdr.p_filesz > 0) {
267            bss.baseAddr = phdr.p_vaddr + phdr.p_filesz;
268            bss.size = phdr.p_memsz - phdr.p_filesz;
269            bss.fileImage = NULL;
270        }
271
272        // Check to see if this is the text or data segment
273        if (phdr.p_vaddr <= textSecStart &&
274                phdr.p_vaddr + phdr.p_filesz > textSecStart) {
275            text.baseAddr = phdr.p_vaddr;
276            text.size = phdr.p_filesz;
277            text.fileImage = fileData + phdr.p_offset;
278        } else if (phdr.p_vaddr <= dataSecStart &&
279                phdr.p_vaddr + phdr.p_filesz > dataSecStart) {
280            data.baseAddr = phdr.p_vaddr;
281            data.size = phdr.p_filesz;
282            data.fileImage = fileData + phdr.p_offset;
283        } else {
284            Segment extra;
285            extra.baseAddr = phdr.p_vaddr;
286            extra.size = phdr.p_filesz;
287            extra.fileImage = fileData + phdr.p_offset;
288            extraSegments.push_back(extra);
289        }
290    }
291
292    // should have found at least one loadable segment
293    assert(text.size != 0);
294
295    DPRINTFR(Loader, "text: 0x%x %d\ndata: 0x%x %d\nbss: 0x%x %d\n",
296             text.baseAddr, text.size, data.baseAddr, data.size,
297             bss.baseAddr, bss.size);
298
299    elf_end(elf);
300
301    // We will actually read the sections when we need to load them
302}
303
304
305bool
306ElfObject::loadSomeSymbols(SymbolTable *symtab, int binding)
307{
308    Elf *elf;
309    int sec_idx = 1; // there is a 0 but it is nothing, go figure
310    Elf_Scn *section;
311    GElf_Shdr shdr;
312    Elf_Data *data;
313    int count, ii;
314    bool found = false;
315    GElf_Sym sym;
316
317    if (!symtab)
318        return false;
319
320    // check that header matches library version
321    if (elf_version(EV_CURRENT) == EV_NONE)
322        panic("wrong elf version number!");
323
324    // get a pointer to elf structure
325    elf = elf_memory((char*)fileData,len);
326
327    assert(elf != NULL);
328
329    // Get the first section
330    section = elf_getscn(elf, sec_idx);
331
332    // While there are no more sections
333    while (section != NULL) {
334        gelf_getshdr(section, &shdr);
335
336        if (shdr.sh_type == SHT_SYMTAB) {
337            found = true;
338            data = elf_getdata(section, NULL);
339            count = shdr.sh_size / shdr.sh_entsize;
340            DPRINTF(Loader, "Found Symbol Table, %d symbols present\n", count);
341
342            // loop through all the symbols, only loading global ones
343            for (ii = 0; ii < count; ++ii) {
344                gelf_getsym(data, ii, &sym);
345                if (GELF_ST_BIND(sym.st_info) == binding) {
346                   symtab->insert(sym.st_value,
347                                  elf_strptr(elf, shdr.sh_link, sym.st_name));
348                }
349            }
350        }
351        ++sec_idx;
352        section = elf_getscn(elf, sec_idx);
353    }
354
355    elf_end(elf);
356
357    return found;
358}
359
360bool
361ElfObject::loadGlobalSymbols(SymbolTable *symtab, Addr addrMask)
362{
363    return loadSomeSymbols(symtab, STB_GLOBAL);
364}
365
366bool
367ElfObject::loadLocalSymbols(SymbolTable *symtab, Addr addrMask)
368{
369    return loadSomeSymbols(symtab, STB_LOCAL);
370}
371
372bool
373ElfObject::loadSections(Port *memPort, Addr addrMask)
374{
375    if (!ObjectFile::loadSections(memPort, addrMask))
376        return false;
377
378    vector<Segment>::iterator extraIt;
379    for (extraIt = extraSegments.begin();
380            extraIt != extraSegments.end(); extraIt++) {
381        if (!loadSection(&(*extraIt), memPort, addrMask)) {
382            return false;
383        }
384    }
385    return true;
386}
387
388void
389ElfObject::getSections()
390{
391    Elf *elf;
392    int sec_idx = 1; // there is a 0 but it is nothing, go figure
393    Elf_Scn *section;
394    GElf_Shdr shdr;
395
396    GElf_Ehdr ehdr;
397
398    assert(!sectionNames.size());
399
400    // check that header matches library version
401    if (elf_version(EV_CURRENT) == EV_NONE)
402        panic("wrong elf version number!");
403
404    // get a pointer to elf structure
405    elf = elf_memory((char*)fileData,len);
406    assert(elf != NULL);
407
408    // Check that we actually have a elf file
409    if (gelf_getehdr(elf, &ehdr) ==0) {
410        panic("Not ELF, shouldn't be here");
411    }
412
413    // Get the first section
414    section = elf_getscn(elf, sec_idx);
415
416    // While there are no more sections
417    while (section != NULL) {
418        gelf_getshdr(section, &shdr);
419        sectionNames.insert(elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name));
420        section = elf_getscn(elf, ++sec_idx);
421    } // while sections
422}
423
424bool
425ElfObject::sectionExists(string sec)
426{
427    if (!sectionNames.size())
428        getSections();
429    return sectionNames.find(sec) != sectionNames.end();
430}
431
432
433