elf_object.cc revision 5335 
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 if (ehdr.e_machine == EM_ARM) {
92            arch = ObjectFile::Arm;
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          case ELFOSABI_ARM:
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_paddr + 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    // initialize segment sizes to 0 in case they're not present
223    text.size = data.size = bss.size = 0;
224
225    int secIdx = 1;
226    Elf_Scn *section;
227    GElf_Shdr shdr;
228
229    // The first address of some important sections.
230    Addr textSecStart = 0;
231    Addr dataSecStart = 0;
232    Addr bssSecStart = 0;
233
234    // Get the first section
235    section = elf_getscn(elf, secIdx);
236
237    // Find the beginning of the most interesting sections.
238    while (section != NULL) {
239        gelf_getshdr(section, &shdr);
240        char * secName = elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name);
241
242        if (!strcmp(".text", secName)) {
243            textSecStart = shdr.sh_addr;
244        } else if (!strcmp(".data", secName)) {
245            dataSecStart = shdr.sh_addr;
246        } else if (!strcmp(".bss", secName)) {
247            bssSecStart = shdr.sh_addr;
248        }
249
250        section = elf_getscn(elf, ++secIdx);
251    }
252
253    // Go through all the segments in the program, record them, and scrape
254    // out information about the text, data, and bss areas needed by other
255    // code.
256    for (int i = 0; i < ehdr.e_phnum; ++i) {
257        GElf_Phdr phdr;
258        if (gelf_getphdr(elf, i, &phdr) == 0) {
259            panic("gelf_getphdr failed for segment %d.", i);
260        }
261
262        // for now we don't care about non-loadable segments
263        if (!(phdr.p_type & PT_LOAD))
264            continue;
265
266        // Check to see if this segment contains the bss section.
267        if (phdr.p_paddr <= bssSecStart &&
268                phdr.p_paddr + phdr.p_memsz > bssSecStart &&
269                phdr.p_memsz - phdr.p_filesz > 0) {
270            bss.baseAddr = phdr.p_paddr + phdr.p_filesz;
271            bss.size = phdr.p_memsz - phdr.p_filesz;
272            bss.fileImage = NULL;
273        }
274
275        // Check to see if this is the text or data segment
276        if (phdr.p_vaddr <= textSecStart &&
277                phdr.p_vaddr + phdr.p_filesz > textSecStart) {
278            text.baseAddr = phdr.p_paddr;
279            text.size = phdr.p_filesz;
280            text.fileImage = fileData + phdr.p_offset;
281        } else if (phdr.p_vaddr <= dataSecStart &&
282                phdr.p_vaddr + phdr.p_filesz > dataSecStart) {
283            data.baseAddr = phdr.p_paddr;
284            data.size = phdr.p_filesz;
285            data.fileImage = fileData + phdr.p_offset;
286        } else {
287            Segment extra;
288            extra.baseAddr = phdr.p_paddr;
289            extra.size = phdr.p_filesz;
290            extra.fileImage = fileData + phdr.p_offset;
291            extraSegments.push_back(extra);
292        }
293    }
294
295    // should have found at least one loadable segment
296    assert(text.size != 0);
297
298    DPRINTFR(Loader, "text: 0x%x %d\ndata: 0x%x %d\nbss: 0x%x %d\n",
299             text.baseAddr, text.size, data.baseAddr, data.size,
300             bss.baseAddr, bss.size);
301
302    elf_end(elf);
303
304    // We will actually read the sections when we need to load them
305}
306
307
308bool
309ElfObject::loadSomeSymbols(SymbolTable *symtab, int binding)
310{
311    Elf *elf;
312    int sec_idx = 1; // there is a 0 but it is nothing, go figure
313    Elf_Scn *section;
314    GElf_Shdr shdr;
315    Elf_Data *data;
316    int count, ii;
317    bool found = false;
318    GElf_Sym sym;
319
320    if (!symtab)
321        return false;
322
323    // check that header matches library version
324    if (elf_version(EV_CURRENT) == EV_NONE)
325        panic("wrong elf version number!");
326
327    // get a pointer to elf structure
328    elf = elf_memory((char*)fileData,len);
329
330    assert(elf != NULL);
331
332    // Get the first section
333    section = elf_getscn(elf, sec_idx);
334
335    // While there are no more sections
336    while (section != NULL) {
337        gelf_getshdr(section, &shdr);
338
339        if (shdr.sh_type == SHT_SYMTAB) {
340            found = true;
341            data = elf_getdata(section, NULL);
342            count = shdr.sh_size / shdr.sh_entsize;
343            DPRINTF(Loader, "Found Symbol Table, %d symbols present\n", count);
344
345            // loop through all the symbols, only loading global ones
346            for (ii = 0; ii < count; ++ii) {
347                gelf_getsym(data, ii, &sym);
348                if (GELF_ST_BIND(sym.st_info) == binding) {
349                   symtab->insert(sym.st_value,
350                                  elf_strptr(elf, shdr.sh_link, sym.st_name));
351                }
352            }
353        }
354        ++sec_idx;
355        section = elf_getscn(elf, sec_idx);
356    }
357
358    elf_end(elf);
359
360    return found;
361}
362
363bool
364ElfObject::loadGlobalSymbols(SymbolTable *symtab, Addr addrMask)
365{
366    return loadSomeSymbols(symtab, STB_GLOBAL);
367}
368
369bool
370ElfObject::loadLocalSymbols(SymbolTable *symtab, Addr addrMask)
371{
372    return loadSomeSymbols(symtab, STB_LOCAL);
373}
374
375bool
376ElfObject::loadSections(Port *memPort, Addr addrMask)
377{
378    if (!ObjectFile::loadSections(memPort, addrMask))
379        return false;
380
381    vector<Segment>::iterator extraIt;
382    for (extraIt = extraSegments.begin();
383            extraIt != extraSegments.end(); extraIt++) {
384        if (!loadSection(&(*extraIt), memPort, addrMask)) {
385            return false;
386        }
387    }
388    return true;
389}
390
391void
392ElfObject::getSections()
393{
394    Elf *elf;
395    int sec_idx = 1; // there is a 0 but it is nothing, go figure
396    Elf_Scn *section;
397    GElf_Shdr shdr;
398
399    GElf_Ehdr ehdr;
400
401    assert(!sectionNames.size());
402
403    // check that header matches library version
404    if (elf_version(EV_CURRENT) == EV_NONE)
405        panic("wrong elf version number!");
406
407    // get a pointer to elf structure
408    elf = elf_memory((char*)fileData,len);
409    assert(elf != NULL);
410
411    // Check that we actually have a elf file
412    if (gelf_getehdr(elf, &ehdr) ==0) {
413        panic("Not ELF, shouldn't be here");
414    }
415
416    // Get the first section
417    section = elf_getscn(elf, sec_idx);
418
419    // While there are no more sections
420    while (section != NULL) {
421        gelf_getshdr(section, &shdr);
422        sectionNames.insert(elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name));
423        section = elf_getscn(elf, ++sec_idx);
424    } // while sections
425}
426
427bool
428ElfObject::sectionExists(string sec)
429{
430    if (!sectionNames.size())
431        getSections();
432    return sectionNames.find(sec) != sectionNames.end();
433}
434
435
436