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/*
* Copyright (c) 2011-2013, 2019 ARM Limited
* All rights reserved
*
* The license below extends only to copyright in the software and shall
* not be construed as granting a license to any other intellectual
* property including but not limited to intellectual property relating
* to a hardware implementation of the functionality of the software
* licensed hereunder. You may use the software subject to the license
* terms below provided that you ensure that this notice is replicated
* unmodified and in its entirety in all distributions of the software,
* modified or unmodified, in source code or in binary form.
*
* Copyright (c) 2003-2005 The Regents of The University of Michigan
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met: redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer;
* redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution;
* neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "base/loader/elf_object.hh"
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <cassert>
#include <string>
#include "base/bitfield.hh"
#include "base/loader/symtab.hh"
#include "base/logging.hh"
#include "base/trace.hh"
#include "debug/Loader.hh"
#include "gelf.h"
#include "sim/byteswap.hh"
namespace Loader
{
ObjectFile *
ElfObjectFormat::load(ImageFileDataPtr ifd)
{
// check that header matches library version
if (elf_version(EV_CURRENT) == EV_NONE)
panic("wrong elf version number!");
ObjectFile *object = nullptr;
// get a pointer to elf structure
// Check that we actually have a elf file
Elf *elf =
elf_memory((char *)const_cast<uint8_t *>(ifd->data()), ifd->len());
assert(elf);
GElf_Ehdr ehdr;
if (gelf_getehdr(elf, &ehdr) == 0)
DPRINTFR(Loader, "Not ELF\n");
else
object = new ElfObject(ifd);
elf_end(elf);
return object;
}
namespace
{
ElfObjectFormat elfObjectFormat;
std::string interpDir;
} // anonymous namespace
void
setInterpDir(const std::string &dirname)
{
fatal_if(!interpDir.empty(),
"Error: setInterpDir has already been called once\n");
interpDir = dirname;
}
ElfObject::ElfObject(ImageFileDataPtr ifd) : ObjectFile(ifd)
{
// get a pointer to elf structure
elf = elf_memory((char *)const_cast<uint8_t *>(imageData->data()),
imageData->len());
assert(elf);
gelf_getehdr(elf, &ehdr);
determineArch();
determineOpSys();
entry = ehdr.e_entry;
_programHeaderCount = ehdr.e_phnum;
_programHeaderSize = ehdr.e_phentsize;
// Go through all the segments in the program and record them.
for (int i = 0; i < ehdr.e_phnum; ++i) {
GElf_Phdr phdr;
if (gelf_getphdr(elf, i, &phdr) == 0) {
panic("gelf_getphdr failed for segment %d.", i);
}
if (phdr.p_type == PT_LOAD)
handleLoadableSegment(phdr, i);
if (phdr.p_type == PT_INTERP) {
// Make sure the interpreter is an valid ELF file.
auto interp_path = getInterpPath(phdr);
ObjectFile *obj = createObjectFile(interp_path);
interpreter = dynamic_cast<ElfObject *>(obj);
assert(interpreter != nullptr);
_symtab.insert(obj->symtab());
}
}
// should have found at least one loadable segment
warn_if(image.segments().empty(),
"No loadable segments in '%s'. ELF file corrupted?\n",
imageData->filename());
for (M5_VAR_USED auto &seg: image.segments())
DPRINTFR(Loader, "%s\n", seg);
// We will actually read the sections when we need to load them
// check that header matches library version
if (elf_version(EV_CURRENT) == EV_NONE)
panic("wrong elf version number!");
// Get the first section
int sec_idx = 1; // there is a 0 but it is nothing, go figure
Elf_Scn *section = elf_getscn(elf, sec_idx);
// While there are no more sections
while (section) {
GElf_Shdr shdr;
gelf_getshdr(section, &shdr);
if (shdr.sh_type == SHT_SYMTAB) {
Elf_Data *data = elf_getdata(section, nullptr);
int count = shdr.sh_size / shdr.sh_entsize;
DPRINTF(Loader, "Found Symbol Table, %d symbols present.", count);
// Loop through all the symbols.
for (int i = 0; i < count; ++i) {
GElf_Sym sym;
gelf_getsym(data, i, &sym);
char *sym_name = elf_strptr(elf, shdr.sh_link, sym.st_name);
if (!sym_name || sym_name[0] == '$')
continue;
Loader::Symbol symbol;
symbol.address = sym.st_value;
symbol.name = sym_name;
switch (GELF_ST_BIND(sym.st_info)) {
case STB_GLOBAL:
symbol.binding = Loader::Symbol::Binding::Global;
break;
case STB_LOCAL:
symbol.binding = Loader::Symbol::Binding::Local;
break;
case STB_WEAK:
symbol.binding = Loader::Symbol::Binding::Weak;
break;
default:
continue;
}
if (_symtab.insert(symbol)) {
DPRINTF(Loader, "Symbol: %-40s value %#x.\n",
symbol.name, symbol.address);
}
}
}
++sec_idx;
section = elf_getscn(elf, sec_idx);
}
}
std::string
ElfObject::getInterpPath(const GElf_Phdr &phdr) const
{
// This is the interpreter path as specified in the elf file
const std::string elf_path = (char *)imageData->data() + phdr.p_offset;
if (!interpDir.empty())
return interpDir + elf_path;
else
return elf_path;
}
void
ElfObject::determineArch()
{
auto &emach = ehdr.e_machine;
auto &eclass = ehdr.e_ident[EI_CLASS];
auto &edata = ehdr.e_ident[EI_DATA];
// Detect the architecture
if (emach == EM_SPARC64 || (emach == EM_SPARC && eclass == ELFCLASS64) ||
emach == EM_SPARCV9) {
arch = SPARC64;
} else if (emach == EM_SPARC32PLUS ||
(emach == EM_SPARC && eclass == ELFCLASS32)) {
arch = SPARC32;
} else if (emach == EM_MIPS && eclass == ELFCLASS32) {
arch = Mips;
if (edata != ELFDATA2LSB) {
fatal("The binary you're trying to load is compiled for big "
"endian MIPS. gem5\nonly supports little endian MIPS. "
"Please recompile your binary.\n");
}
} else if (emach == EM_X86_64 && eclass == ELFCLASS64) {
arch = X86_64;
} else if (emach == EM_386 && eclass == ELFCLASS32) {
arch = I386;
} else if (emach == EM_ARM && eclass == ELFCLASS32) {
arch = bits(ehdr.e_entry, 0) ? Thumb : Arm;
} else if (emach == EM_AARCH64 && eclass == ELFCLASS64) {
arch = Arm64;
} else if (emach == EM_RISCV) {
arch = (eclass == ELFCLASS64) ? Riscv64 : Riscv32;
} else if (emach == EM_PPC && eclass == ELFCLASS32) {
arch = Power;
if (edata != ELFDATA2MSB) {
fatal("The binary you're trying to load is compiled for "
"little endian Power.\ngem5 only supports big "
"endian Power. Please recompile your binary.\n");
}
} else if (emach == EM_PPC64) {
fatal("The binary you're trying to load is compiled for 64-bit "
"Power. M5\n only supports 32-bit Power. Please "
"recompile your binary.\n");
} else {
warn("Unknown architecture: %d\n", emach);
}
}
void
ElfObject::determineOpSys()
{
// Detect the operating system
switch (ehdr.e_ident[EI_OSABI]) {
case ELFOSABI_LINUX:
opSys = Linux;
return;
case ELFOSABI_SOLARIS:
opSys = Solaris;
return;
case ELFOSABI_TRU64:
opSys = Tru64;
return;
case ELFOSABI_ARM:
opSys = LinuxArmOABI;
return;
case ELFOSABI_FREEBSD:
opSys = FreeBSD;
return;
default:
opSys = UnknownOpSys;
}
Elf_Scn *section = elf_getscn(elf, 1);
for (int sec_idx = 1; section; section = elf_getscn(elf, ++sec_idx)) {
GElf_Shdr shdr;
gelf_getshdr(section, &shdr);
char *e_str = elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name);
if (shdr.sh_type == SHT_NOTE && !strcmp(".note.ABI-tag", e_str)) {
// we have found a ABI note section
// Check the 5th 32bit word for OS 0 == linux, 1 == hurd,
// 2 == solaris, 3 == freebsd
Elf_Data *raw_data = elf_rawdata(section, nullptr);
assert(raw_data && raw_data->d_buf);
uint32_t raw_abi = ((uint32_t *)raw_data->d_buf)[4];
bool is_le = ehdr.e_ident[EI_DATA] == ELFDATA2LSB;
uint32_t os_abi = is_le ? htole(raw_abi) : htobe(raw_abi);
switch (os_abi) {
case 0:
opSys = Linux;
return;
case 1:
fatal("gem5 does not support the HURD ABI.\n");
case 2:
opSys = Solaris;
return;
case 3:
opSys = FreeBSD;
return;
}
}
if (!strcmp(".SUNW_version", e_str) || !strcmp(".stab.index", e_str)) {
opSys = Solaris;
return;
}
}
}
void
ElfObject::handleLoadableSegment(GElf_Phdr phdr, int seg_num)
{
auto name = std::to_string(seg_num);
if (phdr.p_memsz == 0) {
warn("Ignoring empty loadable segment %s", name);
return;
}
image.addSegment({ name, phdr.p_paddr, imageData,
phdr.p_offset, phdr.p_filesz });
Addr uninitialized = phdr.p_memsz - phdr.p_filesz;
if (uninitialized) {
// There may be parts of a segment which aren't included in the
// file. In those cases, we need to create a new segment with no
// data to take up the extra space. This should be zeroed when
// loaded into memory.
image.addSegment({ name + "(uninitialized)",
phdr.p_paddr + phdr.p_filesz, uninitialized });
}
const Addr file_start = phdr.p_offset;
const Addr file_end = file_start + phdr.p_filesz;
// If there is a program header table, figure out the virtual
// address of the header table in the final memory image. We use
// the program headers themselves to translate from a file offset
// to the address in the image.
if (file_start <= ehdr.e_phoff && file_end > ehdr.e_phoff)
_programHeaderTable = phdr.p_vaddr + (ehdr.e_phoff - file_start);
}
ElfObject::~ElfObject()
{
elf_end(elf);
}
void
ElfObject::getSections()
{
assert(!sectionNames.size());
// check that header matches library version
if (elf_version(EV_CURRENT) == EV_NONE)
panic("wrong elf version number!");
// get a pointer to elf structure
Elf *elf =
elf_memory((char *)const_cast<uint8_t *>(imageData->data()),
imageData->len());
assert(elf != NULL);
// Check that we actually have a elf file
GElf_Ehdr ehdr;
if (gelf_getehdr(elf, &ehdr) ==0) {
panic("Not ELF, shouldn't be here");
}
// Get the first section
int sec_idx = 1; // there is a 0 but it is nothing, go figure
Elf_Scn *section = elf_getscn(elf, sec_idx);
// While there are no more sections
while (section) {
GElf_Shdr shdr;
gelf_getshdr(section, &shdr);
sectionNames.insert(elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name));
section = elf_getscn(elf, ++sec_idx);
} // while sections
elf_end(elf);
}
bool
ElfObject::sectionExists(std::string sec)
{
if (!sectionNames.size())
getSections();
return sectionNames.find(sec) != sectionNames.end();
}
void
ElfObject::updateBias(Addr bias_addr)
{
// Record the bias.
ldBias = bias_addr;
// Patch the entry point with bias_addr.
entry += bias_addr;
// Patch segments with the bias_addr.
image.offset(bias_addr);
}
} // namespace Loader