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Fixes and cleanup to elf loader code.

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base/loader/elf_object.cc:
    - Use program header instead of section headers for loading.
    The old code doesn't work for Alpha/Linux user binaries.

    - Deal properly with single-segment ELF executables (e.g. kernels)...
    haven't tested this but it looks like it matches the functionality
    of the patch the L4::Pistachio guys sent.

    - Factor load symbol code into one common function.

    - Some formatting to match style conventions.

    - Only include libelf stuff in .cc file, not .hh.
base/loader/elf_object.hh:
    - Use program header instead of section headers for loading.
    The old code doesn't work for Alpha/Linux user binaries.

    - Factor load symbol code into one common function.

    - Only include libelf stuff in .cc file, not .hh.

--HG--
extra : convert_revision : 782062d09d43083b01e65cd645c941f49c27640a
This commit is contained in:
Steve Reinhardt
2004-01-14 22:30:16 -08:00
parent fe32fdece2
commit 9f2aae4e28
2 changed files with 108 additions and 175 deletions
Download Patch File Download Diff File Expand all files Collapse all files

270
base/loader/elf_object.cc
View File

@@ -28,6 +28,14 @@
#include <string>
// Because of the -Wundef flag we have to do this
#define __LIBELF_INTERNAL__ 0
#define __LIBELF64_LINUX 1
#define __LIBELF_NEED_LINK_H 0
#include <libelf/libelf.h>
#include <libelf/gelf.h>
#include "base/loader/elf_object.hh"
#include "mem/functional_mem/functional_memory.hh"
@@ -44,24 +52,21 @@ ElfObject::tryFile(const string &fname, int fd, size_t len, uint8_t *data)
Elf *elf;
GElf_Ehdr ehdr;
/* check that header matches library version */
// check that header matches library version
assert(elf_version(EV_CURRENT) != EV_NONE);
/* get a pointer to elf structure */
// get a pointer to elf structure
elf = elf_memory((char*)data,len);
/* will only fail if fd is invalid */
// will only fail if fd is invalid
assert(elf != NULL);
/* Check that we actually have a elf file */
if(gelf_getehdr(elf, &ehdr) ==0)
{
// Check that we actually have a elf file
if (gelf_getehdr(elf, &ehdr) ==0) {
DPRINTFR(Loader, "Not ELF\n");
elf_end(elf);
return NULL;
}
else
{
else {
if (ehdr.e_ident[EI_CLASS] == ELFCLASS32)
panic("32 bit ELF Binary, Not Supported");
if (ehdr.e_machine != EM_ALPHA)
@@ -81,125 +86,107 @@ ElfObject::ElfObject(const string &_filename, int _fd,
: ObjectFile(_filename, _fd, _len, _data, _arch, _opSys)
{
Elf *elf;
GElf_Ehdr ehdr;
/* check that header matches library version */
// check that header matches library version
assert(elf_version(EV_CURRENT) != EV_NONE);
/* get a pointer to elf structure */
// get a pointer to elf structure
elf = elf_memory((char*)fileData,len);
/* will only fail if fd is invalid */
// will only fail if fd is invalid
assert(elf != NULL);
/* Check that we actually have a elf file */
if(gelf_getehdr(elf, &ehdr) ==0)
{
// Check that we actually have a elf file
if (gelf_getehdr(elf, &ehdr) ==0) {
panic("Not ELF, shouldn't be here");
}
entry = ehdr.e_entry;
// initialize segment sizes to 0 in case they're not present
text.size = data.size = bss.size = 0;
for (int i = 0; i < ehdr.e_phnum; ++i) {
GElf_Phdr phdr;
if (gelf_getphdr(elf, i, &phdr) == 0) {
panic("gelf_getphdr failed for section %d", i);
}
// for now we don't care about non-loadable segments
if (!(phdr.p_type & PT_LOAD))
continue;
// the headers don't explicitly distinguish text from data,
// but empirically the text segment comes first.
if (text.size == 0) { // haven't seen text segment yet
text.baseAddr = phdr.p_vaddr;
text.size = phdr.p_filesz;
// remember where the data is for loadSections()
fileTextBits = fileData + phdr.p_offset;
// if there's any padding at the end that's not in the
// file, call it the bss. This happens in the "text"
// segment if there's only one loadable segment (as for
// kernel images).
bss.size = phdr.p_memsz - phdr.p_filesz;
bss.baseAddr = phdr.p_vaddr + phdr.p_filesz;
}
else if (data.size == 0) { // have text, this must be data
data.baseAddr = phdr.p_vaddr;
data.size = phdr.p_filesz;
// remember where the data is for loadSections()
fileDataBits = fileData + phdr.p_offset;
// if there's any padding at the end that's not in the
// file, call it the bss. Warn if this happens for both
// the text & data segments (should only have one bss).
if (phdr.p_memsz - phdr.p_filesz > 0 && bss.size != 0) {
warn("Two implied bss segments in file!\n");
}
bss.size = phdr.p_memsz - phdr.p_filesz;
bss.baseAddr = phdr.p_vaddr + phdr.p_filesz;
}
}
// should have found at least one loadable segment
assert(text.size != 0);
DPRINTFR(Loader, "text: 0x%x %d\ndata: 0x%x %d\nbss: 0x%x %d\n",
text.baseAddr, text.size, data.baseAddr, data.size,
bss.baseAddr, bss.size);
elf_end(elf);
/* We will actually read the sections when we need to load them*/
// We will actually read the sections when we need to load them
}
bool
ElfObject::loadSections(FunctionalMemory *mem, bool loadPhys)
{
Elf *elf;
int secidx = 1; /* there is a 0 but it is nothing, go figure*/
Elf_Scn *section;
GElf_Shdr shdr;
GElf_Ehdr ehdr;
Addr textAddr = text.baseAddr;
Addr dataAddr = data.baseAddr;
Addr address;
char *secname;
/* check that header matches library version */
assert(elf_version(EV_CURRENT) != EV_NONE);
/* get a pointer to elf structure */
elf = elf_memory((char*)fileData,len);
assert(elf != NULL);
/* Check that we actually have a elf file */
if(gelf_getehdr(elf, &ehdr) ==0)
{
panic("Not ELF, shouldn't be here");
if (loadPhys) {
textAddr &= (ULL(1) << 40) - 1;
dataAddr &= (ULL(1) << 40) - 1;
}
/* Get the first section */
section = elf_getscn(elf, secidx);
/* While there are no more sections */
while (section != NULL)
{
gelf_getshdr(section, &shdr);
if (shdr.sh_flags & SHF_ALLOC)
{
/* we should load this */
DPRINTF(Loader,"Name: %20s Address: 0x%016llx Size: 0x%08llx Offset: 0x%08llx Flags:0x%08llx %s\n",
elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name), shdr.sh_addr,
shdr.sh_size, shdr.sh_offset, shdr.sh_flags, shdr.sh_flags & SHF_ALLOC ? "ALLOC" : "");
secname = elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name);
if(secname)
{
if (strcmp(secname, ".text")==0)
{
text.baseAddr = shdr.sh_addr;
text.size = shdr.sh_size;
}
if (strcmp(secname, ".data")==0)
{
data.baseAddr = shdr.sh_addr;
data.size = shdr.sh_size;
}
if (strcmp(secname, ".bss")==0)
{
bss.baseAddr = shdr.sh_addr;
bss.size = shdr.sh_size;
}
}
if(shdr.sh_size != 0)
{
if (loadPhys)
{
address = shdr.sh_addr &= (ULL(1) << 40) - 1;
mem->prot_write(address, fileData + shdr.sh_offset, shdr.sh_size);
}
else
{
mem->prot_write(shdr.sh_addr, fileData + shdr.sh_offset, shdr.sh_size);
}
}
}
++secidx;
section = elf_getscn(elf, secidx);
}
elf_end(elf);
// Since we don't really have an MMU and all memory is
// zero-filled, there's no need to set up the BSS segment.
if (text.size != 0)
mem->prot_write(textAddr, fileTextBits, text.size);
if (data.size != 0)
mem->prot_write(dataAddr, fileDataBits, data.size);
return true;
}
bool
ElfObject::loadGlobalSymbols(SymbolTable *symtab)
ElfObject::loadSomeSymbols(SymbolTable *symtab, int binding)
{
Elf *elf;
int secidx = 1; /* there is a 0 but it is nothing, go figure*/
int secidx = 1; // there is a 0 but it is nothing, go figure
Elf_Scn *section;
GElf_Shdr shdr;
Elf_Data *data;
@@ -210,38 +197,33 @@ ElfObject::loadGlobalSymbols(SymbolTable *symtab)
if (!symtab)
return false;
/* check that header matches library version */
// check that header matches library version
assert(elf_version(EV_CURRENT) != EV_NONE);
/* get a pointer to elf structure */
// get a pointer to elf structure
elf = elf_memory((char*)fileData,len);
assert(elf != NULL);
/* Get the first section */
// Get the first section
section = elf_getscn(elf, secidx);
/* While there are no more sections */
while (section != NULL)
{
// While there are no more sections
while (section != NULL) {
gelf_getshdr(section, &shdr);
if(shdr.sh_type == SHT_SYMTAB)
{
if (shdr.sh_type == SHT_SYMTAB) {
found = true;
data = elf_getdata(section, NULL);
count = shdr.sh_size / shdr.sh_entsize;
DPRINTF(Loader, "Found Symbol Table, %d symbols present\n", count);
/* loop through all the symbols, only loading global ones*/
for (ii = 0; ii < count; ++ii)
{
// loop through all the symbols, only loading global ones
for (ii = 0; ii < count; ++ii) {
gelf_getsym(data, ii, &sym);
if (GELF_ST_BIND(sym.st_info) & STB_GLOBAL)
{
symtab->insert(sym.st_value, elf_strptr(elf, shdr.sh_link, sym.st_name));
if (GELF_ST_BIND(sym.st_info) & binding) {
symtab->insert(sym.st_value,
elf_strptr(elf, shdr.sh_link, sym.st_name));
}
}
}
@@ -254,62 +236,14 @@ ElfObject::loadGlobalSymbols(SymbolTable *symtab)
return found;
}
bool
ElfObject::loadGlobalSymbols(SymbolTable *symtab)
{
return loadSomeSymbols(symtab, STB_GLOBAL);
}
bool
ElfObject::loadLocalSymbols(SymbolTable *symtab)
{
Elf *elf;
int secidx = 1; /* there is a 0 but it is nothing, go figure*/
Elf_Scn *section;
GElf_Shdr shdr;
Elf_Data *data;
int count, ii;
bool found = false;
GElf_Sym sym;
if (!symtab)
return false;
/* check that header matches library version */
assert(elf_version(EV_CURRENT) != EV_NONE);
/* get a pointer to elf structure */
elf = elf_memory((char*)fileData,len);
assert(elf != NULL);
/* Get the first section */
section = elf_getscn(elf, secidx);
/* While there are no more sections */
while (section != NULL)
{
gelf_getshdr(section, &shdr);
if(shdr.sh_type == SHT_SYMTAB)
{
found = true;
data = elf_getdata(section, NULL);
count = shdr.sh_size / shdr.sh_entsize;
DPRINTF(Loader, "Found Symbol Table, %d symbols present\n", count);
/* loop through all the symbols, only loading global ones*/
for (ii = 0; ii < count; ++ii)
{
gelf_getsym(data, ii, &sym);
if (GELF_ST_BIND(sym.st_info) & STB_LOCAL)
{
symtab->insert(sym.st_value, elf_strptr(elf, shdr.sh_link, sym.st_name));
}
}
}
++secidx;
section = elf_getscn(elf, secidx);
}
elf_end(elf);
return found;
return loadSomeSymbols(symtab, STB_LOCAL);
}

13
base/loader/elf_object.hh
View File

@@ -29,19 +29,18 @@
#ifndef __ELF_OBJECT_HH__
#define __ELF_OBJECT_HH__
/* Because of the -Wundef flag we have to do this */
#define __LIBELF_INTERNAL__ 0
#define __LIBELF64_LINUX 1
#define __LIBELF_NEED_LINK_H 0
#include <libelf/libelf.h>
#include <libelf/gelf.h>
#include "base/loader/object_file.hh"
class ElfObject : public ObjectFile
{
protected:
uint8_t *fileTextBits; //!< Pointer to file's text segment image
uint8_t *fileDataBits; //!< Pointer to file's data segment image
/// Helper functions for loadGlobalSymbols() and loadLocalSymbols().
bool loadSomeSymbols(SymbolTable *symtab, int binding);
ElfObject(const std::string &_filename, int _fd,
size_t _len, uint8_t *_data,
Arch _arch, OpSys _opSys);