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sortix--sortix/sortix/elf.cpp
2013-12-17 14:30:37 +01:00

396 lines
12 KiB
C++

/*******************************************************************************
Copyright(C) Jonas 'Sortie' Termansen 2011, 2012, 2013.
This file is part of Sortix.
Sortix is free software: you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation, either version 3 of the License, or (at your option) any later
version.
Sortix is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
details.
You should have received a copy of the GNU General Public License along with
Sortix. If not, see <http://www.gnu.org/licenses/>.
elf.cpp
Constructs processes from ELF files.
*******************************************************************************/
#include <sys/types.h>
#include <assert.h>
#include <errno.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include <sortix/mman.h>
#include <sortix/kernel/platform.h>
#include <sortix/kernel/memorymanagement.h>
#include <sortix/kernel/process.h>
#include <sortix/kernel/symbol.h>
#include "elf.h"
namespace Sortix {
namespace ELF {
static int ToProgramSectionType(int flags)
{
switch ( flags & (PF_X | PF_R | PF_W) )
{
case 0:
return SEG_NONE;
case PF_X:
case PF_X | PF_R:
case PF_X | PF_W:
case PF_X | PF_R | PF_W:
return SEG_TEXT;
case PF_R:
case PF_W:
case PF_R | PF_W:
default:
return SEG_DATA;
}
}
// TODO: This code doesn't respect that the size of program headers and section
// headers may vary depending on the ELF header and that using a simple
// table indexation isn't enough.
addr_t Construct32(Process* process, const uint8_t* file, size_t filelen)
{
if ( filelen < sizeof(Header32) )
return 0;
const Header32* header = (const Header32*) file;
// Check for little endian.
if ( header->dataencoding != DATA2LSB )
return 0;
if ( header->version != CURRENTVERSION )
return 0;
addr_t entry = header->entry;
// Find the location of the program headers.
addr_t phtbloffset = header->programheaderoffset;
if ( filelen < phtbloffset )
return 0;
addr_t phtblpos = ((addr_t) file) + phtbloffset;
size_t phsize = header->programheaderentrysize;
const ProgramHeader32* phtbl = (const ProgramHeader32*) phtblpos;
// Validate that all program headers are present.
uint16_t numprogheaders = header->numprogramheaderentries;
size_t neededfilelen = phtbloffset + numprogheaders * phsize;
if ( filelen < neededfilelen )
return 0;
// Prepare the process for execution (clean up address space, etc.)
process->ResetForExecute();
// Flush the TLB such that no stale information from the last
// address space is used when creating the new one.
Memory::Flush();
// Create all the segments in the final process.
// TODO: Handle errors on bad/malicious input or out-of-mem!
for ( uint16_t i = 0; i < numprogheaders; i++ )
{
const ProgramHeader32* pht = &(phtbl[i]);
if ( pht->type != PT_LOAD )
continue;
addr_t virtualaddr = pht->virtualaddr;
addr_t mapto = Page::AlignDown(virtualaddr);
addr_t mapbytes = virtualaddr - mapto + pht->memorysize;
assert(pht->offset % pht->align == virtualaddr % pht->align);
assert(pht->offset + pht->filesize < filelen);
assert(pht->filesize <= pht->memorysize);
ProcessSegment* segment = new ProcessSegment;
if ( segment == NULL )
return 0;
segment->position = mapto;
segment->size = Page::AlignUp(mapbytes);
segment->type = ToProgramSectionType(pht->flags);
int prot = PROT_FORK | PROT_KREAD | PROT_KWRITE;
if ( pht->flags & PF_X ) { prot |= PROT_EXEC; }
if ( pht->flags & PF_R ) { prot |= PROT_READ; }
if ( pht->flags & PF_W ) { prot |= PROT_WRITE; }
if ( segment->Intersects(process->segments) )
{
delete segment;
return 0;
}
if ( !Memory::MapRange(mapto, mapbytes, prot) )
// TODO: Memory leak of segment?
return 0;
// Insert our newly allocated memory into the processes segment
// list such that it can be reclaimed later.
if ( process->segments )
process->segments->prev = segment;
segment->next = process->segments;
process->segments = segment;
// Copy as much data as possible and memset the rest to 0.
uint8_t* memdest = (uint8_t*) virtualaddr;
uint8_t* memsource = (uint8_t*) (((addr_t)file) + pht->offset);
memcpy(memdest, memsource, pht->filesize);
memset(memdest + pht->filesize, 0, pht->memorysize - pht->filesize);
}
// Find the location of the section headers.
addr_t shtblpos = (addr_t) file + header->sectionheaderoffset;
const SectionHeader32* shtbl = (const SectionHeader32*) shtblpos;
const SectionHeader32* section_names_section = shtbl + header->sectionheaderstringindex;
const char* section_names = (const char*) (file + section_names_section->offset);
// Find the string table.
const SectionHeader32* string_table_section = NULL;
for ( size_t i = 0; i < header->numsectionheaderentries; i++ )
if ( !strcmp(section_names + shtbl[i].name, ".strtab") )
{
string_table_section = shtbl + i;
break;
}
// Find the symbol table.
const SectionHeader32* symbol_table_section = NULL;
for ( size_t i = 0; i < header->numsectionheaderentries; i++ )
if ( !strcmp(section_names + shtbl[i].name, ".symtab") )
{
symbol_table_section = shtbl + i;
break;
}
if ( !string_table_section || !symbol_table_section )
return entry;
// Prepare copying debug information.
const char* elf_string_table = (const char*) (file + string_table_section->offset);
size_t elf_string_table_size = string_table_section->size;
const Symbol32* elf_symbols = (const Symbol32*) (file + symbol_table_section->offset);
size_t elf_symbol_count = symbol_table_section->size / sizeof(Symbol32);
// Duplicate the string table.
char* string_table = new char[elf_string_table_size];
if ( !string_table )
return entry;
memcpy(string_table, elf_string_table, elf_string_table_size);
// Duplicate the symbol table.
Symbol* symbol_table = new Symbol[elf_symbol_count-1];
if ( !symbol_table )
{
delete[] string_table;
return entry;
}
// Copy all entires except the leading null entry.
for ( size_t i = 1; i < elf_symbol_count; i++ )
{
symbol_table[i-1].address = elf_symbols[i].st_value;
symbol_table[i-1].size = elf_symbols[i].st_size;
symbol_table[i-1].name = string_table + elf_symbols[i].st_name;
}
process->string_table = string_table;
process->string_table_length = elf_string_table_size;
process->symbol_table = symbol_table;
process->symbol_table_length = elf_symbol_count-1;
return entry;
}
addr_t Construct64(Process* process, const uint8_t* file, size_t filelen)
{
#if !defined(__x86_64__)
(void) process;
(void) file;
(void) filelen;
return errno = ENOEXEC, 0;
#else
if ( filelen < sizeof(Header64) )
return 0;
const Header64* header = (const Header64*) file;
// Check for little endian.
if ( header->dataencoding != DATA2LSB )
return 0;
if ( header->version != CURRENTVERSION )
return 0;
addr_t entry = header->entry;
// Find the location of the program headers.
addr_t phtbloffset = header->programheaderoffset;
if ( filelen < phtbloffset )
return 0;
addr_t phtblpos = ((addr_t) file) + phtbloffset;
size_t phsize = header->programheaderentrysize;
const ProgramHeader64* phtbl = (const ProgramHeader64*) phtblpos;
// Validate that all program headers are present.
uint16_t numprogheaders = header->numprogramheaderentries;
size_t neededfilelen = phtbloffset + numprogheaders * phsize;
if ( filelen < neededfilelen )
return 0;
// Prepare the process for execution (clean up address space, etc.)
process->ResetForExecute();
// Flush the TLB such that no stale information from the last
// address space is used when creating the new one.
Memory::Flush();
// Create all the segments in the final process.
// TODO: Handle errors on bad/malicious input or out-of-mem!
for ( uint16_t i = 0; i < numprogheaders; i++ )
{
const ProgramHeader64* pht = &(phtbl[i]);
if ( pht->type != PT_LOAD )
continue;
addr_t virtualaddr = pht->virtualaddr;
addr_t mapto = Page::AlignDown(virtualaddr);
addr_t mapbytes = virtualaddr - mapto + pht->memorysize;
assert(pht->offset % pht->align == virtualaddr % pht->align);
assert(pht->offset + pht->filesize < filelen);
assert(pht->filesize <= pht->memorysize);
ProcessSegment* segment = new ProcessSegment;
if ( segment == NULL )
return 0;
segment->position = mapto;
segment->size = Page::AlignUp(mapbytes);
segment->type = ToProgramSectionType(pht->flags);
int prot = PROT_FORK | PROT_KREAD | PROT_KWRITE;
if ( pht->flags & PF_X ) { prot |= PROT_EXEC; }
if ( pht->flags & PF_R ) { prot |= PROT_READ; }
if ( pht->flags & PF_W ) { prot |= PROT_WRITE; }
if ( segment->Intersects(process->segments) )
{
delete segment;
return 0;
}
if ( !Memory::MapRange(mapto, mapbytes, prot) )
{
// TODO: Memory leak of segment?
return 0;
}
// Insert our newly allocated memory into the processes segment
// list such that it can be reclaimed later.
if ( process->segments )
process->segments->prev = segment;
segment->next = process->segments;
process->segments = segment;
// Copy as much data as possible and memset the rest to 0.
uint8_t* memdest = (uint8_t*) virtualaddr;
uint8_t* memsource = (uint8_t*) (((addr_t)file) + pht->offset);
memcpy(memdest, memsource, pht->filesize);
memset(memdest + pht->filesize, 0, pht->memorysize - pht->filesize);
}
// Find the location of the section headers.
addr_t shtblpos = (addr_t) file + header->sectionheaderoffset;
const SectionHeader64* shtbl = (const SectionHeader64*) shtblpos;
const SectionHeader64* section_names_section = shtbl + header->sectionheaderstringindex;
const char* section_names = (const char*) (file + section_names_section->offset);
// Find the string table.
const SectionHeader64* string_table_section = NULL;
for ( size_t i = 0; i < header->numsectionheaderentries; i++ )
if ( !strcmp(section_names + shtbl[i].name, ".strtab") )
{
string_table_section = shtbl + i;
break;
}
// Find the symbol table.
const SectionHeader64* symbol_table_section = NULL;
for ( size_t i = 0; i < header->numsectionheaderentries; i++ )
if ( !strcmp(section_names + shtbl[i].name, ".symtab") )
{
symbol_table_section = shtbl + i;
break;
}
if ( !string_table_section || !symbol_table_section )
return entry;
// Prepare copying debug information.
const char* elf_string_table = (const char*) (file + string_table_section->offset);
size_t elf_string_table_size = string_table_section->size;
const Symbol64* elf_symbols = (const Symbol64*) (file + symbol_table_section->offset);
size_t elf_symbol_count = symbol_table_section->size / sizeof(Symbol64);
// Duplicate the string table.
char* string_table = new char[elf_string_table_size];
if ( !string_table )
return entry;
memcpy(string_table, elf_string_table, elf_string_table_size);
// Duplicate the symbol table.
Symbol* symbol_table = new Symbol[elf_symbol_count-1];
if ( !symbol_table )
{
delete[] string_table;
return entry;
}
// Copy all entires except the leading null entry.
for ( size_t i = 1; i < elf_symbol_count; i++ )
{
symbol_table[i-1].address = elf_symbols[i].st_value;
symbol_table[i-1].size = elf_symbols[i].st_size;
symbol_table[i-1].name = string_table + elf_symbols[i].st_name;
}
process->string_table = string_table;
process->string_table_length = elf_string_table_size;
process->symbol_table = symbol_table;
process->symbol_table_length = elf_symbol_count-1;
return entry;
#endif
}
addr_t Construct(Process* process, const void* file, size_t filelen)
{
if ( filelen < sizeof(Header) )
return errno = ENOEXEC, 0;
const Header* header = (const Header*) file;
if ( !(header->magic[0] == 0x7F && header->magic[1] == 'E' &&
header->magic[2] == 'L' && header->magic[3] == 'F' ) )
return errno = ENOEXEC, 0;
switch ( header->fileclass )
{
case CLASS32: return Construct32(process, (const uint8_t*) file, filelen);
case CLASS64: return Construct64(process, (const uint8_t*) file, filelen);
default:
return 0;
}
}
} // namespace ELF
} // namespace Sortix