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Small and modular dynamic link-editor.

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bg- 2006-12-01 15:12:27 +00:00
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core/loader/cle.c Normal file
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/*
* Copyright (c) 2006, Swedish Institute of Computer Science
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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.
* 3. Neither the name of the Institute 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 INSTITUTE 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 INSTITUTE 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.
*
* @(#)$Id: cle.c,v 1.1 2006/12/01 15:12:27 bg- Exp $
*/
/*
* The Contiki dynamic Link Editor (CLE), ELF version.
*/
#include <stdio.h>
#include <string.h>
#include "contiki.h"
#include "loader/cle.h"
#include "loader/elf32.h"
#include "loader/symtab.h"
#define NDEBUG
#include "lib/assert.h"
#ifdef NDEBUG
#define PRINTF(...) do {} while (0)
#else
#define PRINTF(...) printf(__VA_ARGS__)
#endif
/*
* Parse object file located at offset start reading data using function
* pread. Save what is useful in info.
*/
int
cle_read_info(struct cle_info *info,
int (*pread)(void *, int, off_t),
off_t start)
{
/*
* Save stackspace by using a union!
*
* Beware that the contents of ehdr is gone when shdr is written!!!
*/
union {
struct elf32_ehdr ehdr;
struct elf32_shdr shdr;
} huge;
#define ehdr huge.ehdr
#define shdr huge.shdr
off_t shdrptr;
cle_off strs;
cle_half shnum; /* number shdrs */
cle_half shentsize; /* sizeof shdr */
cle_word strtabsize = 0;
int i, ret;
memset(info, 0x0, sizeof(*info));
ret = pread(&ehdr, sizeof(ehdr), start);
assert(ret > 0);
/* Make sure that we have a correct and compatible ELF header. */
if(memcmp(ehdr.e_ident, ELF_MAGIC_HEADER, ELF_MAGIC_HEADER_SIZE) != 0) {
return CLE_BAD_HEADER;
}
shdrptr = ehdr.e_shoff;
shentsize = ehdr.e_shentsize;
shnum = ehdr.e_shnum;
/* The string table section: holds the names of the sections. */
ret = pread(&shdr, sizeof(shdr), start + shdrptr + shentsize*ehdr.e_shstrndx);
assert(ret > 0);
/* BEWARE THAT ehdr IS NOW OVERWRITTEN!!! */
/*
* Get a pointer to the actual table of strings. This table holds
* the names of the sections, not the names of other symbols in the
* file (these are in the symtab section).
*/
strs = shdr.sh_offset;
/*
* The ".text" segment holds the actual code from the ELF file, the
* ".data" segment contains initialized data, the ".bss" segment
* holds the size of the unitialized data segment. The ".rela.text"
* and ".rela.data" segments contains relocation information for the
* contents of the ".text" and ".data" segments, respectively. The
* ".symtab" segment contains the symbol table for this file. The
* ".strtab" segment points to the actual string names used by the
* symbol table.
*
* In addition to grabbing pointers to the relevant sections, we
* also save the section index for resolving addresses in the
* relocator code.
*/
for(i = 0; i < shnum; ++i) {
ret = pread(&shdr, sizeof(shdr), shdrptr);
assert(ret > 0);
/* The name of the section is contained in the strings table. */
ret = pread(info->name, sizeof(info->name), start + strs + shdr.sh_name);
assert(ret > 0);
if(strncmp(info->name, ".text", 5) == 0) {
info->textoff = shdr.sh_offset;
info->textsize = shdr.sh_size;
info->text_shndx = i;
} else if(strncmp(info->name, ".rela.text", 10) == 0) {
info->textrelaoff = shdr.sh_offset;
info->textrelasize = shdr.sh_size;
} else if(strncmp(info->name, ".data", 5) == 0) {
info->dataoff = shdr.sh_offset;
info->datasize = shdr.sh_size;
info->data_shndx = i;
} else if(strncmp(info->name, ".rela.data", 10) == 0) {
info->datarelaoff = shdr.sh_offset;
info->datarelasize = shdr.sh_size;
} else if(strncmp(info->name, ".symtab", 7) == 0) {
info->symtaboff = shdr.sh_offset;
info->symtabsize = shdr.sh_size;
} else if(strncmp(info->name, ".strtab", 7) == 0) {
info->strtaboff = shdr.sh_offset;
strtabsize = shdr.sh_size;
} else if(strncmp(info->name, ".bss", 4) == 0) {
info->bsssize = shdr.sh_size;
info->bss_shndx = i;
} else {
info->name[sizeof(info->name) - 1] = 0;
PRINTF("cle: unknown section %.12s\n", info->name);
}
/* Move on to the next section header. */
shdrptr += shentsize;
}
if(info->symtabsize == 0) {
return CLE_NO_SYMTAB;
}
if(strtabsize == 0) {
return CLE_NO_STRTAB;
}
if(info->textsize == 0) {
return CLE_NO_TEXT;
}
return CLE_OK;
}
/*
* Update one reloc.
*
* Writing relocs is machine dependent and this function is MPS430
* specific!
*/
static inline int
cle_upd_reloc(cle_addr segmem, struct elf32_rela *rela, cle_addr addr)
{
memcpy(segmem + rela->r_offset, &addr, 2); /* Write reloc */
return 0;
}
/*
* Relocate one segment that has been copied to the location pointed
* to by segmem.
*
* Relocation info is read from offset reloff to (reloff + relsize)
* and the start of the object file is at start. Data is read using
* function pread.
*/
int
cle_relocate(struct cle_info *info,
int (*pread)(void *, int, off_t),
off_t start, /* Offset to start of file. */
cle_addr segmem, /* Where segment is stored in memory. */
cle_off reloff, /* .rela.<segment> start */
cle_word relsize) /* .rela.<segment> size */
{
struct elf32_rela rela;
struct elf32_sym s;
off_t off;
cle_addr addr;
int ret;
for(off = start + reloff;
off < start + reloff + relsize;
off += sizeof(struct elf32_rela)) {
ret = pread(&rela, sizeof(rela), off);
assert(ret > 0);
ret = pread(&s, sizeof(s),
start + info->symtaboff
+ sizeof(struct elf32_sym)*ELF32_R_SYM(rela.r_info));
assert(ret > 0);
if(s.st_shndx == info->bss_shndx) {
addr = info->bss;
} else if(s.st_shndx == info->data_shndx) {
addr = info->data;
} else if(s.st_shndx == info->text_shndx) {
addr = info->text;
} else {
addr = NULL;
}
if(s.st_name == 0) { /* No name, local symbol? */
if(addr == NULL) {
return CLE_UNKNOWN_SEGMENT;
}
} else {
ret = pread(info->name, sizeof(info->name),
start + info->strtaboff + s.st_name);
assert(ret > 0);
cle_addr sym = symtab_lookup(info->name);
if(addr == NULL && sym != NULL) { /* Imported symbol. */
addr = sym;
} else if(addr != NULL && sym == NULL) { /* Exported symbol. */
addr = addr + s.st_value;
} else if(addr == NULL && sym == NULL) {
PRINTF("cle: undefined reference to %.32s\n", info->name);
return CLE_UNDEFINED; /* Or COMMON symbol. */
} else if(addr != NULL && sym != NULL) {
PRINTF("cle: multiple definitions of %.32s\n", info->name);
return CLE_MULTIPLY_DEFINED;
}
}
addr += rela.r_addend;
cle_upd_reloc(segmem, &rela, addr);
}
return CLE_OK;
}
/*
* Search object file located at offset start using function
* pread. Search for symbol named symbol and return its address after
* relocation or NULL on failure.
*/
void *
cle_lookup(struct cle_info *info,
int (*pread)(void *, int, off_t),
off_t start, /* Offset to start of file. */
const char *symbol)
{
struct elf32_sym s;
off_t a;
cle_addr addr;
int ret;
for(a = start + info->symtaboff;
a < start + info->symtaboff + info->symtabsize;
a += sizeof(s)) {
ret = pread(&s, sizeof(s), a);
assert(ret > 0);
if(s.st_name != 0) {
ret = pread(info->name, sizeof(info->name),
start + info->strtaboff + s.st_name);
assert(ret > 0);
if(strcmp(info->name, symbol) == 0) { /* Exported symbol found. */
if(s.st_shndx == info->bss_shndx) {
addr = info->bss;
} else if(s.st_shndx == info->data_shndx) {
addr = info->data;
} else if(s.st_shndx == info->text_shndx) {
addr = info->text;
} else {
return NULL; /* Really an error! */
}
return addr + s.st_value;
}
}
}
return NULL;
}

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/*
* Copyright (c) 2006, Swedish Institute of Computer Science
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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.
* 3. Neither the name of the Institute 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 INSTITUTE 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 INSTITUTE 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.
*
* @(#)$Id: cle.h,v 1.1 2006/12/01 15:12:27 bg- Exp $
*/
#ifndef CLE_H
#define CLE_H
/*
* The Contiki dynamic Link Editor (CLE) for small systems.
*/
/* These typedefs limits object file size! */
typedef u16_t cle_off; /* Offset from start of file. */
typedef u16_t cle_word;
typedef u16_t cle_half;
/* Also used for address arithmetic (can't be void *). */
typedef unsigned char *cle_addr;
/* typedef uintptr_t cle_addr; */
struct cle_info {
cle_addr text, data, bss;
cle_off textrelaoff, datarelaoff;
cle_word textrelasize, datarelasize;
cle_off textoff, dataoff;
cle_word textsize, datasize, bsssize;
cle_off symtaboff, strtaboff;
cle_word symtabsize;
unsigned char text_shndx;
unsigned char data_shndx;
unsigned char bss_shndx;
unsigned char unused_shndx;
char name[32]; /* Scratch and errmsg buffer. */
};
int
cle_read_info(struct cle_info *info,
int (*read)(void *, int, off_t),
off_t hdr); /* Offset to start of file. */
int
cle_relocate(struct cle_info *info,
int (*read)(void *, int, off_t),
off_t hdr, /* Offset to start of file. */
cle_addr segmem, /* Where segment is stored in memory. */
cle_off reloff, /* .rela.<segment> start */
cle_word relsize); /* .rela.<segment> size */
void *
cle_lookup(struct cle_info *info,
int (*read)(void *, int, off_t),
off_t hdr, /* Offset to start of file. */
const char *symbol);
#define CLE_OK 0
#define CLE_BAD_HEADER 1
#define CLE_NO_SYMTAB 2
#define CLE_NO_STRTAB 3
#define CLE_NO_TEXT 4
#define CLE_UNDEFINED 5
#define CLE_UNKNOWN_SEGMENT 6
#define CLE_MULTIPLY_DEFINED 20
#endif /* CLE_H */

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/*
* Copyright (c) 2006, Swedish Institute of Computer Science
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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.
* 3. Neither the name of the Institute 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 INSTITUTE 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 INSTITUTE 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.
*
* @(#)$Id: elf32.h,v 1.1 2006/12/01 15:12:27 bg- Exp $
*/
/* @(#)$Id: elf32.h,v 1.1 2006/12/01 15:12:27 bg- Exp $ */
#ifndef ELF32_H
#define ELF32_H
/*
* ELF definitions common to all 32-bit architectures.
*/
#define EI_NIDENT 16
typedef unsigned long elf32_word;
typedef signed long elf32_sword;
typedef unsigned short elf32_half;
typedef unsigned long elf32_off;
typedef unsigned long elf32_addr;
struct elf32_ehdr {
unsigned char e_ident[EI_NIDENT]; /* ident bytes */
elf32_half e_type; /* file type */
elf32_half e_machine; /* target machine */
elf32_word e_version; /* file version */
elf32_addr e_entry; /* start address */
elf32_off e_phoff; /* phdr file offset */
elf32_off e_shoff; /* shdr file offset */
elf32_word e_flags; /* file flags */
elf32_half e_ehsize; /* sizeof ehdr */
elf32_half e_phentsize; /* sizeof phdr */
elf32_half e_phnum; /* number phdrs */
elf32_half e_shentsize; /* sizeof shdr */
elf32_half e_shnum; /* number shdrs */
elf32_half e_shstrndx; /* shdr string index */
};
/* Values for e_type. */
#define ET_NONE 0 /* Unknown type. */
#define ET_REL 1 /* Relocatable. */
#define ET_EXEC 2 /* Executable. */
#define ET_DYN 3 /* Shared object. */
#define ET_CORE 4 /* Core file. */
struct elf32_shdr {
elf32_word sh_name; /* section name */
elf32_word sh_type; /* SHT_... */
elf32_word sh_flags; /* SHF_... */
elf32_addr sh_addr; /* virtual address */
elf32_off sh_offset; /* file offset */
elf32_word sh_size; /* section size */
elf32_word sh_link; /* misc info */
elf32_word sh_info; /* misc info */
elf32_word sh_addralign; /* memory alignment */
elf32_word sh_entsize; /* entry size if table */
};
/* sh_type */
#define SHT_NULL 0 /* inactive */
#define SHT_PROGBITS 1 /* program defined information */
#define SHT_SYMTAB 2 /* symbol table section */
#define SHT_STRTAB 3 /* string table section */
#define SHT_RELA 4 /* relocation section with addends*/
#define SHT_HASH 5 /* symbol hash table section */
#define SHT_DYNAMIC 6 /* dynamic section */
#define SHT_NOTE 7 /* note section */
#define SHT_NOBITS 8 /* no space section */
#define SHT_REL 9 /* relation section without addends */
#define SHT_SHLIB 10 /* reserved - purpose unknown */
#define SHT_DYNSYM 11 /* dynamic symbol table section */
#define SHT_LOPROC 0x70000000 /* reserved range for processor */
#define SHT_HIPROC 0x7fffffff /* specific section header types */
#define SHT_LOUSER 0x80000000 /* reserved range for application */
#define SHT_HIUSER 0xffffffff /* specific indexes */
struct elf32_rel {
elf32_addr r_offset; /* Location to be relocated. */
elf32_word r_info; /* Relocation type and symbol index. */
};
struct elf32_rela {
elf32_addr r_offset; /* Location to be relocated. */
elf32_word r_info; /* Relocation type and symbol index. */
elf32_sword r_addend; /* Addend. */
};
struct elf32_sym {
elf32_word st_name; /* String table index of name. */
elf32_addr st_value; /* Symbol value. */
elf32_word st_size; /* Size of associated object. */
unsigned char st_info; /* Type and binding information. */
unsigned char st_other; /* Reserved (not used). */
elf32_half st_shndx; /* Section index of symbol. */
};
#define ELF32_R_SYM(info) ((info) >> 8)
#define ELF32_R_TYPE(info) ((unsigned char)(info))
#define ELF_MAGIC_HEADER "\177ELF\001\001\001"
#define ELF_MAGIC_HEADER_SIZE 7
#endif /* ELF32_H */