contiki/core/loader/cle.c

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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 1.3 2007/01/12 13:36:27 bg- Exp $
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*/
/*
* 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 hdr reading data using function
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* pread. Save what is useful in info.
*/
int
cle_read_info(struct cle_info *info,
int (*pread)(void *, int, off_t),
off_t hdr)
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{
/*
* 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 shoff;
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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), hdr);
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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;
}
shoff = hdr + ehdr.e_shoff;
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shentsize = ehdr.e_shentsize;
shnum = ehdr.e_shnum;
/* The string table section: holds the names of the sections. */
ret = pread(&shdr, sizeof(shdr), shoff + shentsize*ehdr.e_shstrndx);
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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), shoff);
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assert(ret > 0);
/* The name of the section is contained in the strings table. */
ret = pread(info->name, sizeof(info->name), hdr + strs + shdr.sh_name);
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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. */
shoff += shentsize;
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}
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 MSP430
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* 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 hdr. Data is read using
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* function pread.
*/
int
cle_relocate(struct cle_info *info,
int (*pread)(void *, int, off_t),
off_t hdr, /* Offset to start of file. */
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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 = hdr + reloff;
off < hdr + reloff + relsize;
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off += sizeof(struct elf32_rela)) {
ret = pread(&rela, sizeof(rela), off);
assert(ret > 0);
ret = pread(&s, sizeof(s),
hdr + info->symtaboff
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+ 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),
hdr + info->strtaboff + s.st_name);
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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 (%d)\n",
info->name, s.st_info);
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return CLE_UNDEFINED; /* Or COMMON symbol. */
} else if(addr != NULL && sym != NULL) {
PRINTF("cle: multiple definitions of %.32s (%d)\n",
info->name, s.st_info);
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return CLE_MULTIPLY_DEFINED;
}
}
addr += rela.r_addend;
cle_upd_reloc(segmem, &rela, addr);
}
return CLE_OK;
}
/*
* Search object file located at offset hdr using function
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* 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 hdr, /* Offset to start of file. */
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const char *symbol)
{
struct elf32_sym s;
off_t a;
cle_addr addr;
int ret;
for(a = hdr + info->symtaboff;
a < hdr + info->symtaboff + info->symtabsize;
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a += sizeof(s)) {
ret = pread(&s, sizeof(s), a);
assert(ret > 0);
if(s.st_name != 0) {
ret = pread(info->name, sizeof(info->name),
hdr + info->strtaboff + s.st_name);
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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;
}