/*
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* Copyright (c) 2006, Swedish Institute of Computer Science
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the Institute nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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*/
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/*
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* The Contiki dynamic Link Editor (CLE), ELF version.
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*/
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#include <stdio.h>
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#include <string.h>
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#include "contiki.h"
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#include "loader/elf32.h"
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#include "loader/cle.h"
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#include "loader/sym.h"
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#define NDEBUG
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#include "lib/assert.h"
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#ifdef NDEBUG
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#define PRINTF(...) do {} while (0)
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#else
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#define PRINTF(...) printf(__VA_ARGS__)
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#endif
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#define NOLL 0
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#ifdef __AVR__
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/*
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* On the AVR, GNU C squeezes function addresses into 16 bits. Some of
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* this code is explicitly written to deal with this.
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*/
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#ifndef __GNUC__
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#eror "You lose!!!"
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#endif
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#endif
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/*
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* Parse object file located at offset hdr reading data using function
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* pread. Save what is useful in info.
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*/
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int
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cle_read_info(struct cle_info *info,
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int (*pread)(void *, int, off_t),
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off_t hdr)
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{
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/*
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* Save stackspace by using a union!
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*
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* Beware that the contents of ehdr is gone when shdr is written!!!
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*/
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union {
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struct elf32_ehdr ehdr;
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struct elf32_shdr shdr;
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} huge;
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#define ehdr huge.ehdr
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#define shdr huge.shdr
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off_t shoff;
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cle_off strs;
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cle_half shnum; /* number shdrs */
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cle_half shentsize; /* sizeof shdr */
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cle_word strtabsize = 0;
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int i, ret;
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memset(info, 0x0, sizeof(*info));
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ret = pread(&ehdr, sizeof(ehdr), hdr);
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assert(ret > 0);
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/* Make sure that we have a correct and compatible ELF header. */
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if(memcmp(ehdr.e_ident, ELF_MAGIC_HEADER, ELF_MAGIC_HEADER_SIZE) != 0) {
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return CLE_BAD_HEADER;
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}
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shoff = hdr + ehdr.e_shoff;
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shentsize = ehdr.e_shentsize;
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shnum = ehdr.e_shnum;
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/* The string table section: holds the names of the sections. */
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ret = pread(&shdr, sizeof(shdr), shoff + shentsize*ehdr.e_shstrndx);
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assert(ret > 0);
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/* BEWARE THAT ehdr IS NOW OVERWRITTEN!!! */
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/*
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* Get a pointer to the actual table of strings. This table holds
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* the names of the sections, not the names of other symbols in the
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* file (these are in the symtab section).
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*/
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strs = shdr.sh_offset;
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/*
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* The ".text" segment holds the actual code from the ELF file, the
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* ".data" segment contains initialized data, the ".bss" segment
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* holds the size of the unitialized data segment. The ".rela.text"
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* and ".rela.data" segments contains relocation information for the
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* contents of the ".text" and ".data" segments, respectively. The
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* ".symtab" segment contains the symbol table for this file. The
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* ".strtab" segment points to the actual string names used by the
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* symbol table.
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*
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* In addition to grabbing pointers to the relevant sections, we
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* also save the section index for resolving addresses in the
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* relocator code.
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*/
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for(i = 0; i < shnum; ++i) {
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ret = pread(&shdr, sizeof(shdr), shoff);
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assert(ret > 0);
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/* The name of the section is contained in the strings table. */
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ret = pread(info->name, sizeof(info->name), hdr + strs + shdr.sh_name);
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assert(ret > 0);
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if(strncmp(info->name, ".text", 5) == 0) {
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info->textoff = shdr.sh_offset;
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info->textsize = shdr.sh_size;
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info->text_shndx = i;
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} else if(strncmp(info->name, ".rela.text", 10) == 0) {
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info->textrelaoff = shdr.sh_offset;
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info->textrelasize = shdr.sh_size;
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} else if(strncmp(info->name, ".data", 5) == 0) {
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info->dataoff = shdr.sh_offset;
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info->datasize = shdr.sh_size;
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info->data_shndx = i;
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} else if(strncmp(info->name, ".rela.data", 10) == 0) {
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info->datarelaoff = shdr.sh_offset;
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info->datarelasize = shdr.sh_size;
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} else if(strncmp(info->name, ".symtab", 7) == 0) {
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info->symtaboff = shdr.sh_offset;
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info->symtabsize = shdr.sh_size;
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} else if(strncmp(info->name, ".strtab", 7) == 0) {
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info->strtaboff = shdr.sh_offset;
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strtabsize = shdr.sh_size;
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} else if(strncmp(info->name, ".bss", 4) == 0) {
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info->bsssize = shdr.sh_size;
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info->bss_shndx = i;
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} else {
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info->name[sizeof(info->name) - 1] = 0;
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PRINTF("cle: unknown section %.12s\n", info->name);
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}
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/* Move on to the next section header. */
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shoff += shentsize;
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}
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if(info->symtabsize == 0) {
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return CLE_NO_SYMTAB;
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}
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if(strtabsize == 0) {
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return CLE_NO_STRTAB;
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}
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if(info->textsize == 0) {
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return CLE_NO_TEXT;
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}
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return CLE_OK;
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}
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/*
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* Relocate one segment that has been copied to the location pointed
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* to by segmem.
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*
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* Relocation info is read from offset reloff to (reloff + relsize)
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* and the start of the object file is at hdr. Data is read using
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* function pread.
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*/
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int
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cle_relocate(struct cle_info *info,
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int (*pread)(void *, int, off_t),
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off_t hdr, /* Offset to start of file. */
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void *segmem, /* Where segment is stored in memory. */
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cle_off reloff, /* .rela.<segment> start */
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cle_word relsize) /* .rela.<segment> size */
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{
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struct elf32_rela rela;
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struct elf32_sym s;
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off_t off;
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cle_addr addr;
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int ret;
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for(off = hdr + reloff;
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off < hdr + reloff + relsize;
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off += sizeof(struct elf32_rela)) {
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ret = pread(&rela, sizeof(rela), off);
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assert(ret > 0);
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ret = pread(&s, sizeof(s),
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hdr + info->symtaboff
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+ sizeof(struct elf32_sym)*ELF32_R_SYM(rela.r_info));
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assert(ret > 0);
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if(s.st_shndx == info->bss_shndx) {
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addr = (cle_addr)(uintptr_t)info->bss;
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} else if(s.st_shndx == info->data_shndx) {
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addr = (cle_addr)(uintptr_t)info->data;
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} else if(s.st_shndx == info->text_shndx) {
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addr = info->text;
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} else {
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addr = NOLL;
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}
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if(s.st_name == 0) { /* No name, local symbol? */
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if(addr == NOLL) {
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return CLE_UNKNOWN_SEGMENT;
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}
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} else {
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ret = pread(info->name, sizeof(info->name),
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hdr + info->strtaboff + s.st_name);
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assert(ret > 0);
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cle_addr sym = (cle_addr)(uintptr_t)sym_function(info->name);
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#ifdef __AVR__
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if(sym != NOLL)
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sym = sym << 1;
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#endif
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if(sym == NOLL)
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sym = (cle_addr)(uintptr_t)sym_object(info->name);
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if(addr == NOLL && sym != NOLL) { /* Imported symbol. */
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addr = sym;
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} else if(addr != NOLL && sym == NOLL) { /* Exported symbol. */
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addr = addr + s.st_value;
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} else if(addr == NOLL && sym == NOLL) {
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PRINTF("cle: undefined reference to %.32s (%d)\n",
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info->name, s.st_info);
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return CLE_UNDEFINED; /* Or COMMON symbol. */
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} else if(addr != NOLL && sym != NOLL) {
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PRINTF("cle: multiple definitions of %.32s (%d)\n",
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info->name, s.st_info);
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return CLE_MULTIPLY_DEFINED;
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}
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}
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addr += rela.r_addend;
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ret = cle_write_reloc(segmem + rela.r_offset, &rela, addr, info);
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if(ret != CLE_OK) {
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return ret;
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}
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}
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return CLE_OK;
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}
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/*
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* Search object file located at offset hdr using function
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* pread. Search for symbol named symbol and return its address after
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* relocation or NULL on failure.
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*/
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void *
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cle_lookup(struct cle_info *info,
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int (*pread)(void *, int, off_t),
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off_t hdr, /* Offset to start of file. */
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const char *symbol)
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{
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struct elf32_sym s;
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off_t a;
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cle_addr addr;
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int ret;
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for(a = hdr + info->symtaboff;
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a < hdr + info->symtaboff + info->symtabsize;
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a += sizeof(s)) {
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ret = pread(&s, sizeof(s), a);
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assert(ret > 0);
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if(s.st_name != 0) {
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ret = pread(info->name, sizeof(info->name),
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hdr + info->strtaboff + s.st_name);
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assert(ret > 0);
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if(strcmp(info->name, symbol) == 0) { /* Exported symbol found. */
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if(s.st_shndx == info->bss_shndx) {
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addr = (cle_addr)(uintptr_t)info->bss;
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} else if(s.st_shndx == info->data_shndx) {
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addr = (cle_addr)(uintptr_t)info->data;
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} else if(s.st_shndx == info->text_shndx) {
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addr = info->text;
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#ifdef __AVR__
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return (void *)(uintptr_t)((addr + s.st_value) >> 1);
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#endif
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} else {
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return NULL; /* Really an error! */
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}
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return (void *)(uintptr_t)(addr + s.st_value);
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}
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}
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}
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return NULL;
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}
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