/****************************************************************************
* binfmt/libelf/libelf_symbols.c
*
* Copyright (C) 2012 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* 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 NuttX 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 COPYRIGHT HOLDERS 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
* COPYRIGHT OWNER 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.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <stdlib.h>
#include <string.h>
#include <elf32.h>
#include <errno.h>
#include <debug.h>
#include <nuttx/binfmt/elf.h>
#include <nuttx/binfmt/symtab.h>
#include "libelf.h"
/****************************************************************************
* Pre-Processor Definitions
****************************************************************************/
#ifndef CONFIG_ELF_BUFFERINCR
# define CONFIG_ELF_BUFFERINCR 32
#endif
/****************************************************************************
* Private Constant Data
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: elf_symname
*
* Description:
* Get the symbol name in loadinfo->iobuffer[].
*
* Returned Value:
* 0 (OK) is returned on success and a negated errno is returned on
* failure.
*
****************************************************************************/
static int elf_symname(FAR struct elf_loadinfo_s *loadinfo,
FAR const Elf32_Sym *sym)
{
FAR uint8_t *buffer;
off_t offset;
size_t readlen;
size_t bytesread;
int ret;
/* Get the file offset to the string that is the name of the symbol. The
* st_name member holds an offset into the file's symbol string table.
*/
if (sym->st_name == 0)
{
bdbg("Symbol has no name\n");
return -ENOENT;
}
offset = loadinfo->shdr[loadinfo->strtabidx].sh_offset + sym->st_name;
/* Loop until we get the entire symbol name into memory */
bytesread = 0;
for (;;)
{
/* Get the number of bytes to read */
readlen = loadinfo->buflen - bytesread;
if (offset + readlen > loadinfo->filelen)
{
readlen = loadinfo->filelen - offset;
if (readlen <= 0)
{
bdbg("At end of file\n");
return -EINVAL;
}
}
/* Read that number of bytes into the array */
buffer = &loadinfo->iobuffer[bytesread];
ret = elf_read(loadinfo, buffer, readlen, offset);
if (ret < 0)
{
bdbg("elf_read failed: %d\n", ret);
return ret;
}
bytesread += readlen;
/* Did we read the NUL terminator? */
if (memchr(buffer, '\0', readlen) != NULL)
{
/* Yes, the buffer contains a NUL terminator. */
return OK;
}
/* No.. then we have to read more */
ret = elf_reallocbuffer(loadinfo, CONFIG_ELF_BUFFERINCR);
if (ret < 0)
{
bdbg("elf_reallocbuffer failed: %d\n", ret);
return ret;
}
}
/* We will not get here */
return OK;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: elf_findsymtab
*
* Description:
* Find the symbol table section.
*
* Returned Value:
* 0 (OK) is returned on success and a negated errno is returned on
* failure.
*
****************************************************************************/
int elf_findsymtab(FAR struct elf_loadinfo_s *loadinfo)
{
int i;
/* Find the symbol table section header and its associated string table */
for (i = 1; i < loadinfo->ehdr.e_shnum; i++)
{
if (loadinfo->shdr[i].sh_type == SHT_SYMTAB)
{
loadinfo->symtabidx = i;
loadinfo->strtabidx = loadinfo->shdr[i].sh_link;
break;
}
}
/* Verify that there is a symbol and string table */
if (loadinfo->symtabidx == 0)
{
bdbg("No symbols in ELF file\n");
return -EINVAL;
}
return OK;
}
/****************************************************************************
* Name: elf_readsym
*
* Description:
* Read the ELFT symbol structure at the specfied index into memory.
*
* Input Parameters:
* loadinfo - Load state information
* index - Symbol table index
* sym - Location to return the table entry
*
* Returned Value:
* 0 (OK) is returned on success and a negated errno is returned on
* failure.
*
****************************************************************************/
int elf_readsym(FAR struct elf_loadinfo_s *loadinfo, int index,
FAR Elf32_Sym *sym)
{
FAR Elf32_Shdr *symtab = &loadinfo->shdr[loadinfo->symtabidx];
off_t offset;
/* Verify that the symbol table index lies within symbol table */
if (index < 0 || index > (symtab->sh_size / sizeof(Elf32_Sym)))
{
bdbg("Bad relocation symbol index: %d\n", index);
return -EINVAL;
}
/* Get the file offset to the symbol table entry */
offset = symtab->sh_offset + sizeof(Elf32_Sym) * index;
/* And, finally, read the symbol table entry into memory */
return elf_read(loadinfo, (FAR uint8_t*)sym, sizeof(Elf32_Sym), offset);
}
/****************************************************************************
* Name: elf_symvalue
*
* Description:
* Get the value of a symbol. The updated value of the symbol is returned
* in the st_value field of the symbol table entry.
*
* Input Parameters:
* loadinfo - Load state information
* sym - Symbol table entry (value might be undefined)
*
* Returned Value:
* 0 (OK) is returned on success and a negated errno is returned on
* failure.
*
****************************************************************************/
int elf_symvalue(FAR struct elf_loadinfo_s *loadinfo, FAR Elf32_Sym *sym,
FAR const struct symtab_s *exports, int nexports)
{
FAR const struct symtab_s *symbol;
uintptr_t secbase;
int ret;
switch (sym->st_shndx)
{
case SHN_COMMON:
{
/* NuttX ELF modules should be compiled with -fno-common. */
bdbg("SHN_COMMON: Re-compile with -fno-common\n");
return -EINVAL;
}
case SHN_ABS:
{
/* st_value already holds the correct value */
bvdbg("SHN_ABS: st_value=%08lx\n", (long)sym->st_value);
return OK;
}
case SHN_UNDEF:
{
/* Get the name of the undefined symbol */
ret = elf_symname(loadinfo, sym);
if (ret < 0)
{
bdbg("SHN_UNDEF: Failed to get symbol name: %d\n", ret);
return ret;
}
/* Check if the base code exports a symbol of this name */
#ifdef CONFIG_SYMTAB_ORDEREDBYNAME
symbol = symtab_findorderedbyname(exports, (FAR char *)loadinfo->iobuffer, nexports);
#else
symbol = symtab_findbyname(exports, (FAR char *)loadinfo->iobuffer, nexports);
#endif
if (!symbol)
{
bdbg("SHN_UNDEF: Exported symbol \"%s\" not found\n", loadinfo->iobuffer);
return -ENOENT;
}
/* Yes... add the exported symbol value to the ELF symbol table entry */
bvdbg("SHN_ABS: name=%s %08x+%08x=%08x\n",
loadinfo->iobuffer, sym->st_value, symbol->sym_value,
sym->st_value + symbol->sym_value);
sym->st_value += (Elf32_Word)((uintptr_t)symbol->sym_value);
}
break;
default:
{
secbase = loadinfo->shdr[sym->st_shndx].sh_addr;
bvdbg("Other: %08x+%08x=%08x\n",
sym->st_value, secbase, sym->st_value + secbase);
sym->st_value += secbase;
}
break;
}
return OK;
}
