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nuttx/libc/modlib/modlib_symbols.c

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/****************************************************************************
* libc/modlib/modlib_symbols.c
*
* Copyright (C) 2015, 2017 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/module.h>
#include <nuttx/lib/modlib.h>
#include <nuttx/binfmt/symtab.h>
#include "modlib/modlib.h"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/* Amount to reallocate buffer when buffer is full */
#ifndef CONFIG_MODLIB_BUFFERINCR
# define CONFIG_MODLIB_BUFFERINCR 32
#endif
/* Return values search for exported modules */
#define SYM_NOT_FOUND 0
#define SYM_FOUND 1
/****************************************************************************
* Private Types
****************************************************************************/
struct mod_exportinfo_s
{
FAR const char *name; /* Symbol name to find */
FAR struct module_s *modp; /* The module that needs the symbol */
FAR const struct symtab_s *symbol; /* Symbol info returned (if found) */
};
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: modlib_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.
*
* EINVAL - There is something inconsistent in the symbol table (should only
* happen if the file is corrupted).
* ESRCH - Symbol has no name
*
****************************************************************************/
static int modlib_symname(FAR struct mod_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)
{
serr("ERROR: Symbol has no name\n");
return -ESRCH;
}
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)
{
if (loadinfo->filelen <= offset)
{
serr("ERROR: At end of file\n");
return -EINVAL;
}
readlen = loadinfo->filelen - offset;
}
/* Read that number of bytes into the array */
buffer = &loadinfo->iobuffer[bytesread];
ret = modlib_read(loadinfo, buffer, readlen, offset);
if (ret < 0)
{
serr("ERROR: modlib_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 = modlib_reallocbuffer(loadinfo, CONFIG_MODLIB_BUFFERINCR);
if (ret < 0)
{
serr("ERROR: mod_reallocbuffer failed: %d\n", ret);
return ret;
}
}
/* We will not get here */
return OK;
}
/****************************************************************************
* Name: modlib_symcallback
*
* Description:
* modlib_registry_foreach() callback function. Test if the provided module,
* modp, exports the symbol of interest. If so, return that symbol value
* and setup the module dependency relationship.
*
* Returned Value:
* 0 (OK) is returned on success and a negated errno is returned on
* failure.
*
****************************************************************************/
static int modlib_symcallback(FAR struct module_s *modp, FAR void *arg)
{
FAR struct mod_exportinfo_s *exportinfo = (FAR struct mod_exportinfo_s *)arg;
int ret;
/* Check if this module exports a symbol of that name */
#ifdef CONFIG_SYMTAB_ORDEREDBYNAME
exportinfo->symbol = symtab_findorderedbyname(modp->modinfo.exports,
exportinfo->name,
modp->modinfo.nexports);
#else
exportinfo->symbol = symtab_findbyname(modp->modinfo.exports,
exportinfo->name,
modp->modinfo.nexports);
#endif
if (exportinfo->symbol != NULL)
{
/* Yes.. save the dependency relationship and return SYM_FOUND to
* stop the traversal.
*/
ret = modlib_depend(exportinfo->modp, modp);
if (ret < 0)
{
serr("ERROR: modlib_depend failed: %d\n", ret);
return ret;
}
return SYM_FOUND;
}
return SYM_NOT_FOUND;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: modlib_findsymtab
*
* Description:
* Find the symbol table section.
*
* Returned Value:
* 0 (OK) is returned on success and a negated errno is returned on
* failure.
*
****************************************************************************/
int modlib_findsymtab(FAR struct mod_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)
{
serr("ERROR: No symbols in ELF file\n");
return -EINVAL;
}
return OK;
}
/****************************************************************************
* Name: modlib_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 modlib_readsym(FAR struct mod_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)))
{
serr("ERROR: 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 modlib_read(loadinfo, (FAR uint8_t *)sym, sizeof(Elf32_Sym), offset);
}
/****************************************************************************
* Name: modlib_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:
* modp - Module state information
* 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.
*
* EINVAL - There is something inconsistent in the symbol table (should only
* happen if the file is corrupted).
* ENOSYS - Symbol lies in common
* ESRCH - Symbol has no name
* ENOENT - Symbol undefined and not provided via a symbol table
*
****************************************************************************/
int modlib_symvalue(FAR struct module_s *modp,
FAR struct mod_loadinfo_s *loadinfo, FAR Elf32_Sym *sym)
{
FAR const struct symtab_s *symbol;
struct mod_exportinfo_s exportinfo;
uintptr_t secbase;
int ret;
switch (sym->st_shndx)
{
case SHN_COMMON:
{
/* NuttX ELF modules should be compiled with -fno-common. */
serr("ERROR: SHN_COMMON: Re-compile with -fno-common\n");
return -ENOSYS;
}
case SHN_ABS:
{
/* st_value already holds the correct value */
sinfo("SHN_ABS: st_value=%08lx\n", (long)sym->st_value);
return OK;
}
case SHN_UNDEF:
{
/* Get the name of the undefined symbol */
ret = modlib_symname(loadinfo, sym);
if (ret < 0)
{
/* There are a few relocations for a few architectures that do
* no depend upon a named symbol. We don't know if that is the
* case here, but return and special error to the caller to
* indicate the nameless symbol.
*/
serr("ERROR: SHN_UNDEF: Failed to get symbol name: %d\n", ret);
return ret;
}
/* First check if the symbol is exported by an installed module.
* Newest modules are installed at the head of the list. Therefore,
* if the symbol is exported by numerous modules, then the most
* recently installed will take precedence.
*/
exportinfo.name = (FAR const char *)loadinfo->iobuffer;
exportinfo.modp = modp;
exportinfo.symbol = NULL;
ret = modlib_registry_foreach(modlib_symcallback, (FAR void *)&exportinfo);
if (ret < 0)
{
serr("ERROR: modlib_symcallback failed: \n", ret);
return ret;
}
symbol = exportinfo.symbol;
/* If the symbol is not exported by any module, then check if the
* base code exports a symbol of this name.
*/
if (symbol == NULL)
{
#ifdef CONFIG_SYMTAB_ORDEREDBYNAME
symbol = symtab_findorderedbyname(g_modlib_symtab, exportinfo.name,
g_modlib_nsymbols);
#else
symbol = symtab_findbyname(g_modlib_symtab, exportinfo.name,
g_modlib_nsymbols);
#endif
}
/* Was the symbol found from any exporter? */
if (symbol == NULL)
{
serr("ERROR: SHN_UNDEF: Exported symbol \"%s\" not found\n",
loadinfo->iobuffer);
return -ENOENT;
}
/* Yes... add the exported symbol value to the ELF symbol table entry */
sinfo("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;
sinfo("Other: %08x+%08x=%08x\n",
sym->st_value, secbase, sym->st_value + secbase);
sym->st_value += secbase;
}
break;
}
return OK;
}
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