libdwfl/dwfl_module_addrsym.c - platform/external/elfutils - Gitiles

 /* Find debugging and symbol information for a module in libdwfl.
    Copyright (C) 2005-2012 Red Hat, Inc.
    This file is part of elfutils.

    This file is free software; you can redistribute it and/or modify
    it under the terms of either

      * the GNU Lesser General Public License as published by the Free
        Software Foundation; either version 3 of the License, or (at
        your option) any later version

    or

      * the GNU General Public License as published by the Free
        Software Foundation; either version 2 of the License, or (at
        your option) any later version

    or both in parallel, as here.

    elfutils is distributed in the hope that it will be useful, but
    WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    General Public License for more details.

    You should have received copies of the GNU General Public License and
    the GNU Lesser General Public License along with this program.  If
    not, see <http://www.gnu.org/licenses/>.  */

 #include "libdwflP.h"

 /* Returns the name of the symbol "closest" to ADDR.
    Never returns symbols at addresses above ADDR.  */

 const char *
 dwfl_module_addrsym (Dwfl_Module *mod, GElf_Addr addr,
 		     GElf_Sym *closest_sym, GElf_Word *shndxp)
 {
   int syments = INTUSE(dwfl_module_getsymtab) (mod);
   if (syments < 0)
     return NULL;

   /* Return true iff we consider ADDR to lie in the same section as SYM.  */
   GElf_Word addr_shndx = SHN_UNDEF;
   inline bool same_section (const GElf_Sym *sym, struct dwfl_file *symfile,
 			    GElf_Word shndx)
     {
       /* For absolute symbols and the like, only match exactly.  */
       if (shndx >= SHN_LORESERVE)
 	return sym->st_value == addr;

       /* Figure out what section ADDR lies in.  */
       if (addr_shndx == SHN_UNDEF)
 	{
 	  GElf_Addr mod_addr = dwfl_deadjust_st_value (mod, symfile, addr);
 	  Elf_Scn *scn = NULL;
 	  addr_shndx = SHN_ABS;
 	  while ((scn = elf_nextscn (symfile->elf, scn)) != NULL)
 	    {
 	      GElf_Shdr shdr_mem;
 	      GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
 	      if (likely (shdr != NULL)
 		  && mod_addr >= shdr->sh_addr
 		  && mod_addr < shdr->sh_addr + shdr->sh_size)
 		{
 		  addr_shndx = elf_ndxscn (scn);
 		  break;
 		}
 	    }
 	}

       return shndx == addr_shndx;
     }

   /* Keep track of the closest symbol we have seen so far.
      Here we store only symbols with nonzero st_size.  */
   const char *closest_name = NULL;
   GElf_Word closest_shndx = SHN_UNDEF;

   /* Keep track of an eligible symbol with st_size == 0 as a fallback.  */
   const char *sizeless_name = NULL;
   GElf_Sym sizeless_sym = { 0, 0, 0, 0, 0, SHN_UNDEF };
   GElf_Word sizeless_shndx = SHN_UNDEF;

   /* Keep track of the lowest address a relevant sizeless symbol could have.  */
   GElf_Addr min_label = 0;

   /* Look through the symbol table for a matching symbol.  */
   inline void search_table (int start, int end)
     {
       for (int i = start; i < end; ++i)
 	{
 	  GElf_Sym sym;
 	  GElf_Word shndx;
 	  const char *name = INTUSE(dwfl_module_getsym) (mod, i, &sym, &shndx);
 	  if (name != NULL && name[0] != '\0'
 	      && sym.st_shndx != SHN_UNDEF
 	      && sym.st_value <= addr
 	      && GELF_ST_TYPE (sym.st_info) != STT_SECTION
 	      && GELF_ST_TYPE (sym.st_info) != STT_FILE
 	      && GELF_ST_TYPE (sym.st_info) != STT_TLS)
 	    {
 	      /* Even if we don't choose this symbol, its existence excludes
 		 any sizeless symbol (assembly label) that is below its upper
 		 bound.  */
 	      if (sym.st_value + sym.st_size > min_label)
 		min_label = sym.st_value + sym.st_size;

 	      if (sym.st_size == 0 || addr - sym.st_value < sym.st_size)
 		{
 		  /* Return GELF_ST_BIND as higher-is-better integer.  */
 		  inline int binding_value (const GElf_Sym *symp)
 		    {
 		      switch (GELF_ST_BIND (symp->st_info))
 		      {
 			case STB_GLOBAL:
 			  return 3;
 			case STB_WEAK:
 			  return 2;
 			case STB_LOCAL:
 			  return 1;
 			default:
 			  return 0;
 		      }
 		    }
 		  /* This symbol is a better candidate than the current one
 		     if it's closer to ADDR or is global when it was local.  */
 		  if (closest_name == NULL
 		      || closest_sym->st_value < sym.st_value
 		      || binding_value (closest_sym) < binding_value (&sym))
 		    {
 		      if (sym.st_size != 0)
 			{
 			  *closest_sym = sym;
 			  closest_shndx = shndx;
 			  closest_name = name;
 			}
 		      else if (closest_name == NULL
 			       && sym.st_value >= min_label
 			       && same_section (&sym,
 						((size_t) i < mod->syments
 						 ? mod->symfile
 						 : &mod->aux_sym),
 						shndx))
 			{
 			  /* Handwritten assembly symbols sometimes have no
 			     st_size.  If no symbol with proper size includes
 			     the address, we'll use the closest one that is in
 			     the same section as ADDR.  */
 			  sizeless_sym = sym;
 			  sizeless_shndx = shndx;
 			  sizeless_name = name;
 			}
 		    }
 		  /* When the beginning of its range is no closer,
 		     the end of its range might be.  Otherwise follow
 		     GELF_ST_BIND preference.  If all are equal prefer
 		     the first symbol found.  */
 		  else if (sym.st_size != 0
 			   && closest_sym->st_value == sym.st_value
 			   && ((closest_sym->st_size > sym.st_size
 			        && (binding_value (closest_sym)
 				    <= binding_value (&sym)))
 			       || (closest_sym->st_size >= sym.st_size
 				   && (binding_value (closest_sym)
 				       < binding_value (&sym)))))
 		    {
 		      *closest_sym = sym;
 		      closest_shndx = shndx;
 		      closest_name = name;
 		    }
 		}
 	    }
 	}
     }

   /* First go through global symbols.  mod->first_global and
      mod->aux_first_global are setup by dwfl_module_getsymtab to the
      index of the first global symbol in those symbol tables.  Both
      are non-zero when the table exist, except when there is only a
      dynsym table loaded through phdrs, then first_global is zero and
      there will be no auxiliary table.  All symbols with local binding
      come first in the symbol table, then all globals.  The zeroth,
      null entry, in the auxiliary table is skipped if there is a main
      table.  */
   int first_global = mod->first_global + mod->aux_first_global;
   if (mod->syments > 0 && mod->aux_syments > 0)
     first_global--;
   search_table (first_global == 0 ? 1 : first_global, syments);

   /* If we found nothing searching the global symbols, then try the locals.
      Unless we have a global sizeless symbol that matches exactly.  */
   if (closest_name == NULL && first_global > 1
       && (sizeless_name == NULL || sizeless_sym.st_value != addr))
     search_table (1, first_global);

   /* If we found no proper sized symbol to use, fall back to the best
      candidate sizeless symbol we found, if any.  */
   if (closest_name == NULL
       && sizeless_name != NULL && sizeless_sym.st_value >= min_label)
     {
       *closest_sym = sizeless_sym;
       closest_shndx = sizeless_shndx;
       closest_name = sizeless_name;
     }

   if (shndxp != NULL)
     *shndxp = closest_shndx;
   return closest_name;
 }
 INTDEF (dwfl_module_addrsym)
	/* Find debugging and symbol information for a module in libdwfl.
	Copyright (C) 2005-2012 Red Hat, Inc.
	This file is part of elfutils.

	This file is free software; you can redistribute it and/or modify
	it under the terms of either

	* the GNU Lesser General Public License as published by the Free
	Software Foundation; either version 3 of the License, or (at
	your option) any later version

	or

	* the GNU General Public License as published by the Free
	Software Foundation; either version 2 of the License, or (at
	your option) any later version

	or both in parallel, as here.

	elfutils is distributed in the hope that it will be useful, but
	WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	General Public License for more details.

	You should have received copies of the GNU General Public License and
	the GNU Lesser General Public License along with this program. If
	not, see <http://www.gnu.org/licenses/>. */

	#include "libdwflP.h"

	/* Returns the name of the symbol "closest" to ADDR.
	Never returns symbols at addresses above ADDR. */

	const char *
	dwfl_module_addrsym (Dwfl_Module *mod, GElf_Addr addr,
	GElf_Sym closest_sym, GElf_Word shndxp)
	{
	int syments = INTUSE(dwfl_module_getsymtab) (mod);
	if (syments < 0)
	return NULL;

	/* Return true iff we consider ADDR to lie in the same section as SYM. */
	GElf_Word addr_shndx = SHN_UNDEF;
	inline bool same_section (const GElf_Sym sym, struct dwfl_file symfile,
	GElf_Word shndx)
	{
	/* For absolute symbols and the like, only match exactly. */
	if (shndx >= SHN_LORESERVE)
	return sym->st_value == addr;

	/* Figure out what section ADDR lies in. */
	if (addr_shndx == SHN_UNDEF)
	{
	GElf_Addr mod_addr = dwfl_deadjust_st_value (mod, symfile, addr);
	Elf_Scn *scn = NULL;
	addr_shndx = SHN_ABS;
	while ((scn = elf_nextscn (symfile->elf, scn)) != NULL)
	{
	GElf_Shdr shdr_mem;
	GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
	if (likely (shdr != NULL)
	&& mod_addr >= shdr->sh_addr
	&& mod_addr < shdr->sh_addr + shdr->sh_size)
	{
	addr_shndx = elf_ndxscn (scn);
	break;
	}
	}
	}

	return shndx == addr_shndx;
	}

	/* Keep track of the closest symbol we have seen so far.
	Here we store only symbols with nonzero st_size. */
	const char *closest_name = NULL;
	GElf_Word closest_shndx = SHN_UNDEF;

	/* Keep track of an eligible symbol with st_size == 0 as a fallback. */
	const char *sizeless_name = NULL;
	GElf_Sym sizeless_sym = { 0, 0, 0, 0, 0, SHN_UNDEF };
	GElf_Word sizeless_shndx = SHN_UNDEF;

	/* Keep track of the lowest address a relevant sizeless symbol could have. */
	GElf_Addr min_label = 0;

	/* Look through the symbol table for a matching symbol. */
	inline void search_table (int start, int end)
	{
	for (int i = start; i < end; ++i)
	{
	GElf_Sym sym;
	GElf_Word shndx;
	const char *name = INTUSE(dwfl_module_getsym) (mod, i, &sym, &shndx);
	if (name != NULL && name[0] != '\0'
	&& sym.st_shndx != SHN_UNDEF
	&& sym.st_value <= addr
	&& GELF_ST_TYPE (sym.st_info) != STT_SECTION
	&& GELF_ST_TYPE (sym.st_info) != STT_FILE
	&& GELF_ST_TYPE (sym.st_info) != STT_TLS)
	{
	/* Even if we don't choose this symbol, its existence excludes
	any sizeless symbol (assembly label) that is below its upper
	bound. */
	if (sym.st_value + sym.st_size > min_label)
	min_label = sym.st_value + sym.st_size;

	if (sym.st_size == 0 \|\| addr - sym.st_value < sym.st_size)
	{
	/* Return GELF_ST_BIND as higher-is-better integer. */
	inline int binding_value (const GElf_Sym *symp)
	{
	switch (GELF_ST_BIND (symp->st_info))
	{
	case STB_GLOBAL:
	return 3;
	case STB_WEAK:
	return 2;
	case STB_LOCAL:
	return 1;
	default:
	return 0;
	}
	}
	/* This symbol is a better candidate than the current one
	if it's closer to ADDR or is global when it was local. */
	if (closest_name == NULL
	\|\| closest_sym->st_value < sym.st_value
	\|\| binding_value (closest_sym) < binding_value (&sym))
	{
	if (sym.st_size != 0)
	{
	*closest_sym = sym;
	closest_shndx = shndx;
	closest_name = name;
	}
	else if (closest_name == NULL
	&& sym.st_value >= min_label
	&& same_section (&sym,
	((size_t) i < mod->syments
	? mod->symfile
	: &mod->aux_sym),
	shndx))
	{
	/* Handwritten assembly symbols sometimes have no
	st_size. If no symbol with proper size includes
	the address, we'll use the closest one that is in
	the same section as ADDR. */
	sizeless_sym = sym;
	sizeless_shndx = shndx;
	sizeless_name = name;
	}
	}
	/* When the beginning of its range is no closer,
	the end of its range might be. Otherwise follow
	GELF_ST_BIND preference. If all are equal prefer
	the first symbol found. */
	else if (sym.st_size != 0
	&& closest_sym->st_value == sym.st_value
	&& ((closest_sym->st_size > sym.st_size
	&& (binding_value (closest_sym)
	<= binding_value (&sym)))
	\|\| (closest_sym->st_size >= sym.st_size
	&& (binding_value (closest_sym)
	< binding_value (&sym)))))
	{
	*closest_sym = sym;
	closest_shndx = shndx;
	closest_name = name;
	}
	}
	}
	}
	}

	/* First go through global symbols. mod->first_global and
	mod->aux_first_global are setup by dwfl_module_getsymtab to the
	index of the first global symbol in those symbol tables. Both
	are non-zero when the table exist, except when there is only a
	dynsym table loaded through phdrs, then first_global is zero and
	there will be no auxiliary table. All symbols with local binding
	come first in the symbol table, then all globals. The zeroth,
	null entry, in the auxiliary table is skipped if there is a main
	table. */
	int first_global = mod->first_global + mod->aux_first_global;
	if (mod->syments > 0 && mod->aux_syments > 0)
	first_global--;
	search_table (first_global == 0 ? 1 : first_global, syments);

	/* If we found nothing searching the global symbols, then try the locals.
	Unless we have a global sizeless symbol that matches exactly. */
	if (closest_name == NULL && first_global > 1
	&& (sizeless_name == NULL \|\| sizeless_sym.st_value != addr))
	search_table (1, first_global);

	/* If we found no proper sized symbol to use, fall back to the best
	candidate sizeless symbol we found, if any. */
	if (closest_name == NULL
	&& sizeless_name != NULL && sizeless_sym.st_value >= min_label)
	{
	*closest_sym = sizeless_sym;
	closest_shndx = sizeless_shndx;
	closest_name = sizeless_name;
	}

	if (shndxp != NULL)
	*shndxp = closest_shndx;
	return closest_name;
	}
	INTDEF (dwfl_module_addrsym)