libdwfl/dwfl_module_addrsym.c - external/elfutils - Git at Google

 /* Find debugging and symbol information for a module in libdwfl.
    Copyright (C) 2005-2013 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/>.  */

 #ifdef HAVE_CONFIG_H
 # include <config.h>
 #endif

 #include "libdwflP.h"

 struct search_state
 {
   Dwfl_Module *mod;
   GElf_Addr addr;

   GElf_Sym *closest_sym;
   bool adjust_st_value;
   GElf_Word addr_shndx;
   Elf *addr_symelf;

   /* Keep track of the closest symbol we have seen so far.
      Here we store only symbols with nonzero st_size.  */
   const char *closest_name;
   GElf_Addr closest_value;
   GElf_Word closest_shndx;
   Elf *closest_elf;

   /* Keep track of an eligible symbol with st_size == 0 as a fallback.  */
   const char *sizeless_name;
   GElf_Sym sizeless_sym;
   GElf_Addr sizeless_value;
   GElf_Word sizeless_shndx;
   Elf *sizeless_elf;

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

 /* Return true iff we consider ADDR to lie in the same section as SYM.  */
 static inline bool
 same_section (struct search_state *state,
 	      GElf_Addr value, Elf *symelf, GElf_Word shndx)
 {
   /* For absolute symbols and the like, only match exactly.  */
   if (shndx >= SHN_LORESERVE)
     return value == state->addr;

   /* If value might not be st_value, the shndx of the symbol might
       not match the section of the value. Explicitly look both up.  */
   if (! state->adjust_st_value)
     {
       Dwarf_Addr v;
       if (state->addr_shndx == SHN_UNDEF)
         {
           v = state->addr;
           state->addr_shndx = __libdwfl_find_section_ndx (state->mod, &v);
         }

       v = value;
       return state->addr_shndx == __libdwfl_find_section_ndx (state->mod, &v);
     }

   /* Figure out what section ADDR lies in.  */
   if (state->addr_shndx == SHN_UNDEF || state->addr_symelf != symelf)
     {
       GElf_Addr mod_addr = dwfl_deadjust_st_value (state->mod, symelf,
 						   state->addr);
       Elf_Scn *scn = NULL;
       state->addr_shndx = SHN_ABS;
       state->addr_symelf = symelf;
       while ((scn = elf_nextscn (symelf, 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)
             {
               state->addr_shndx = elf_ndxscn (scn);
               break;
             }
         }
     }

   return shndx == state->addr_shndx && state->addr_symelf == symelf;
 }

 /* Return GELF_ST_BIND as higher-is-better integer.  */
 static 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;
     }
 }

 /* Try one symbol and associated value from the search table.  */
 static inline void
 try_sym_value (struct search_state *state,
                GElf_Addr value, GElf_Sym *sym,
                const char *name, GElf_Word shndx,
                Elf *elf, bool resolved)
 {
     /* Even if we don't choose this symbol, its existence excludes
        any sizeless symbol (assembly label) that is below its upper
        bound.  */
     if (value + sym->st_size > state->min_label)
       state->min_label = value + sym->st_size;

     if (sym->st_size == 0 || state->addr - value < sym->st_size)
       {
 	/* This symbol is a better candidate than the current one
 	   if it's closer to ADDR or is global when it was local.  */
 	if (state->closest_name == NULL
 	    || state->closest_value < value
 	    || binding_value (state->closest_sym) < binding_value (sym))
 	  {
 	    if (sym->st_size != 0)
 	      {
 		*state->closest_sym = *sym;
 		state->closest_value = value;
 		state->closest_shndx = shndx;
 		state->closest_elf = elf;
 		state->closest_name = name;
 	      }
 	    else if (state->closest_name == NULL
 		     && value >= state->min_label
 		     && same_section (state, value,
 				      resolved ? state->mod->main.elf : elf,
 				      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.  */
 		state->sizeless_sym = *sym;
 		state->sizeless_value = value;
 		state->sizeless_shndx = shndx;
 		state->sizeless_elf = elf;
 		state->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
 		 && state->closest_value == value
 		 && ((state->closest_sym->st_size > sym->st_size
 		      && (binding_value (state->closest_sym)
 			  <= binding_value (sym)))
 		     || (state->closest_sym->st_size >= sym->st_size
 			 && (binding_value (state->closest_sym)
 			     < binding_value (sym)))))
 	  {
 	    *state->closest_sym = *sym;
 	    state->closest_value = value;
 	    state->closest_shndx = shndx;
 	    state->closest_elf = elf;
 	    state->closest_name = name;
 	  }
       }
 }

 /* Look through the symbol table for a matching symbol.  */
 static inline void
 search_table (struct search_state *state, int start, int end)
 {
       for (int i = start; i < end; ++i)
 	{
 	  GElf_Sym sym;
 	  GElf_Addr value;
 	  GElf_Word shndx;
 	  Elf *elf;
 	  bool resolved;
 	  const char *name = __libdwfl_getsym (state->mod, i, &sym, &value,
 					       &shndx, &elf, NULL,
 					       &resolved,
 					       state->adjust_st_value);
 	  if (name != NULL && name[0] != '\0'
 	      && sym.st_shndx != SHN_UNDEF
 	      && value <= state->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)
 	    {
 	      try_sym_value (state, value, &sym, name, shndx, elf, resolved);

 	      /* If this is an addrinfo variant and the value could be
 		 resolved then also try matching the (adjusted) st_value.  */
 	      if (resolved && state->mod->e_type != ET_REL)
 		{
 		  GElf_Addr adjusted_st_value;
 		  adjusted_st_value = dwfl_adjusted_st_value (state->mod, elf,
 							      sym.st_value);
 		  if (value != adjusted_st_value
 		      && adjusted_st_value <= state->addr)
 		    try_sym_value (state, adjusted_st_value, &sym, name, shndx,
 				   elf, false);
 		}
 	    }
 	}
 }

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

    Wrapper for old dwfl_module_addrsym and new dwfl_module_addrinfo.
    adjust_st_value set to true returns adjusted SYM st_value, set to false
    it will not adjust SYM at all, but does match against resolved values.   */
 static const char *
 __libdwfl_addrsym (Dwfl_Module *_mod, GElf_Addr _addr, GElf_Off *off,
 		   GElf_Sym *_closest_sym, GElf_Word *shndxp,
 		   Elf **elfp, Dwarf_Addr *biasp, bool _adjust_st_value)
 {
   int syments = INTUSE(dwfl_module_getsymtab) (_mod);
   if (syments < 0)
     return NULL;

   struct search_state state =
     {
       .addr = _addr,
       .mod = _mod,
       .closest_sym = _closest_sym,
       .adjust_st_value = _adjust_st_value,
       .addr_shndx = SHN_UNDEF,
       .addr_symelf = NULL,
       .closest_name = NULL,
       .closest_value = 0,
       .closest_shndx = SHN_UNDEF,
       .closest_elf = NULL,
       .sizeless_name = NULL,
       .sizeless_sym = { 0, 0, 0, 0, 0, SHN_UNDEF },
       .sizeless_value = 0,
       .sizeless_shndx = SHN_UNDEF,
       .sizeless_elf = NULL,
       .min_label = 0
     };

   /* 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 = INTUSE (dwfl_module_getsymtab_first_global) (state.mod);
   if (first_global < 0)
     return NULL;
   search_table (&state, 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 (state.closest_name == NULL && first_global > 1
       && (state.sizeless_name == NULL || state.sizeless_value != state.addr))
     search_table (&state, 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 (state.closest_name == NULL
       && state.sizeless_name != NULL
       && state.sizeless_value >= state.min_label)
     {
       *state.closest_sym = state.sizeless_sym;
       state.closest_value = state.sizeless_value;
       state.closest_shndx = state.sizeless_shndx;
       state.closest_elf = state.sizeless_elf;
       state.closest_name = state.sizeless_name;
     }

   *off = state.addr - state.closest_value;

   if (shndxp != NULL)
     *shndxp = state.closest_shndx;
   if (elfp != NULL)
     *elfp = state.closest_elf;
   if (biasp != NULL)
     *biasp = dwfl_adjusted_st_value (state.mod, state.closest_elf, 0);
   return state.closest_name;
 }


 const char *
 dwfl_module_addrsym (Dwfl_Module *mod, GElf_Addr addr,
 		     GElf_Sym *closest_sym, GElf_Word *shndxp)
 {
   GElf_Off off;
   return __libdwfl_addrsym (mod, addr, &off, closest_sym, shndxp,
 			    NULL, NULL, true);
 }
 INTDEF (dwfl_module_addrsym)

 const char
 *dwfl_module_addrinfo (Dwfl_Module *mod, GElf_Addr address,
 		       GElf_Off *offset, GElf_Sym *sym,
 		       GElf_Word *shndxp, Elf **elfp, Dwarf_Addr *bias)
 {
   return __libdwfl_addrsym (mod, address, offset, sym, shndxp, elfp, bias,
 			    false);
 }
 INTDEF (dwfl_module_addrinfo)
	/* Find debugging and symbol information for a module in libdwfl.
	Copyright (C) 2005-2013 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/>. */

	#ifdef HAVE_CONFIG_H
	# include <config.h>
	#endif

	#include "libdwflP.h"

	struct search_state
	{
	Dwfl_Module *mod;
	GElf_Addr addr;

	GElf_Sym *closest_sym;
	bool adjust_st_value;
	GElf_Word addr_shndx;
	Elf *addr_symelf;

	/* Keep track of the closest symbol we have seen so far.
	Here we store only symbols with nonzero st_size. */
	const char *closest_name;
	GElf_Addr closest_value;
	GElf_Word closest_shndx;
	Elf *closest_elf;

	/* Keep track of an eligible symbol with st_size == 0 as a fallback. */
	const char *sizeless_name;
	GElf_Sym sizeless_sym;
	GElf_Addr sizeless_value;
	GElf_Word sizeless_shndx;
	Elf *sizeless_elf;

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

	/* Return true iff we consider ADDR to lie in the same section as SYM. */
	static inline bool
	same_section (struct search_state *state,
	GElf_Addr value, Elf *symelf, GElf_Word shndx)
	{
	/* For absolute symbols and the like, only match exactly. */
	if (shndx >= SHN_LORESERVE)
	return value == state->addr;

	/* If value might not be st_value, the shndx of the symbol might
	not match the section of the value. Explicitly look both up. */
	if (! state->adjust_st_value)
	{
	Dwarf_Addr v;
	if (state->addr_shndx == SHN_UNDEF)
	{
	v = state->addr;
	state->addr_shndx = __libdwfl_find_section_ndx (state->mod, &v);
	}

	v = value;
	return state->addr_shndx == __libdwfl_find_section_ndx (state->mod, &v);
	}

	/* Figure out what section ADDR lies in. */
	if (state->addr_shndx == SHN_UNDEF \|\| state->addr_symelf != symelf)
	{
	GElf_Addr mod_addr = dwfl_deadjust_st_value (state->mod, symelf,
	state->addr);
	Elf_Scn *scn = NULL;
	state->addr_shndx = SHN_ABS;
	state->addr_symelf = symelf;
	while ((scn = elf_nextscn (symelf, 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)
	{
	state->addr_shndx = elf_ndxscn (scn);
	break;
	}
	}
	}

	return shndx == state->addr_shndx && state->addr_symelf == symelf;
	}

	/* Return GELF_ST_BIND as higher-is-better integer. */
	static 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;
	}
	}

	/* Try one symbol and associated value from the search table. */
	static inline void
	try_sym_value (struct search_state *state,
	GElf_Addr value, GElf_Sym *sym,
	const char *name, GElf_Word shndx,
	Elf *elf, bool resolved)
	{
	/* Even if we don't choose this symbol, its existence excludes
	any sizeless symbol (assembly label) that is below its upper
	bound. */
	if (value + sym->st_size > state->min_label)
	state->min_label = value + sym->st_size;

	if (sym->st_size == 0 \|\| state->addr - value < sym->st_size)
	{
	/* This symbol is a better candidate than the current one
	if it's closer to ADDR or is global when it was local. */
	if (state->closest_name == NULL
	\|\| state->closest_value < value
	\|\| binding_value (state->closest_sym) < binding_value (sym))
	{
	if (sym->st_size != 0)
	{
	state->closest_sym = sym;
	state->closest_value = value;
	state->closest_shndx = shndx;
	state->closest_elf = elf;
	state->closest_name = name;
	}
	else if (state->closest_name == NULL
	&& value >= state->min_label
	&& same_section (state, value,
	resolved ? state->mod->main.elf : elf,
	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. */
	state->sizeless_sym = *sym;
	state->sizeless_value = value;
	state->sizeless_shndx = shndx;
	state->sizeless_elf = elf;
	state->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
	&& state->closest_value == value
	&& ((state->closest_sym->st_size > sym->st_size
	&& (binding_value (state->closest_sym)
	<= binding_value (sym)))
	\|\| (state->closest_sym->st_size >= sym->st_size
	&& (binding_value (state->closest_sym)
	< binding_value (sym)))))
	{
	state->closest_sym = sym;
	state->closest_value = value;
	state->closest_shndx = shndx;
	state->closest_elf = elf;
	state->closest_name = name;
	}
	}
	}

	/* Look through the symbol table for a matching symbol. */
	static inline void
	search_table (struct search_state *state, int start, int end)
	{
	for (int i = start; i < end; ++i)
	{
	GElf_Sym sym;
	GElf_Addr value;
	GElf_Word shndx;
	Elf *elf;
	bool resolved;
	const char *name = __libdwfl_getsym (state->mod, i, &sym, &value,
	&shndx, &elf, NULL,
	&resolved,
	state->adjust_st_value);
	if (name != NULL && name[0] != '\0'
	&& sym.st_shndx != SHN_UNDEF
	&& value <= state->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)
	{
	try_sym_value (state, value, &sym, name, shndx, elf, resolved);

	/* If this is an addrinfo variant and the value could be
	resolved then also try matching the (adjusted) st_value. */
	if (resolved && state->mod->e_type != ET_REL)
	{
	GElf_Addr adjusted_st_value;
	adjusted_st_value = dwfl_adjusted_st_value (state->mod, elf,
	sym.st_value);
	if (value != adjusted_st_value
	&& adjusted_st_value <= state->addr)
	try_sym_value (state, adjusted_st_value, &sym, name, shndx,
	elf, false);
	}
	}
	}
	}

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

	Wrapper for old dwfl_module_addrsym and new dwfl_module_addrinfo.
	adjust_st_value set to true returns adjusted SYM st_value, set to false
	it will not adjust SYM at all, but does match against resolved values. */
	static const char *
	__libdwfl_addrsym (Dwfl_Module _mod, GElf_Addr _addr, GElf_Off off,
	GElf_Sym _closest_sym, GElf_Word shndxp,
	Elf *elfp, Dwarf_Addr biasp, bool _adjust_st_value)
	{
	int syments = INTUSE(dwfl_module_getsymtab) (_mod);
	if (syments < 0)
	return NULL;

	struct search_state state =
	{
	.addr = _addr,
	.mod = _mod,
	.closest_sym = _closest_sym,
	.adjust_st_value = _adjust_st_value,
	.addr_shndx = SHN_UNDEF,
	.addr_symelf = NULL,
	.closest_name = NULL,
	.closest_value = 0,
	.closest_shndx = SHN_UNDEF,
	.closest_elf = NULL,
	.sizeless_name = NULL,
	.sizeless_sym = { 0, 0, 0, 0, 0, SHN_UNDEF },
	.sizeless_value = 0,
	.sizeless_shndx = SHN_UNDEF,
	.sizeless_elf = NULL,
	.min_label = 0
	};

	/* 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 = INTUSE (dwfl_module_getsymtab_first_global) (state.mod);
	if (first_global < 0)
	return NULL;
	search_table (&state, 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 (state.closest_name == NULL && first_global > 1
	&& (state.sizeless_name == NULL \|\| state.sizeless_value != state.addr))
	search_table (&state, 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 (state.closest_name == NULL
	&& state.sizeless_name != NULL
	&& state.sizeless_value >= state.min_label)
	{
	*state.closest_sym = state.sizeless_sym;
	state.closest_value = state.sizeless_value;
	state.closest_shndx = state.sizeless_shndx;
	state.closest_elf = state.sizeless_elf;
	state.closest_name = state.sizeless_name;
	}

	*off = state.addr - state.closest_value;

	if (shndxp != NULL)
	*shndxp = state.closest_shndx;
	if (elfp != NULL)
	*elfp = state.closest_elf;
	if (biasp != NULL)
	*biasp = dwfl_adjusted_st_value (state.mod, state.closest_elf, 0);
	return state.closest_name;
	}


	const char *
	dwfl_module_addrsym (Dwfl_Module *mod, GElf_Addr addr,
	GElf_Sym closest_sym, GElf_Word shndxp)
	{
	GElf_Off off;
	return __libdwfl_addrsym (mod, addr, &off, closest_sym, shndxp,
	NULL, NULL, true);
	}
	INTDEF (dwfl_module_addrsym)

	const char
	dwfl_module_addrinfo (Dwfl_Module mod, GElf_Addr address,
	GElf_Off offset, GElf_Sym sym,
	GElf_Word shndxp, Elf elfp, Dwarf_Addr bias)
	{
	return __libdwfl_addrsym (mod, address, offset, sym, shndxp, elfp, bias,
	false);
	}
	INTDEF (dwfl_module_addrinfo)