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/* Find debugging and symbol information for a module in libdwfl.
Copyright (C) 2005, 2006, 2007, 2008 Red Hat, Inc.
This file is part of Red Hat elfutils.
Red Hat elfutils is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by the
Free Software Foundation; version 2 of the License.
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WITHOUT ANY WARRANTY; without even the implied warranty of
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In addition, as a special exception, Red Hat, Inc. gives You the
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<>. */
#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, 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 = addr - mod->symfile->bias;
Elf_Scn *scn = NULL;
addr_shndx = SHN_ABS;
while ((scn = elf_nextscn (mod->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);
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. */
for (int i = 1; i < syments; ++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)
/* 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
|| (GELF_ST_BIND (closest_sym->st_info)
< GELF_ST_BIND (sym.st_info)))
if (sym.st_size != 0)
*closest_sym = sym;
closest_shndx = shndx;
closest_name = name;
else if (same_section (&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. But do not
replace a global symbol with a local! */
else if (sym.st_size != 0
&& closest_sym->st_value == sym.st_value
&& closest_sym->st_size > sym.st_size
&& (GELF_ST_BIND (closest_sym->st_info)
<= GELF_ST_BIND (sym.st_info)))
*closest_sym = sym;
closest_shndx = shndx;
closest_name = name;
/* 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)