libdwfl/dwfl_module_getsym.c

/* Find debugging and symbol information for a module in libdwfl.
   Copyright (C) 2006,2007,2009 Red Hat, Inc.
   This file is part of Red Hat elfutils.

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   it under the terms of the GNU General Public License as published by the
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   this file solely under the GPL without exception.

   Red Hat elfutils is an included package of the Open Invention Network.
   An included package of the Open Invention Network is a package for which
   Open Invention Network licensees cross-license their patents.  No patent
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#include "libdwflP.h"

const char *
dwfl_module_getsym (Dwfl_Module *mod, int ndx,
		    GElf_Sym *sym, GElf_Word *shndxp)
{
  if (unlikely (mod == NULL))
    return NULL;

  if (unlikely (mod->symdata == NULL))
    {
      int result = INTUSE(dwfl_module_getsymtab) (mod);
      if (result < 0)
	return NULL;
    }

  GElf_Word shndx;
  sym = gelf_getsymshndx (mod->symdata, mod->symxndxdata, ndx, sym, &shndx);
  if (unlikely (sym == NULL))
    {
      __libdwfl_seterrno (DWFL_E_LIBELF);
      return NULL;
    }

  if (sym->st_shndx != SHN_XINDEX)
    shndx = sym->st_shndx;

  /* Figure out whether this symbol points into an SHF_ALLOC section.  */
  bool alloc = true;
  if ((shndxp != NULL || mod->e_type != ET_REL)
      && (sym->st_shndx == SHN_XINDEX
	  || (sym->st_shndx < SHN_LORESERVE && sym->st_shndx != SHN_UNDEF)))
    {
      GElf_Shdr shdr_mem;
      GElf_Shdr *shdr = gelf_getshdr (elf_getscn (mod->symfile->elf, shndx),
				      &shdr_mem);
      alloc = unlikely (shdr == NULL) || (shdr->sh_flags & SHF_ALLOC);
    }

  if (shndxp != NULL)
    /* Yield -1 in case of a non-SHF_ALLOC section.  */
    *shndxp = alloc ? shndx : (GElf_Word) -1;

  switch (sym->st_shndx)
    {
    case SHN_ABS:		/* XXX sometimes should use bias?? */
    case SHN_UNDEF:
    case SHN_COMMON:
      break;

    default:
      if (mod->e_type == ET_REL)
	{
	  /* In an ET_REL file, the symbol table values are relative
	     to the section, not to the module's load base.  */
	  size_t symshstrndx = SHN_UNDEF;
	  Dwfl_Error result = __libdwfl_relocate_value (mod, mod->symfile->elf,
							&symshstrndx,
							shndx, &sym->st_value);
	  if (unlikely (result != DWFL_E_NOERROR))
	    {
	      __libdwfl_seterrno (result);
	      return NULL;
	    }
	}
      else if (alloc)
	/* Apply the bias to the symbol value.  */
	sym->st_value += mod->symfile->bias;
      break;
    }

  if (unlikely (sym->st_name >= mod->symstrdata->d_size))
    {
      __libdwfl_seterrno (DWFL_E_BADSTROFF);
      return NULL;
    }
  return (const char *) mod->symstrdata->d_buf + sym->st_name;
}
INTDEF (dwfl_module_getsym)