Re: [RFA] DLLs without debugging symbols (repost)

Elena Zannoni
2003-02-20T02:18:39Z

Raoul Gough writes:
> Apparently my copyright assignment forms have now been processed, so
> my patches for extracting minimal symbols from DLLs could now be
> entered into CVS. This message includes up-to-date diffs with the
> latest versions of the relevant files, as well as some documentation
> that I've added to gdb.texinfo (basically, there's a new node under
> the Cygwin Native node entitled "Non-debug DLL symbols" which explains
> some of the tricks involved).
>
> Regards,
> Raoul Gough.

Argh, my mailer cut out the new files from the reply....I thought you
didn't post them. See below.

You can run the new files through the gdb_indent.sh script before
committing them. That will format them porperly, getting rid of long
lines too. The script is in the gdb directory.

/* Interface to coff-pe-read.c (portable-executable-specific symbol =
reader).

Copyright 2003 Free Software Foundation, Inc.

This file is part of GDB.

This program 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; either version 2 of the License, or
(at your option) any later version.

This program 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 a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.

Contributed by Raoul M. Gough (RaoulGough@yahoo.co.uk). */

#if !defined (COFF_PE_READ_H)
#define COFF_PE_READ_H

struct objfile;

/* Read the export table and convert it to minimal symbol table entries =
*/
void read_pe_exported_syms (struct objfile *objfile);

^^^^^^ extern

Rest is ok

elena

#endif /* !defined (COFF_PE_READ_H) */

/* Read the export table symbols from a portable executable and
convert to internal format, for GDB. Used as a last resort if no
debugging symbols recognized.

Copyright 2003 Free Software Foundation, Inc.

This file is part of GDB.

This program 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; either version 2 of the License, or
(at your option) any later version.

This program 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 a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.

Contributed by Raoul M. Gough (RaoulGough@yahoo.co.uk). */

#include "coff-pe-read.h"

#include "bfd.h"

#include "defs.h"
#include "gdbtypes.h"

#include "symtab.h"
#include "symfile.h"
#include "objfiles.h"

/* Internal section information */

struct read_pe_section_data
{
CORE_ADDR vma_offset; /* Offset to loaded address of =
section.*/
unsigned long rva_start; /* Start offset within the pe. */
unsigned long rva_end; /* End offset within the pe. */
enum minimal_symbol_type ms_type; /* Type to assign symbols in =
section. */
};

#define PE_SECTION_INDEX_TEXT 0
#define PE_SECTION_INDEX_DATA 1
#define PE_SECTION_INDEX_BSS 2
#define PE_SECTION_TABLE_SIZE 3
#define PE_SECTION_INDEX_INVALID -1
=0C
/* Get the index of the named section in our own array, which contains
text, data and bss in that order. Return PE_SECTION_INDEX_INVALID
if passed an unrecognised section name. */

static int
read_pe_section_index (const char *section_name)
{
if (strcmp (section_name, ".text") =3D=3D 0)
{
return PE_SECTION_INDEX_TEXT;
}

else if (strcmp (section_name, ".data") =3D=3D 0)
{
return PE_SECTION_INDEX_DATA;
}

else if (strcmp (section_name, ".bss") =3D=3D 0)
{
return PE_SECTION_INDEX_BSS;
}

else
{
return PE_SECTION_INDEX_INVALID;
}
}

/* Record the virtual memory address of a section. */

static void
get_section_vmas (bfd *abfd, asection *sectp, void *context)
{
struct read_pe_section_data *sections =3D context;
int sectix =3D read_pe_section_index (sectp->name);

if (sectix !=3D PE_SECTION_INDEX_INVALID)
{
/* Data within the section start at rva_start in the pe and at
bfd_get_section_vma() within memory. Store the offset. */

sections[sectix].vma_offset
=3D bfd_get_section_vma (abfd, sectp) - sections[sectix].rva_start;
}
}
=0C
/* Create a minimal symbol entry for an exported symbol. */

static void
add_pe_exported_sym (char *sym_name,
unsigned long func_rva,
const struct read_pe_section_data *section_data,
const char *dll_name,
struct objfile *objfile)
{
/* Add the stored offset to get the loaded address of the symbol. */

CORE_ADDR vma =3D func_rva + section_data->vma_offset;

char *qualified_name =3D 0;
int dll_name_len =3D strlen (dll_name);
int count;

/* Generate a (hopefully unique) qualified name using the first part
of the dll name, e.g. KERNEL32!AddAtomA. This matches the style
used by windbg from the "Microsoft Debugging Tools for Windows". */

qualified_name =3D xmalloc (dll_name_len + strlen (sym_name) + 2);

strncpy (qualified_name, dll_name, dll_name_len);
qualified_name[dll_name_len] =3D '!';
strcpy (qualified_name + dll_name_len + 1, sym_name);

prim_record_minimal_symbol (qualified_name,
vma,
section_data->ms_type,
objfile);

xfree (qualified_name);

/* Enter the plain name as well, which might not be unique. */
prim_record_minimal_symbol (sym_name,
vma,
section_data->ms_type,
objfile);
}

/* Truncate a dll_name at the first dot character. */

static void
read_pe_truncate_name (char *dll_name)
{
while (*dll_name)
{
if ((*dll_name) =3D=3D '.')
{
*dll_name =3D '\0'; /* truncates and causes loop exit. */
}

else
{
++dll_name;
}
}
}
=0C
/* Low-level support functions, direct from the ld module pe-dll.c. */
static unsigned int
pe_get16 (bfd *abfd, int where)
{
unsigned char b[2];

bfd_seek (abfd, (file_ptr) where, SEEK_SET);
bfd_bread (b, (bfd_size_type) 2, abfd);
return b[0] + (b[1] << 8);
}

static unsigned int
pe_get32 (bfd *abfd, int where)
{
unsigned char b[4];

bfd_seek (abfd, (file_ptr) where, SEEK_SET);
bfd_bread (b, (bfd_size_type) 4, abfd);
return b[0] + (b[1] << 8) + (b[2] << 16) + (b[3] << 24);
}

static unsigned int
pe_as32 (void *ptr)
{
unsigned char *b =3D ptr;

return b[0] + (b[1] << 8) + (b[2] << 16) + (b[3] << 24);
}
=0C
/* Read the (non-debug) export symbol table from a portable
executable. Code originally lifted from the ld function
pe_implied_import_dll in pe-dll.c. */

void
read_pe_exported_syms (struct objfile *objfile)
{
bfd *dll =3D objfile->obfd;
unsigned long pe_header_offset, opthdr_ofs, num_entries, i;
unsigned long export_rva, export_size, nsections, secptr, expptr;
unsigned long exp_funcbase;
unsigned char *expdata, *erva;
unsigned long name_rvas, ordinals, nexp, ordbase;
char *dll_name;

/* Array elements are for text, data and bss in that order
Initialization with start_rva > end_rva guarantees that
unused sections won't be matched. */
struct read_pe_section_data section_data[PE_SECTION_TABLE_SIZE]
=3D { {0, 1, 0, mst_text},
{0, 1, 0, mst_data},
{0, 1, 0, mst_bss} };

struct cleanup *back_to =3D 0;

char const *target =3D bfd_get_target (objfile->obfd);

if ((strcmp (target, "pe-i386") !=3D 0) && (strcmp (target, =
"pei-i386") !=3D 0))
{
/* This is not an i386 format file. Abort now, because the code
is untested on anything else. *FIXME* test on further
architectures and loosen or remove this test. */
return;
}

/* Get pe_header, optional header and numbers of export entries. */
pe_header_offset =3D pe_get32 (dll, 0x3c);
opthdr_ofs =3D pe_header_offset + 4 + 20;
num_entries =3D pe_get32 (dll, opthdr_ofs + 92);

if (num_entries < 1) /* No exports. */
{
return;
}

export_rva =3D pe_get32 (dll, opthdr_ofs + 96);
export_size =3D pe_get32 (dll, opthdr_ofs + 100);
nsections =3D pe_get16 (dll, pe_header_offset + 4 + 2);
secptr =3D (pe_header_offset + 4 + 20 +
pe_get16 (dll, pe_header_offset + 4 + 16));
expptr =3D 0;

/* Get the rva and size of the export section. */=20
for (i =3D 0; i < nsections; i++)
{
char sname[8];
unsigned long secptr1 =3D secptr + 40 * i;
unsigned long vaddr =3D pe_get32 (dll, secptr1 + 12);
unsigned long vsize =3D pe_get32 (dll, secptr1 + 16);
unsigned long fptr =3D pe_get32 (dll, secptr1 + 20);

bfd_seek (dll, (file_ptr) secptr1, SEEK_SET);
bfd_bread (sname, (bfd_size_type) 8, dll);

if (vaddr <=3D export_rva && vaddr + vsize > export_rva)
{
expptr =3D fptr + (export_rva - vaddr);
if (export_rva + export_size > vaddr + vsize)
export_size =3D vsize - (export_rva - vaddr);
break;
}
}

if (export_size =3D=3D 0)
{
/* Empty export table. */
return;
}

/* Scan sections and store the base and size of the relevant sections. =
*/
for (i =3D 0; i < nsections; i++)
{
unsigned long secptr1 =3D secptr + 40 * i;
unsigned long vsize =3D pe_get32 (dll, secptr1 + 8);
unsigned long vaddr =3D pe_get32 (dll, secptr1 + 12);
unsigned long flags =3D pe_get32 (dll, secptr1 + 36);
char sec_name[9];
int sectix;

sec_name[8] =3D '\0';
bfd_seek (dll, (file_ptr) secptr1 + 0, SEEK_SET);
bfd_bread (sec_name, (bfd_size_type) 8, dll);

sectix =3D read_pe_section_index (sec_name);

if (sectix !=3D PE_SECTION_INDEX_INVALID)
{
section_data[sectix].rva_start =3D vaddr;
section_data[sectix].rva_end =3D vaddr + vsize;
}
}

expdata =3D (unsigned char *) xmalloc (export_size);
back_to =3D make_cleanup (xfree, expdata);

bfd_seek (dll, (file_ptr) expptr, SEEK_SET);
bfd_bread (expdata, (bfd_size_type) export_size, dll);
erva =3D expdata - export_rva;

nexp =3D pe_as32 (expdata + 24);
name_rvas =3D pe_as32 (expdata + 32);
ordinals =3D pe_as32 (expdata + 36);
ordbase =3D pe_as32 (expdata + 16);
exp_funcbase =3D pe_as32 (expdata + 28);

/* Use internal dll name instead of full pathname. */
dll_name =3D pe_as32 (expdata + 12) + erva;

bfd_map_over_sections (dll, get_section_vmas, section_data);

/* Adjust the vma_offsets in case this PE got relocated. This
assumes that *all* sections share the same relocation offset
as the text section. */
for (i =3D 0; i < PE_SECTION_TABLE_SIZE; i++)
{
section_data[i].vma_offset
+=3D ANOFFSET (objfile->section_offsets, SECT_OFF_TEXT (objfile));
}

printf_filtered ("Minimal symbols from %s...", dll_name);
wrap_here ("");

/* Truncate name at first dot. Should maybe also convert to all
lower case for convenience on Windows. */
read_pe_truncate_name (dll_name);

/* Iterate through the list of symbols. */
for (i =3D 0; i < nexp; i++)
{
/* Pointer to the names vector. */
unsigned long name_rva =3D pe_as32 (erva + name_rvas + i * 4);

/* Pointer to the function address vector. */=20
unsigned long func_rva =3D pe_as32 (erva + exp_funcbase + i * 4);

/* Find this symbol's section in our own array. */
int sectix =3D 0;

for (sectix =3D 0; sectix < PE_SECTION_TABLE_SIZE; ++sectix)
{
if ((func_rva >=3D section_data[sectix].rva_start)
&& (func_rva < section_data[sectix].rva_end))
{
add_pe_exported_sym (erva + name_rva,
func_rva,
section_data + sectix,
dll_name,
objfile);
break;
}
}
}

/* discard expdata. */
do_cleanups (back_to);
}