[RFC-v2] Fix .text section offset for windows DLL (was Calling __stdcall functions in the inferior)

["Pierre Muller" <pierre.muller@ics-cnrs.unistra.fr>]

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  I wrote a new version of the patch
that tries to implement most of the things we talked about.

  It works quite nicely on my windows 7 64-bit using
cygwin, mingw32 or a cross-built mingw64 binary.

  Interestingly, it seems that the mingw64 binary is
not really affected by this issue because the 64-bit system DLLs
do have a section offset of 0x1000 for .text section,
while the 32-bit DLLs have 0x10000.



  
Pierre Muller


2012-11-06  Pierre Muller  <muller@sourceware.org>

        * coff-pe-read.h (pe_text_section_offset): Declare new function.
        * coff-pe-read.c (debug_coff_pe_read): New static variable.
        (struct read_pe_section_data): Add section_name field.
        (pe_as16): New function.
        (IMAGE_SCN_CNT_CODE): New macro, if not already defined.
        (IMAGE_SCN_CNT_INITIALIZED_DATA): Ditto.
        (IMAGE_SCN_CNT_UNINITIALIZED_DATA): Ditto.
        (add_pe_exported_sym): Handle unnamed exported function.
        (add_pe_forwarded_sym): New function.
        (read_pe_exported_syms): Use ordinal of function to
        retrieve correct RVA address of function and handle
        forwarded symbol.
        (pe_text_section_offset): New function.
        (show_debug_coff_pe_read): New function.
        (_initialize_coff_pe_read): New function adding
        'set/show debug coff_pe_read' commands.

        * windows-tdep.c (windows_xfer_shared_library): Use
        pe_text_section_offset function instead of possibly wrong
        0x1000 constant for .text sextion offset.



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2012-11-06  Pierre Muller  <muller@sourceware.org>

	* coff-pe-read.h (pe_text_section_offset): Declare new function.
	* coff-pe-read.c (debug_coff_pe_read): New static variable.
	(struct read_pe_section_data): Add section_name field.
	(pe_as16): New function.
	(IMAGE_SCN_CNT_CODE): New macro, if not already defined.
	(IMAGE_SCN_CNT_INITIALIZED_DATA): Ditto.
	(IMAGE_SCN_CNT_UNINITIALIZED_DATA): Ditto.
	(add_pe_exported_sym): Handle unnamed exported function.
	(add_pe_forwarded_sym): New function.
	(read_pe_exported_syms): Use ordinal of function to
	retrieve correct RVA address of function and handle
	forwarded symbol.
	(pe_text_section_offset): New function.
	(show_debug_coff_pe_read): New function.
	(_initialize_coff_pe_read): New function adding
	'set/show debug coff_pe_read' commands.

	* windows-tdep.c (windows_xfer_shared_library): Use
	pe_text_section_offset function instead of possibly wrong
	0x1000 constant for .text sextion offset.




Index: coff-pe-read.h
===================================================================
RCS file: /cvs/src/src/gdb/coff-pe-read.h,v
retrieving revision 1.11
diff -u -p -r1.11 coff-pe-read.h
--- coff-pe-read.h	4 Jan 2012 08:17:00 -0000	1.11
+++ coff-pe-read.h	6 Nov 2012 13:37:01 -0000
@@ -21,11 +21,17 @@
 
 #if !defined (COFF_PE_READ_H)
 #define COFF_PE_READ_H
+#include "defs.h"
 
 struct objfile;
+struct bfd;
 
 /* Read the export table and convert it to minimal symbol table
    entries */
 extern void read_pe_exported_syms (struct objfile *objfile);
 
+/* Extract for ABFD the offset of the .text section.
+   Returns default value 0x1000 if information is not found.  */
+extern CORE_ADDR pe_text_section_offset (struct bfd *abfd);
+
 #endif /* !defined (COFF_PE_READ_H) */
Index: coff-pe-read.c
===================================================================
RCS file: /cvs/src/src/gdb/coff-pe-read.c,v
retrieving revision 1.17
diff -u -p -r1.17 coff-pe-read.c
--- coff-pe-read.c	4 Jan 2012 08:17:00 -0000	1.17
+++ coff-pe-read.c	6 Nov 2012 13:37:01 -0000
@@ -23,16 +23,26 @@
 
 #include "coff-pe-read.h"
 
+#include <ctype.h>
 #include "defs.h"
 #include "bfd.h"
 #include "gdbtypes.h"
 
+#include "command.h"
+#include "gdbcmd.h"
 #include "symtab.h"
 #include "symfile.h"
 #include "objfiles.h"
+#include "common/common-utils.h"
 
 /* Internal section information */
 
+/* Coff PE read debugging flag:
+   default value is 0,
+   value 1 outputs problems encountered while parsing PE file,
+   value above 1 also lists all generated minimal symbols.  */
+static unsigned int debug_coff_pe_read;
+
 struct read_pe_section_data
 {
   CORE_ADDR vma_offset;		/* Offset to loaded address of section.  */
@@ -40,8 +50,18 @@ struct read_pe_section_data
   unsigned long rva_end;	/* End offset within the pe.  */
   enum minimal_symbol_type ms_type;	/* Type to assign symbols in
 					   section.  */
+  char *section_name;		/* Recorded section name.  */
 };
 
+#ifndef IMAGE_SCN_CNT_CODE
+# define IMAGE_SCN_CNT_CODE 0x20
+#endif
+#ifndef IMAGE_SCN_CNT_INITIALIZED_DATA
+# define IMAGE_SCN_CNT_INITIALIZED_DATA 0x40
+#endif
+#ifndef IMAGE_SCN_CNT_UNINITIALIZED_DATA
+# define IMAGE_SCN_CNT_UNINITIALIZED_DATA 0x80
+#endif
 #define PE_SECTION_INDEX_TEXT     0
 #define PE_SECTION_INDEX_DATA     1
 #define PE_SECTION_INDEX_BSS      2
@@ -99,9 +119,11 @@ get_section_vmas (bfd *abfd, asection *s
 static void
 add_pe_exported_sym (char *sym_name,
 		     unsigned long func_rva,
+		     int ordinal,
 		     const struct read_pe_section_data *section_data,
 		     const char *dll_name, struct objfile *objfile)
 {
+  char ordinal_name[10];
   /* Add the stored offset to get the loaded address of the symbol.  */
 
   CORE_ADDR vma = func_rva + section_data->vma_offset;
@@ -113,39 +135,130 @@ add_pe_exported_sym (char *sym_name,
      of the dll name, e.g. KERNEL32!AddAtomA.  This matches the style
      used by windbg from the "Microsoft Debugging Tools for Windows".  */
 
+  if (*sym_name == '\0')
+    {
+      xsnprintf (ordinal_name, sizeof (ordinal_name), "#%d", ordinal);
+      sym_name = ordinal_name;
+    }
+
   qualified_name = xmalloc (dll_name_len + strlen (sym_name) + 2);
 
   strncpy (qualified_name, dll_name, dll_name_len);
   qualified_name[dll_name_len] = '!';
   strcpy (qualified_name + dll_name_len + 1, sym_name);
 
+  if ((section_data->ms_type == mst_unknown) && debug_coff_pe_read)
+    printf_filtered (_("Unknown section type for \"%s\" for entry \"%s\" \
+in dll \"%s\"\n"),
+		     section_data->section_name, sym_name, dll_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, 
+  prim_record_minimal_symbol (sym_name, vma,
 			      section_data->ms_type, objfile);
+  if (debug_coff_pe_read > 1)
+    printf_filtered (_("Adding exported symbol \"%s\" in dll \"%s\"\n"),
+		     sym_name, dll_name);
 }
 
-/* Truncate a dll_name at the first dot character.  */
+/* Create a minimal symbol entry for an exported forward symbol.
+   Returns 1 if the forwarded function was found 0 otherwise.  */
 
-static void
-read_pe_truncate_name (char *dll_name)
+static int
+add_pe_forwarded_sym (char *sym_name, char *forward_dll_name,
+		      char *forward_func_name, int ordinal,
+		      const char *dll_name, struct objfile *objfile)
 {
-  while (*dll_name)
+  char ordinal_name[10];
+  int forward_dll_name_len = strlen (forward_dll_name);
+  int forward_func_name_len = strlen (forward_func_name);
+  CORE_ADDR vma;
+  struct objfile *forward_objfile;
+  struct minimal_symbol *msymbol;
+  short section;
+  enum minimal_symbol_type msymtype;
+  char *qualified_name = 0;
+  int dll_name_len = strlen (dll_name);
+  char *forward_minimal_name = xmalloc (forward_dll_name_len +
+					forward_func_name_len + 2);
+
+  strncpy (forward_minimal_name, forward_dll_name, forward_dll_name_len);
+  forward_minimal_name[forward_dll_name_len] = '!';
+  strcpy (forward_minimal_name + forward_dll_name_len + 1, forward_func_name);
+
+
+  msymbol = lookup_minimal_symbol_and_objfile (forward_minimal_name,
+					       &forward_objfile);
+
+  if (!msymbol)
     {
-      if ((*dll_name) == '.')
-	{
-	  *dll_name = '\0';	/* truncates and causes loop exit.  */
-	}
+      int i;
+      for (i = 0; i < forward_dll_name_len; i++)
+	forward_minimal_name[i] = tolower (forward_minimal_name[i]);
+      msymbol = lookup_minimal_symbol_and_objfile (forward_minimal_name,
+						   &forward_objfile);
+    }
 
-      else
-	{
-	  ++dll_name;
-	}
+  if (debug_coff_pe_read > 1)
+    printf_filtered (_("Adding forwarded exported symbol \"%s\" "
+		       "in dll \"%s\", pointing to \"%s\"\n"),
+		     sym_name, dll_name, forward_minimal_name);
+
+  xfree (forward_minimal_name);
+
+  if (!msymbol)
+    {
+      if (debug_coff_pe_read)
+	printf_filtered (_("Unable to find function \"%s\" in dll \"%s\" "
+			   ", forward of \"%s\" in dll \"%s\"\n"),
+			 forward_func_name, forward_dll_name, sym_name,
+			 dll_name);
+      return 0;
     }
+
+  vma = SYMBOL_VALUE_ADDRESS (msymbol);
+  section = SYMBOL_SECTION (msymbol);
+  msymtype = MSYMBOL_TYPE (msymbol);
+
+  /* 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".  */
+
+  if (*sym_name == '\0')
+    {
+      xsnprintf (ordinal_name, sizeof (ordinal_name), "#%d", ordinal);
+      sym_name = ordinal_name;
+    }
+
+  qualified_name = xmalloc (dll_name_len + strlen (sym_name) + 2);
+
+  strncpy (qualified_name, dll_name, dll_name_len);
+  qualified_name[dll_name_len] = '!';
+  strcpy (qualified_name + dll_name_len + 1, sym_name);
+
+  prim_record_minimal_symbol (qualified_name,
+			      vma, msymtype, objfile);
+
+  xfree (qualified_name);
+
+  /* Enter the plain name as well, which might not be unique.  */
+  prim_record_minimal_symbol (sym_name, vma,
+			      msymtype, objfile);
+  return 1;
+}
+
+/* Truncate a dll_name at the last dot character.  */
+
+static void
+read_pe_truncate_name (char *dll_name)
+{
+  char * last_point = strrchr (dll_name, '.');
+  if (last_point != NULL)
+    *last_point = '\0';
 }
 \f
 /* Low-level support functions, direct from the ld module pe-dll.c.  */
@@ -170,6 +283,14 @@ pe_get32 (bfd *abfd, int where)
 }
 
 static unsigned int
+pe_as16 (void *ptr)
+{
+  unsigned char *b = ptr;
+
+  return b[0] + (b[1] << 8);
+}
+
+static unsigned int
 pe_as32 (void *ptr)
 {
   unsigned char *b = ptr;
@@ -185,35 +306,50 @@ void
 read_pe_exported_syms (struct objfile *objfile)
 {
   bfd *dll = objfile->obfd;
+  unsigned long nbnormal, nbforward;
   unsigned long pe_header_offset, opthdr_ofs, num_entries, i;
+  unsigned long export_opthdrrva, export_opthdrsize;
   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;
+  char *dll_name = (char *) dll->filename;
+  int otherix = PE_SECTION_TABLE_SIZE;
+  int exportix = -1;
   int is_pe64 = 0;
   int is_pe32 = 0;
 
   /* Array elements are for text, data and bss in that order
-     Initialization with start_rva > end_rva guarantees that
+     Initialization with RVA_START > RVA_END guarantees that
      unused sections won't be matched.  */
-  struct read_pe_section_data section_data[PE_SECTION_TABLE_SIZE]
-    = { {0, 1, 0, mst_text},
-  {0, 1, 0, mst_data},
-  {0, 1, 0, mst_bss}
-  };
+  struct read_pe_section_data *section_data;
 
   struct cleanup *back_to = 0;
 
   char const *target = bfd_get_target (objfile->obfd);
 
+  section_data = xzalloc (PE_SECTION_TABLE_SIZE
+			 * sizeof (struct read_pe_section_data));
+
+  for (i=0; i < PE_SECTION_TABLE_SIZE; i++)
+    {
+      section_data[i].vma_offset = 0;
+      section_data[i].rva_start = 1;
+      section_data[i].rva_end = 0;
+    };
+  section_data[PE_SECTION_INDEX_TEXT].ms_type = mst_text;
+  section_data[PE_SECTION_INDEX_TEXT].section_name = ".text";
+  section_data[PE_SECTION_INDEX_DATA].ms_type = mst_data;
+  section_data[PE_SECTION_INDEX_DATA].section_name = ".data";
+  section_data[PE_SECTION_INDEX_BSS].ms_type = mst_bss;
+  section_data[PE_SECTION_INDEX_BSS].section_name = ".bss";
+
   is_pe64 = (strcmp (target, "pe-x86-64") == 0
 	     || strcmp (target, "pei-x86-64") == 0);
   is_pe32 = (strcmp (target, "pe-i386") == 0
 	     || strcmp (target, "pei-i386") == 0
 	     || strcmp (target, "pe-arm-wince-little") == 0
 	     || strcmp (target, "pei-arm-wince-little") == 0);
-
   if (!is_pe32 && !is_pe64)
     {
       /* This is not a recognized PE format file.  Abort now, because
@@ -234,21 +370,21 @@ read_pe_exported_syms (struct objfile *o
     {
       return;
     }
-
   if (is_pe64)
     {
-      export_rva = pe_get32 (dll, opthdr_ofs + 112);
-      export_size = pe_get32 (dll, opthdr_ofs + 116);
+      export_opthdrrva = pe_get32 (dll, opthdr_ofs + 112);
+      export_opthdrsize = pe_get32 (dll, opthdr_ofs + 116);
     }
   else
     {
-      export_rva = pe_get32 (dll, opthdr_ofs + 96);
-      export_size = pe_get32 (dll, opthdr_ofs + 100);
+      export_opthdrrva = pe_get32 (dll, opthdr_ofs + 96);
+      export_opthdrsize = pe_get32 (dll, opthdr_ofs + 100);
     }
   nsections = pe_get16 (dll, pe_header_offset + 4 + 2);
   secptr = (pe_header_offset + 4 + 20 +
 	    pe_get16 (dll, pe_header_offset + 4 + 16));
   expptr = 0;
+  export_size = 0;
 
   /* Get the rva and size of the export section.  */
   for (i = 0; i < nsections; i++)
@@ -262,15 +398,30 @@ read_pe_exported_syms (struct objfile *o
       bfd_seek (dll, (file_ptr) secptr1, SEEK_SET);
       bfd_bread (sname, (bfd_size_type) 8, dll);
 
-      if (vaddr <= export_rva && vaddr + vsize > export_rva)
+      if ((strcmp (sname, ".edata") == 0)
+	  || ((vaddr <= export_opthdrrva)
+	      && (export_opthdrrva < vaddr + vsize)))
 	{
-	  expptr = fptr + (export_rva - vaddr);
-	  if (export_rva + export_size > vaddr + vsize)
-	    export_size = vsize - (export_rva - vaddr);
+	  if (strcmp (sname, ".edata") != 0)
+	    {
+	      if (debug_coff_pe_read)
+		printf_filtered (_("Export RVA for dll "
+				   "\"%s\" is in section \"%s\"\n"),
+				 dll_name, sname);
+	    }
+	  else if ((export_opthdrrva != vaddr) && debug_coff_pe_read)
+	    printf_filtered (_("Wrong value of export RVA for dll \"%s\": "
+			       "0x%lx instead of 0x%lx\n"),
+			     dll_name, export_opthdrrva, vaddr);
+	  expptr = fptr + (export_opthdrrva - vaddr);
+	  exportix = i;
 	  break;
 	}
     }
 
+  export_rva = export_opthdrrva;
+  export_size = export_opthdrsize;
+
   if (export_size == 0)
     {
       /* Empty export table.  */
@@ -284,6 +435,7 @@ read_pe_exported_syms (struct objfile *o
       unsigned long secptr1 = secptr + 40 * i;
       unsigned long vsize = pe_get32 (dll, secptr1 + 8);
       unsigned long vaddr = pe_get32 (dll, secptr1 + 12);
+      unsigned long characteristics = pe_get32 (dll, secptr1 + 36);
       char sec_name[9];
       int sectix;
 
@@ -298,6 +450,24 @@ read_pe_exported_syms (struct objfile *o
 	  section_data[sectix].rva_start = vaddr;
 	  section_data[sectix].rva_end = vaddr + vsize;
 	}
+      else
+	{
+	  otherix++;
+	  section_data = xrealloc (section_data, otherix
+				   * sizeof (struct read_pe_section_data));
+	  section_data[otherix - 1].section_name = xstrdup (sec_name);
+	  section_data[otherix - 1].rva_start = vaddr;
+	  section_data[otherix - 1].rva_end = vaddr + vsize;
+	  section_data[otherix - 1].vma_offset = 0;
+	  if (characteristics & IMAGE_SCN_CNT_CODE)
+	    section_data[otherix - 1].ms_type = mst_text;
+	  else if (characteristics & IMAGE_SCN_CNT_INITIALIZED_DATA)
+	    section_data[otherix - 1].ms_type = mst_data;
+	  else if (characteristics & IMAGE_SCN_CNT_UNINITIALIZED_DATA)
+	    section_data[otherix - 1].ms_type = mst_bss;
+	  else
+	    section_data[otherix - 1].ms_type = mst_unknown;
+	}
     }
 
   expdata = (unsigned char *) xmalloc (export_size);
@@ -321,7 +491,7 @@ read_pe_exported_syms (struct objfile *o
   /* 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 = 0; i < PE_SECTION_TABLE_SIZE; i++)
+  for (i = 0; i < otherix; i++)
     {
       section_data[i].vma_offset
 	+= ANOFFSET (objfile->section_offsets, SECT_OFF_TEXT (objfile));
@@ -331,31 +501,183 @@ read_pe_exported_syms (struct objfile *o
      lower case for convenience on Windows.  */
   read_pe_truncate_name (dll_name);
 
+  if (debug_coff_pe_read)
+    printf_filtered (_("DLL \"%s\" has %ld export entries, base=%ld\n"),
+		     dll_name, nexp, ordbase);
+  nbforward = 0;
+  nbnormal = 0;
   /* Iterate through the list of symbols.  */
   for (i = 0; i < nexp; i++)
     {
       /* Pointer to the names vector.  */
       unsigned long name_rva = pe_as32 (erva + name_rvas + i * 4);
+      /* Retrieve ordinal value */
+
+      unsigned long ordinal = pe_as16 (erva + ordinals + i * 2);
+
 
       /* Pointer to the function address vector.  */
-      unsigned long func_rva = pe_as32 (erva + exp_funcbase + i * 4);
+      /* This is relatived to ordinal value. */
+      unsigned long func_rva = pe_as32 (erva + exp_funcbase +
+                                        ordinal * 4);
 
       /* Find this symbol's section in our own array.  */
       int sectix = 0;
+      int section_found = 0;
+
+      /* First handle forward cases.  */
+      if ((func_rva >= export_rva)
+	  && (func_rva < export_rva + export_size))
+	{
+	  char *forward_name = (char *) (erva + func_rva);
+	  char *funcname = (char *) (erva + name_rva);
+	  char *forward_dll_name = forward_name;
+	  char *forward_func_name = forward_name;
+	  char *sep = strchr (forward_name, '.');
+
+	  if (sep)
+	    {
+	      int len = (int) (sep - forward_name);
+	      forward_dll_name = xmalloc (len + 1);
+	      strncpy (forward_dll_name, forward_name, len);
+	      forward_dll_name[len] = '\0';
+	      forward_func_name = ++sep;
+	    }
+	  if (add_pe_forwarded_sym (funcname, forward_dll_name,
+				    forward_func_name, ordinal,
+				    dll_name, objfile) != 0)
+	    ++nbforward;
+	  if (sep)
+	    xfree (forward_dll_name);
+	  continue;
+	}
 
-      for (sectix = 0; sectix < PE_SECTION_TABLE_SIZE; ++sectix)
+      for (sectix = 0; sectix < otherix; ++sectix)
 	{
 	  if ((func_rva >= section_data[sectix].rva_start)
 	      && (func_rva < section_data[sectix].rva_end))
 	    {
+	      section_found = 1;
 	      add_pe_exported_sym (erva + name_rva,
-				   func_rva,
+				   func_rva, ordinal,
 				   section_data + sectix, dll_name, objfile);
+	      ++nbnormal;
 	      break;
 	    }
 	}
+      if (!section_found)
+	{
+	  char *funcname = (char *) (erva + name_rva);
+
+	  if (name_rva == 0)
+	    {
+	      static char null_char = '\0';
+
+	      add_pe_exported_sym (&null_char, func_rva, ordinal,
+				   section_data, dll_name, objfile);
+	      ++nbnormal;
+	    }
+	  else if (debug_coff_pe_read)
+	    printf_filtered (_("Export name \"%s\" ord. %lu, RVA 0x%lx \
+in dll \"%s\" not handled\n"),
+		     funcname, ordinal, func_rva, dll_name);
+	}
     }
 
+  if (debug_coff_pe_read)
+    printf_filtered (_("Finished reading \"%s\", exports %ld, forwards \
+%ld, total %ld/%ld.\n"),
+	     dll_name, nbnormal, nbforward,
+	     nbnormal + nbforward, nexp);
   /* Discard expdata.  */
   do_cleanups (back_to);
 }
+
+/* Extract for BFD the offset of the .text section.
+   This offset is mainly related to the offset within the file.
+   The value was previously expected to be 0x1000 for all files,
+   but some Windows OS core DLLs seem to use 0x10000 section alignement
+   which modified the return value of that function.
+   Still return default 0x1000 value if ABFD is NULL or
+   if '.text' section is not found, but that should not happen...  */
+
+#define DEFAULT_COFF_PE_TEXT_SECTION_OFFSET 0x1000
+
+CORE_ADDR
+pe_text_section_offset (struct bfd *abfd)
+
+{
+  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;
+  int is_pe64 = 0;
+  int is_pe32 = 0;
+  char const *target;
+
+  if (!abfd)
+    return DEFAULT_COFF_PE_TEXT_SECTION_OFFSET;
+
+  target = bfd_get_target (abfd);
+
+  is_pe64 = (strcmp (target, "pe-x86-64") == 0
+	     || strcmp (target, "pei-x86-64") == 0);
+  is_pe32 = (strcmp (target, "pe-i386") == 0
+	     || strcmp (target, "pei-i386") == 0
+	     || strcmp (target, "pe-arm-wince-little") == 0
+	     || strcmp (target, "pei-arm-wince-little") == 0);
+
+  if (!is_pe32 && !is_pe64)
+    {
+      /* This is not a recognized PE format file.  Abort now, because
+	 the code is untested on anything else.  *FIXME* test on
+	 further architectures and loosen or remove this test.  */
+      return DEFAULT_COFF_PE_TEXT_SECTION_OFFSET;
+    }
+
+  /* Get pe_header, optional header and numbers of sections.  */
+  pe_header_offset = pe_get32 (abfd, 0x3c);
+  opthdr_ofs = pe_header_offset + 4 + 20;
+  nsections = pe_get16 (abfd, pe_header_offset + 4 + 2);
+  secptr = (pe_header_offset + 4 + 20 +
+	    pe_get16 (abfd, pe_header_offset + 4 + 16));
+
+  /* Get the rva and size of the export section.  */
+  for (i = 0; i < nsections; i++)
+    {
+      char sname[8];
+      unsigned long secptr1 = secptr + 40 * i;
+      unsigned long vaddr = pe_get32 (abfd, secptr1 + 12);
+
+      bfd_seek (abfd, (file_ptr) secptr1, SEEK_SET);
+      bfd_bread (sname, (bfd_size_type) 8, abfd);
+      if (strcmp (sname, ".text") == 0)
+	return vaddr;
+    }
+
+  return DEFAULT_COFF_PE_TEXT_SECTION_OFFSET;
+}
+
+static void
+show_debug_coff_pe_read (struct ui_file *file, int from_tty,
+		struct cmd_list_element *c, const char *value)
+{
+  fprintf_filtered (file, _("Coff PE read debugging is %s.\n"), value);
+}
+
+void _initialize_coff_pe_read (void);
+
+void
+_initialize_coff_pe_read (void)
+{
+  add_setshow_uinteger_cmd ("coff_pe_read", class_maintenance,
+			    &debug_coff_pe_read,
+			    _("Set coff PE read debugging."),
+			    _("Show coff PE read debugging."),
+			    _("When set, debugging messages for coff reading "
+			      "of exported symbols are displayed."),
+			    NULL, show_debug_coff_pe_read,
+			    &setdebuglist, &showdebuglist);
+}
Index: windows-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/windows-tdep.c,v
retrieving revision 1.16
diff -u -p -r1.16 windows-tdep.c
--- windows-tdep.c	5 Jun 2012 13:50:57 -0000	1.16
+++ windows-tdep.c	6 Nov 2012 13:37:01 -0000
@@ -27,6 +27,10 @@
 #include "gdbcmd.h"
 #include "gdbthread.h"
 #include "objfiles.h"
+#include "symfile.h"
+#include "coff-pe-read.h"
+#include "gdb_bfd.h"
+#include "complaints.h"
 
 struct cmd_list_element *info_w32_cmdlist;
 
@@ -387,15 +391,21 @@ windows_xfer_shared_library (const char*
 			     struct gdbarch *gdbarch, struct obstack *obstack)
 {
   char *p;
+  struct bfd * dll;
+  CORE_ADDR text_offset;
+
   obstack_grow_str (obstack, "<library name=\"");
   p = xml_escape_text (so_name);
   obstack_grow_str (obstack, p);
   xfree (p);
   obstack_grow_str (obstack, "\"><segment address=\"");
-  /* The symbols in a dll are offset by 0x1000, which is the
-     offset from 0 of the first byte in an image - because of the file
-     header and the section alignment.  */
-  obstack_grow_str (obstack, paddress (gdbarch, load_addr + 0x1000));
+  dll = gdb_bfd_open_maybe_remote (so_name);
+  /* The following calls are OK even if dll is NULL.
+     The default value 0x1000 is returned by pe_text_section_offset
+     in that case.  */
+  text_offset = pe_text_section_offset (dll);
+  gdb_bfd_unref (dll);
+  obstack_grow_str (obstack, paddress (gdbarch, load_addr + text_offset));
   obstack_grow_str (obstack, "\"/></library>");
 }