[Bug win32/12716] New: addresses of exported symbols of a DLL shouldbe looked up by ordinal

["pebolle at tiscali dot nl" <sourceware-bugzilla at sourceware dot org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=12716

           Summary: addresses of exported symbols of a DLL should be
                    looked up by ordinal
           Product: gdb
           Version: 7.2
            Status: NEW
          Severity: normal
          Priority: P2
         Component: win32
        AssignedTo: unassigned@sourceware.org
        ReportedBy: pebolle@tiscali.nl


0) I ran into a PE32 DLL that exports a number of symbols. objdump shows it
uses an "Export Address Table", a "Name Pointer Table" and an "Ordinal Table".

1) If you look at objdump's dump of the EA table and the "[Ordinal/Name
Pointer] Table" one sees that the O/NP table is (basically) unsorted: it's
neither sorted on ordinal nor (alphabetically) on the symbols. BUT (the version
of) gdb (that I use) looks up the address of a symbol in the O/NP table as if
that tables has the same order as the EA table. But what gdb actually should do
is: look up a symbol in the O/NP table, get its ordinal and look up an address
in the EA table using that ordinal.

2) I just happened to use gdb with a couple of symbols (which, as I knew from
wine's debugging output, were really used) that gdb mapped to addresses that
simply were not used at all in the code paths I apparently ran. This confusing
behaviour quickly made me think that gdb never set pending breakpoints in that
DLL (which I knew as loaded at runtime through LoadLibraryA). Hence the feeling
I ran into the issue reported in bug #9474.

3) A (still untested) patch for this issue:

diff --git a/gdb/coff-pe-read.c b/gdb/coff-pe-read.c
index ca87b72..0483158 100644
--- a/gdb/coff-pe-read.c
+++ b/gdb/coff-pe-read.c
@@ -150,6 +150,14 @@ read_pe_truncate_name (char *dll_name)
     }
 }


+static unsigned int
+pe_as16 (void *ptr)
+{
+  unsigned char *b = ptr;
+
+  return b[0] + (b[1] << 8);
+}
+
 /* Low-level support functions, direct from the ld module pe-dll.c.  */
 static unsigned int
 pe_get16 (bfd *abfd, int where)
@@ -309,11 +317,11 @@ read_pe_exported_syms (struct objfile *objfile)
   bfd_bread (expdata, (bfd_size_type) export_size, dll);
   erva = expdata - export_rva;

+  ordbase = pe_as32 (expdata + 16); /* unused */
   nexp = pe_as32 (expdata + 24);
+  exp_funcbase = pe_as32 (expdata + 28);
   name_rvas = pe_as32 (expdata + 32);
   ordinals = pe_as32 (expdata + 36);
-  ordbase = pe_as32 (expdata + 16);
-  exp_funcbase = pe_as32 (expdata + 28);

   /* Use internal dll name instead of full pathname.  */
   dll_name = pe_as32 (expdata + 12) + erva;
@@ -339,8 +347,10 @@ read_pe_exported_syms (struct objfile *objfile)
       /* Pointer to the names vector.  */
       unsigned long name_rva = pe_as32 (erva + name_rvas + i * 4);

+      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);
+      unsigned long func_rva = pe_as32 (erva + exp_funcbase + ordinal * 4);

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

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