Re: Patch : gdbserver get_image_name on CE

[Danny Backx <danny.backx@scarlet.be>]

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Ping ?

On Wed, 2009-07-08 at 13:33 +0200, Danny Backx wrote:
> On Wed, 2009-07-08 at 11:55 +0200, Danny Backx wrote:
> > It looks like ReadProcessMemory refuses to read from an address beyond
> > the pointer, but it does work from the pointer itself.
> > 
> > I've changed my code such that it loops, and tries to read a bigger
> > chunk of memory at each iteration.
> > 
> > I'm not bothering you with that code or its debug output right now.
> > 
> > In that way, the code appears to work, and it complies with the
> > documentation saying not to read more than required.
> > 
> > Shall I submit a new patch based on this ?
> > 
> > 	Danny
> 
> Ignore that question, here's the patch.
> 
> Please comment on its contents and on my adherence to the coding
> standards. Apologies for that, I seem to have a hard time learning that.
> 
> 	Danny
> 
> 2009-07-08  Danny Backx  <dannybackx@users.sourceforge.net>
> 
> 	* win32-low.c (get_image_name) : Work around ReadProcessMemory
> 	failure when reading at arbitrary addresses.
> 
-- 
Danny Backx ; danny.backx - at - scarlet.be ; http://danny.backx.info

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? win32-low.c.ok
? x
Index: win32-low.c
===================================================================
RCS file: /cvs/src/src/gdb/gdbserver/win32-low.c,v
retrieving revision 1.38
diff -u -r1.38 win32-low.c
--- win32-low.c	4 Jul 2009 18:13:28 -0000	1.38
+++ win32-low.c	8 Jul 2009 11:29:25 -0000
@@ -922,7 +922,6 @@
   DWORD size = unicode ? sizeof (WCHAR) : sizeof (char);
   char *address_ptr;
   int len = 0;
-  char b[2];
   DWORD done;
 
   /* Attempt to read the name of the dll that was detected.
@@ -945,21 +944,23 @@
     return NULL;
 #endif
 
-  /* Find the length of the string */
-  while (ReadProcessMemory (h, address_ptr + len++ * size, &b, size, &done)
-	 && (b[0] != 0 || b[size - 1] != 0) && done == size)
-    continue;
+  /* ReadProcessMemory sometimes fails when reading a (w)char at a time, but
+   * we can't just read MAX_PATH (w)chars either : msdn says not to cross the
+   * boundary into inaccessible areas.
+   * So we loop, reading more characters each time, until we find the NULL.
+   */
+  WCHAR *wbuf = alloca ((MAX_PATH + 1) * size);
+  while (1)
+    {
+      ReadProcessMemory (h, address_ptr, wbuf, ++len * size, &done);
+      if (wbuf[len - 1] == 0)
+        break;
+    }
 
   if (!unicode)
     ReadProcessMemory (h, address_ptr, buf, len, &done);
   else
-    {
-      WCHAR *unicode_address = (WCHAR *) alloca (len * sizeof (WCHAR));
-      ReadProcessMemory (h, address_ptr, unicode_address, len * sizeof (WCHAR),
-			 &done);
-
-      WideCharToMultiByte (CP_ACP, 0, unicode_address, len, buf, len, 0, 0);
-    }
+    WideCharToMultiByte (CP_ACP, 0, wbuf, len, buf, len, 0, 0);
 
   return buf;
 }