Re: Patch : gdbserver get_image_name on CE

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

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On Tue, 2009-06-30 at 22:58 +0100, Pedro Alves wrote:
> On Tuesday 30 June 2009 22:07:19, Danny Backx wrote:
> > 
> > > Is the rest of my patch acceptable or are there things I need to
> > > address ?
> > >
> 
> Did you get to confirm what really that ERROR_PIPE_NOT_CONNECTED
> is about?
> 
>  http://sourceware.org/ml/gdb-patches/2009-06/msg00373.html
> 
> Could you post an updated, cleaned up patch, without any extra
> unnecessary bits removed, along with change log entry, using
> 'cvs diff -up'?

Attached. Comments, as always, welcome.

	Danny
-- 
Danny Backx ; danny.backx - at - scarlet.be ; http://danny.backx.info

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2009-07-01  Danny Backx  <dannybackx@users.sourceforge.net>

	* win32-i386-low.c (i386_get_thread_context): Avoid failure by
	calling GetThreadContext with flags that don't work on every
	processor. Fall back to querying less registers if that happens.
	* win32-i386-low.c (the_low_target, i386_wince_breakpoint) : Implement
	breakpoints.
	* win32-low.c (get_image_name): Don't rely on return value of
	ReadProcessMemory. Comment where some of the code still relies on
	sizeof(WCHAR) == 2.
	* win32-low.c (get_child_debug_event): Detect and work around a known
	case where CreateProcess reports success but the inferior dies
	immediately.

Index: win32-i386-low.c
===================================================================
RCS file: /cvs/src/src/gdb/gdbserver/win32-i386-low.c,v
retrieving revision 1.14
diff -u -u -p -r1.14 win32-i386-low.c
--- win32-i386-low.c	3 Jan 2009 05:57:57 -0000	1.14
+++ win32-i386-low.c	1 Jul 2009 19:28:15 -0000
@@ -39,16 +39,36 @@ i386_initial_stuff (void)
   debug_registers_used = 0;
 }
 
+/*
+ * According to Mike Stall's .net debugging blog
+ * (http://blogs.msdn.com/jmstall/archive/2005/01/18/355697.aspx)
+ * the CONTEXT_EXTENDED_REGISTERS flag must be omitted if hardware doesn't
+ * support it. So I guess the only reasonable thing to do is just try.
+ */
 static void
 i386_get_thread_context (win32_thread_info *th, DEBUG_EVENT* current_event)
 {
-  th->context.ContextFlags = \
-    CONTEXT_FULL | \
-    CONTEXT_FLOATING_POINT | \
-    CONTEXT_EXTENDED_REGISTERS | \
+  /* try all flags */
+  th->context.ContextFlags =
+    CONTEXT_FULL |
+    CONTEXT_FLOATING_POINT |
+    CONTEXT_EXTENDED_REGISTERS |
     CONTEXT_DEBUG_REGISTERS;
 
-  GetThreadContext (th->h, &th->context);
+  if (GetThreadContext (th->h, &th->context) == 0) {
+    DWORD e = GetLastError();
+
+    if (e == ERROR_INVALID_PARAMETER) {
+      /* try limited set */
+      th->context.ContextFlags = CONTEXT_FULL |
+	CONTEXT_FLOATING_POINT | CONTEXT_DEBUG_REGISTERS;
+      if (GetThreadContext (th->h, &th->context) == 0) {
+	DWORD e = GetLastError();
+	printf("GetThreadContext failure %d\n", e);
+	return;
+      }
+    }
+  }
 
   debug_registers_changed = 0;
 
@@ -193,6 +213,12 @@ i386_store_inferior_register (win32_thre
   collect_register (r, context_offset);
 }
 
+/*
+ * The INT 3 instruction is used for x86 platform breakpointing.
+ */
+static const unsigned char i386_wince_breakpoint = 0xCC;
+#define i386_wince_breakpoint_len 1
+
 struct win32_target_ops the_low_target = {
   init_registers_i386,
   sizeof (mappings) / sizeof (mappings[0]),
@@ -203,6 +229,6 @@ struct win32_target_ops the_low_target =
   i386_fetch_inferior_register,
   i386_store_inferior_register,
   i386_single_step,
-  NULL, /* breakpoint */
-  0, /* breakpoint_len */
+  &i386_wince_breakpoint, /* breakpoint */
+  i386_wince_breakpoint_len, /* breakpoint_len */
 };
Index: win32-low.c
===================================================================
RCS file: /cvs/src/src/gdb/gdbserver/win32-low.c,v
retrieving revision 1.35
diff -u -u -p -r1.35 win32-low.c
--- win32-low.c	1 Apr 2009 22:50:24 -0000	1.35
+++ win32-low.c	1 Jul 2009 19:28:15 -0000
@@ -873,14 +873,19 @@ win32_add_one_solib (const char *name, C
   loaded_dll (buf2, load_addr);
 }
 
+/*
+ * Warning : some parts of this function rely on sizeof(WCHAR) == 2
+ */
 static char *
 get_image_name (HANDLE h, void *address, int unicode)
 {
-  static char buf[(2 * MAX_PATH) + 1];
+  static char buf[(2 * MAX_PATH) + 1]; /* here */
   DWORD size = unicode ? sizeof (WCHAR) : sizeof (char);
   char *address_ptr;
+#ifndef _WIN32_WCE
   int len = 0;
-  char b[2];
+  char b[2]; /* here */
+#endif
   DWORD done;
 
   /* Attempt to read the name of the dll that was detected.
@@ -903,9 +908,28 @@ get_image_name (HANDLE h, void *address,
     return NULL;
 #endif
 
+#ifdef _WIN32_WCE
+  /* Always unicode */
+  /* Assume you can read it all in one go, or otherwise the done variable will
+   * tell you how far you've read.
+   */
+  WCHAR *wbuf = alloca ((MAX_PATH + 1) * size);
+  ReadProcessMemory (h, address_ptr, wbuf, MAX_PATH * size, &done);
+  if (done < 0 || done > MAX_PATH * size)
+	  buf[0] = '\0';
+  else {
+    int n;
+    n = wcstombs (buf, wbuf, done);
+    if (n == (size_t)-1)
+      buf[0] = '\0';
+    /* No need to address the length limit case of the wcstombs call,
+     * buf has been allocated large enough. */
+  }
+  return buf;
+#else
   /* 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)
+	 && (b[0] != 0 || b[size - 1] != 0) && done == size) /* here */
     continue;
 
   if (!unicode)
@@ -920,6 +944,7 @@ get_image_name (HANDLE h, void *address,
     }
 
   return buf;
+#endif
 }
 
 typedef BOOL (WINAPI *winapi_EnumProcessModules) (HANDLE, HMODULE *,
@@ -1365,7 +1390,20 @@ get_child_debug_event (struct target_wai
 	 interruption, but high enough so gdbserver doesn't become a
 	 bottleneck.  */
       if (!WaitForDebugEvent (&current_event, 250))
-	return 0;
+        {
+	  /*
+	   * Sometimes an application will just not start up.
+	   * Detect this here, return in such a way that the loop ends.
+	   */
+	  DWORD e = GetLastError();
+
+	  if (e == ERROR_PIPE_NOT_CONNECTED)
+	    {
+	      ourstatus->kind = TARGET_WAITKIND_EXITED;
+	      return 1;	/* break the loop in our caller */
+	    }
+   	  return 0;
+        }
     }
 
  gotevent: