nameless LOAD_DLL_DEBUG_EVENT causes ntdll.dll to be missing

This is the gdbserver-equivalent of the change made in GDB to handle
the case, in x64 windows version 2012, where the kernel produces
a LOAD_DLL_DEBUG_EVENT where the name of the associated DLL cannot
be determined at that time, and thus has to be processed later.

The visible symptom is that ntdll.dll is missing from the list of
shared libraries known to be mapped by the inferior, with other
side-effects such as failure to unwind through code provided by
that DLL (such as exception handling routines).

gdb/gdbserver/ChangeLog:

	* Makefile.in (safe-ctype.o, lbasename.o): New rules.
	* configure.srv: Add safe-ctype.o and lbasename.o to srv_tgtobj
	for all targets that use win32-low.c.
	* win32-low.c (win32_ensure_ntdll_loaded): New function.
	(do_initial_child_stuff): Add call to win32_ensure_ntdll_loaded.

4 files changed, 107 insertions, 0 deletions

diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index 9f8eb9e..c73840f 100644
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,3 +1,11 @@
+2013-12-13  Joel Brobecker  <brobecker@adacore.com>
+
+	* Makefile.in (safe-ctype.o, lbasename.o): New rules.
+	* configure.srv: Add safe-ctype.o and lbasename.o to srv_tgtobj
+	for all targets that use win32-low.c.
+	* win32-low.c (win32_ensure_ntdll_loaded): New function.
+	(do_initial_child_stuff): Add call to win32_ensure_ntdll_loaded.
+
 2013-12-13  Pedro Alves  <palves@redhat.com>
 
 	* target.c (mywait): Set OURSTATUS->KIND to TARGET_WAITKIND_STOPPED
diff --git a/gdb/gdbserver/Makefile.in b/gdb/gdbserver/Makefile.in
index 641ea17..c8d971b 100644
--- a/gdb/gdbserver/Makefile.in
+++ b/gdb/gdbserver/Makefile.in
@@ -543,6 +543,12 @@ vasprintf.o: $(srcdir)/../../libiberty/vasprintf.c
 vsnprintf.o: $(srcdir)/../../libiberty/vsnprintf.c
 	$(COMPILE) $<
 	$(POSTCOMPILE)
+safe-ctype.o: $(srcdir)/../../libiberty/safe-ctype.c
+	$(COMPILE) $<
+	$(POSTCOMPILE)
+lbasename.o: $(srcdir)/../../libiberty/lbasename.c
+	$(COMPILE) $<
+	$(POSTCOMPILE)
 
 aarch64.c : $(srcdir)/../regformats/aarch64.dat $(regdat_sh)
 	$(SHELL) $(regdat_sh) $(srcdir)/../regformats/aarch64.dat aarch64.c
diff --git a/gdb/gdbserver/configure.srv b/gdb/gdbserver/configure.srv
index 32d935a..f4e6154 100644
--- a/gdb/gdbserver/configure.srv
+++ b/gdb/gdbserver/configure.srv
@@ -77,6 +77,7 @@ case "${target}" in
 			;;
   arm*-*-mingw32ce*)	srv_regobj=reg-arm.o
 			srv_tgtobj="win32-low.o win32-arm-low.o"
+			srv_tgtobj="${srv_tgtobj} safe-ctype.o lbasename.o"
 			srv_tgtobj="${srv_tgtobj} wincecompat.o"
 			# hostio_last_error implementation is in win32-low.c
 			srv_hostio_err_objs=""
@@ -100,6 +101,7 @@ case "${target}" in
 			;;
   i[34567]86-*-cygwin*)	srv_regobj="$srv_i386_regobj"
 			srv_tgtobj="i386-low.o win32-low.o win32-i386-low.o"
+			srv_tgtobj="${srv_tgtobj} safe-ctype.o lbasename.o"
 			srv_xmlfiles="$srv_i386_xmlfiles"
 			;;
   i[34567]86-*-linux*)	srv_regobj="$srv_i386_linux_regobj"
@@ -126,6 +128,7 @@ case "${target}" in
   i[34567]86-*-mingw32ce*)
 			srv_regobj="$srv_i386_regobj"
 			srv_tgtobj="i386-low.o win32-low.o win32-i386-low.o"
+			srv_tgtobj="${srv_tgtobj} safe-ctype.o lbasename.o"
 			srv_tgtobj="${srv_tgtobj} wincecompat.o"
 			srv_xmlfiles="$srv_i386_xmlfiles"
 			# hostio_last_error implementation is in win32-low.c
@@ -135,6 +138,7 @@ case "${target}" in
 			;;
   i[34567]86-*-mingw*)	srv_regobj="$srv_i386_regobj"
 			srv_tgtobj="i386-low.o win32-low.o win32-i386-low.o"
+			srv_tgtobj="${srv_tgtobj} safe-ctype.o lbasename.o"
 			srv_xmlfiles="$srv_i386_xmlfiles"
 			srv_mingw=yes
 			;;
@@ -326,11 +330,13 @@ case "${target}" in
 			;;
   x86_64-*-mingw*)	srv_regobj="$srv_amd64_regobj"
 			srv_tgtobj="i386-low.o i387-fp.o win32-low.o win32-i386-low.o"
+			srv_tgtobj="${srv_tgtobj} safe-ctype.o lbasename.o"
 			srv_xmlfiles="$srv_i386_xmlfiles $srv_amd64_xmlfiles"
 			srv_mingw=yes
 			;;
   x86_64-*-cygwin*)	srv_regobj="$srv_amd64_regobj"
 			srv_tgtobj="i386-low.o i387-fp.o win32-low.o win32-i386-low.o"
+			srv_tgtobj="${srv_tgtobj} safe-ctype.o lbasename.o"
 			srv_xmlfiles="$srv_i386_xmlfiles"
 			;;
 
diff --git a/gdb/gdbserver/win32-low.c b/gdb/gdbserver/win32-low.c
index a4c9e77..bcc77fb 100644
--- a/gdb/gdbserver/win32-low.c
+++ b/gdb/gdbserver/win32-low.c
@@ -105,6 +105,9 @@ typedef BOOL (WINAPI *winapi_GenerateConsoleCtrlEvent) (DWORD, DWORD);
 static ptid_t win32_wait (ptid_t ptid, struct target_waitstatus *ourstatus,
 			  int options);
 static void win32_resume (struct thread_resume *resume_info, size_t n);
+#ifndef _WIN32_WCE
+static void win32_ensure_ntdll_loaded (void);
+#endif
 
 /* Get the thread ID from the current selected inferior (the current
    thread).  */
@@ -371,6 +374,10 @@ do_initial_child_stuff (HANDLE proch, DWORD pid, int attached)
 	win32_resume (&resume, 1);
       }
     }
+
+#ifndef _WIN32_WCE
+  win32_ensure_ntdll_loaded ();
+#endif
 }
 
 /* Resume all artificially suspended threads if we are continuing
@@ -1134,6 +1141,86 @@ failed:
   return 0;
 }
 
+#ifndef _WIN32_WCE
+/* On certain versions of Windows, the information about ntdll.dll
+   is not available yet at the time we get the LOAD_DLL_DEBUG_EVENT,
+   thus preventing us from reporting this DLL as an SO. This has been
+   witnessed on Windows 8.1, for instance.  A possible explanation
+   is that ntdll.dll might be mapped before the SO info gets created
+   by the Windows system -- ntdll.dll is the first DLL to be reported
+   via LOAD_DLL_DEBUG_EVENT and other DLLs do not seem to suffer from
+   that problem.
+
+   If we indeed are missing ntdll.dll, this function tries to recover
+   from this issue, after the fact.  Do nothing if we encounter any
+   issue trying to locate that DLL.  */
+
+static void
+win32_ensure_ntdll_loaded (void)
+{
+  struct inferior_list_entry *dll_e;
+  size_t i;
+  HMODULE dh_buf[1];
+  HMODULE *DllHandle = dh_buf;
+  DWORD cbNeeded;
+  BOOL ok;
+
+  for (dll_e = all_dlls.head; dll_e != NULL; dll_e = dll_e->next)
+    {
+      struct dll_info *dll = (struct dll_info *) dll_e;
+
+      if (strcasecmp (lbasename (dll->name), "ntdll.dll") == 0)
+	return;
+    }
+
+  if (!load_psapi ())
+    return;
+
+  cbNeeded = 0;
+  ok = (*win32_EnumProcessModules) (current_process_handle,
+				    DllHandle,
+				    sizeof (HMODULE),
+				    &cbNeeded);
+
+  if (!ok || !cbNeeded)
+    return;
+
+  DllHandle = (HMODULE *) alloca (cbNeeded);
+  if (!DllHandle)
+    return;
+
+  ok = (*win32_EnumProcessModules) (current_process_handle,
+				    DllHandle,
+				    cbNeeded,
+				    &cbNeeded);
+  if (!ok)
+    return;
+
+  for (i = 0; i < ((size_t) cbNeeded / sizeof (HMODULE)); i++)
+    {
+      MODULEINFO mi;
+      char dll_name[MAX_PATH];
+
+      if (!(*win32_GetModuleInformation) (current_process_handle,
+					  DllHandle[i],
+					  &mi,
+					  sizeof (mi)))
+	continue;
+      if ((*win32_GetModuleFileNameExA) (current_process_handle,
+					 DllHandle[i],
+					 dll_name,
+					 MAX_PATH) == 0)
+	continue;
+      if (strcasecmp (lbasename (dll_name), "ntdll.dll") == 0)
+	{
+	  win32_add_one_solib (dll_name,
+			       (CORE_ADDR) (uintptr_t) mi.lpBaseOfDll);
+	  return;
+	}
+    }
+}
+#endif
+
 typedef HANDLE (WINAPI *winapi_CreateToolhelp32Snapshot) (DWORD, DWORD);
 typedef BOOL (WINAPI *winapi_Module32First) (HANDLE, LPMODULEENTRY32);
 typedef BOOL (WINAPI *winapi_Module32Next) (HANDLE, LPMODULEENTRY32);