Cygwin: dll_list: stat_real_file_once with ntname

NtQueryVirtualMemory for MemorySectionName may return some old path even
if the process was just started, for when some directory in between was
renamed - maybe because the NT file cache is hot for the old path still.
This was seen during gcc bootstrap, returning a MemorySectionName of
".../gcc/xgcc.exe" even if started as ".../prev-gcc/xgcc.exe", where the
directory rename from "gcc" to "prev-gcc" was done the moment before.
As we stat the module's real file right after loading now, there is no
point in using NtQueryVirtualMemory with MemorySectionName any more, and
we can use what GetModuleFileName returned instead.

2 files changed, 8 insertions, 34 deletions

diff --git a/winsup/cygwin/dll_init.cc b/winsup/cygwin/dll_init.cc
index 4ba1bd22d..6a4ed269e 100644
--- a/winsup/cygwin/dll_init.cc
+++ b/winsup/cygwin/dll_init.cc
@@ -381,7 +381,7 @@ dll_list::alloc (HINSTANCE h, per_process *p, dll_type type)
 	  *d->forkable_ntname = L'\0';
 	}
       if (forkables_supported ())
-	d->stat_real_file_once (); /* uses nt_max_path_buf () */
+	d->stat_real_file_once ();
       append (d);
       if (type == DLL_LOAD)
 	loaded_dlls++;
diff --git a/winsup/cygwin/forkable.cc b/winsup/cygwin/forkable.cc
index 1dcafe5e1..4fbc2abb3 100644
--- a/winsup/cygwin/forkable.cc
+++ b/winsup/cygwin/forkable.cc
@@ -161,44 +161,18 @@ dll::stat_real_file_once ()
   if (fii.IndexNumber.QuadPart != -1LL)
     return true;
 
-  tmp_pathbuf tp;
-
-  HANDLE fhandle = INVALID_HANDLE_VALUE;
-  NTSTATUS status, fstatus;
-  PMEMORY_SECTION_NAME pmsi1;
-  MEMORY_SECTION_NAME msi2;
-  pmsi1 = (PMEMORY_SECTION_NAME) dll_list::nt_max_path_buf ();
-  RtlInitEmptyUnicodeString (&msi2.SectionFileName, tp.w_get (), 65535);
-
-  /* Retry opening the real file name until that does not change any more. */
-  status = NtQueryVirtualMemory (NtCurrentProcess (), handle,
-				 MemorySectionName, pmsi1, 65536, NULL);
-  while (NT_SUCCESS (status) &&
-	!RtlEqualUnicodeString (&msi2.SectionFileName,
-				&pmsi1->SectionFileName, FALSE))
+  NTSTATUS fstatus;
+  HANDLE fhandle = dll_list::ntopenfile (ntname, &fstatus);
+  if (fhandle == INVALID_HANDLE_VALUE)
     {
-      debug_printf ("for %s at %p got memory section name '%W'",
-	ntname, handle, pmsi1->SectionFileName.Buffer);
-      RtlCopyUnicodeString (&msi2.SectionFileName, &pmsi1->SectionFileName);
-      if (fhandle != INVALID_HANDLE_VALUE)
-	NtClose (fhandle);
-      pmsi1->SectionFileName.Buffer[pmsi1->SectionFileName.Length] = L'\0';
-      fhandle = dll_list::ntopenfile (pmsi1->SectionFileName.Buffer, &fstatus);
-      status = NtQueryVirtualMemory (NtCurrentProcess (), handle,
-				     MemorySectionName, pmsi1, 65536, NULL);
+      system_printf ("WARNING: Unable (ntstatus %y) to open real file %W",
+		     fstatus, ntname);
+      return false;
     }
-  if (!NT_SUCCESS (status))
-    system_printf ("WARNING: Unable (ntstatus %y) to query real file for %W",
-		   status, ntname);
-  else if (fhandle == INVALID_HANDLE_VALUE)
-    system_printf ("WARNING: Unable (ntstatus %y) to open real file for %W",
-		   fstatus, ntname);
-  if (fhandle == INVALID_HANDLE_VALUE)
-    return false;
 
   if (!dll_list::read_fii (fhandle, &fii))
     system_printf ("WARNING: Unable to read real file attributes for %W",
-		   pmsi1->SectionFileName.Buffer);
+		   ntname);
 
   NtClose (fhandle);
   return fii.IndexNumber.QuadPart != -1LL;