Re: [PATCH] Cygwin: pipe: Give up to use query_hdl for non-cygwin apps.

[Takashi Yano <takashi.yano@nifty.ne.jp>]

[-- Attachment #1: Type: text/plain, Size: 4475 bytes --]

On Tue, 5 Mar 2024 17:54:19 +0100
Corinna Vinschen wrote:
> On Mar  5 23:47, Takashi Yano wrote:
> > On Tue, 5 Mar 2024 11:14:46 +0100
> > Corinna Vinschen wrote:
> > > This doesn't affect your patch, but while looking into this, what
> > > strikes me as weird is that fhandler_pipe::temporary_query_hdl() calls
> > > NtQueryObject() and assembles the pipe name via swscanf() every time it
> > > is called.
> > > 
> > > Wouldn't it make sense to store the name in the fhandler's
> > > path_conv::wide_path/uni_path at creation time instead?
> > > The wide_path member is not used at all in pipes, ostensibly.
> > 
> > Is the patch attached as you intended?
> 
> Yes, but it looks like it misses a few potential simplifications:
> 
> > diff --git a/winsup/cygwin/fhandler/pipe.cc b/winsup/cygwin/fhandler/pipe.cc
> > index c877d89d7..0611dd1c3 100644
> > --- a/winsup/cygwin/fhandler/pipe.cc
> > +++ b/winsup/cygwin/fhandler/pipe.cc
> > @@ -93,6 +93,19 @@ fhandler_pipe::init (HANDLE f, DWORD a, mode_t mode, int64_t uniq_id)
> >         even with FILE_SYNCHRONOUS_IO_NONALERT. */
> >      set_pipe_non_blocking (get_device () == FH_PIPER ?
> >  			   true : is_nonblocking ());
> > +
> > +  /* Store pipe name to path_conv pc for query_hdl check */
> > +  if (get_dev () == FH_PIPEW)
> > +    {
> > +      ULONG len;
> > +      tmp_pathbuf tp;
> > +      OBJECT_NAME_INFORMATION *ntfn = (OBJECT_NAME_INFORMATION *) tp.w_get ();
> > +      NTSTATUS status = NtQueryObject (f, ObjectNameInformation, ntfn,
> > +				       65536, &len);
> > +      if (NT_SUCCESS (status) && ntfn->Name.Buffer)
> > +	pc.set_nt_native_path (&ntfn->Name);
> 
> We don't have to call NtQueryObject.  The name is created in nt_create()
> and we know the unique id, so the name is
> 
>   "%S%S-%u-pipe-nt-%p", &ro_u_ntfs, &cygheap->installation_key,
>   			GetCurrentProcessId (), unique_id);
> 
> Do you think it's cheaper to call NtQueryObject()?  If so, no worries,
> but NtQueryObject() has to call into the kernel, while just creating
> the name by ourselves doesn't.
> 
> > @@ -1149,6 +1162,9 @@ fhandler_pipe::temporary_query_hdl ()
> >    tmp_pathbuf tp;
> >    OBJECT_NAME_INFORMATION *ntfn = (OBJECT_NAME_INFORMATION *) tp.w_get ();
> >  
> > +  UNICODE_STRING *name = pc.get_nt_native_path (NULL);
> > +  name->Buffer[name->Length / sizeof (WCHAR)] = L'\0';
> 
> The string returned by get_nt_native_path() is always NUL-terminated.
> 
> >    /* Try process handle opened and pipe handle value cached first
> >       in order to reduce overhead. */
> >    if (query_hdl_proc && query_hdl_value)
> > @@ -1161,14 +1177,7 @@ fhandler_pipe::temporary_query_hdl ()
> >        status = NtQueryObject (h, ObjectNameInformation, ntfn, 65536, &len);
> >        if (!NT_SUCCESS (status) || !ntfn->Name.Buffer)
> >  	goto hdl_err;
> > -      ntfn->Name.Buffer[ntfn->Name.Length / sizeof (WCHAR)] = L'\0';
> > -      uint64_t key;
> > -      DWORD pid;
> > -      LONG id;
> > -      if (swscanf (ntfn->Name.Buffer,
> > -		   L"\\Device\\NamedPipe\\%llx-%u-pipe-nt-0x%x",
> > -		   &key, &pid, &id) == 3 &&
> > -	  key == pipename_key && pid == pipename_pid && id == pipename_id)
> > +      if (RtlEqualUnicodeString (name, &ntfn->Name, FALSE))
> >  	return h;
> >  hdl_err:
> >        CloseHandle (h);
> > @@ -1178,19 +1187,9 @@ cache_err:
> >        query_hdl_value = NULL;
> >      }
> >  
> > -  status = NtQueryObject (get_handle (), ObjectNameInformation, ntfn,
> > -			  65536, &len);
> > -  if (!NT_SUCCESS (status) || !ntfn->Name.Buffer)
> > +  if (name->Length == 0 || name->Buffer == NULL)
> >      return NULL; /* Non cygwin pipe? */
> > -  WCHAR name[MAX_PATH];
> > -  int namelen = min (ntfn->Name.Length / sizeof (WCHAR), MAX_PATH-1);
> > -  memcpy (name, ntfn->Name.Buffer, namelen * sizeof (WCHAR));
> > -  name[namelen] = L'\0';
> > -  if (swscanf (name, L"\\Device\\NamedPipe\\%llx-%u-pipe-nt-0x%x",
> > -	       &pipename_key, &pipename_pid, &pipename_id) != 3)
> > -    return NULL; /* Non cygwin pipe? */
> > -
> > -  return get_query_hdl_per_process (name, ntfn); /* Since Win8 */
> > +  return get_query_hdl_per_process (name->Buffer, ntfn); /* Since Win8 */
> 
> Given the name is stored in the fhandler, get_query_hdl_per_process()
> doesn't need it as argument, and get_query_hdl_per_process() can just
> call RtlCompareUnicodeString() instead of adding a \0 and calling
> wcscmp().

Thanks for advice. I have revised the patch.

-- 
Takashi Yano <takashi.yano@nifty.ne.jp>

[-- Attachment #2: v2-0001-Cygwin-pipe-Simplify-chhecking-procedure-of-query.patch --]
[-- Type: text/plain, Size: 5000 bytes --]

From aac59194af8bb80a6b9a0891a27fd7de9d0b69fc Mon Sep 17 00:00:00 2001
From: Takashi Yano <takashi.yano@nifty.ne.jp>
Date: Tue, 5 Mar 2024 23:34:21 +0900
Subject: [PATCH v2] Cygwin: pipe: Simplify chhecking procedure of query_hdl.

This patch eliminates verbose NtQueryObject() calls in the procedure
to get query_hdl by storing pipe name into fhandler_base::pc when
the pipe is created.  fhandler_pipe::temporary_query_hdl() uses the
storedpipe name rather than the name retrieved by NtQueryObject().

Suggested-by: Corinna Vinschen <corinna@vinschen.de>
Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>
---
 winsup/cygwin/fhandler/pipe.cc          | 47 ++++++++++++-------------
 winsup/cygwin/local_includes/fhandler.h |  5 +--
 2 files changed, 24 insertions(+), 28 deletions(-)

diff --git a/winsup/cygwin/fhandler/pipe.cc b/winsup/cygwin/fhandler/pipe.cc
index c877d89d7..0d57f5585 100644
--- a/winsup/cygwin/fhandler/pipe.cc
+++ b/winsup/cygwin/fhandler/pipe.cc
@@ -93,6 +93,21 @@ fhandler_pipe::init (HANDLE f, DWORD a, mode_t mode, int64_t uniq_id)
        even with FILE_SYNCHRONOUS_IO_NONALERT. */
     set_pipe_non_blocking (get_device () == FH_PIPER ?
 			   true : is_nonblocking ());
+
+  /* Store pipe name to path_conv pc for query_hdl check */
+  if (get_dev () == FH_PIPEW)
+    {
+      UNICODE_STRING name;
+      WCHAR pipename_buf[MAX_PATH];
+      __small_swprintf (pipename_buf, L"%S%S-%u-pipe-nt-%p",
+			&ro_u_npfs, &cygheap->installation_key,
+			GetCurrentProcessId (), unique_id >> 32);
+      name.Length = wcslen (pipename_buf) * sizeof (WCHAR);
+      name.MaximumLength = MAX_PATH * sizeof (WCHAR);
+      name.Buffer = pipename_buf;
+      pc.set_nt_native_path (&name);
+    }
+
   return 1;
 }
 
@@ -1149,6 +1164,8 @@ fhandler_pipe::temporary_query_hdl ()
   tmp_pathbuf tp;
   OBJECT_NAME_INFORMATION *ntfn = (OBJECT_NAME_INFORMATION *) tp.w_get ();
 
+  UNICODE_STRING *name = pc.get_nt_native_path (NULL);
+
   /* Try process handle opened and pipe handle value cached first
      in order to reduce overhead. */
   if (query_hdl_proc && query_hdl_value)
@@ -1161,14 +1178,7 @@ fhandler_pipe::temporary_query_hdl ()
       status = NtQueryObject (h, ObjectNameInformation, ntfn, 65536, &len);
       if (!NT_SUCCESS (status) || !ntfn->Name.Buffer)
 	goto hdl_err;
-      ntfn->Name.Buffer[ntfn->Name.Length / sizeof (WCHAR)] = L'\0';
-      uint64_t key;
-      DWORD pid;
-      LONG id;
-      if (swscanf (ntfn->Name.Buffer,
-		   L"\\Device\\NamedPipe\\%llx-%u-pipe-nt-0x%x",
-		   &key, &pid, &id) == 3 &&
-	  key == pipename_key && pid == pipename_pid && id == pipename_id)
+      if (RtlEqualUnicodeString (name, &ntfn->Name, FALSE))
 	return h;
 hdl_err:
       CloseHandle (h);
@@ -1178,24 +1188,13 @@ cache_err:
       query_hdl_value = NULL;
     }
 
-  status = NtQueryObject (get_handle (), ObjectNameInformation, ntfn,
-			  65536, &len);
-  if (!NT_SUCCESS (status) || !ntfn->Name.Buffer)
-    return NULL; /* Non cygwin pipe? */
-  WCHAR name[MAX_PATH];
-  int namelen = min (ntfn->Name.Length / sizeof (WCHAR), MAX_PATH-1);
-  memcpy (name, ntfn->Name.Buffer, namelen * sizeof (WCHAR));
-  name[namelen] = L'\0';
-  if (swscanf (name, L"\\Device\\NamedPipe\\%llx-%u-pipe-nt-0x%x",
-	       &pipename_key, &pipename_pid, &pipename_id) != 3)
+  if (name->Length == 0 || name->Buffer == NULL)
     return NULL; /* Non cygwin pipe? */
-
-  return get_query_hdl_per_process (name, ntfn); /* Since Win8 */
+  return get_query_hdl_per_process (ntfn); /* Since Win8 */
 }
 
 HANDLE
-fhandler_pipe::get_query_hdl_per_process (WCHAR *name,
-					  OBJECT_NAME_INFORMATION *ntfn)
+fhandler_pipe::get_query_hdl_per_process (OBJECT_NAME_INFORMATION *ntfn)
 {
   winpids pids ((DWORD) 0);
 
@@ -1272,8 +1271,8 @@ fhandler_pipe::get_query_hdl_per_process (WCHAR *name,
 				  ntfn, 65536, &len);
 	  if (!NT_SUCCESS (status) || !ntfn->Name.Buffer)
 	    goto close_handle;
-	  ntfn->Name.Buffer[ntfn->Name.Length / sizeof (WCHAR)] = L'\0';
-	  if (wcscmp (name, ntfn->Name.Buffer) == 0)
+	  if (RtlEqualUnicodeString (pc.get_nt_native_path (),
+				     &ntfn->Name, FALSE))
 	    {
 	      query_hdl_proc = proc;
 	      query_hdl_value = (HANDLE)(intptr_t) phi->Handles[j].HandleValue;
diff --git a/winsup/cygwin/local_includes/fhandler.h b/winsup/cygwin/local_includes/fhandler.h
index 6ddf37370..8729eb276 100644
--- a/winsup/cygwin/local_includes/fhandler.h
+++ b/winsup/cygwin/local_includes/fhandler.h
@@ -1216,11 +1216,8 @@ private:
   HANDLE query_hdl_proc;
   HANDLE query_hdl_value;
   HANDLE query_hdl_close_req_evt;
-  uint64_t pipename_key;
-  DWORD pipename_pid;
-  LONG pipename_id;
   void release_select_sem (const char *);
-  HANDLE get_query_hdl_per_process (WCHAR *, OBJECT_NAME_INFORMATION *);
+  HANDLE get_query_hdl_per_process (OBJECT_NAME_INFORMATION *);
 public:
   fhandler_pipe ();
 
-- 
2.43.0