[PATCH] Cygwin: pipe: Give up to use query_hdl for non-cygwin apps.
Corinna Vinschen
corinna-cygwin@cygwin.com
Tue Mar 5 16:54:19 GMT 2024
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,
Corinna
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