Re: [PATCH] sysconf: Fix missing definition of UIO_MAXIOV on Linux [BZ #22321]

[Carlos O'Donell <carlos at redhat dot com>]

On 10/19/2017 11:32 AM, Florian Weimer wrote:
> 2017-10-19  Florian Weimer  <fweimer@redhat.com>
> 
> 	[BZ #22321]
> 	sysconf: Fix missing definition of UIO_MAXIOV on Linux.
> 	* sysdeps/posix/sysconf.c: Include <sys/uio.h>.
> 	* sysdeps/unix/sysv/linux/Makefile (tests): Add tst-sysconf-iov_max.
> 	(tst-sysconf-iov_max): Link with tst-sysconf-iov_max-uapi.o.
> 	* sysdeps/unix/sysv/linux/tst-sysconf-iov_max.c: New file.
> 	* sysdeps/unix/sysv/linux/tst-sysconf-iov_max-uapi.c: Likewise.

Looks good to me. I had some questions though, see below.

OK to commit if the answer to the questions is "Yes." and we
add additional tests.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

> diff --git a/sysdeps/posix/sysconf.c b/sysdeps/posix/sysconf.c
> index a95e1b3f05..254f87c437 100644
> --- a/sysdeps/posix/sysconf.c
> +++ b/sysdeps/posix/sysconf.c
> @@ -29,6 +29,7 @@
>  #include <sys/stat.h>
>  #include <sys/sysinfo.h>
>  #include <sys/types.h>
> +#include <sys/uio.h>

OK. Inclusion of define enables returned result.

>  #include <regex.h>
>  
>  #define NEED_SPEC_ARRAY 0
> diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
> index 30bd167bae..0c8a009b5e 100644
> --- a/sysdeps/unix/sysv/linux/Makefile
> +++ b/sysdeps/unix/sysv/linux/Makefile
> @@ -50,7 +50,7 @@ sysdep_headers += sys/mount.h sys/acct.h sys/sysctl.h \
>  		  bits/siginfo-arch.h bits/siginfo-consts-arch.h
>  
>  tests += tst-clone tst-clone2 tst-clone3 tst-fanotify tst-personality \
> -	 tst-quota tst-sync_file_range test-errno-linux
> +	 tst-quota tst-sync_file_range test-errno-linux tst-sysconf-iov_max

OK.

Thanks for the new test.

>  
>  # Generate the list of SYS_* macros for the system calls (__NR_*
>  # macros).  The file syscall-names.list contains all possible system
> @@ -95,6 +95,9 @@ $(objpfx)tst-syscall-list.out: \
>    $(objpfx)tst-syscall-list-sys.list
>  	$(BASH) $^ $(AWK) > $@; $(evaluate-test)
>  
> +# Separate object file for access to the constant from the UAPI header.
> +$(objpfx)tst-sysconf-iov_max: $(objpfx)tst-sysconf-iov_max-uapi.o
> +
>  endif # $(subdir) == misc
>  
>  ifeq ($(subdir),time)
> diff --git a/sysdeps/unix/sysv/linux/tst-sysconf-iov_max-uapi.c b/sysdeps/unix/sysv/linux/tst-sysconf-iov_max-uapi.c
> new file mode 100644
> index 0000000000..1240b846e6
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/tst-sysconf-iov_max-uapi.c
> @@ -0,0 +1,27 @@
> +/* Check IOV_MAX definition: Helper function to capture UAPI header value.
> +   Copyright (C) 2017 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <http://www.gnu.org/licenses/>.  */
> +
> +/* Use a separate function to avoid header compatibility issues.  */

OK. Clever use of the distinct object file.

> +
> +#include <linux/uio.h>
> +
> +long
> +uio_maxiov_value (void)
> +{
> +  return UIO_MAXIOV;
> +}
> diff --git a/sysdeps/unix/sysv/linux/tst-sysconf-iov_max.c b/sysdeps/unix/sysv/linux/tst-sysconf-iov_max.c
> new file mode 100644
> index 0000000000..e85bd59550
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/tst-sysconf-iov_max.c
> @@ -0,0 +1,38 @@
> +/* Check IOV_MAX definition for consistency (bug 22321).
> +   Copyright (C) 2017 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <http://www.gnu.org/licenses/>.  */
> +
> +/* Defined in tst-sysconf-iov_max-uapi.c.  */
> +long uio_maxiov_value (void);
> +
> +
> +#include <limits.h>
> +#include <support/check.h>
> +#include <sys/uio.h>
> +#include <unistd.h>
> +
> +static int
> +do_test (void)
> +{
> +  TEST_VERIFY (IOV_MAX == uio_maxiov_value ());
> +  TEST_VERIFY (UIO_MAXIOV == uio_maxiov_value ());
> +  TEST_VERIFY (sysconf (_SC_UIO_MAXIOV) == uio_maxiov_value ());
> +  TEST_VERIFY (sysconf (_SC_IOV_MAX) == uio_maxiov_value ());

Is there an expectation that the value, although consistent,
should not be -1?

e.g.
TEST_VERIFY (IOV_MAX != -1);
TEST_VERIFY (UIOV_MAX != -1);

Do we need to verify it is >= _XOPEN_IOV_MAX?

e.g.
TEST_VERIFY (IOV_MAX >= _XOPEN_IOV_MAX);
TEST_VERIFY (UIOV_MAX >= _XOPEN_IOV_MAX);


> +  return 0;
> +}
> +
> +#include <support/test-driver.c>
> 


-- 
Cheers,
Carlos.