linux: Implement tmpfile with O_TMPFILE (BZ#21530)
Commit Message
This patch adds support to use O_TMPFILE on tmpfile on Linux. This is
similar previous suggestion by Andreas Schwab [1] with the difference
the file descriptor creation is parameterized to compartmentalize Linux
only open flags (O_TMPFILE) on sysdep folder.
Checked on x86_64-linux-gnu.
Adhemerval Zanella <adhemerval.zanella@linaro.org>
Andreas Schwab <schwab@suse.de>
[BZ #21530]
* include/stdio.h (__gen_tempfd): New function.
* stdio-common/Makefile (routines): Add gentempfd.
* stdio-common/gentempfd.c: New file.
* sysdeps/unix/sysv/linux/gentempfd.c: Likewise.
* stdio-common/tmpfile.c (tmpfile): First try to use a system specific
unnamed file first.
[1] https://sourceware.org/ml/libc-alpha/2017-06/msg01293.html
---
ChangeLog | 11 +++++++++++
include/stdio.h | 3 +++
stdio-common/Makefile | 2 +-
stdio-common/gentempfd.c | 26 ++++++++++++++++++++++++++
stdio-common/tmpfile.c | 29 ++++++++++++++++++++---------
sysdeps/unix/sysv/linux/gentempfd.c | 34 ++++++++++++++++++++++++++++++++++
6 files changed, 95 insertions(+), 10 deletions(-)
create mode 100644 stdio-common/gentempfd.c
create mode 100644 sysdeps/unix/sysv/linux/gentempfd.c
Comments
On 08/31/2017 03:34 PM, Adhemerval Zanella wrote:
> This patch adds support to use O_TMPFILE on tmpfile on Linux. This is
> similar previous suggestion by Andreas Schwab [1] with the difference
> the file descriptor creation is parameterized to compartmentalize Linux
> only open flags (O_TMPFILE) on sysdep folder.
>
> Checked on x86_64-linux-gnu.
>
> Adhemerval Zanella <adhemerval.zanella@linaro.org>
> Andreas Schwab <schwab@suse.de>
>
> [BZ #21530]
> * include/stdio.h (__gen_tempfd): New function.
> * stdio-common/Makefile (routines): Add gentempfd.
> * stdio-common/gentempfd.c: New file.
> * sysdeps/unix/sysv/linux/gentempfd.c: Likewise.
> * stdio-common/tmpfile.c (tmpfile): First try to use a system specific
> unnamed file first.
Looks good to me.
> [1] https://sourceware.org/ml/libc-alpha/2017-06/msg01293.html
> ---
> ChangeLog | 11 +++++++++++
> include/stdio.h | 3 +++
> stdio-common/Makefile | 2 +-
> stdio-common/gentempfd.c | 26 ++++++++++++++++++++++++++
> stdio-common/tmpfile.c | 29 ++++++++++++++++++++---------
> sysdeps/unix/sysv/linux/gentempfd.c | 34 ++++++++++++++++++++++++++++++++++
> 6 files changed, 95 insertions(+), 10 deletions(-)
> create mode 100644 stdio-common/gentempfd.c
> create mode 100644 sysdeps/unix/sysv/linux/gentempfd.c
>
> diff --git a/include/stdio.h b/include/stdio.h
> index 509447c..87e0e10 100644
> --- a/include/stdio.h
> +++ b/include/stdio.h
> @@ -191,5 +191,8 @@ libc_hidden_proto (__obstack_vprintf_chk)
> extern FILE * __fmemopen (void *buf, size_t len, const char *mode);
> libc_hidden_proto (__fmemopen)
>
> +extern int __gen_tempfd (int flags);
> +libc_hidden_proto (__gen_tempfd)
OK.
> +
> # endif /* not _ISOMAC */
> #endif /* stdio.h */
> diff --git a/stdio-common/Makefile b/stdio-common/Makefile
> index 397e0c2..2c3c2e5 100644
> --- a/stdio-common/Makefile
> +++ b/stdio-common/Makefile
> @@ -39,7 +39,7 @@ routines := \
> flockfile ftrylockfile funlockfile \
> isoc99_scanf isoc99_vscanf isoc99_fscanf isoc99_vfscanf isoc99_sscanf \
> isoc99_vsscanf \
> - psiginfo
> + psiginfo gentempfd
OK.
>
> aux := errlist siglist printf-parsemb printf-parsewc fxprintf
>
> diff --git a/stdio-common/gentempfd.c b/stdio-common/gentempfd.c
> new file mode 100644
> index 0000000..d40c57d
> --- /dev/null
> +++ b/stdio-common/gentempfd.c
> @@ -0,0 +1,26 @@
> +/* Generate a temporary file descriptor. Generic/POSIX version.
> + 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/>. */
> +
> +#include <stdio.h>
> +
> +int
> +__gen_tempfd (int flags)
> +{
> + return -1;
> +}
OK.
> +libc_hidden_def (__gen_tempfd)
> diff --git a/stdio-common/tmpfile.c b/stdio-common/tmpfile.c
> index e6030be..3e35345 100644
> --- a/stdio-common/tmpfile.c
> +++ b/stdio-common/tmpfile.c
> @@ -34,23 +34,34 @@
> FILE *
> tmpfile (void)
> {
> - char buf[FILENAME_MAX];
> int fd;
> FILE *f;
> -
> - if (__path_search (buf, FILENAME_MAX, NULL, "tmpf", 0))
> - return NULL;
> int flags = 0;
> #ifdef FLAGS
> flags = FLAGS;
> #endif
> - fd = __gen_tempname (buf, 0, flags, __GT_FILE);
> +
> + /* First try a system specific method. */
> + fd = __gen_tempfd (flags);
> +
OK.
> if (fd < 0)
> - return NULL;
> + {
> + char buf[FILENAME_MAX];
>
> - /* Note that this relies on the Unix semantics that
> - a file is not really removed until it is closed. */
> - (void) __unlink (buf);
> + if (__path_search (buf, sizeof buf, NULL, "tmpf", 0))
> + return NULL;
> +
> + fd = __gen_tempname (buf, 0, flags, __GT_FILE);
> + if (fd < 0)
> + return NULL;
> +
> + /* Note that this relies on the Unix semantics that
> + a file is not really removed until it is closed. */
> + (void) __unlink (buf);
OK.
> + }
> +
> + if (fd < 0)
> + return NULL;
>
> if ((f = __fdopen (fd, "w+b")) == NULL)
> __close (fd);
> diff --git a/sysdeps/unix/sysv/linux/gentempfd.c b/sysdeps/unix/sysv/linux/gentempfd.c
> new file mode 100644
> index 0000000..902cbe2
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/gentempfd.c
> @@ -0,0 +1,34 @@
> +/* Generate a temporary file descriptor. Linux version.
> + 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/>. */
> +
> +#include <stdio.h>
> +#include <fcntl.h>
> +#include <errno.h>
> +
> +int
> +__gen_tempfd (int flags)
> +{
> + int fd = __open (P_tmpdir, O_RDWR | O_TMPFILE | O_EXCL | flags,
OK.
I assume we don't care that on < 3.11 this will consistently fail,
or < 3.15 (XFS) or < 3.16 (BTRFS).
We might have remembered that failure and avoided the open(), but
then again one open() is not that costly in a long sequence of syscalls
that are going to create a temporary file.
> + S_IRUSR | S_IWUSR);
> + if (fd < 0 && errno == ENOENT && strcmp (P_tmpdir, "/tmp") != 0)
> + fd = __open ("/tmp", O_RDWR | O_TMPFILE | O_EXCL | flags,
> + S_IRUSR | S_IWUSR);
> +
> + return fd;
> +}
> +libc_hidden_def (__gen_tempfd)
>
On Thu, Aug 31, 2017 at 05:34:16PM -0300, Adhemerval Zanella wrote:
> This patch adds support to use O_TMPFILE on tmpfile on Linux. This is
... adds O_TMPFILE support to tmpfile on Linux.
> similar previous suggestion by Andreas Schwab [1] with the difference
similar to the previous ... with the difference that
> the file descriptor creation is parameterized to compartmentalize Linux
> only open flags (O_TMPFILE) on sysdep folder.
... into sysdeps.
[...]
> diff --git a/stdio-common/tmpfile.c b/stdio-common/tmpfile.c
> index e6030be..3e35345 100644
> --- a/stdio-common/tmpfile.c
> +++ b/stdio-common/tmpfile.c
> @@ -34,23 +34,34 @@
> FILE *
> tmpfile (void)
> {
> - char buf[FILENAME_MAX];
> int fd;
> FILE *f;
> -
> - if (__path_search (buf, FILENAME_MAX, NULL, "tmpf", 0))
> - return NULL;
> int flags = 0;
> #ifdef FLAGS
> flags = FLAGS;
> #endif
> - fd = __gen_tempname (buf, 0, flags, __GT_FILE);
> +
> + /* First try a system specific method. */
> + fd = __gen_tempfd (flags);
> +
> if (fd < 0)
> - return NULL;
> + {
> + char buf[FILENAME_MAX];
>
> - /* Note that this relies on the Unix semantics that
> - a file is not really removed until it is closed. */
> - (void) __unlink (buf);
> + if (__path_search (buf, sizeof buf, NULL, "tmpf", 0))
> + return NULL;
> +
> + fd = __gen_tempname (buf, 0, flags, __GT_FILE);
> + if (fd < 0)
> + return NULL;
> +
> + /* Note that this relies on the Unix semantics that
> + a file is not really removed until it is closed. */
> + (void) __unlink (buf);
> + }
> +
> + if (fd < 0)
> + return NULL;
The last "if (fd < 0)" check is redundant.
On 31/08/2017 21:39, Dmitry V. Levin wrote:
> On Thu, Aug 31, 2017 at 05:34:16PM -0300, Adhemerval Zanella wrote:
>> This patch adds support to use O_TMPFILE on tmpfile on Linux. This is
>
> ... adds O_TMPFILE support to tmpfile on Linux.
Ack.
>
>> similar previous suggestion by Andreas Schwab [1] with the difference
>
> similar to the previous ... with the difference that
Ack.
>
>> the file descriptor creation is parameterized to compartmentalize Linux
>> only open flags (O_TMPFILE) on sysdep folder.
>
> ... into sysdeps.
Ack.
>
> [...]
>> diff --git a/stdio-common/tmpfile.c b/stdio-common/tmpfile.c
>> index e6030be..3e35345 100644
>> --- a/stdio-common/tmpfile.c
>> +++ b/stdio-common/tmpfile.c
>> @@ -34,23 +34,34 @@
>> FILE *
>> tmpfile (void)
>> {
>> - char buf[FILENAME_MAX];
>> int fd;
>> FILE *f;
>> -
>> - if (__path_search (buf, FILENAME_MAX, NULL, "tmpf", 0))
>> - return NULL;
>> int flags = 0;
>> #ifdef FLAGS
>> flags = FLAGS;
>> #endif
>> - fd = __gen_tempname (buf, 0, flags, __GT_FILE);
>> +
>> + /* First try a system specific method. */
>> + fd = __gen_tempfd (flags);
>> +
>> if (fd < 0)
>> - return NULL;
>> + {
>> + char buf[FILENAME_MAX];
>>
>> - /* Note that this relies on the Unix semantics that
>> - a file is not really removed until it is closed. */
>> - (void) __unlink (buf);
>> + if (__path_search (buf, sizeof buf, NULL, "tmpf", 0))
>> + return NULL;
>> +
>> + fd = __gen_tempname (buf, 0, flags, __GT_FILE);
>> + if (fd < 0)
>> + return NULL;
>> +
>> + /* Note that this relies on the Unix semantics that
>> + a file is not really removed until it is closed. */
>> + (void) __unlink (buf);
>> + }
>> +
>> + if (fd < 0)
>> + return NULL;
>
> The last "if (fd < 0)" check is redundant.
Ack. I fixed the commit wording and removed the redundant tests, thanks.
@@ -191,5 +191,8 @@ libc_hidden_proto (__obstack_vprintf_chk)
extern FILE * __fmemopen (void *buf, size_t len, const char *mode);
libc_hidden_proto (__fmemopen)
+extern int __gen_tempfd (int flags);
+libc_hidden_proto (__gen_tempfd)
+
# endif /* not _ISOMAC */
#endif /* stdio.h */
@@ -39,7 +39,7 @@ routines := \
flockfile ftrylockfile funlockfile \
isoc99_scanf isoc99_vscanf isoc99_fscanf isoc99_vfscanf isoc99_sscanf \
isoc99_vsscanf \
- psiginfo
+ psiginfo gentempfd
aux := errlist siglist printf-parsemb printf-parsewc fxprintf
new file mode 100644
@@ -0,0 +1,26 @@
+/* Generate a temporary file descriptor. Generic/POSIX version.
+ 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/>. */
+
+#include <stdio.h>
+
+int
+__gen_tempfd (int flags)
+{
+ return -1;
+}
+libc_hidden_def (__gen_tempfd)
@@ -34,23 +34,34 @@
FILE *
tmpfile (void)
{
- char buf[FILENAME_MAX];
int fd;
FILE *f;
-
- if (__path_search (buf, FILENAME_MAX, NULL, "tmpf", 0))
- return NULL;
int flags = 0;
#ifdef FLAGS
flags = FLAGS;
#endif
- fd = __gen_tempname (buf, 0, flags, __GT_FILE);
+
+ /* First try a system specific method. */
+ fd = __gen_tempfd (flags);
+
if (fd < 0)
- return NULL;
+ {
+ char buf[FILENAME_MAX];
- /* Note that this relies on the Unix semantics that
- a file is not really removed until it is closed. */
- (void) __unlink (buf);
+ if (__path_search (buf, sizeof buf, NULL, "tmpf", 0))
+ return NULL;
+
+ fd = __gen_tempname (buf, 0, flags, __GT_FILE);
+ if (fd < 0)
+ return NULL;
+
+ /* Note that this relies on the Unix semantics that
+ a file is not really removed until it is closed. */
+ (void) __unlink (buf);
+ }
+
+ if (fd < 0)
+ return NULL;
if ((f = __fdopen (fd, "w+b")) == NULL)
__close (fd);
new file mode 100644
@@ -0,0 +1,34 @@
+/* Generate a temporary file descriptor. Linux version.
+ 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/>. */
+
+#include <stdio.h>
+#include <fcntl.h>
+#include <errno.h>
+
+int
+__gen_tempfd (int flags)
+{
+ int fd = __open (P_tmpdir, O_RDWR | O_TMPFILE | O_EXCL | flags,
+ S_IRUSR | S_IWUSR);
+ if (fd < 0 && errno == ENOENT && strcmp (P_tmpdir, "/tmp") != 0)
+ fd = __open ("/tmp", O_RDWR | O_TMPFILE | O_EXCL | flags,
+ S_IRUSR | S_IWUSR);
+
+ return fd;
+}
+libc_hidden_def (__gen_tempfd)