[glibc] fcntl-linux.h: add F_OFD_*32 constants
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Message ID 1471521815-4340-1-git-send-email-jlayton@redhat.com
State New
Headers show

Commit Message

Jeff Layton Aug. 18, 2016, 12:03 p.m. UTC
The original assumption with OFD lock support was that userland would
always pass in a struct flock that has been set up for large file
support (LFS). It's possible however for someone to build a 32-bit
program without large file support, and still try to use OFD locks. If
that happens then it will send a non-LFS struct flock to the kernel,
which will then try to interpret it as a LFS one, which can cause
unexpected results.

My original idea was to just ensure that the build would fail in this
case by not defining the F_OFD_* constants when LFS support was not
enabled.

Instead though, it's probably better long-term to just go ahead and
support OFD locks with non-LFS struct flock. To do that without breaking
programs that are already working, we add a set of F_OFD_*32 constants,
and add the plumbing to the kernel to make those do the right thing.

This patch adds the same constants to glibc, and has it redefine the
"normal" F_OFD_* constants to their *32 equvalents when LFS support is
not in use.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
---
 ChangeLog                                  |  4 ++++
 sysdeps/unix/sysv/linux/bits/fcntl-linux.h | 17 +++++++++++++----
 2 files changed, 17 insertions(+), 4 deletions(-)

Comments

Mike Frysinger Aug. 18, 2016, 1:04 p.m. UTC | #1
On 18 Aug 2016 08:03, Jeff Layton wrote:
> +2016-08-18  Jeff Layton <jlayton@redhat.com>
> +	* sysdeps/unix/sysv/linux/bits/fcntl-linux.h:
> +	Add F_OFD_GETLK32, F_OFD_SETLK32, F_OFD_SETLKW32

Should be a blank line after the first one.  look at all the other
entries in this file as an example.

> --- a/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
> +++ b/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
> @@ -127,11 +127,20 @@
>     This means that they are inherited across fork or clone with CLONE_FILES
>     like BSD (flock) locks, and they are only released automatically when the
>     last reference to the the file description against which they were acquired
> -   is put. */
> +   is put.  */
>  #ifdef __USE_GNU
> -# define F_OFD_GETLK	36
> -# define F_OFD_SETLK	37
> -# define F_OFD_SETLKW	38
> +# if __OFF_T_MATCHES_OFF64_T || defined __USE_FILE_OFFSET64
> +#  define F_OFD_GETLK		36
> +#  define F_OFD_SETLK		37
> +#  define F_OFD_SETLKW		38
> +# else
> +#  define F_OFD_GETLK32		39
> +#  define F_OFD_SETLK32		40
> +#  define F_OFD_SETLKW32	41
> +#  define F_OFD_GETLK		F_OFD_GETLK32
> +#  define F_OFD_SETLK		F_OFD_SETLK32
> +#  define F_OFD_SETLKW		F_OFD_SETLKW32
> +# endif
>  #endif

i think we should define *64 and *32 variants all the time, and
then route the F_OFD_GETLK/etc... to them based on compile mode.
-mike
Jeff Layton Aug. 18, 2016, 1:49 p.m. UTC | #2
On Thu, 2016-08-18 at 06:04 -0700, Mike Frysinger wrote:
> On 18 Aug 2016 08:03, Jeff Layton wrote:
> > 
> > > > +2016-08-18  Jeff Layton <jlayton@redhat.com>
> > > > +	* sysdeps/unix/sysv/linux/bits/fcntl-linux.h:
> > > > +	Add F_OFD_GETLK32, F_OFD_SETLK32, F_OFD_SETLKW32
> 
> Should be a blank line after the first one.  look at all the other
> entries in this file as an example.
> 

Ok, will fix...


> > 
> > --- a/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
> > +++ b/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
> > @@ -127,11 +127,20 @@
> >     This means that they are inherited across fork or clone with CLONE_FILES
> >     like BSD (flock) locks, and they are only released automatically when the
> >     last reference to the the file description against which they were acquired
> > -   is put. */
> > +   is put.  */
> >  #ifdef __USE_GNU
> > > > -# define F_OFD_GETLK	36
> > > > -# define F_OFD_SETLK	37
> > > > -# define F_OFD_SETLKW	38
> > +# if __OFF_T_MATCHES_OFF64_T || defined __USE_FILE_OFFSET64
> > > > +#  define F_OFD_GETLK		36
> > > > +#  define F_OFD_SETLK		37
> > > > +#  define F_OFD_SETLKW		38
> > +# else
> > > > +#  define F_OFD_GETLK32		39
> > > > +#  define F_OFD_SETLK32		40
> > > > +#  define F_OFD_SETLKW32	41
> > > > +#  define F_OFD_GETLK		F_OFD_GETLK32
> > > > +#  define F_OFD_SETLK		F_OFD_SETLK32
> > > > +#  define F_OFD_SETLKW		F_OFD_SETLKW32
> > +# endif
> >  #endif
> 
> i think we should define *64 and *32 variants all the time, and
> then route the F_OFD_GETLK/etc... to them based on compile mode.
> -mike

Sorry, I don't quite understand here. The whole point is that the
existing F_OFD_* constants are already implicitly 64-bit. Why do we
need separate constants postfixed with "64" that no one will ever use?
Mike Frysinger Aug. 18, 2016, 4 p.m. UTC | #3
On 18 Aug 2016 09:49, Jeff Layton wrote:
> On Thu, 2016-08-18 at 06:04 -0700, Mike Frysinger wrote:
> > On 18 Aug 2016 08:03, Jeff Layton wrote:
> > > --- a/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
> > > +++ b/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
> > > @@ -127,11 +127,20 @@
> > >     This means that they are inherited across fork or clone with CLONE_FILES
> > >     like BSD (flock) locks, and they are only released automatically when the
> > >     last reference to the the file description against which they were acquired
> > > -   is put. */
> > > +   is put.  */
> > >  #ifdef __USE_GNU
> > > > > -# define F_OFD_GETLK	36
> > > > > -# define F_OFD_SETLK	37
> > > > > -# define F_OFD_SETLKW	38
> > > +# if __OFF_T_MATCHES_OFF64_T || defined __USE_FILE_OFFSET64
> > > > > +#  define F_OFD_GETLK		36
> > > > > +#  define F_OFD_SETLK		37
> > > > > +#  define F_OFD_SETLKW		38
> > > +# else
> > > > > +#  define F_OFD_GETLK32		39
> > > > > +#  define F_OFD_SETLK32		40
> > > > > +#  define F_OFD_SETLKW32	41
> > > > > +#  define F_OFD_GETLK		F_OFD_GETLK32
> > > > > +#  define F_OFD_SETLK		F_OFD_SETLK32
> > > > > +#  define F_OFD_SETLKW		F_OFD_SETLKW32
> > > +# endif
> > >  #endif
> > 
> > i think we should define *64 and *32 variants all the time, and
> > then route the F_OFD_GETLK/etc... to them based on compile mode.
> 
> Sorry, I don't quite understand here. The whole point is that the
> existing F_OFD_* constants are already implicitly 64-bit. Why do we
> need separate constants postfixed with "64" that no one will ever use?

you're making them not explicitly 64-bit when off_t!=off64_t.
all the other commands in this file have used the convention:
	<cmd>: automatically 32-bit or 64-bit
	<cmd>64: always 64-bit

so the header would do:
#define F_OFD_GETLK64 36
#define F_OFD_SETLK64 37
#define F_OFD_SETLKW64 38
#if __OFF_T_MATCHES_OFF64_T || defined __USE_FILE_OFFSET64
# define F_OFD_GETLK F_OFD_GETLK64
# define F_OFD_SETLK F_OFD_SETLK64
# define F_OFD_SETLKW F_OFD_SETLKW64
#else
# define F_OFD_GETLK 39
# define F_OFD_SETLK 40
# define F_OFD_SETLKW 41
#endif

the defines deviate a bit from the names used on the kernel side,
but we've already done that, and you're proposed patch does too.
-mike

Patch
diff mbox

diff --git a/ChangeLog b/ChangeLog
index 59c68d8b9d0d..4a2488b50054 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@ 
+2016-08-18  Jeff Layton <jlayton@redhat.com>
+	* sysdeps/unix/sysv/linux/bits/fcntl-linux.h:
+	Add F_OFD_GETLK32, F_OFD_SETLK32, F_OFD_SETLKW32
+
 2016-08-18  Stefan Liebler  <stli@linux.vnet.ibm.com>
 
 	* sysdeps/ieee754/dbl-64/k_rem_pio2.c (__kernel_rem_pio2):
diff --git a/sysdeps/unix/sysv/linux/bits/fcntl-linux.h b/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
index 7e5b0aecdcb4..9cb1b5f6f3ec 100644
--- a/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
+++ b/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
@@ -127,11 +127,20 @@ 
    This means that they are inherited across fork or clone with CLONE_FILES
    like BSD (flock) locks, and they are only released automatically when the
    last reference to the the file description against which they were acquired
-   is put. */
+   is put.  */
 #ifdef __USE_GNU
-# define F_OFD_GETLK	36
-# define F_OFD_SETLK	37
-# define F_OFD_SETLKW	38
+# if __OFF_T_MATCHES_OFF64_T || defined __USE_FILE_OFFSET64
+#  define F_OFD_GETLK		36
+#  define F_OFD_SETLK		37
+#  define F_OFD_SETLKW		38
+# else
+#  define F_OFD_GETLK32		39
+#  define F_OFD_SETLK32		40
+#  define F_OFD_SETLKW32	41
+#  define F_OFD_GETLK		F_OFD_GETLK32
+#  define F_OFD_SETLK		F_OFD_SETLK32
+#  define F_OFD_SETLKW		F_OFD_SETLKW32
+# endif
 #endif
 
 #ifdef __USE_LARGEFILE64