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@xxxxxxxxxx>
---
ChangeLog | 4 ++++
sysdeps/unix/sysv/linux/bits/fcntl-linux.h | 17 +++++++++++++----
2 files changed, 17 insertions(+), 4 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 59c68d8b9d0d..4a2488b50054 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2016-08-18 Jeff Layton <jlayton@xxxxxxxxxx>
+ * sysdeps/unix/sysv/linux/bits/fcntl-linux.h:
+ Add F_OFD_GETLK32, F_OFD_SETLK32, F_OFD_SETLKW32
+
2016-08-18 Stefan Liebler <stli@xxxxxxxxxxxxxxxxxx>
* 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
--
2.7.4
--
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