From: Mike Frysinger <vapier@gentoo.org>
To: Jeff Layton <jlayton@redhat.com>
Cc: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>,
libc-alpha@sourceware.org, linux-fsdevel@vger.kernel.org,
Carlos O'Donell <carlos@redhat.com>,
Yuriy Kolerov <Yuriy.Kolerov@synopsys.com>
Subject: Re: [glibc PATCH] fcntl: put F_OFD_* constants under #ifdef __USE_FILE_OFFSET64
Date: Wed, 17 Aug 2016 20:37:00 -0000 [thread overview]
Message-ID: <20160817203746.GF21655@vapier.lan> (raw)
In-Reply-To: <1471464343.3196.125.camel@redhat.com>
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On 17 Aug 2016 16:05, Jeff Layton wrote:
> The way it works now is that when you define _FILE_OFFSET_BITS=64 and
> call fcntl(fd, F_SETLK, fl) glibc swaps in a struct flock64 for your
> struct flock, and F_SETLK64 for the F_SETLK.
does it ? doesn't seem like it does to me. here's glibc's fcntl.c:
io/fcntl.c - generic stub that sets ENOSYS
sysdeps/unix/sysv/linux/fcntl.c - just calls syscall(fcntl)
sysdeps/unix/sysv/linux/generic/wordsize-32/fcntl.c - just calls syscall(fcntl64)
sysdeps/unix/sysv/linux/i386/fcntl.c - same as above
<all the other 32-bit arches include the i386 file>
the kernel is where it gets interesting:
fs/compat.c:
COMPAT_SYSCALL_DEFINE3(fcntl):
rejects all 64-bit commands w/EINVAL
passes all other calls to compat_sys_fcntl64
COMPAT_SYSCALL_DEFINE3(fcntl64):
rewrites 32-bit flock struct to 64-bit flock struct
passes args to sys_fcntl
fs/fcntl.c:
SYSCALL_DEFINE3(fcntl):
passes all args to do_fcntl
SYSCALL_DEFINE3(fcntl64):
handles 64-bit flock commands
passes all others commands to do_fcntl
do_fcntl:
handles all commands using native sized flock struct
so for a 32-bit system (e.g. i386), you must match LFS & command usage.
if LFS is turned on, then using 32-bit commands w/struct flock fails.
if LFS is turned off, then using 64-bit commands w/struct flock fails.
-mike
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next prev parent reply other threads:[~2016-08-17 20:37 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-17 14:47 Jeff Layton
2016-08-17 15:44 ` Joseph Myers
2016-08-17 17:50 ` Jeff Layton
2016-08-17 17:57 ` Joseph Myers
2016-08-17 18:23 ` Jeff Layton
2016-08-17 16:13 ` Mike Frysinger
2016-08-17 17:34 ` Florian Weimer
2016-08-17 17:40 ` Jeff Layton
2016-08-17 18:02 ` Florian Weimer
2016-08-17 18:21 ` Jeff Layton
2016-08-17 18:51 ` Florian Weimer
2016-08-17 19:20 ` Jeff Layton
2016-08-18 8:44 ` Florian Weimer
2016-08-18 8:59 ` Andreas Schwab
2016-08-17 20:52 ` Andreas Schwab
2016-08-18 8:45 ` Florian Weimer
2016-08-17 18:43 ` Mike Frysinger
2016-08-17 19:15 ` Jeff Layton
2016-08-17 19:59 ` Michael Kerrisk (man-pages)
2016-08-17 20:05 ` Jeff Layton
2016-08-17 20:37 ` Mike Frysinger [this message]
2016-08-17 20:58 ` Jeff Layton
2016-08-17 21:35 ` Mike Frysinger
2016-08-17 21:48 ` Jeff Layton
2016-08-18 9:00 ` Florian Weimer
2016-08-23 11:09 ` Cyril Hrubis
2016-08-23 11:36 ` Jeff Layton
2016-08-23 11:43 ` Cyril Hrubis
2016-08-23 21:11 ` Michael Kerrisk (man-pages)
2016-11-14 13:45 ` Cyril Hrubis
2016-11-22 18:41 ` Florian Weimer
2016-08-18 8:57 ` Florian Weimer
2016-08-17 20:03 ` Mike Frysinger
2016-08-17 21:35 ` Cyril Hrubis
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