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Subject[PATCH 07/18] flag parameters: timerfd_create
The timerfd_create syscall already has a flags parameter.  It just is
unused so far. This patch changes this by introducing the TFD_CLOEXEC
flag to set the close-on-exec flag for the returned file descriptor.

A new flag TFD_CLOEXEC is used instead of reusing O_CLOEXEC to prevent
exhaustion of the int bit field in case we need more flags.

The following test must be adjusted for architectures other than x86 and
x86-64 and in case the syscall numbers changed.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#include <fcntl.h>
#include <stdio.h>
#include <time.h>
#include <unistd.h>
#include <sys/syscall.h>

#ifndef __NR_timerfd_create
# ifdef __x86_64__
# define __NR_timerfd_create 283
# elif defined __i386__
# define __NR_timerfd_create 322
# else
# error "need __NR_timerfd_create"
# endif
#endif

#define TFD_CLOEXEC (1 << 0)

int
main (void)
{
int fd = syscall (__NR_timerfd_create, CLOCK_REALTIME, 0);
if (fd == -1)
{
puts ("timerfd_create(0) failed");
return 1;
}
int coe = fcntl (fd, F_GETFD);
if (coe == -1)
{
puts ("fcntl failed");
return 1;
}
if (coe & FD_CLOEXEC)
{
puts ("timerfd_create(0) set close-on-exec flag");
return 1;
}
close (fd);

fd = syscall (__NR_timerfd_create, CLOCK_REALTIME, TFD_CLOEXEC);
if (fd == -1)
{
puts ("timerfd_create(TFD_CLOEXEC) failed");
return 1;
}
coe = fcntl (fd, F_GETFD);
if (coe == -1)
{
puts ("fcntl failed");
return 1;
}
if ((coe & FD_CLOEXEC) == 0)
{
puts ("timerfd_create(TFD_CLOEXEC) set close-on-exec flag");
return 1;
}
close (fd);

puts ("OK");

return 0;
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

fs/timerfd.c | 12 ++++++++++--
include/linux/timerfd.h | 4 +++-
2 files changed, 13 insertions(+), 3 deletions(-)


Signed-off-by: Ulrich Drepper <drepper@redhat.com>

diff --git a/fs/timerfd.c b/fs/timerfd.c
index d87d354..f998991 100644
--- a/fs/timerfd.c
+++ b/fs/timerfd.c
@@ -21,6 +21,7 @@
#include <linux/anon_inodes.h>
#include <linux/timerfd.h>
#include <linux/syscalls.h>
+#include <linux/flagsremap.h>

struct timerfd_ctx {
struct hrtimer tmr;
@@ -179,12 +180,19 @@ static struct file *timerfd_fget(int fd)
return file;
}

+static const struct flags_rmap timerfd_file_flags_remap[] = {
+ { TFD_CLOEXEC, O_CLOEXEC },
+};
+
asmlinkage long sys_timerfd_create(int clockid, int flags)
{
int ufd;
struct timerfd_ctx *ctx;
+ int fflags;

- if (flags)
+ if (flags_remap(timerfd_file_flags_remap,
+ ARRAY_SIZE(timerfd_file_flags_remap),
+ flags, &fflags))
return -EINVAL;
if (clockid != CLOCK_MONOTONIC &&
clockid != CLOCK_REALTIME)
@@ -198,7 +207,7 @@ asmlinkage long sys_timerfd_create(int clockid, int flags)
ctx->clockid = clockid;
hrtimer_init(&ctx->tmr, clockid, HRTIMER_MODE_ABS);

- ufd = anon_inode_getfd("[timerfd]", &timerfd_fops, ctx, 0);
+ ufd = anon_inode_getfd("[timerfd]", &timerfd_fops, ctx, fflags);
if (ufd < 0)
kfree(ctx);

diff --git a/include/linux/timerfd.h b/include/linux/timerfd.h
index cf2b10d..c2fb04e 100644
--- a/include/linux/timerfd.h
+++ b/include/linux/timerfd.h
@@ -8,9 +8,11 @@
#ifndef _LINUX_TIMERFD_H
#define _LINUX_TIMERFD_H

-
+/* Flags for timerfd_settime. */
#define TFD_TIMER_ABSTIME (1 << 0)

+/* Flags for timerfd_create. */
+#define TFD_CLOEXEC (1 << 0)


#endif /* _LINUX_TIMERFD_H */

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