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Subject[PATCH 08/18] flag parameters: epoll_create
This patch adds the new epoll_create2 syscall.  It extends the old epoll_create
syscall by one parameter which is meant to hold a flag value. In this
patch the only flag support is EPOLL_CLOEXEC which causes the close-on-exec
flag for the returned file descriptor to be set.

A new flag EPOLL_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_epoll_create2
# ifdef __x86_64__
# define __NR_epoll_create2 291
# elif defined __i386__
# define __NR_epoll_create2 329
# else
# error "need __NR_epoll_create2"
# endif
#endif

#define EPOLL_CLOEXEC (1 << 0)

int
main (void)
{
int fd = syscall (__NR_epoll_create2, 1, 0);
if (fd == -1)
{
puts ("epoll_create2(0) failed");
return 1;
}
int coe = fcntl (fd, F_GETFD);
if (coe == -1)
{
puts ("fcntl failed");
return 1;
}
if (coe & FD_CLOEXEC)
{
puts ("epoll_create2(0) set close-on-exec flag");
return 1;
}
close (fd);
fd = syscall (__NR_epoll_create2, 1, EPOLL_CLOEXEC);
if (fd == -1)
{
puts ("epoll_create2(EPOLL_CLOEXEC) failed");
return 1;
}
coe = fcntl (fd, F_GETFD);
if (coe == -1)
{
puts ("fcntl failed");
return 1;
}
if ((coe & FD_CLOEXEC) == 0)
{
puts ("epoll_create2(EPOLL_CLOEXEC) set close-on-exec flag");
return 1;
}
close (fd);
puts ("OK");

return 0;
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
arch/x86/ia32/ia32entry.S | 1 +
arch/x86/kernel/syscall_table_32.S | 1 +
fs/eventpoll.c | 20 ++++++++++++++++++--
include/asm-x86/unistd_32.h | 1 +
include/asm-x86/unistd_64.h | 2 ++
include/linux/eventpoll.h | 2 ++
include/linux/syscalls.h | 1 +
7 files changed, 26 insertions(+), 2 deletions(-)

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

diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index b5e329d..37e4992 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -733,4 +733,5 @@ ia32_sys_call_table:
.quad compat_sys_timerfd_gettime
.quad compat_sys_signalfd4
.quad sys_eventfd2
+ .quad sys_epoll_create2
ia32_syscall_end:
diff --git a/arch/x86/kernel/syscall_table_32.S b/arch/x86/kernel/syscall_table_32.S
index adff556..f59aba5 100644
--- a/arch/x86/kernel/syscall_table_32.S
+++ b/arch/x86/kernel/syscall_table_32.S
@@ -328,3 +328,4 @@ ENTRY(sys_call_table)
.long sys_timerfd_gettime
.long sys_signalfd4
.long sys_eventfd2
+ .long sys_epoll_create2
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 990c01d..7714e91 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -33,6 +33,7 @@
#include <linux/bitops.h>
#include <linux/mutex.h>
#include <linux/anon_inodes.h>
+#include <linux/flagsremap.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <asm/io.h>
@@ -1040,16 +1041,26 @@ retry:
return res;
}

+static const struct flags_rmap epoll_file_flags_remap[] = {
+ { EPOLL_CLOEXEC, O_CLOEXEC }
+};
+
/*
* It opens an eventpoll file descriptor. The "size" parameter is there
* for historical reasons, when epoll was using an hash instead of an
* RB tree. With the current implementation, the "size" parameter is ignored
* (besides sanity checks).
*/
-asmlinkage long sys_epoll_create(int size)
+asmlinkage long sys_epoll_create2(int size, int flags)
{
int error, fd = -1;
struct eventpoll *ep;
+ int fflags;
+
+ if (flags_remap(epoll_file_flags_remap,
+ ARRAY_SIZE(epoll_file_flags_remap),
+ flags, &fflags))
+ return -EINVAL;

DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d)\n",
current, size));
@@ -1068,7 +1079,7 @@ asmlinkage long sys_epoll_create(int size)
* Creates all the items needed to setup an eventpoll file. That is,
* a file structure and a free file descriptor.
*/
- fd = anon_inode_getfd("[eventpoll]", &eventpoll_fops, ep, 0);
+ fd = anon_inode_getfd("[eventpoll]", &eventpoll_fops, ep, fflags);
if (fd < 0)
ep_free(ep);

@@ -1079,6 +1090,11 @@ error_return:
return fd;
}

+asmlinkage long sys_epoll_create(int size)
+{
+ return sys_epoll_create2(size, 0);
+}
+
/*
* The following function implements the controller interface for
* the eventpoll file that enables the insertion/removal/change of
diff --git a/include/linux/eventpoll.h b/include/linux/eventpoll.h
index cf79853..ca3a6e8 100644
--- a/include/linux/eventpoll.h
+++ b/include/linux/eventpoll.h
@@ -16,6 +16,8 @@

#include <linux/types.h>

+/* Flags for epoll_create2. */
+#define EPOLL_CLOEXEC (1 << 0)

/* Valid opcodes to issue to sys_epoll_ctl() */
#define EPOLL_CTL_ADD 1
diff --git a/include/asm-x86/unistd_32.h b/include/asm-x86/unistd_32.h
index 8317d94..b3daf50 100644
--- a/include/asm-x86/unistd_32.h
+++ b/include/asm-x86/unistd_32.h
@@ -334,6 +334,7 @@
#define __NR_timerfd_gettime 326
#define __NR_signalfd4 327
#define __NR_eventfd2 328
+#define __NR_epoll_create2 329

#ifdef __KERNEL__

diff --git a/include/asm-x86/unistd_64.h b/include/asm-x86/unistd_64.h
index fe26e36..5ef6778 100644
--- a/include/asm-x86/unistd_64.h
+++ b/include/asm-x86/unistd_64.h
@@ -645,6 +645,8 @@ __SYSCALL(__NR_fallocate, sys_fallocate)
__SYSCALL(__NR_signalfd4, sys_signalfd4)
#define __NR_eventfd2 290
__SYSCALL(__NR_eventfd2, sys_eventfd2)
+#define __NR_epoll_create2 291
+__SYSCALL(__NR_epoll_create2, sys_epoll_create2)


#ifndef __NO_STUBS
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 0522f36..aeb2df8 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -430,6 +430,7 @@ asmlinkage long sys_poll(struct pollfd __user *ufds, unsigned int nfds,
asmlinkage long sys_select(int n, fd_set __user *inp, fd_set __user *outp,
fd_set __user *exp, struct timeval __user *tvp);
asmlinkage long sys_epoll_create(int size);
+asmlinkage long sys_epoll_create2(int size, int flags);
asmlinkage long sys_epoll_ctl(int epfd, int op, int fd,
struct epoll_event __user *event);
asmlinkage long sys_epoll_wait(int epfd, struct epoll_event __user *events,

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