flag parameters: dup2

This patch adds the new dup3 syscall.  It extends the old dup2 syscall by one
parameter which is meant to hold a flag value.  Support for the O_CLOEXEC flag
is added in this patch.

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_dup3
# ifdef __x86_64__
#  define __NR_dup3 292
# elif defined __i386__
#  define __NR_dup3 330
# else
#  error "need __NR_dup3"
# endif
#endif

int
main (void)
{
  int fd = syscall (__NR_dup3, 1, 4, 0);
  if (fd == -1)
    {
      puts ("dup3(0) failed");
      return 1;
    }
  int coe = fcntl (fd, F_GETFD);
  if (coe == -1)
    {
      puts ("fcntl failed");
      return 1;
    }
  if (coe & FD_CLOEXEC)
    {
      puts ("dup3(0) set close-on-exec flag");
      return 1;
    }
  close (fd);

  fd = syscall (__NR_dup3, 1, 4, O_CLOEXEC);
  if (fd == -1)
    {
      puts ("dup3(O_CLOEXEC) failed");
      return 1;
    }
  coe = fcntl (fd, F_GETFD);
  if (coe == -1)
    {
      puts ("fcntl failed");
      return 1;
    }
  if ((coe & FD_CLOEXEC) == 0)
    {
      puts ("dup3(O_CLOEXEC) set close-on-exec flag");
      return 1;
    }
  close (fd);

  puts ("OK");

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

Signed-off-by: Ulrich Drepper <drepper@redhat.com>
Acked-by: Davide Libenzi <davidel@xmailserver.org>
Cc: Michael Kerrisk <mtk.manpages@googlemail.com>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 4 insertions, 0 deletions

diff --git a/include/asm-x86/unistd_32.h b/include/asm-x86/unistd_32.h
index a37d6b0c4e1..a1f6383bf69 100644
--- a/include/asm-x86/unistd_32.h
+++ b/include/asm-x86/unistd_32.h
@@ -335,6 +335,7 @@
 #define __NR_signalfd4		327
 #define __NR_eventfd2		328
 #define __NR_epoll_create2	329
+#define __NR_dup3		330
 
 #ifdef __KERNEL__
 
diff --git a/include/asm-x86/unistd_64.h b/include/asm-x86/unistd_64.h
index a1a4a5b6e5e..f0fb2bd40cd 100644
--- a/include/asm-x86/unistd_64.h
+++ b/include/asm-x86/unistd_64.h
@@ -647,6 +647,8 @@ __SYSCALL(__NR_signalfd4, sys_signalfd4)
 __SYSCALL(__NR_eventfd2, sys_eventfd2)
 #define __NR_epoll_create2			291
 __SYSCALL(__NR_epoll_create2, sys_epoll_create2)
+#define __NR_dup3				292
+__SYSCALL(__NR_dup3, sys_dup3)
 
 
 #ifndef __NO_STUBS
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 85953240f28..034d3358549 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -305,6 +305,7 @@ asmlinkage long sys_fcntl64(unsigned int fd,
 #endif
 asmlinkage long sys_dup(unsigned int fildes);
 asmlinkage long sys_dup2(unsigned int oldfd, unsigned int newfd);
+asmlinkage long sys_dup3(unsigned int oldfd, unsigned int newfd, int flags);
 asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int on);
 asmlinkage long sys_ioctl(unsigned int fd, unsigned int cmd,
 				unsigned long arg);