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>

6 files changed, 19 insertions, 2 deletions

diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index 04366f08f424..5614a8f7bed4 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -829,4 +829,5 @@ ia32_sys_call_table:
         .quad compat_sys_signalfd4
         .quad sys_eventfd2
         .quad sys_epoll_create2
+        .quad sys_dup3                  /* 330 */
 ia32_syscall_end:
diff --git a/arch/x86/kernel/syscall_table_32.S b/arch/x86/kernel/syscall_table_32.S
index 4d7007ca263d..24a3f1ea6a0e 100644
--- a/arch/x86/kernel/syscall_table_32.S
+++ b/arch/x86/kernel/syscall_table_32.S
@@ -329,3 +329,4 @@ ENTRY(sys_call_table)
         .long sys_signalfd4
         .long sys_eventfd2
         .long sys_epoll_create2
+        .long sys_dup3                  /* 330 */
diff --git a/fs/fcntl.c b/fs/fcntl.c
index 330a7d782591..9679fcbdeaa0 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -125,13 +125,16 @@ static int dupfd(struct file *file, unsigned int start, int cloexec)
         return fd;
 }
 
-asmlinkage long sys_dup2(unsigned int oldfd, unsigned int newfd)
+asmlinkage long sys_dup3(unsigned int oldfd, unsigned int newfd, int flags)
 {
         int err = -EBADF;
         struct file * file, *tofree;
         struct files_struct * files = current->files;
         struct fdtable *fdt;
 
+        if ((flags & ~O_CLOEXEC) != 0)
+                return -EINVAL;
+
         spin_lock(&files->file_lock);
         if (!(file = fcheck(oldfd)))
                 goto out_unlock;
@@ -163,7 +166,10 @@ asmlinkage long sys_dup2(unsigned int oldfd, unsigned int newfd)
 
         rcu_assign_pointer(fdt->fd[newfd], file);
         FD_SET(newfd, fdt->open_fds);
-        FD_CLR(newfd, fdt->close_on_exec);
+        if (flags & O_CLOEXEC)
+                FD_SET(newfd, fdt->close_on_exec);
+        else
+                FD_CLR(newfd, fdt->close_on_exec);
         spin_unlock(&files->file_lock);
 
         if (tofree)
@@ -181,6 +187,11 @@ out_fput:
         goto out;
 }
 
+asmlinkage long sys_dup2(unsigned int oldfd, unsigned int newfd)
+{
+        return sys_dup3(oldfd, newfd, 0);
+}
+
 asmlinkage long sys_dup(unsigned int fildes)
 {
         int ret = -EBADF;
diff --git a/include/asm-x86/unistd_32.h b/include/asm-x86/unistd_32.h
index a37d6b0c4e1e..a1f6383bf695 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 a1a4a5b6e5ee..f0fb2bd40cdb 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 85953240f28c..034d3358549e 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);