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linux-next/kernel/sys_ni.c
Ulrich Drepper de11defebf reintroduce accept4 
Introduce a new accept4() system call.  The addition of this system call
matches analogous changes in 2.6.27 (dup3(), evenfd2(), signalfd4(),
inotify_init1(), epoll_create1(), pipe2()) which added new system calls
that differed from analogous traditional system calls in adding a flags
argument that can be used to access additional functionality.

The accept4() system call is exactly the same as accept(), except that
it adds a flags bit-mask argument.  Two flags are initially implemented.
(Most of the new system calls in 2.6.27 also had both of these flags.)

SOCK_CLOEXEC causes the close-on-exec (FD_CLOEXEC) flag to be enabled
for the new file descriptor returned by accept4().  This is a useful
security feature to avoid leaking information in a multithreaded
program where one thread is doing an accept() at the same time as
another thread is doing a fork() plus exec().  More details here:
http://udrepper.livejournal.com/20407.html "Secure File Descriptor Handling",
Ulrich Drepper).

The other flag is SOCK_NONBLOCK, which causes the O_NONBLOCK flag
to be enabled on the new open file description created by accept4().
(This flag is merely a convenience, saving the use of additional calls
fcntl(F_GETFL) and fcntl (F_SETFL) to achieve the same result.

Here's a test program.  Works on x86-32.  Should work on x86-64, but
I (mtk) don't have a system to hand to test with.

It tests accept4() with each of the four possible combinations of
SOCK_CLOEXEC and SOCK_NONBLOCK set/clear in 'flags', and verifies
that the appropriate flags are set on the file descriptor/open file
description returned by accept4().

I tested Ulrich's patch in this thread by applying against 2.6.28-rc2,
and it passes according to my test program.

/* test_accept4.c

  Copyright (C) 2008, Linux Foundation, written by Michael Kerrisk
       <mtk.manpages@gmail.com>

  Licensed under the GNU GPLv2 or later.
*/
#define _GNU_SOURCE
#include <unistd.h>
#include <sys/syscall.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <stdlib.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>

#define PORT_NUM 33333

#define die(msg) do { perror(msg); exit(EXIT_FAILURE); } while (0)

/**********************************************************************/

/* The following is what we need until glibc gets a wrapper for
  accept4() */

/* Flags for socket(), socketpair(), accept4() */
#ifndef SOCK_CLOEXEC
#define SOCK_CLOEXEC    O_CLOEXEC
#endif
#ifndef SOCK_NONBLOCK
#define SOCK_NONBLOCK   O_NONBLOCK
#endif

#ifdef __x86_64__
#define SYS_accept4 288
#elif __i386__
#define USE_SOCKETCALL 1
#define SYS_ACCEPT4 18
#else
#error "Sorry -- don't know the syscall # on this architecture"
#endif

static int
accept4(int fd, struct sockaddr *sockaddr, socklen_t *addrlen, int flags)
{
   printf("Calling accept4(): flags = %x", flags);
   if (flags != 0) {
       printf(" (");
       if (flags & SOCK_CLOEXEC)
           printf("SOCK_CLOEXEC");
       if ((flags & SOCK_CLOEXEC) && (flags & SOCK_NONBLOCK))
           printf(" ");
       if (flags & SOCK_NONBLOCK)
           printf("SOCK_NONBLOCK");
       printf(")");
   }
   printf("\n");

#if USE_SOCKETCALL
   long args[6];

   args[0] = fd;
   args[1] = (long) sockaddr;
   args[2] = (long) addrlen;
   args[3] = flags;

   return syscall(SYS_socketcall, SYS_ACCEPT4, args);
#else
   return syscall(SYS_accept4, fd, sockaddr, addrlen, flags);
#endif
}

/**********************************************************************/

static int
do_test(int lfd, struct sockaddr_in *conn_addr,
       int closeonexec_flag, int nonblock_flag)
{
   int connfd, acceptfd;
   int fdf, flf, fdf_pass, flf_pass;
   struct sockaddr_in claddr;
   socklen_t addrlen;

   printf("=======================================\n");

   connfd = socket(AF_INET, SOCK_STREAM, 0);
   if (connfd == -1)
       die("socket");
   if (connect(connfd, (struct sockaddr *) conn_addr,
               sizeof(struct sockaddr_in)) == -1)
       die("connect");

   addrlen = sizeof(struct sockaddr_in);
   acceptfd = accept4(lfd, (struct sockaddr *) &claddr, &addrlen,
                      closeonexec_flag | nonblock_flag);
   if (acceptfd == -1) {
       perror("accept4()");
       close(connfd);
       return 0;
   }

   fdf = fcntl(acceptfd, F_GETFD);
   if (fdf == -1)
       die("fcntl:F_GETFD");
   fdf_pass = ((fdf & FD_CLOEXEC) != 0) ==
              ((closeonexec_flag & SOCK_CLOEXEC) != 0);
   printf("Close-on-exec flag is %sset (%s); ",
           (fdf & FD_CLOEXEC) ? "" : "not ",
           fdf_pass ? "OK" : "failed");

   flf = fcntl(acceptfd, F_GETFL);
   if (flf == -1)
       die("fcntl:F_GETFD");
   flf_pass = ((flf & O_NONBLOCK) != 0) ==
              ((nonblock_flag & SOCK_NONBLOCK) !=0);
   printf("nonblock flag is %sset (%s)\n",
           (flf & O_NONBLOCK) ? "" : "not ",
           flf_pass ? "OK" : "failed");

   close(acceptfd);
   close(connfd);

   printf("Test result: %s\n", (fdf_pass && flf_pass) ? "PASS" : "FAIL");
   return fdf_pass && flf_pass;
}

static int
create_listening_socket(int port_num)
{
   struct sockaddr_in svaddr;
   int lfd;
   int optval;

   memset(&svaddr, 0, sizeof(struct sockaddr_in));
   svaddr.sin_family = AF_INET;
   svaddr.sin_addr.s_addr = htonl(INADDR_ANY);
   svaddr.sin_port = htons(port_num);

   lfd = socket(AF_INET, SOCK_STREAM, 0);
   if (lfd == -1)
       die("socket");

   optval = 1;
   if (setsockopt(lfd, SOL_SOCKET, SO_REUSEADDR, &optval,
                  sizeof(optval)) == -1)
       die("setsockopt");

   if (bind(lfd, (struct sockaddr *) &svaddr,
            sizeof(struct sockaddr_in)) == -1)
       die("bind");

   if (listen(lfd, 5) == -1)
       die("listen");

   return lfd;
}

int
main(int argc, char *argv[])
{
   struct sockaddr_in conn_addr;
   int lfd;
   int port_num;
   int passed;

   passed = 1;

   port_num = (argc > 1) ? atoi(argv[1]) : PORT_NUM;

   memset(&conn_addr, 0, sizeof(struct sockaddr_in));
   conn_addr.sin_family = AF_INET;
   conn_addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
   conn_addr.sin_port = htons(port_num);

   lfd = create_listening_socket(port_num);

   if (!do_test(lfd, &conn_addr, 0, 0))
       passed = 0;
   if (!do_test(lfd, &conn_addr, SOCK_CLOEXEC, 0))
       passed = 0;
   if (!do_test(lfd, &conn_addr, 0, SOCK_NONBLOCK))
       passed = 0;
   if (!do_test(lfd, &conn_addr, SOCK_CLOEXEC, SOCK_NONBLOCK))
       passed = 0;

   close(lfd);

   exit(passed ? EXIT_SUCCESS : EXIT_FAILURE);
}

[mtk.manpages@gmail.com: rewrote changelog, updated test program]
Signed-off-by: Ulrich Drepper <drepper@redhat.com>
Tested-by: Michael Kerrisk <mtk.manpages@gmail.com>
Acked-by: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: <linux-api@vger.kernel.org>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-11-19 18:49:57 -08:00

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#include <linux/linkage.h>
#include <linux/errno.h>
#include <asm/unistd.h>
/* we can't #include <linux/syscalls.h> here,
but tell gcc to not warn with -Wmissing-prototypes */
asmlinkage long sys_ni_syscall(void);
/*
* Non-implemented system calls get redirected here.
*/
asmlinkage long sys_ni_syscall(void)
{
return -ENOSYS;
}
cond_syscall(sys_nfsservctl);
cond_syscall(sys_quotactl);
cond_syscall(sys32_quotactl);
cond_syscall(sys_acct);
cond_syscall(sys_lookup_dcookie);
cond_syscall(sys_swapon);
cond_syscall(sys_swapoff);
cond_syscall(sys_kexec_load);
cond_syscall(compat_sys_kexec_load);
cond_syscall(sys_init_module);
cond_syscall(sys_delete_module);
cond_syscall(sys_socketpair);
cond_syscall(sys_bind);
cond_syscall(sys_listen);
cond_syscall(sys_accept);
cond_syscall(sys_accept4);
cond_syscall(sys_connect);
cond_syscall(sys_getsockname);
cond_syscall(sys_getpeername);
cond_syscall(sys_sendto);
cond_syscall(sys_send);
cond_syscall(sys_recvfrom);
cond_syscall(sys_recv);
cond_syscall(sys_socket);
cond_syscall(sys_setsockopt);
cond_syscall(compat_sys_setsockopt);
cond_syscall(sys_getsockopt);
cond_syscall(compat_sys_getsockopt);
cond_syscall(sys_shutdown);
cond_syscall(sys_sendmsg);
cond_syscall(compat_sys_sendmsg);
cond_syscall(sys_recvmsg);
cond_syscall(compat_sys_recvmsg);
cond_syscall(sys_socketcall);
cond_syscall(sys_futex);
cond_syscall(compat_sys_futex);
cond_syscall(sys_set_robust_list);
cond_syscall(compat_sys_set_robust_list);
cond_syscall(sys_get_robust_list);
cond_syscall(compat_sys_get_robust_list);
cond_syscall(sys_epoll_create);
cond_syscall(sys_epoll_create1);
cond_syscall(sys_epoll_ctl);
cond_syscall(sys_epoll_wait);
cond_syscall(sys_epoll_pwait);
cond_syscall(compat_sys_epoll_pwait);
cond_syscall(sys_semget);
cond_syscall(sys_semop);
cond_syscall(sys_semtimedop);
cond_syscall(sys_semctl);
cond_syscall(sys_msgget);
cond_syscall(sys_msgsnd);
cond_syscall(sys_msgrcv);
cond_syscall(sys_msgctl);
cond_syscall(sys_shmget);
cond_syscall(sys_shmat);
cond_syscall(sys_shmdt);
cond_syscall(sys_shmctl);
cond_syscall(sys_mq_open);
cond_syscall(sys_mq_unlink);
cond_syscall(sys_mq_timedsend);
cond_syscall(sys_mq_timedreceive);
cond_syscall(sys_mq_notify);
cond_syscall(sys_mq_getsetattr);
cond_syscall(compat_sys_mq_open);
cond_syscall(compat_sys_mq_timedsend);
cond_syscall(compat_sys_mq_timedreceive);
cond_syscall(compat_sys_mq_notify);
cond_syscall(compat_sys_mq_getsetattr);
cond_syscall(sys_mbind);
cond_syscall(sys_get_mempolicy);
cond_syscall(sys_set_mempolicy);
cond_syscall(compat_sys_mbind);
cond_syscall(compat_sys_get_mempolicy);
cond_syscall(compat_sys_set_mempolicy);
cond_syscall(sys_add_key);
cond_syscall(sys_request_key);
cond_syscall(sys_keyctl);
cond_syscall(compat_sys_keyctl);
cond_syscall(compat_sys_socketcall);
cond_syscall(sys_inotify_init);
cond_syscall(sys_inotify_init1);
cond_syscall(sys_inotify_add_watch);
cond_syscall(sys_inotify_rm_watch);
cond_syscall(sys_migrate_pages);
cond_syscall(sys_move_pages);
cond_syscall(sys_chown16);
cond_syscall(sys_fchown16);
cond_syscall(sys_getegid16);
cond_syscall(sys_geteuid16);
cond_syscall(sys_getgid16);
cond_syscall(sys_getgroups16);
cond_syscall(sys_getresgid16);
cond_syscall(sys_getresuid16);
cond_syscall(sys_getuid16);
cond_syscall(sys_lchown16);
cond_syscall(sys_setfsgid16);
cond_syscall(sys_setfsuid16);
cond_syscall(sys_setgid16);
cond_syscall(sys_setgroups16);
cond_syscall(sys_setregid16);
cond_syscall(sys_setresgid16);
cond_syscall(sys_setresuid16);
cond_syscall(sys_setreuid16);
cond_syscall(sys_setuid16);
cond_syscall(sys_vm86old);
cond_syscall(sys_vm86);
cond_syscall(compat_sys_ipc);
cond_syscall(compat_sys_sysctl);
cond_syscall(sys_flock);
cond_syscall(sys_io_setup);
cond_syscall(sys_io_destroy);
cond_syscall(sys_io_submit);
cond_syscall(sys_io_cancel);
cond_syscall(sys_io_getevents);
/* arch-specific weak syscall entries */
cond_syscall(sys_pciconfig_read);
cond_syscall(sys_pciconfig_write);
cond_syscall(sys_pciconfig_iobase);
cond_syscall(sys32_ipc);
cond_syscall(sys32_sysctl);
cond_syscall(ppc_rtas);
cond_syscall(sys_spu_run);
cond_syscall(sys_spu_create);
cond_syscall(sys_subpage_prot);
/* mmu depending weak syscall entries */
cond_syscall(sys_mprotect);
cond_syscall(sys_msync);
cond_syscall(sys_mlock);
cond_syscall(sys_munlock);
cond_syscall(sys_mlockall);
cond_syscall(sys_munlockall);
cond_syscall(sys_mincore);
cond_syscall(sys_madvise);
cond_syscall(sys_mremap);
cond_syscall(sys_remap_file_pages);
cond_syscall(compat_sys_move_pages);
cond_syscall(compat_sys_migrate_pages);
/* block-layer dependent */
cond_syscall(sys_bdflush);
cond_syscall(sys_ioprio_set);
cond_syscall(sys_ioprio_get);
/* New file descriptors */
cond_syscall(sys_signalfd);
cond_syscall(sys_signalfd4);
cond_syscall(compat_sys_signalfd);
cond_syscall(compat_sys_signalfd4);
cond_syscall(sys_timerfd_create);
cond_syscall(sys_timerfd_settime);
cond_syscall(sys_timerfd_gettime);
cond_syscall(compat_sys_timerfd_settime);
cond_syscall(compat_sys_timerfd_gettime);
cond_syscall(sys_eventfd);
cond_syscall(sys_eventfd2);
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