1
linux/arch/x86/include/asm
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
..
bigsmp
es7000 x86: fix APIC_DEBUG with inquire_remote_apic 2008-10-28 16:43:48 +01:00
mach-default x86: fix APIC_DEBUG with inquire_remote_apic 2008-10-28 16:43:48 +01:00
mach-generic
mach-rdc321x
mach-voyager
numaq
summit
uv x86, uv: fix compile error in uv_hub.h 2008-10-30 19:38:46 +01:00
visws
xen
a.out-core.h
a.out.h
acpi.h ACPI: pci_link: remove acpi_irq_balance_set() interface 2008-11-11 21:12:05 -05:00
agp.h
alternative-asm.h
alternative.h
amd_iommu_types.h
amd_iommu.h
apic.h
apicdef.h
arch_hooks.h
asm.h
atomic_32.h
atomic_64.h
atomic.h
auxvec.h
bios_ebda.h
bitops.h
boot.h
bootparam.h
bug.h
bugs.h
byteorder.h
cache.h
cacheflush.h
calgary.h
calling.h
checksum_32.h
checksum_64.h
checksum.h
cmpxchg_32.h
cmpxchg_64.h
cmpxchg.h
compat.h
cpu.h
cpufeature.h x86: fix AMDC1E and XTOPOLOGY conflict in cpufeature 2008-10-31 11:01:40 +01:00
cputime.h
current.h
debugreg.h
delay.h
desc_defs.h
desc.h
device.h
div64.h
dma-mapping.h
dma.h
dmi.h
ds.h
dwarf2.h
e820.h
edac.h
efi.h
elf.h
emergency-restart.h
errno.h
fb.h
fcntl.h
fixmap_32.h x86: add iomap_atomic*()/iounmap_atomic() on 32-bit using fixmaps 2008-10-31 10:12:38 +01:00
fixmap_64.h
fixmap.h x86: add iomap_atomic*()/iounmap_atomic() on 32-bit using fixmaps 2008-10-31 10:12:38 +01:00
floppy.h
frame.h
ftrace.h
futex.h
gart.h
genapic_32.h
genapic_64.h
genapic.h
geode.h
gpio.h
hardirq_32.h
hardirq_64.h
hardirq.h
highmem.h x86: add iomap_atomic*()/iounmap_atomic() on 32-bit using fixmaps 2008-10-31 10:12:38 +01:00
hpet.h
hugetlb.h
hw_irq.h
hypertransport.h
i387.h
i8253.h
i8259.h
ia32_unistd.h
ia32.h
idle.h
intel_arch_perfmon.h
io_32.h
io_64.h
io_apic.h
io.h x86: start annotating early ioremap pointers with __iomem 2008-10-29 08:05:14 +01:00
ioctl.h
ioctls.h
iommu.h Revert "x86: blacklist DMAR on Intel G31/G33 chipsets" 2008-11-15 11:37:16 -08:00
ipcbuf.h
ipi.h
irq_regs_32.h
irq_regs_64.h
irq_regs.h
irq_remapping.h
irq_vectors.h x86: remove VISWS and PARAVIRT around NR_IRQS puzzle 2008-11-06 09:35:34 +01:00
irq.h
irqflags.h
ist.h
k8.h
Kbuild
kdebug.h
kexec.h
kgdb.h
kmap_types.h
kprobes.h
kvm_host.h
kvm_para.h
kvm_x86_emulate.h
kvm.h
ldt.h
lguest_hcall.h
lguest.h
linkage.h
local.h
math_emu.h
mc146818rtc.h
mca_dma.h
mca.h
mce.h
microcode.h
mman.h
mmconfig.h
mmu_context_32.h
mmu_context_64.h
mmu_context.h
mmu.h
mmx.h
mmzone_32.h
mmzone_64.h
mmzone.h
module.h
mpspec_def.h
mpspec.h
msgbuf.h
msidef.h
msr-index.h
msr.h sched: improve sched_clock() performance 2008-11-08 16:48:19 +01:00
mtrr.h
mutex_32.h
mutex_64.h
mutex.h
nmi.h
nops.h
numa_32.h
numa_64.h
numa.h
numaq.h
olpc.h
page_32.h
page_64.h
page.h
param.h
paravirt.h
parport.h
pat.h
pci_32.h
pci_64.h
pci-direct.h
pci.h
pda.h
percpu.h
pgalloc.h
pgtable_32.h
pgtable_64.h
pgtable-2level-defs.h
pgtable-2level.h
pgtable-3level-defs.h
pgtable-3level.h i386/PAE: fix pud_page() 2008-10-30 11:47:50 +01:00
pgtable.h
poll.h
posix_types_32.h
posix_types_64.h
posix_types.h
prctl.h
processor-cyrix.h
processor-flags.h
processor.h
proto.h
ptrace-abi.h
ptrace.h
pvclock-abi.h
pvclock.h
reboot_fixups.h
reboot.h
required-features.h
resource.h
resume-trace.h
rio.h
rtc.h
rwlock.h
rwsem.h
scatterlist.h
seccomp_32.h
seccomp_64.h
seccomp.h
sections.h
segment.h
sembuf.h
serial.h
setup.h
shmbuf.h
shmparam.h
sigcontext32.h
sigcontext.h
siginfo.h
signal.h
smp.h x86/voyager: fix compile breakage caused by dc1e35c6e9 2008-10-31 00:19:33 +01:00
socket.h
sockios.h
sparsemem.h
spinlock_types.h
spinlock.h
srat.h
stacktrace.h
stat.h
statfs.h
string_32.h
string_64.h
string.h
suspend_32.h
suspend_64.h
suspend.h
swiotlb.h
sync_bitops.h
syscall.h
syscalls.h
system_64.h
system.h
tce.h
termbits.h
termios.h
therm_throt.h
thread_info.h
time.h
timer.h
timex.h
tlb.h
tlbflush.h
topology.h sched: re-tune balancing 2008-11-05 18:04:38 +01:00
trampoline.h
traps.h
tsc.h sched: improve sched_clock() performance 2008-11-08 16:48:19 +01:00
types.h
uaccess_32.h
uaccess_64.h
uaccess.h
ucontext.h
unaligned.h
unistd_32.h
unistd_64.h reintroduce accept4 2008-11-19 18:49:57 -08:00
unistd.h
unwind.h
user32.h
user_32.h
user_64.h
user.h
vdso.h
vga.h
vgtod.h
vic.h
vm86.h
vmi_time.h
vmi.h
voyager.h x86, voyager: fix smp_intr_init() compile breakage 2008-11-03 10:52:21 +01:00
vsyscall.h
xcr.h
xor_32.h
xor_64.h
xor.h
xsave.h