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Subject[PATCH 05/18] flag parameters: signalfd
This patch adds the new signalfd4 syscall.  It extends the old signalfd
syscall by one parameter which is meant to hold a flag value. In this
patch the only flag support is SFD_CLOEXEC which causes the close-on-exec
flag for the returned file descriptor to be set.

A new flag SFD_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 <signal.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/syscall.h>

#ifndef __NR_signalfd4
# ifdef __x86_64__
# define __NR_signalfd4 289
# elif defined __i386__
# define __NR_signalfd4 327
# else
# error "need __NR_signalfd4"
# endif
#endif

#define SFD_CLOEXEC (1 << 0)

int
main (void)
{
sigset_t ss;
sigemptyset (&ss);
sigaddset (&ss, SIGUSR1);
int fd = syscall (__NR_signalfd4, -1, &ss, 8, 0);
if (fd == -1)
{
puts ("signalfd4(0) failed");
return 1;
}
int coe = fcntl (fd, F_GETFD);
if (coe == -1)
{
puts ("fcntl failed");
return 1;
}
if (coe & FD_CLOEXEC)
{
puts ("signalfd4(0) set close-on-exec flag");
return 1;
}
close (fd);

fd = syscall (__NR_signalfd4, -1, &ss, 8, SFD_CLOEXEC);
if (fd == -1)
{
puts ("signalfd4(SFD_CLOEXEC) failed");
return 1;
}
coe = fcntl (fd, F_GETFD);
if (coe == -1)
{
puts ("fcntl failed");
return 1;
}
if ((coe & FD_CLOEXEC) == 0)
{
puts ("signalfd4(SFD_CLOEXEC) does not 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/compat.c | 14 ++++++++++----
fs/signalfd.c | 22 ++++++++++++++++++++--
include/asm-x86/unistd_32.h | 1 +
include/asm-x86/unistd_64.h | 2 ++
include/linux/signalfd.h | 3 +++
include/linux/syscalls.h | 1 +
8 files changed, 39 insertions(+), 6 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
@@ -731,4 +731,5 @@ ia32_sys_call_table:
.quad sys32_fallocate
.quad compat_sys_timerfd_settime /* 325 */
.quad compat_sys_timerfd_gettime
+ .quad compat_sys_signalfd4
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
@@ -326,3 +326,4 @@ ENTRY(sys_call_table)
.long sys_fallocate
.long sys_timerfd_settime /* 325 */
.long sys_timerfd_gettime
+ .long sys_signalfd4
diff --git a/fs/compat.c b/fs/compat.c
index 332a869..2ab01c5 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -2131,9 +2131,9 @@ asmlinkage long compat_sys_epoll_pwait(int epfd,

#ifdef CONFIG_SIGNALFD

-asmlinkage long compat_sys_signalfd(int ufd,
- const compat_sigset_t __user *sigmask,
- compat_size_t sigsetsize)
+asmlinkage long compat_sys_signalfd4(int ufd,
+ const compat_sigset_t __user *sigmask,
+ compat_size_t sigsetsize, int flags)
{
compat_sigset_t ss32;
sigset_t tmp;
@@ -2148,9 +2148,15 @@ asmlinkage long compat_sys_signalfd(int ufd,
if (copy_to_user(ksigmask, &tmp, sizeof(sigset_t)))
return -EFAULT;

- return sys_signalfd(ufd, ksigmask, sizeof(sigset_t));
+ return sys_signalfd4(ufd, ksigmask, sizeof(sigset_t), flags);
}

+asmlinkage long compat_sys_signalfd(int ufd,
+ const compat_sigset_t __user *sigmask,
+ compat_size_t sigsetsize)
+{
+ return compat_sys_signalfd4(ufd, sigmask, sigsetsize, 0);
+}
#endif /* CONFIG_SIGNALFD */

#ifdef CONFIG_TIMERFD
diff --git a/fs/signalfd.c b/fs/signalfd.c
index 6197256..a73333b 100644
--- a/fs/signalfd.c
+++ b/fs/signalfd.c
@@ -28,6 +28,7 @@
#include <linux/anon_inodes.h>
#include <linux/signalfd.h>
#include <linux/syscalls.h>
+#include <linux/flagsremap.h>

struct signalfd_ctx {
sigset_t sigmask;
@@ -205,10 +206,21 @@ static const struct file_operations signalfd_fops = {
.read = signalfd_read,
};

-asmlinkage long sys_signalfd(int ufd, sigset_t __user *user_mask, size_t sizemask)
+static const struct flags_rmap signalfd_file_flags_remap[] = {
+ { SFD_CLOEXEC, O_CLOEXEC },
+};
+
+asmlinkage long sys_signalfd4(int ufd, sigset_t __user *user_mask,
+ size_t sizemask, int flags)
{
sigset_t sigmask;
struct signalfd_ctx *ctx;
+ int fflags;
+
+ if (flags_remap(signalfd_file_flags_remap,
+ ARRAY_SIZE(signalfd_file_flags_remap),
+ flags, &fflags))
+ return -EINVAL;

if (sizemask != sizeof(sigset_t) ||
copy_from_user(&sigmask, user_mask, sizeof(sigmask)))
@@ -228,7 +240,7 @@ asmlinkage long sys_signalfd(int ufd, sigset_t __user *user_mask, size_t sizemas
* anon_inode_getfd() will install the fd.
*/
ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx,
- 0);
+ fflags);
if (ufd < 0)
kfree(ctx);
} else {
@@ -250,3 +262,9 @@ asmlinkage long sys_signalfd(int ufd, sigset_t __user *user_mask, size_t sizemas

return ufd;
}
+
+asmlinkage long sys_signalfd(int ufd, sigset_t __user *user_mask,
+ size_t sizemask)
+{
+ return sys_signalfd4(ufd, user_mask, sizemask, 0);
+}
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
@@ -332,6 +332,7 @@
#define __NR_fallocate 324
#define __NR_timerfd_settime 325
#define __NR_timerfd_gettime 326
+#define __NR_signalfd4 327

#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
@@ -641,6 +641,8 @@ __SYSCALL(__NR_fallocate, sys_fallocate)
__SYSCALL(__NR_timerfd_gettime, sys_timerfd_gettime)
#define __NR_paccept 288
__SYSCALL(__NR_paccept, sys_paccept)
+#define __NR_signalfd4 289
+__SYSCALL(__NR_signalfd4, sys_signalfd4)


#ifndef __NO_STUBS
diff --git a/include/linux/signalfd.h b/include/linux/signalfd.h
index ea037f2..98a749a 100644
--- a/include/linux/signalfd.h
+++ b/include/linux/signalfd.h
@@ -9,6 +9,9 @@
#define _LINUX_SIGNALFD_H


+/* Flags for signalfd4. */
+#define SFD_CLOEXEC (1 << 0)
+
struct signalfd_siginfo {
__u32 ssi_signo;
__s32 ssi_errno;
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
@@ -610,6 +610,7 @@ asmlinkage long sys_set_robust_list(struct robust_list_head __user *head,
size_t len);
asmlinkage long sys_getcpu(unsigned __user *cpu, unsigned __user *node, struct getcpu_cache __user *cache);
asmlinkage long sys_signalfd(int ufd, sigset_t __user *user_mask, size_t sizemask);
+asmlinkage long sys_signalfd4(int ufd, sigset_t __user *user_mask, size_t sizemask, int flags);
asmlinkage long sys_timerfd_create(int clockid, int flags);
asmlinkage long sys_timerfd_settime(int ufd, int flags,
const struct itimerspec __user *utmr,

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