generic compat_sys_rt_sigqueueinfo()

conditional on GENERIC_COMPAT_RT_SIGQUEUEINFO; by the end of that series
it will become the same thing as COMPAT and conditional will die out.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

arch/Kconfig

@@ -365,6 +365,9 @@ config GENERIC_COMPAT_RT_SIGPROCMASK
 config GENERIC_COMPAT_RT_SIGPENDING
 	bool
 
+config GENERIC_COMPAT_RT_SIGQUEUEINFO
+	bool
+
 #
 # ABI hall of shame
 #

include/linux/compat.h

@@ -602,6 +602,10 @@ asmlinkage long compat_sys_rt_sigprocmask(int how, compat_sigset_t __user *set,
 asmlinkage long compat_sys_rt_sigpending(compat_sigset_t __user *uset,
 					 compat_size_t sigsetsize);
 #endif
+#ifdef CONFIG_GENERIC_COMPAT_RT_SIGQUEUEINFO
+asmlinkage long compat_sys_rt_sigqueueinfo(compat_pid_t pid, int sig,
+				struct compat_siginfo __user *uinfo);
+#endif
 asmlinkage long compat_sys_sysinfo(struct compat_sysinfo __user *info);
 asmlinkage long compat_sys_ioctl(unsigned int fd, unsigned int cmd,
 				 unsigned long arg);

kernel/signal.c

@@ -2983,6 +2983,22 @@ SYSCALL_DEFINE2(tkill, pid_t, pid, int, sig)
 	return do_tkill(0, pid, sig);
 }
 
+static int do_rt_sigqueueinfo(pid_t pid, int sig, siginfo_t *info)
+{
+	/* Not even root can pretend to send signals from the kernel.
+	 * Nor can they impersonate a kill()/tgkill(), which adds source info.
+	 */
+	if (info->si_code >= 0 || info->si_code == SI_TKILL) {
+		/* We used to allow any < 0 si_code */
+		WARN_ON_ONCE(info->si_code < 0);
+		return -EPERM;
+	}
+	info->si_signo = sig;
+
+	/* POSIX.1b doesn't mention process groups.  */
+	return kill_proc_info(sig, info, pid);
+}
+
 /**
  *  sys_rt_sigqueueinfo - send signal information to a signal
  *  @pid: the PID of the thread
@@ -2993,23 +3009,26 @@ SYSCALL_DEFINE3(rt_sigqueueinfo, pid_t, pid, int, sig,
 		siginfo_t __user *, uinfo)
 {
 	siginfo_t info;
-
 	if (copy_from_user(&info, uinfo, sizeof(siginfo_t)))
 		return -EFAULT;
+	return do_rt_sigqueueinfo(pid, sig, &info);
+}
 
-	/* Not even root can pretend to send signals from the kernel.
-	 * Nor can they impersonate a kill()/tgkill(), which adds source info.
-	 */
-	if (info.si_code >= 0 || info.si_code == SI_TKILL) {
-		/* We used to allow any < 0 si_code */
-		WARN_ON_ONCE(info.si_code < 0);
-		return -EPERM;
-	}
-	info.si_signo = sig;
-
-	/* POSIX.1b doesn't mention process groups.  */
-	return kill_proc_info(sig, &info, pid);
+#ifdef CONFIG_COMPAT
+#ifdef CONFIG_GENERIC_COMPAT_RT_SIGQUEUEINFO
+COMPAT_SYSCALL_DEFINE3(rt_sigqueueinfo,
+			compat_pid_t, pid,
+			int, sig,
+			struct compat_siginfo __user *, uinfo)
+{
+	siginfo_t info;
+	int ret = copy_siginfo_from_user32(&info, uinfo);
+	if (unlikely(ret))
+		return ret;
+	return do_rt_sigqueueinfo(pid, sig, &info);
 }
+#endif
+#endif
 
 long do_rt_tgsigqueueinfo(pid_t tgid, pid_t pid, int sig, siginfo_t *info)
 {