generic sys_compat_rt_sigaction()

Again, protected by a temporary config symbol (GENERIC_COMPAT_RT_SIGACTION);
will be gone by the end of series.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

arch/Kconfig

@@ -368,6 +368,9 @@ config GENERIC_COMPAT_RT_SIGPENDING
 config GENERIC_COMPAT_RT_SIGQUEUEINFO
 	bool
 
+config GENERIC_COMPAT_RT_SIGACTION
+	bool
+
 #
 # ABI hall of shame
 #

include/linux/compat.h

@@ -142,6 +142,22 @@ typedef struct {
 	compat_sigset_word	sig[_COMPAT_NSIG_WORDS];
 } compat_sigset_t;
 
+#ifdef CONFIG_GENERIC_COMPAT_RT_SIGACTION
+struct compat_sigaction {
+#ifndef __ARCH_HAS_ODD_SIGACTION
+	compat_uptr_t			sa_handler;
+	compat_ulong_t			sa_flags;
+#else
+	compat_ulong_t			sa_flags;
+	compat_uptr_t			sa_handler;
+#endif
+#ifdef __ARCH_HAS_SA_RESTORER
+	compat_uptr_t			sa_restorer;
+#endif
+	compat_sigset_t			sa_mask __packed;
+};
+#endif
+
 /*
  * These functions operate strictly on struct compat_time*
  */
@@ -602,6 +618,14 @@ 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
+#ifndef CONFIG_ODD_RT_SIGACTION
+#ifdef CONFIG_GENERIC_COMPAT_RT_SIGACTION
+asmlinkage long compat_sys_rt_sigaction(int,
+				 const struct compat_sigaction __user *,
+				 struct compat_sigaction __user *,
+				 compat_size_t);
+#endif
+#endif
 #ifdef CONFIG_GENERIC_COMPAT_RT_SIGQUEUEINFO
 asmlinkage long compat_sys_rt_sigqueueinfo(compat_pid_t pid, int sig,
 				struct compat_siginfo __user *uinfo);

kernel/signal.c

@@ -3358,6 +3358,55 @@ SYSCALL_DEFINE4(rt_sigaction, int, sig,
 out:
 	return ret;
 }
+#ifdef CONFIG_COMPAT
+#ifdef CONFIG_GENERIC_COMPAT_RT_SIGACTION
+COMPAT_SYSCALL_DEFINE4(rt_sigaction, int, sig,
+		const struct compat_sigaction __user *, act,
+		struct compat_sigaction __user *, oact,
+		compat_size_t, sigsetsize)
+{
+	struct k_sigaction new_ka, old_ka;
+	compat_sigset_t mask;
+#ifdef __ARCH_HAS_SA_RESTORER
+	compat_uptr_t restorer;
+#endif
+	int ret;
+
+	/* XXX: Don't preclude handling different sized sigset_t's.  */
+	if (sigsetsize != sizeof(compat_sigset_t))
+		return -EINVAL;
+
+	if (act) {
+		compat_uptr_t handler;
+		ret = get_user(handler, &act->sa_handler);
+		new_ka.sa.sa_handler = compat_ptr(handler);
+#ifdef __ARCH_HAS_SA_RESTORER
+		ret |= get_user(restorer, &act->sa_restorer);
+		new_ka.sa.sa_restorer = compat_ptr(restorer);
+#endif
+		ret |= copy_from_user(&mask, &act->sa_mask, sizeof(mask));
+		ret |= __get_user(new_ka.sa.sa_flags, &act->sa_flags);
+		if (ret)
+			return -EFAULT;
+		sigset_from_compat(&new_ka.sa.sa_mask, &mask);
+	}
+
+	ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
+	if (!ret && oact) {
+		sigset_to_compat(&mask, &old_ka.sa.sa_mask);
+		ret = put_user(ptr_to_compat(old_ka.sa.sa_handler), 
+			       &oact->sa_handler);
+		ret |= copy_to_user(&oact->sa_mask, &mask, sizeof(mask));
+		ret |= __put_user(old_ka.sa.sa_flags, &oact->sa_flags);
+#ifdef __ARCH_HAS_SA_RESTORER
+		ret |= put_user(ptr_to_compat(old_ka.sa.sa_restorer),
+				&oact->sa_restorer);
+#endif
+	}
+	return ret;
+}
+#endif
+#endif
 #endif /* !CONFIG_ODD_RT_SIGACTION */
 
 #ifdef __ARCH_WANT_SYS_SGETMASK