generic compat_sys_rt_sigprocmask()

conditional on GENERIC_COMPAT_RT_SIGPROCMASK; 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

@@ -359,6 +359,9 @@ config MODULES_USE_ELF_REL
 config GENERIC_SIGALTSTACK
 	bool
 
+config GENERIC_COMPAT_RT_SIGPROCMASK
+	bool
+
 #
 # ABI hall of shame
 #

include/linux/compat.h

@@ -401,7 +401,8 @@ asmlinkage long compat_sys_settimeofday(struct compat_timeval __user *tv,
 asmlinkage long compat_sys_adjtimex(struct compat_timex __user *utp);
 
 extern int compat_printk(const char *fmt, ...);
-extern void sigset_from_compat(sigset_t *set, compat_sigset_t *compat);
+extern void sigset_from_compat(sigset_t *set, const compat_sigset_t *compat);
+extern void sigset_to_compat(compat_sigset_t *compat, const sigset_t *set);
 
 asmlinkage long compat_sys_migrate_pages(compat_pid_t pid,
 		compat_ulong_t maxnode, const compat_ulong_t __user *old_nodes,
@@ -592,6 +593,11 @@ asmlinkage long compat_sys_rt_sigtimedwait(compat_sigset_t __user *uthese,
 		struct compat_timespec __user *uts, compat_size_t sigsetsize);
 asmlinkage long compat_sys_rt_sigsuspend(compat_sigset_t __user *unewset,
 					 compat_size_t sigsetsize);
+#ifdef CONFIG_GENERIC_COMPAT_RT_SIGPROCMASK
+asmlinkage long compat_sys_rt_sigprocmask(int how, compat_sigset_t __user *set,
+					  compat_sigset_t __user *oset,
+					  compat_size_t sigsetsize);
+#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/compat.c

@@ -971,7 +971,7 @@ long compat_put_bitmap(compat_ulong_t __user *umask, unsigned long *mask,
 }
 
 void
-sigset_from_compat (sigset_t *set, compat_sigset_t *compat)
+sigset_from_compat(sigset_t *set, const compat_sigset_t *compat)
 {
 	switch (_NSIG_WORDS) {
 	case 4: set->sig[3] = compat->sig[6] | (((long)compat->sig[7]) << 32 );
@@ -982,6 +982,17 @@ sigset_from_compat (sigset_t *set, compat_sigset_t *compat)
 }
 EXPORT_SYMBOL_GPL(sigset_from_compat);
 
+void
+sigset_to_compat(compat_sigset_t *compat, const sigset_t *set)
+{
+	switch (_NSIG_WORDS) {
+	case 4: compat->sig[7] = (set->sig[3] >> 32); compat->sig[6] = set->sig[3];
+	case 3: compat->sig[5] = (set->sig[2] >> 32); compat->sig[4] = set->sig[2];
+	case 2: compat->sig[3] = (set->sig[1] >> 32); compat->sig[2] = set->sig[1];
+	case 1: compat->sig[1] = (set->sig[0] >> 32); compat->sig[0] = set->sig[0];
+	}
+}
+
 asmlinkage long
 compat_sys_rt_sigtimedwait (compat_sigset_t __user *uthese,
 		struct compat_siginfo __user *uinfo,

kernel/signal.c

@@ -2613,6 +2613,47 @@ SYSCALL_DEFINE4(rt_sigprocmask, int, how, sigset_t __user *, nset,
 	return 0;
 }
 
+#ifdef CONFIG_COMPAT
+#ifdef CONFIG_GENERIC_COMPAT_RT_SIGPROCMASK
+COMPAT_SYSCALL_DEFINE4(rt_sigprocmask, int, how, compat_sigset_t __user *, nset,
+		compat_sigset_t __user *, oset, compat_size_t, sigsetsize)
+{
+#ifdef __BIG_ENDIAN
+	sigset_t old_set = current->blocked;
+
+	/* XXX: Don't preclude handling different sized sigset_t's.  */
+	if (sigsetsize != sizeof(sigset_t))
+		return -EINVAL;
+
+	if (nset) {
+		compat_sigset_t new32;
+		sigset_t new_set;
+		int error;
+		if (copy_from_user(&new32, nset, sizeof(compat_sigset_t)))
+			return -EFAULT;
+
+		sigset_from_compat(&new_set, &new32);
+		sigdelsetmask(&new_set, sigmask(SIGKILL)|sigmask(SIGSTOP));
+
+		error = sigprocmask(how, &new_set, NULL);
+		if (error)
+			return error;
+	}
+	if (oset) {
+		compat_sigset_t old32;
+		sigset_to_compat(&old32, &old_set);
+		if (copy_to_user(oset, &old_set, sizeof(sigset_t)))
+			return -EFAULT;
+	}
+	return 0;
+#else
+	return sys_rt_sigprocmask(how, (sigset_t __user *)nset,
+				  (sigset_t __user *)oset, sigsetsize);
+#endif
+}
+#endif
+#endif
+
 long do_sigpending(void __user *set, unsigned long sigsetsize)
 {
 	long error = -EINVAL;