introduce generic sys_sigaltstack(), switch x86 and um to it

Conditional on CONFIG_GENERIC_SIGALTSTACK; architectures that do not
select it are completely unaffected

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 9fe5f946526e..6ca1e08210c6 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -63,6 +63,7 @@ struct getcpu_cache;
 struct old_linux_dirent;
 struct perf_event_attr;
 struct file_handle;
+struct sigaltstack;
 
 #include <linux/types.h>
 #include <linux/aio_abi.h>
@@ -299,6 +300,11 @@ asmlinkage long sys_personality(unsigned int personality);
 asmlinkage long sys_sigpending(old_sigset_t __user *set);
 asmlinkage long sys_sigprocmask(int how, old_sigset_t __user *set,
                                 old_sigset_t __user *oset);
+#ifdef CONFIG_GENERIC_SIGALTSTACK
+asmlinkage long sys_sigaltstack(const struct sigaltstack __user *uss,
+                                struct sigaltstack __user *uoss);
+#endif
+
 asmlinkage long sys_getitimer(int which, struct itimerval __user *value);
 asmlinkage long sys_setitimer(int which,
                                 struct itimerval __user *value,