new helpers: __save_altstack/__compat_save_altstack, switch x86 and um to those

note that they are relying on access_ok() already checked by caller.

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

1 files changed, 16 insertions, 0 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index aee85bd76b8a..f072513302c3 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -3117,6 +3117,14 @@ int restore_altstack(const stack_t __user *uss)
         return err == -EFAULT ? err : 0;
 }
 
+int __save_altstack(stack_t __user *uss, unsigned long sp)
+{
+        struct task_struct *t = current;
+        return  __put_user((void __user *)t->sas_ss_sp, &uss->ss_sp) |
+                __put_user(sas_ss_flags(sp), &uss->ss_flags) |
+                __put_user(t->sas_ss_size, &uss->ss_size);
+}
+
 #ifdef CONFIG_COMPAT
 #ifdef CONFIG_GENERIC_SIGALTSTACK
 asmlinkage long compat_sys_sigaltstack(const compat_stack_t __user *uss_ptr,
@@ -3158,6 +3166,14 @@ int compat_restore_altstack(const compat_stack_t __user *uss)
         /* squash all but -EFAULT for now */
         return err == -EFAULT ? err : 0;
 }
+
+int __compat_save_altstack(compat_stack_t __user *uss, unsigned long sp)
+{
+        struct task_struct *t = current;
+        return  __put_user(ptr_to_compat((void __user *)t->sas_ss_sp), &uss->ss_sp) |
+                __put_user(sas_ss_flags(sp), &uss->ss_flags) |
+                __put_user(t->sas_ss_size, &uss->ss_size);
+}
 #endif
 #endif