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>

3 files changed, 7 insertions, 25 deletions

diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
index a866411a2fcc..a1daf4a65009 100644
--- a/arch/x86/ia32/ia32_signal.c
+++ b/arch/x86/ia32/ia32_signal.c
@@ -467,10 +467,7 @@ int ia32_setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
                 else
                         put_user_ex(0, &frame->uc.uc_flags);
                 put_user_ex(0, &frame->uc.uc_link);
-                put_user_ex(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
-                put_user_ex(sas_ss_flags(regs->sp),
-                            &frame->uc.uc_stack.ss_flags);
-                put_user_ex(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
+                err |= __compat_save_altstack(&frame->uc.uc_stack, regs->sp);
 
                 if (ka->sa.sa_flags & SA_RESTORER)
                         restorer = ka->sa.sa_restorer;
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index b17ed37c61a2..a6c8a347b8c6 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -363,10 +363,7 @@ static int __setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
                 else
                         put_user_ex(0, &frame->uc.uc_flags);
                 put_user_ex(0, &frame->uc.uc_link);
-                put_user_ex(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
-                put_user_ex(sas_ss_flags(regs->sp),
-                            &frame->uc.uc_stack.ss_flags);
-                put_user_ex(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
+                err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
 
                 /* Set up to return from userspace.  */
                 restorer = VDSO32_SYMBOL(current->mm->context.vdso, rt_sigreturn);
@@ -413,7 +410,6 @@ static int __setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
         struct rt_sigframe __user *frame;
         void __user *fp = NULL;
         int err = 0;
-        struct task_struct *me = current;
 
         frame = get_sigframe(ka, regs, sizeof(struct rt_sigframe), &fp);
 
@@ -432,10 +428,7 @@ static int __setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
                 else
                         put_user_ex(0, &frame->uc.uc_flags);
                 put_user_ex(0, &frame->uc.uc_link);
-                put_user_ex(me->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
-                put_user_ex(sas_ss_flags(regs->sp),
-                            &frame->uc.uc_stack.ss_flags);
-                put_user_ex(me->sas_ss_size, &frame->uc.uc_stack.ss_size);
+                err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
 
                 /* Set up to return from userspace.  If provided, use a stub
                    already in userspace.  */
@@ -502,10 +495,7 @@ static int x32_setup_rt_frame(int sig, struct k_sigaction *ka,
                 else
                         put_user_ex(0, &frame->uc.uc_flags);
                 put_user_ex(0, &frame->uc.uc_link);
-                put_user_ex(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
-                put_user_ex(sas_ss_flags(regs->sp),
-                            &frame->uc.uc_stack.ss_flags);
-                put_user_ex(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
+                err |= __compat_save_altstack(&frame->uc.uc_stack, regs->sp);
                 put_user_ex(0, &frame->uc.uc__pad0);
 
                 if (ka->sa.sa_flags & SA_RESTORER) {
@@ -651,7 +641,7 @@ long sys_rt_sigreturn(struct pt_regs *regs)
         if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &ax))
                 goto badframe;
 
-        if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->sp) == -EFAULT)
+        if (restore_altstack(&frame->uc.uc_stack))
                 goto badframe;
 
         return ax;
diff --git a/arch/x86/um/signal.c b/arch/x86/um/signal.c
index bdaa08cfbcf4..71cef48ea5cd 100644
--- a/arch/x86/um/signal.c
+++ b/arch/x86/um/signal.c
@@ -342,9 +342,7 @@ static int copy_ucontext_to_user(struct ucontext __user *uc,
 {
         int err = 0;
 
-        err |= put_user(current->sas_ss_sp, &uc->uc_stack.ss_sp);
-        err |= put_user(sas_ss_flags(sp), &uc->uc_stack.ss_flags);
-        err |= put_user(current->sas_ss_size, &uc->uc_stack.ss_size);
+        err |= __save_altstack(&uc->uc_stack, sp);
         err |= copy_sc_to_user(&uc->uc_mcontext, fp, &current->thread.regs, 0);
         err |= copy_to_user(&uc->uc_sigmask, set, sizeof(*set));
         return err;
@@ -529,10 +527,7 @@ int setup_signal_stack_si(unsigned long stack_top, int sig,
         /* Create the ucontext.  */
         err |= __put_user(0, &frame->uc.uc_flags);
         err |= __put_user(0, &frame->uc.uc_link);
-        err |= __put_user(me->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
-        err |= __put_user(sas_ss_flags(PT_REGS_SP(regs)),
-                          &frame->uc.uc_stack.ss_flags);
-        err |= __put_user(me->sas_ss_size, &frame->uc.uc_stack.ss_size);
+        err |= __save_altstack(&frame->uc.uc_stack, PT_REGS_SP(regs));
         err |= copy_sc_to_user(&frame->uc.uc_mcontext, &frame->fpstate, regs,
                                set->sig[0]);
         err |= __put_user(&frame->fpstate, &frame->uc.uc_mcontext.fpstate);