arm64: switch to generic sigaltstack

Signed-off-by: Al Viro <[e-mail]>

arch/arm64/Kconfig

···
 	select GENERIC_IOMAP
 	select GENERIC_IRQ_PROBE
 	select GENERIC_IRQ_SHOW
+	select GENERIC_SIGALTSTACK
 	select GENERIC_SMP_IDLE_THREAD
 	select GENERIC_TIME_VSYSCALL
 	select HARDIRQS_SW_RESEND

arch/arm64/include/asm/syscalls.h

···
  * System call wrappers implemented in kernel/entry.S.
  */
 asmlinkage long sys_rt_sigreturn_wrapper(void);
-asmlinkage long sys_sigaltstack_wrapper(const stack_t __user *uss,
-					stack_t __user *uoss);
 
 #include <asm-generic/syscalls.h>
 

arch/arm64/include/asm/unistd32.h

···
 __SYSCALL(183, sys_getcwd)
 __SYSCALL(184, sys_capget)
 __SYSCALL(185, sys_capset)
-__SYSCALL(186, compat_sys_sigaltstack_wrapper)
+__SYSCALL(186, compat_sys_sigaltstack)
 __SYSCALL(187, compat_sys_sendfile)
 __SYSCALL(188, sys_ni_syscall)			/* 188 reserved */
 __SYSCALL(189, sys_ni_syscall)			/* 189 reserved */

arch/arm64/kernel/entry.S

···
 	b	sys_rt_sigreturn
 ENDPROC(sys_rt_sigreturn_wrapper)
 
-ENTRY(sys_sigaltstack_wrapper)
-	ldr	x2, [sp, #S_SP]
-	b	sys_sigaltstack
-ENDPROC(sys_sigaltstack_wrapper)
-
 ENTRY(handle_arch_irq)
 	.quad	0

arch/arm64/kernel/signal.c

···
 	if (restore_sigframe(regs, frame))
 		goto badframe;
 
-	if (do_sigaltstack(&frame->uc.uc_stack,
-			   NULL, regs->sp) == -EFAULT)
+	if (restore_altstack(&frame->uc.uc_stack))
 		goto badframe;
 
 	return regs->regs[0];
···
 				    regs->pc, regs->sp);
 	force_sig(SIGSEGV, current);
 	return 0;
-}
-
-asmlinkage long sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss,
-				unsigned long sp)
-{
-	return do_sigaltstack(uss, uoss, sp);
 }
 
 static int setup_sigframe(struct rt_sigframe __user *sf,
···
 			  sigset_t *set, struct pt_regs *regs)
 {
 	struct rt_sigframe __user *frame;
-	stack_t stack;
 	int err = 0;
 
 	frame = get_sigframe(ka, regs);
···
 	__put_user_error(0, &frame->uc.uc_flags, err);
 	__put_user_error(NULL, &frame->uc.uc_link, err);
 
-	memset(&stack, 0, sizeof(stack));
-	stack.ss_sp = (void __user *)current->sas_ss_sp;
-	stack.ss_flags = sas_ss_flags(regs->sp);
-	stack.ss_size = current->sas_ss_size;
-	err |= __copy_to_user(&frame->uc.uc_stack, &stack, sizeof(stack));
-
+	err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
 	err |= setup_sigframe(frame, regs, set);
 	if (err == 0) {
 		setup_return(regs, ka, frame, usig);

arch/arm64/kernel/signal32.c

···
 	compat_uptr_t			sa_restorer;
 };
 
-typedef struct compat_sigaltstack {
-	compat_uptr_t			ss_sp;
-	int				ss_flags;
-	compat_size_t			ss_size;
-} compat_stack_t;
-
 struct compat_sigcontext {
 	/* We always set these two fields to 0 */
 	compat_ulong_t			trap_no;
···
 	return ret;
 }
 
-int compat_do_sigaltstack(compat_uptr_t compat_uss, compat_uptr_t compat_uoss,
-			  compat_ulong_t sp)
-{
-	compat_stack_t __user *newstack = compat_ptr(compat_uss);
-	compat_stack_t __user *oldstack = compat_ptr(compat_uoss);
-	compat_uptr_t ss_sp;
-	int ret;
-	mm_segment_t old_fs;
-	stack_t uss, uoss;
-
-	/* Marshall the compat new stack into a stack_t */
-	if (newstack) {
-		if (get_user(ss_sp, &newstack->ss_sp) ||
-		    __get_user(uss.ss_flags, &newstack->ss_flags) ||
-		    __get_user(uss.ss_size, &newstack->ss_size))
-			return -EFAULT;
-		uss.ss_sp = compat_ptr(ss_sp);
-	}
-
-	old_fs = get_fs();
-	set_fs(KERNEL_DS);
-	/* The __user pointer casts are valid because of the set_fs() */
-	ret = do_sigaltstack(
-		newstack ? (stack_t __user *) &uss : NULL,
-		oldstack ? (stack_t __user *) &uoss : NULL,
-		(unsigned long)sp);
-	set_fs(old_fs);
-
-	/* Convert the old stack_t into a compat stack. */
-	if (!ret && oldstack &&
-		(put_user(ptr_to_compat(uoss.ss_sp), &oldstack->ss_sp) ||
-		 __put_user(uoss.ss_flags, &oldstack->ss_flags) ||
-		 __put_user(uoss.ss_size, &oldstack->ss_size)))
-		return -EFAULT;
-	return ret;
-}
-
 static int compat_restore_sigframe(struct pt_regs *regs,
 				   struct compat_sigframe __user *sf)
 {
···
 	if (compat_restore_sigframe(regs, &frame->sig))
 		goto badframe;
 
-	if (compat_do_sigaltstack(ptr_to_compat(&frame->sig.uc.uc_stack),
-				 ptr_to_compat((void __user *)NULL),
-				 regs->compat_sp) == -EFAULT)
+	if (compat_restore_altstack(&frame->sig.uc.uc_stack))
 		goto badframe;
 
 	return regs->regs[0];
···
 	__put_user_error(0, &frame->sig.uc.uc_flags, err);
 	__put_user_error(NULL, &frame->sig.uc.uc_link, err);
 
-	memset(&stack, 0, sizeof(stack));
-	stack.ss_sp = (compat_uptr_t)current->sas_ss_sp;
-	stack.ss_flags = sas_ss_flags(regs->compat_sp);
-	stack.ss_size = current->sas_ss_size;
-	err |= __copy_to_user(&frame->sig.uc.uc_stack, &stack, sizeof(stack));
+	err |= __compat_save_altstack(&frame->sig.uc.uc_stack, regs->compat_sp);
 
 	err |= compat_setup_sigframe(&frame->sig, regs, set);
 

arch/arm64/kernel/sys.c

···
  * Wrappers to pass the pt_regs argument.
  */
 #define sys_rt_sigreturn	sys_rt_sigreturn_wrapper
-#define sys_sigaltstack		sys_sigaltstack_wrapper
 
 #include <asm/syscalls.h>
 

arch/arm64/kernel/sys32.S

···
 	b	compat_sys_rt_sigreturn
 ENDPROC(compat_sys_rt_sigreturn_wrapper)
 
-compat_sys_sigaltstack_wrapper:
-	ldr	x2, [sp, #S_COMPAT_SP]
-	b	compat_do_sigaltstack
-ENDPROC(compat_sys_sigaltstack_wrapper)
-
 compat_sys_statfs64_wrapper:
 	mov	w3, #84
 	cmp	w1, #88