sparc: prepare kernel/ for unification

o sparc32 files with identical names to sparc64 renamed to <name>_32.S o introduced a few Kconfig helpers to simplify Makefile logic o refactored Makefile to prepare for unification - use obj-$(CONFIG_SPARC32) for sparc32 specific files - use <name>_$(BITS) for files where sparc64 has a _64 variant - sparc64 directly include a few files where sparc32 builds them, refer to these files directly (no BITS) - sneaked in -Werror as used by sparc64 o modified sparc/Makefile to use the new names for head/init_task Signed-off-by: Sam Ravnborg <sam@ravnborg.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2008-12-03 03:08:37 -08:00
parent 478b8fecda
commit d670bd4f80
28 changed files with 73 additions and 20 deletions
--- a/arch/sparc/kernel/signal_32.c
+++ b/arch/sparc/kernel/signal_32.c
@@ -0,0 +1,631 @@
+/*  linux/arch/sparc/kernel/signal.c
+ *
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ *  Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
+ *  Copyright (C) 1996 Miguel de Icaza (miguel@nuclecu.unam.mx)
+ *  Copyright (C) 1997 Eddie C. Dost   (ecd@skynet.be)
+ */
+
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <linux/signal.h>
+#include <linux/errno.h>
+#include <linux/wait.h>
+#include <linux/ptrace.h>
+#include <linux/unistd.h>
+#include <linux/mm.h>
+#include <linux/tty.h>
+#include <linux/smp.h>
+#include <linux/binfmts.h>	/* do_coredum */
+#include <linux/bitops.h>
+#include <linux/tracehook.h>
+
+#include <asm/uaccess.h>
+#include <asm/ptrace.h>
+#include <asm/pgalloc.h>
+#include <asm/pgtable.h>
+#include <asm/cacheflush.h>	/* flush_sig_insns */
+
+#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
+
+extern void fpsave(unsigned long *fpregs, unsigned long *fsr,
+		   void *fpqueue, unsigned long *fpqdepth);
+extern void fpload(unsigned long *fpregs, unsigned long *fsr);
+
+struct signal_frame {
+	struct sparc_stackf	ss;
+	__siginfo_t		info;
+	__siginfo_fpu_t __user	*fpu_save;
+	unsigned long		insns[2] __attribute__ ((aligned (8)));
+	unsigned int		extramask[_NSIG_WORDS - 1];
+	unsigned int		extra_size; /* Should be 0 */
+	__siginfo_fpu_t		fpu_state;
+};
+
+struct rt_signal_frame {
+	struct sparc_stackf	ss;
+	siginfo_t		info;
+	struct pt_regs		regs;
+	sigset_t		mask;
+	__siginfo_fpu_t __user	*fpu_save;
+	unsigned int		insns[2];
+	stack_t			stack;
+	unsigned int		extra_size; /* Should be 0 */
+	__siginfo_fpu_t		fpu_state;
+};
+
+/* Align macros */
+#define SF_ALIGNEDSZ  (((sizeof(struct signal_frame) + 7) & (~7)))
+#define RT_ALIGNEDSZ  (((sizeof(struct rt_signal_frame) + 7) & (~7)))
+
+static int _sigpause_common(old_sigset_t set)
+{
+	set &= _BLOCKABLE;
+	spin_lock_irq(&current->sighand->siglock);
+	current->saved_sigmask = current->blocked;
+	siginitset(&current->blocked, set);
+	recalc_sigpending();
+	spin_unlock_irq(&current->sighand->siglock);
+
+	current->state = TASK_INTERRUPTIBLE;
+	schedule();
+	set_thread_flag(TIF_RESTORE_SIGMASK);
+
+	return -ERESTARTNOHAND;
+}
+
+asmlinkage int sys_sigsuspend(old_sigset_t set)
+{
+	return _sigpause_common(set);
+}
+
+static inline int
+restore_fpu_state(struct pt_regs *regs, __siginfo_fpu_t __user *fpu)
+{
+	int err;
+#ifdef CONFIG_SMP
+	if (test_tsk_thread_flag(current, TIF_USEDFPU))
+		regs->psr &= ~PSR_EF;
+#else
+	if (current == last_task_used_math) {
+		last_task_used_math = NULL;
+		regs->psr &= ~PSR_EF;
+	}
+#endif
+	set_used_math();
+	clear_tsk_thread_flag(current, TIF_USEDFPU);
+
+	if (!access_ok(VERIFY_READ, fpu, sizeof(*fpu)))
+		return -EFAULT;
+
+	err = __copy_from_user(&current->thread.float_regs[0], &fpu->si_float_regs[0],
+			       (sizeof(unsigned long) * 32));
+	err |= __get_user(current->thread.fsr, &fpu->si_fsr);
+	err |= __get_user(current->thread.fpqdepth, &fpu->si_fpqdepth);
+	if (current->thread.fpqdepth != 0)
+		err |= __copy_from_user(&current->thread.fpqueue[0],
+					&fpu->si_fpqueue[0],
+					((sizeof(unsigned long) +
+					(sizeof(unsigned long *)))*16));
+	return err;
+}
+
+asmlinkage void do_sigreturn(struct pt_regs *regs)
+{
+	struct signal_frame __user *sf;
+	unsigned long up_psr, pc, npc;
+	sigset_t set;
+	__siginfo_fpu_t __user *fpu_save;
+	int err;
+
+	/* Always make any pending restarted system calls return -EINTR */
+	current_thread_info()->restart_block.fn = do_no_restart_syscall;
+
+	synchronize_user_stack();
+
+	sf = (struct signal_frame __user *) regs->u_regs[UREG_FP];
+
+	/* 1. Make sure we are not getting garbage from the user */
+	if (!access_ok(VERIFY_READ, sf, sizeof(*sf)))
+		goto segv_and_exit;
+
+	if (((unsigned long) sf) & 3)
+		goto segv_and_exit;
+
+	err = __get_user(pc,  &sf->info.si_regs.pc);
+	err |= __get_user(npc, &sf->info.si_regs.npc);
+
+	if ((pc | npc) & 3)
+		goto segv_and_exit;
+
+	/* 2. Restore the state */
+	up_psr = regs->psr;
+	err |= __copy_from_user(regs, &sf->info.si_regs, sizeof(struct pt_regs));
+
+	/* User can only change condition codes and FPU enabling in %psr. */
+	regs->psr = (up_psr & ~(PSR_ICC | PSR_EF))
+		  | (regs->psr & (PSR_ICC | PSR_EF));
+
+	/* Prevent syscall restart.  */
+	pt_regs_clear_syscall(regs);
+
+	err |= __get_user(fpu_save, &sf->fpu_save);
+
+	if (fpu_save)
+		err |= restore_fpu_state(regs, fpu_save);
+
+	/* This is pretty much atomic, no amount locking would prevent
+	 * the races which exist anyways.
+	 */
+	err |= __get_user(set.sig[0], &sf->info.si_mask);
+	err |= __copy_from_user(&set.sig[1], &sf->extramask,
+			        (_NSIG_WORDS-1) * sizeof(unsigned int));
+			   
+	if (err)
+		goto segv_and_exit;
+
+	sigdelsetmask(&set, ~_BLOCKABLE);
+	spin_lock_irq(&current->sighand->siglock);
+	current->blocked = set;
+	recalc_sigpending();
+	spin_unlock_irq(&current->sighand->siglock);
+	return;
+
+segv_and_exit:
+	force_sig(SIGSEGV, current);
+}
+
+asmlinkage void do_rt_sigreturn(struct pt_regs *regs)
+{
+	struct rt_signal_frame __user *sf;
+	unsigned int psr, pc, npc;
+	__siginfo_fpu_t __user *fpu_save;
+	mm_segment_t old_fs;
+	sigset_t set;
+	stack_t st;
+	int err;
+
+	synchronize_user_stack();
+	sf = (struct rt_signal_frame __user *) regs->u_regs[UREG_FP];
+	if (!access_ok(VERIFY_READ, sf, sizeof(*sf)) ||
+	    (((unsigned long) sf) & 0x03))
+		goto segv;
+
+	err = __get_user(pc, &sf->regs.pc);
+	err |= __get_user(npc, &sf->regs.npc);
+	err |= ((pc | npc) & 0x03);
+
+	err |= __get_user(regs->y, &sf->regs.y);
+	err |= __get_user(psr, &sf->regs.psr);
+
+	err |= __copy_from_user(&regs->u_regs[UREG_G1],
+				&sf->regs.u_regs[UREG_G1], 15 * sizeof(u32));
+
+	regs->psr = (regs->psr & ~PSR_ICC) | (psr & PSR_ICC);
+
+	/* Prevent syscall restart.  */
+	pt_regs_clear_syscall(regs);
+
+	err |= __get_user(fpu_save, &sf->fpu_save);
+
+	if (fpu_save)
+		err |= restore_fpu_state(regs, fpu_save);
+	err |= __copy_from_user(&set, &sf->mask, sizeof(sigset_t));
+	
+	err |= __copy_from_user(&st, &sf->stack, sizeof(stack_t));
+	
+	if (err)
+		goto segv;
+		
+	regs->pc = pc;
+	regs->npc = npc;
+	
+	/* It is more difficult to avoid calling this function than to
+	 * call it and ignore errors.
+	 */
+	old_fs = get_fs();
+	set_fs(KERNEL_DS);
+	do_sigaltstack((const stack_t __user *) &st, NULL, (unsigned long)sf);
+	set_fs(old_fs);
+
+	sigdelsetmask(&set, ~_BLOCKABLE);
+	spin_lock_irq(&current->sighand->siglock);
+	current->blocked = set;
+	recalc_sigpending();
+	spin_unlock_irq(&current->sighand->siglock);
+	return;
+segv:
+	force_sig(SIGSEGV, current);
+}
+
+/* Checks if the fp is valid */
+static inline int invalid_frame_pointer(void __user *fp, int fplen)
+{
+	if ((((unsigned long) fp) & 7) ||
+	    !__access_ok((unsigned long)fp, fplen) ||
+	    ((sparc_cpu_model == sun4 || sparc_cpu_model == sun4c) &&
+	     ((unsigned long) fp < 0xe0000000 && (unsigned long) fp >= 0x20000000)))
+		return 1;
+	
+	return 0;
+}
+
+static inline void __user *get_sigframe(struct sigaction *sa, struct pt_regs *regs, unsigned long framesize)
+{
+	unsigned long sp = regs->u_regs[UREG_FP];
+
+	/*
+	 * If we are on the alternate signal stack and would overflow it, don't.
+	 * Return an always-bogus address instead so we will die with SIGSEGV.
+	 */
+	if (on_sig_stack(sp) && !likely(on_sig_stack(sp - framesize)))
+		return (void __user *) -1L;
+
+	/* This is the X/Open sanctioned signal stack switching.  */
+	if (sa->sa_flags & SA_ONSTACK) {
+		if (sas_ss_flags(sp) == 0)
+			sp = current->sas_ss_sp + current->sas_ss_size;
+	}
+
+	/* Always align the stack frame.  This handles two cases.  First,
+	 * sigaltstack need not be mindful of platform specific stack
+	 * alignment.  Second, if we took this signal because the stack
+	 * is not aligned properly, we'd like to take the signal cleanly
+	 * and report that.
+	 */
+	sp &= ~7UL;
+
+	return (void __user *)(sp - framesize);
+}
+
+static inline int
+save_fpu_state(struct pt_regs *regs, __siginfo_fpu_t __user *fpu)
+{
+	int err = 0;
+#ifdef CONFIG_SMP
+	if (test_tsk_thread_flag(current, TIF_USEDFPU)) {
+		put_psr(get_psr() | PSR_EF);
+		fpsave(&current->thread.float_regs[0], &current->thread.fsr,
+		       &current->thread.fpqueue[0], &current->thread.fpqdepth);
+		regs->psr &= ~(PSR_EF);
+		clear_tsk_thread_flag(current, TIF_USEDFPU);
+	}
+#else
+	if (current == last_task_used_math) {
+		put_psr(get_psr() | PSR_EF);
+		fpsave(&current->thread.float_regs[0], &current->thread.fsr,
+		       &current->thread.fpqueue[0], &current->thread.fpqdepth);
+		last_task_used_math = NULL;
+		regs->psr &= ~(PSR_EF);
+	}
+#endif
+	err |= __copy_to_user(&fpu->si_float_regs[0],
+			      &current->thread.float_regs[0],
+			      (sizeof(unsigned long) * 32));
+	err |= __put_user(current->thread.fsr, &fpu->si_fsr);
+	err |= __put_user(current->thread.fpqdepth, &fpu->si_fpqdepth);
+	if (current->thread.fpqdepth != 0)
+		err |= __copy_to_user(&fpu->si_fpqueue[0],
+				      &current->thread.fpqueue[0],
+				      ((sizeof(unsigned long) +
+				      (sizeof(unsigned long *)))*16));
+	clear_used_math();
+	return err;
+}
+
+static void setup_frame(struct k_sigaction *ka, struct pt_regs *regs,
+			int signo, sigset_t *oldset)
+{
+	struct signal_frame __user *sf;
+	int sigframe_size, err;
+
+	/* 1. Make sure everything is clean */
+	synchronize_user_stack();
+
+	sigframe_size = SF_ALIGNEDSZ;
+	if (!used_math())
+		sigframe_size -= sizeof(__siginfo_fpu_t);
+
+	sf = (struct signal_frame __user *)
+		get_sigframe(&ka->sa, regs, sigframe_size);
+
+	if (invalid_frame_pointer(sf, sigframe_size))
+		goto sigill_and_return;
+
+	if (current_thread_info()->w_saved != 0)
+		goto sigill_and_return;
+
+	/* 2. Save the current process state */
+	err = __copy_to_user(&sf->info.si_regs, regs, sizeof(struct pt_regs));
+	
+	err |= __put_user(0, &sf->extra_size);
+
+	if (used_math()) {
+		err |= save_fpu_state(regs, &sf->fpu_state);
+		err |= __put_user(&sf->fpu_state, &sf->fpu_save);
+	} else {
+		err |= __put_user(0, &sf->fpu_save);
+	}
+
+	err |= __put_user(oldset->sig[0], &sf->info.si_mask);
+	err |= __copy_to_user(sf->extramask, &oldset->sig[1],
+			      (_NSIG_WORDS - 1) * sizeof(unsigned int));
+	err |= __copy_to_user(sf, (char *) regs->u_regs[UREG_FP],
+			      sizeof(struct reg_window));
+	if (err)
+		goto sigsegv;
+	
+	/* 3. signal handler back-trampoline and parameters */
+	regs->u_regs[UREG_FP] = (unsigned long) sf;
+	regs->u_regs[UREG_I0] = signo;
+	regs->u_regs[UREG_I1] = (unsigned long) &sf->info;
+	regs->u_regs[UREG_I2] = (unsigned long) &sf->info;
+
+	/* 4. signal handler */
+	regs->pc = (unsigned long) ka->sa.sa_handler;
+	regs->npc = (regs->pc + 4);
+
+	/* 5. return to kernel instructions */
+	if (ka->ka_restorer)
+		regs->u_regs[UREG_I7] = (unsigned long)ka->ka_restorer;
+	else {
+		regs->u_regs[UREG_I7] = (unsigned long)(&(sf->insns[0]) - 2);
+
+		/* mov __NR_sigreturn, %g1 */
+		err |= __put_user(0x821020d8, &sf->insns[0]);
+
+		/* t 0x10 */
+		err |= __put_user(0x91d02010, &sf->insns[1]);
+		if (err)
+			goto sigsegv;
+
+		/* Flush instruction space. */
+		flush_sig_insns(current->mm, (unsigned long) &(sf->insns[0]));
+	}
+	return;
+
+sigill_and_return:
+	do_exit(SIGILL);
+sigsegv:
+	force_sigsegv(signo, current);
+}
+
+static void setup_rt_frame(struct k_sigaction *ka, struct pt_regs *regs,
+			   int signo, sigset_t *oldset, siginfo_t *info)
+{
+	struct rt_signal_frame __user *sf;
+	int sigframe_size;
+	unsigned int psr;
+	int err;
+
+	synchronize_user_stack();
+	sigframe_size = RT_ALIGNEDSZ;
+	if (!used_math())
+		sigframe_size -= sizeof(__siginfo_fpu_t);
+	sf = (struct rt_signal_frame __user *)
+		get_sigframe(&ka->sa, regs, sigframe_size);
+	if (invalid_frame_pointer(sf, sigframe_size))
+		goto sigill;
+	if (current_thread_info()->w_saved != 0)
+		goto sigill;
+
+	err  = __put_user(regs->pc, &sf->regs.pc);
+	err |= __put_user(regs->npc, &sf->regs.npc);
+	err |= __put_user(regs->y, &sf->regs.y);
+	psr = regs->psr;
+	if (used_math())
+		psr |= PSR_EF;
+	err |= __put_user(psr, &sf->regs.psr);
+	err |= __copy_to_user(&sf->regs.u_regs, regs->u_regs, sizeof(regs->u_regs));
+	err |= __put_user(0, &sf->extra_size);
+
+	if (psr & PSR_EF) {
+		err |= save_fpu_state(regs, &sf->fpu_state);
+		err |= __put_user(&sf->fpu_state, &sf->fpu_save);
+	} else {
+		err |= __put_user(0, &sf->fpu_save);
+	}
+	err |= __copy_to_user(&sf->mask, &oldset->sig[0], sizeof(sigset_t));
+	
+	/* Setup sigaltstack */
+	err |= __put_user(current->sas_ss_sp, &sf->stack.ss_sp);
+	err |= __put_user(sas_ss_flags(regs->u_regs[UREG_FP]), &sf->stack.ss_flags);
+	err |= __put_user(current->sas_ss_size, &sf->stack.ss_size);
+	
+	err |= __copy_to_user(sf, (char *) regs->u_regs[UREG_FP],
+			      sizeof(struct reg_window));	
+
+	err |= copy_siginfo_to_user(&sf->info, info);
+
+	if (err)
+		goto sigsegv;
+
+	regs->u_regs[UREG_FP] = (unsigned long) sf;
+	regs->u_regs[UREG_I0] = signo;
+	regs->u_regs[UREG_I1] = (unsigned long) &sf->info;
+	regs->u_regs[UREG_I2] = (unsigned long) &sf->regs;
+
+	regs->pc = (unsigned long) ka->sa.sa_handler;
+	regs->npc = (regs->pc + 4);
+
+	if (ka->ka_restorer)
+		regs->u_regs[UREG_I7] = (unsigned long)ka->ka_restorer;
+	else {
+		regs->u_regs[UREG_I7] = (unsigned long)(&(sf->insns[0]) - 2);
+
+		/* mov __NR_sigreturn, %g1 */
+		err |= __put_user(0x821020d8, &sf->insns[0]);
+
+		/* t 0x10 */
+		err |= __put_user(0x91d02010, &sf->insns[1]);
+		if (err)
+			goto sigsegv;
+
+		/* Flush instruction space. */
+		flush_sig_insns(current->mm, (unsigned long) &(sf->insns[0]));
+	}
+	return;
+
+sigill:
+	do_exit(SIGILL);
+sigsegv:
+	force_sigsegv(signo, current);
+}
+
+static inline void
+handle_signal(unsigned long signr, struct k_sigaction *ka,
+	      siginfo_t *info, sigset_t *oldset, struct pt_regs *regs)
+{
+	if (ka->sa.sa_flags & SA_SIGINFO)
+		setup_rt_frame(ka, regs, signr, oldset, info);
+	else
+		setup_frame(ka, regs, signr, oldset);
+
+	spin_lock_irq(&current->sighand->siglock);
+	sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
+	if (!(ka->sa.sa_flags & SA_NOMASK))
+		sigaddset(&current->blocked, signr);
+	recalc_sigpending();
+	spin_unlock_irq(&current->sighand->siglock);
+}
+
+static inline void syscall_restart(unsigned long orig_i0, struct pt_regs *regs,
+				   struct sigaction *sa)
+{
+	switch(regs->u_regs[UREG_I0]) {
+	case ERESTART_RESTARTBLOCK:
+	case ERESTARTNOHAND:
+	no_system_call_restart:
+		regs->u_regs[UREG_I0] = EINTR;
+		regs->psr |= PSR_C;
+		break;
+	case ERESTARTSYS:
+		if (!(sa->sa_flags & SA_RESTART))
+			goto no_system_call_restart;
+		/* fallthrough */
+	case ERESTARTNOINTR:
+		regs->u_regs[UREG_I0] = orig_i0;
+		regs->pc -= 4;
+		regs->npc -= 4;
+	}
+}
+
+/* Note that 'init' is a special process: it doesn't get signals it doesn't
+ * want to handle. Thus you cannot kill init even with a SIGKILL even by
+ * mistake.
+ */
+static void do_signal(struct pt_regs *regs, unsigned long orig_i0)
+{
+	struct k_sigaction ka;
+	int restart_syscall;
+	sigset_t *oldset;
+	siginfo_t info;
+	int signr;
+
+	if (pt_regs_is_syscall(regs) && (regs->psr & PSR_C))
+		restart_syscall = 1;
+	else
+		restart_syscall = 0;
+
+	if (test_thread_flag(TIF_RESTORE_SIGMASK))
+		oldset = &current->saved_sigmask;
+	else
+		oldset = &current->blocked;
+
+	signr = get_signal_to_deliver(&info, &ka, regs, NULL);
+
+	/* If the debugger messes with the program counter, it clears
+	 * the software "in syscall" bit, directing us to not perform
+	 * a syscall restart.
+	 */
+	if (restart_syscall && !pt_regs_is_syscall(regs))
+		restart_syscall = 0;
+
+	if (signr > 0) {
+		if (restart_syscall)
+			syscall_restart(orig_i0, regs, &ka.sa);
+		handle_signal(signr, &ka, &info, oldset, regs);
+
+		/* a signal was successfully delivered; the saved
+		 * sigmask will have been stored in the signal frame,
+		 * and will be restored by sigreturn, so we can simply
+		 * clear the TIF_RESTORE_SIGMASK flag.
+		 */
+		if (test_thread_flag(TIF_RESTORE_SIGMASK))
+			clear_thread_flag(TIF_RESTORE_SIGMASK);
+
+		tracehook_signal_handler(signr, &info, &ka, regs, 0);
+		return;
+	}
+	if (restart_syscall &&
+	    (regs->u_regs[UREG_I0] == ERESTARTNOHAND ||
+	     regs->u_regs[UREG_I0] == ERESTARTSYS ||
+	     regs->u_regs[UREG_I0] == ERESTARTNOINTR)) {
+		/* replay the system call when we are done */
+		regs->u_regs[UREG_I0] = orig_i0;
+		regs->pc -= 4;
+		regs->npc -= 4;
+	}
+	if (restart_syscall &&
+	    regs->u_regs[UREG_I0] == ERESTART_RESTARTBLOCK) {
+		regs->u_regs[UREG_G1] = __NR_restart_syscall;
+		regs->pc -= 4;
+		regs->npc -= 4;
+	}
+
+	/* if there's no signal to deliver, we just put the saved sigmask
+	 * back
+	 */
+	if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
+		clear_thread_flag(TIF_RESTORE_SIGMASK);
+		sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
+	}
+}
+
+void do_notify_resume(struct pt_regs *regs, unsigned long orig_i0,
+		      unsigned long thread_info_flags)
+{
+	if (thread_info_flags & (_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK))
+		do_signal(regs, orig_i0);
+	if (thread_info_flags & _TIF_NOTIFY_RESUME) {
+		clear_thread_flag(TIF_NOTIFY_RESUME);
+		tracehook_notify_resume(regs);
+	}
+}
+
+asmlinkage int
+do_sys_sigstack(struct sigstack __user *ssptr, struct sigstack __user *ossptr,
+		unsigned long sp)
+{
+	int ret = -EFAULT;
+
+	/* First see if old state is wanted. */
+	if (ossptr) {
+		if (put_user(current->sas_ss_sp + current->sas_ss_size,
+			     &ossptr->the_stack) ||
+		    __put_user(on_sig_stack(sp), &ossptr->cur_status))
+			goto out;
+	}
+
+	/* Now see if we want to update the new state. */
+	if (ssptr) {
+		char *ss_sp;
+
+		if (get_user(ss_sp, &ssptr->the_stack))
+			goto out;
+		/* If the current stack was set with sigaltstack, don't
+		   swap stacks while we are on it.  */
+		ret = -EPERM;
+		if (current->sas_ss_sp && on_sig_stack(sp))
+			goto out;
+
+		/* Since we don't know the extent of the stack, and we don't
+		   track onstack-ness, but rather calculate it, we must
+		   presume a size.  Ho hum this interface is lossy.  */
+		current->sas_ss_sp = (unsigned long)ss_sp - SIGSTKSZ;
+		current->sas_ss_size = SIGSTKSZ;
+	}
+	ret = 0;
+out:
+	return ret;
+}