PPC32: Rework signal code and add a swapcontext system call.

The main thing here is that the signal delivery/return code for real-time
signals has been changed so that the layout of the registers corresponds
with the new ucontext_t definition being used by glibc.  The old ucontext_t
didn't have space to actually store the registers, just a pointer to them,
which made it impossible to implement set/getcontext et al.  The new
ucontext_t includes a mcontext_t which actually contains space to store
all of the general, floating pointer and vector registers.

We now also save the altivec registers on signal delivery and restore them
on return from the signal if the process has ever used altivec (since the
last exec).

Finally this adds a swapcontext system call.  Swapcontext really needs to be
done in the kernel since on PPC, only privileged code can set all three of
CTR, LR and NIA (next instruction address) to arbitrary values.  Also the kernel
know if the process currently owns the FP and altivec units and can optimize
in the case where it doesn't.

5 files changed, 358 insertions, 257 deletions

diff --git a/arch/ppc/kernel/asm-offsets.c b/arch/ppc/kernel/asm-offsets.c
index 6e6f78e4e3a0..e41af4ff4dc6 100644
--- a/arch/ppc/kernel/asm-offsets.c
+++ b/arch/ppc/kernel/asm-offsets.c
@@ -52,6 +52,7 @@ main(void)
 	DEFINE(THREAD_VR0, offsetof(struct thread_struct, vr[0]));
 	DEFINE(THREAD_VRSAVE, offsetof(struct thread_struct, vrsave));
 	DEFINE(THREAD_VSCR, offsetof(struct thread_struct, vscr));
+	DEFINE(THREAD_USED_VR, offsetof(struct thread_struct, used_vr));
 #endif /* CONFIG_ALTIVEC */
 	/* Interrupt register frame */
 	DEFINE(STACK_FRAME_OVERHEAD, STACK_FRAME_OVERHEAD);
@@ -101,7 +102,7 @@ main(void)
 	DEFINE(_XER, STACK_FRAME_OVERHEAD+offsetof(struct pt_regs, xer));
 	DEFINE(_DAR, STACK_FRAME_OVERHEAD+offsetof(struct pt_regs, dar));
 	DEFINE(_DSISR, STACK_FRAME_OVERHEAD+offsetof(struct pt_regs, dsisr));
-	/* The PowerPC 400-class processors have neither the DAR nor the DSISR
+	/* The PowerPC 400-class & Book-E processors have neither the DAR nor the DSISR
 	 * SPRs. Hence, we overload them to hold the similar DEAR and ESR SPRs
 	 * for such processors.  For critical interrupts we use them to
 	 * hold SRR0 and SRR1.
diff --git a/arch/ppc/kernel/head.S b/arch/ppc/kernel/head.S
index 0311ae117dee..af68a4ee38d8 100644
--- a/arch/ppc/kernel/head.S
+++ b/arch/ppc/kernel/head.S
@@ -915,7 +915,9 @@ load_up_altivec:
 	/* enable use of AltiVec after return */
 	oris	r9,r9,MSR_VEC@h
 	mfspr	r5,SPRG3		/* current task's THREAD (phys) */
+	li	r4,1
 	li	r10,THREAD_VSCR
+	stw	r4,THREAD_USED_VR(r5)
 	lvx	vr0,r10,r5
 	mtvscr	vr0
 	REST_32VR(0,r10,r5)
diff --git a/arch/ppc/kernel/misc.S b/arch/ppc/kernel/misc.S
index a41d10ee1614..b5f86a6d3267 100644
--- a/arch/ppc/kernel/misc.S
+++ b/arch/ppc/kernel/misc.S
@@ -1379,7 +1379,7 @@ _GLOBAL(sys_call_table)
 	.long sys_clock_gettime
 	.long sys_clock_getres
 	.long sys_clock_nanosleep
-	.long sys_ni_syscall	/* reserved for swapcontext */
+	.long sys_swapcontext
 	.long sys_tgkill	/* 250 */
 	.long sys_utimes
 	.long sys_statfs64
diff --git a/arch/ppc/kernel/process.c b/arch/ppc/kernel/process.c
index f0a608eb1a6e..82e09cc776bc 100644
--- a/arch/ppc/kernel/process.c
+++ b/arch/ppc/kernel/process.c
@@ -415,6 +415,7 @@ void start_thread(struct pt_regs *regs, unsigned long nip, unsigned long sp)
 	memset(current->thread.vr, 0, sizeof(current->thread.vr));
 	memset(&current->thread.vscr, 0, sizeof(current->thread.vscr));
 	current->thread.vrsave = 0;
+	current->thread.used_vr = 0;
 #endif /* CONFIG_ALTIVEC */
 }
 
diff --git a/arch/ppc/kernel/signal.c b/arch/ppc/kernel/signal.c
index 41efaef2153a..c737078db5b0 100644
--- a/arch/ppc/kernel/signal.c
+++ b/arch/ppc/kernel/signal.c
@@ -41,18 +41,6 @@ extern void sigreturn_exit(struct pt_regs *);
 
 #define GP_REGS_SIZE	min(sizeof(elf_gregset_t), sizeof(struct pt_regs))
 
-/* 
- * These are the flags in the MSR that the user is allowed to change
- * by modifying the saved value of the MSR on the stack.  SE and BE
- * should not be in this list since gdb may want to change these.  I.e,
- * you should be able to step out of a signal handler to see what
- * instruction executes next after the signal handler completes.
- * Alternately, if you stepped into a signal handler, you should be
- * able to continue 'til the next breakpoint from within the signal
- * handler, even if the handler returns.
- */
-#define MSR_USERCHANGE	(MSR_FE0 | MSR_FE1)
-
 int do_signal(sigset_t *oldset, struct pt_regs *regs);
 
 /*
@@ -72,8 +60,8 @@ sys_sigsuspend(old_sigset_t mask, int p2, int p3, int p4, int p6, int p7,
 	spin_unlock_irq(&current->sighand->siglock);
 
 	regs->result = -EINTR;
-	regs->ccr |= 0x10000000;
 	regs->gpr[3] = EINTR;
+	regs->ccr |= 0x10000000;
 	while (1) {
 		current->state = TASK_INTERRUPTIBLE;
 		schedule();
@@ -103,8 +91,8 @@ sys_rt_sigsuspend(sigset_t __user *unewset, size_t sigsetsize, int p3, int p4,
 	spin_unlock_irq(&current->sighand->siglock);
 
 	regs->result = -EINTR;
-	regs->ccr |= 0x10000000;
 	regs->gpr[3] = EINTR;
+	regs->ccr |= 0x10000000;
 	while (1) {
 		current->state = TASK_INTERRUPTIBLE;
 		schedule();
@@ -164,305 +152,389 @@ sys_sigaction(int sig, const struct old_sigaction __user *act,
  *
  */
 struct sigregs {
-	elf_gregset_t	gp_regs;
-	double		fp_regs[ELF_NFPREG];
-	unsigned long	tramp[2];
+	struct mcontext	mctx;		/* all the register values */
 	/* Programs using the rs6000/xcoff abi can save up to 19 gp regs
 	   and 18 fp regs below sp before decrementing it. */
 	int		abigap[56];
 };
 
-struct rt_sigframe
-{
-	unsigned long	_unused[2];
-	struct siginfo *pinfo;
-	void *puc;
-	struct siginfo info;
-	struct ucontext uc;
-};
-
+/* We use the mc_pad field for the signal return trampoline. */
+#define tramp	mc_pad
 
 /*
  *  When we have rt signals to deliver, we set up on the
  *  user stack, going down from the original stack pointer:
- *	   a sigregs struct
- *	   one rt_sigframe struct (siginfo + ucontext)
- *	   a gap of __SIGNAL_FRAMESIZE bytes
+ *	one rt_sigframe struct (siginfo + ucontext + ABI gap)
+ *	a gap of __SIGNAL_FRAMESIZE+16 bytes
+ *  (the +16 is to get the siginfo and ucontext in the same
+ *  positions as in older kernels).
  *
  *  Each of these things must be a multiple of 16 bytes in size.
  *
  */
-int sys_rt_sigreturn(int r3, int r4, int r5, int r6, int r7, int r8,
-		     struct pt_regs *regs)
+struct rt_sigframe
 {
-	struct rt_sigframe __user *rt_sf;
-	struct sigcontext sigctx;
-	struct sigregs __user *sr;
-	elf_gregset_t saved_regs;  /* an array of ELF_NGREG unsigned longs */
-	sigset_t set;
-	stack_t st;
+	struct siginfo info;
+	struct ucontext uc;
+	/* Programs using the rs6000/xcoff abi can save up to 19 gp regs
+	   and 18 fp regs below sp before decrementing it. */
+	int		abigap[56];
+};
 
-	rt_sf = (struct rt_sigframe __user *)(regs->gpr[1] + __SIGNAL_FRAMESIZE);
-	if (copy_from_user(&sigctx, &rt_sf->uc.uc_mcontext, sizeof(sigctx))
-	    || copy_from_user(&set, &rt_sf->uc.uc_sigmask, sizeof(set))
-	    || copy_from_user(&st, &rt_sf->uc.uc_stack, sizeof(st)))
-		goto badframe;
-	sigdelsetmask(&set, ~_BLOCKABLE);
-	spin_lock_irq(&current->sighand->siglock);
-	current->blocked = set;
-	recalc_sigpending();
-	spin_unlock_irq(&current->sighand->siglock);
+/*
+ * Save the current user registers on the user stack.
+ * We only save the altivec registers if the process has used
+ * altivec instructions at some point.
+ */
+static int
+save_user_regs(struct pt_regs *regs, struct mcontext *frame, int sigret)
+{
+	/* save general and floating-point registers */
+	CHECK_FULL_REGS(regs);
 	if (regs->msr & MSR_FP)
 		giveup_fpu(current);
+	if (__copy_to_user(&frame->mc_gregs, regs, GP_REGS_SIZE)
+	    || __copy_to_user(&frame->mc_fregs, current->thread.fpr,
+			      ELF_NFPREG * sizeof(double)))
+		return 1;
 
-	/* restore registers -
-	 * sigctx is initialized to point to the 
-	 * preamble frame (where registers are stored) 
-	 * see handle_signal()
+	current->thread.fpscr = 0;	/* turn off all fp exceptions */
+
+#ifdef CONFIG_ALTIVEC
+	/* save altivec registers */
+	if (current->thread.used_vr) {
+		if (regs->msr & MSR_VEC)
+			giveup_altivec(current);
+		if (__copy_to_user(&frame->mc_vregs, current->thread.vr,
+				   ELF_NVRREG * sizeof(vector128)))
+			return 1;
+		/* set MSR_VEC in the saved MSR value to indicate that
+		   frame->mc_vregs contains valid data */
+		if (__put_user(regs->msr | MSR_VEC, &frame->mc_gregs[PT_MSR]))
+			return 1;
+	}
+	/* else assert((regs->msr & MSR_VEC) == 0) */
+
+	/* We always copy to/from vrsave, it's 0 if we don't have or don't
+	 * use altivec. Since VSCR only contains 32 bits saved in the least
+	 * significant bits of a vector, we "cheat" and stuff VRSAVE in the
+	 * most significant bits of that same vector. --BenH
 	 */
-	sr = (struct sigregs __user *) sigctx.regs;
-	if (copy_from_user(saved_regs, &sr->gp_regs, sizeof(sr->gp_regs)))
-		goto badframe;
-	saved_regs[PT_MSR] = (regs->msr & ~MSR_USERCHANGE)
-		| (saved_regs[PT_MSR] & MSR_USERCHANGE);
-	memcpy(regs, saved_regs, GP_REGS_SIZE);
-	if (copy_from_user(current->thread.fpr, &sr->fp_regs,
-			   sizeof(sr->fp_regs)))
-		goto badframe;
+	if (__put_user(current->thread.vrsave, (u32 *)&frame->mc_vregs[32]))
+		return 1;
+#endif /* CONFIG_ALTIVEC */
+
+	if (sigret) {
+		/* Set up the sigreturn trampoline: li r0,sigret; sc */
+		if (__put_user(0x38000000UL + sigret, &frame->tramp[0])
+		    || __put_user(0x44000002UL, &frame->tramp[1]))
+			return 1;
+		flush_icache_range((unsigned long) &frame->tramp[0],
+				   (unsigned long) &frame->tramp[2]);
+	}
 
-	sigreturn_exit(regs);		/* doesn't return here */
 	return 0;
+}
 
-badframe:
-	do_exit(SIGSEGV);
+/*
+ * Restore the current user register values from the user stack,
+ * (except for MSR).
+ */
+static int
+restore_user_regs(struct pt_regs *regs, struct mcontext __user *sr)
+{
+#ifdef CONFIG_ALTIVEC
+	unsigned long msr;
+#endif
+
+	/* copy up to but not including MSR */
+	if (__copy_from_user(regs, &sr->mc_gregs, PT_MSR * sizeof(elf_greg_t)))
+		return 1;
+	/* copy from orig_r3 (the word after the MSR) up to the end */
+	if (__copy_from_user(&regs->orig_gpr3, &sr->mc_gregs[PT_ORIG_R3],
+			     GP_REGS_SIZE - PT_ORIG_R3 * sizeof(elf_greg_t)))
+		return 1;
+
+	/* force the process to reload the FP registers from
+	   current->thread when it next does FP instructions */
+	regs->msr &= ~MSR_FP;
+	if (__copy_from_user(current->thread.fpr, &sr->mc_fregs,
+			     sizeof(sr->mc_fregs)))
+		return 1;
+
+#ifdef CONFIG_ALTIVEC
+	/* force the process to reload the altivec registers from
+	   current->thread when it next does altivec instructions */
+	regs->msr &= ~MSR_VEC;
+	if (!__get_user(msr, &sr->mc_gregs[PT_MSR]) && (msr & MSR_VEC) != 0) {
+		/* restore altivec registers from the stack */
+		if (__copy_from_user(current->thread.vr, &sr->mc_vregs,
+				     sizeof(sr->mc_vregs)))
+			return 1;
+	} else if (current->thread.used_vr)
+		memset(&current->thread.vr, 0, sizeof(current->thread.vr));
+
+	/* Always get VRSAVE back */
+	if (__get_user(current->thread.vrsave, (u32 *)&sr->mc_vregs[32]))
+		return 1;
+#endif /* CONFIG_ALTIVEC */
+
+	return 0;
 }
 
+/*
+ * Restore the user process's signal mask
+ */
 static void
-setup_rt_frame(struct pt_regs *regs, struct sigregs __user *frame,
-	       signed long newsp)
+restore_sigmask(sigset_t *set)
 {
-	struct rt_sigframe __user *rt_sf = (struct rt_sigframe __user *) newsp;
+	sigdelsetmask(set, ~_BLOCKABLE);
+	spin_lock_irq(&current->sighand->siglock);
+	current->blocked = *set;
+	recalc_sigpending();
+	spin_unlock_irq(&current->sighand->siglock);
+}
 
-	/* Set up preamble frame */
-	if (verify_area(VERIFY_WRITE, frame, sizeof(*frame)))
+/*
+ * Set up a signal frame for a "real-time" signal handler
+ * (one which gets siginfo).
+ */
+static void
+handle_rt_signal(unsigned long sig, struct k_sigaction *ka,
+		 siginfo_t *info, sigset_t *oldset, struct pt_regs * regs,
+		 unsigned long newsp)
+{
+	struct rt_sigframe __user *rt_sf;
+	struct mcontext __user *frame;
+	unsigned long origsp = newsp;
+
+	/* Set up Signal Frame */
+	/* Put a Real Time Context onto stack */
+	newsp -= sizeof(*rt_sf);
+	rt_sf = (struct rt_sigframe __user *) newsp;
+
+	/* create a stack frame for the caller of the handler */
+	newsp -= __SIGNAL_FRAMESIZE + 16;
+
+	if (verify_area(VERIFY_WRITE, (void __user *) newsp, origsp - newsp))
 		goto badframe;
-	CHECK_FULL_REGS(regs);
-	if (regs->msr & MSR_FP)
-		giveup_fpu(current);
-	if (__copy_to_user(&frame->gp_regs, regs, GP_REGS_SIZE)
-	    || __copy_to_user(&frame->fp_regs, current->thread.fpr,
-			      ELF_NFPREG * sizeof(double))
-	/* Set up to return from user space.
-	   It calls the sc exception at offset 0x9999 
-	   for sys_rt_sigreturn().
-	*/
-	    || __put_user(0x38000000UL + __NR_rt_sigreturn, &frame->tramp[0])
-	    || __put_user(0x44000002UL, &frame->tramp[1]))	/* sc */
+
+	/* Put the siginfo & fill in most of the ucontext */
+	if (copy_siginfo_to_user(&rt_sf->info, info)
+	    || __put_user(0, &rt_sf->uc.uc_flags)
+	    || __put_user(0, &rt_sf->uc.uc_link)
+	    || __put_user(current->sas_ss_sp, &rt_sf->uc.uc_stack.ss_sp)
+	    || __put_user(sas_ss_flags(regs->gpr[1]), 
+			  &rt_sf->uc.uc_stack.ss_flags)
+	    || __put_user(current->sas_ss_size, &rt_sf->uc.uc_stack.ss_size)
+	    || __put_user(&rt_sf->uc.uc_mcontext, &rt_sf->uc.uc_regs)
+	    || __copy_to_user(&rt_sf->uc.uc_oldsigmask, oldset, sizeof(*oldset))
+	    || __copy_to_user(&rt_sf->uc.uc_sigmask, oldset, sizeof(*oldset)))
 		goto badframe;
-	flush_icache_range((unsigned long) &frame->tramp[0],
-			   (unsigned long) &frame->tramp[2]);
-	current->thread.fpscr = 0;	/* turn off all fp exceptions */
 
-	/* Retrieve rt_sigframe from stack and
-	   set up registers for signal handler
-	*/
-	newsp -= __SIGNAL_FRAMESIZE;
-	if (put_user(regs->gpr[1], (unsigned long __user *)newsp)
-	    || get_user(regs->nip, &rt_sf->uc.uc_mcontext.handler)
-	    || get_user(regs->gpr[3], &rt_sf->uc.uc_mcontext.signal)
-	    || get_user(regs->gpr[4], (unsigned long __user *)&rt_sf->pinfo)
-	    || get_user(regs->gpr[5], (unsigned long __user *)&rt_sf->puc))
+	/* Save user registers on the stack */
+	frame = &rt_sf->uc.uc_mcontext;
+	if (save_user_regs(regs, frame, __NR_rt_sigreturn))
 		goto badframe;
 
+	if (put_user(regs->gpr[1], (unsigned long __user *)newsp))
+		goto badframe;
 	regs->gpr[1] = newsp;
+	regs->gpr[3] = sig;
+	regs->gpr[4] = (unsigned long) &rt_sf->info;
+	regs->gpr[5] = (unsigned long) &rt_sf->uc;
 	regs->gpr[6] = (unsigned long) rt_sf;
+	regs->nip = (unsigned long) ka->sa.sa_handler;
 	regs->link = (unsigned long) frame->tramp;
+	regs->trap = 0;
 
 	return;
 
 badframe:
 #if DEBUG_SIG
-	printk("badframe in setup_rt_frame, regs=%p frame=%p newsp=%lx\n",
+	printk("badframe in handle_rt_signal, regs=%p frame=%p newsp=%lx\n",
 	       regs, frame, newsp);
 #endif
-	do_exit(SIGSEGV);
+	if (sig == SIGSEGV)
+		ka->sa.sa_handler = SIG_DFL;
+	force_sig(SIGSEGV, current);
 }
 
-/*
- * Do a signal return; undo the signal stack.
- */
-int sys_sigreturn(int r3, int r4, int r5, int r6, int r7, int r8,
-		  struct pt_regs *regs)
+static int do_setcontext(struct ucontext __user *ucp, struct pt_regs *regs)
 {
-	struct sigcontext __user *sc;
-	struct sigcontext sigctx;
-	struct sigregs __user *sr;
-	elf_gregset_t saved_regs;  /* an array of ELF_NGREG unsigned longs */
 	sigset_t set;
 
-	sc = (struct sigcontext __user *)(regs->gpr[1] + __SIGNAL_FRAMESIZE);
-	if (copy_from_user(&sigctx, sc, sizeof(sigctx)))
-		goto badframe;
+	if (__copy_from_user(&set, &ucp->uc_sigmask, sizeof(set)))
+		return -EFAULT;
+	restore_sigmask(&set);
 
-	set.sig[0] = sigctx.oldmask;
-#if _NSIG_WORDS > 1
-	set.sig[1] = sigctx._unused[3];
-#endif
-	sigdelsetmask(&set, ~_BLOCKABLE);
-	spin_lock_irq(&current->sighand->siglock);
-	current->blocked = set;
-	recalc_sigpending();
-	spin_unlock_irq(&current->sighand->siglock);
-	if (regs->msr & MSR_FP )
-		giveup_fpu(current);
+	if (restore_user_regs(regs, &ucp->uc_mcontext))
+		return -EFAULT;
 
-	/* restore registers */
-	sr = (struct sigregs __user *) sigctx.regs;
-	if (copy_from_user(saved_regs, &sr->gp_regs, sizeof(sr->gp_regs)))
-		goto badframe;
-	saved_regs[PT_MSR] = (regs->msr & ~MSR_USERCHANGE)
-		| (saved_regs[PT_MSR] & MSR_USERCHANGE);
-	memcpy(regs, saved_regs, GP_REGS_SIZE);
+	return 0;
+}
 
-	if (copy_from_user(current->thread.fpr, &sr->fp_regs,
-			   sizeof(sr->fp_regs)))
-		goto badframe;
+int sys_swapcontext(struct ucontext __user *old_ctx,
+		    struct ucontext __user *new_ctx,
+		    int r5, int r6, int r7, int r8, struct pt_regs *regs)
+{
+	unsigned char tmp;
+
+	if (old_ctx != NULL) {
+		if (verify_area(VERIFY_WRITE, old_ctx, sizeof(*old_ctx))
+		    || save_user_regs(regs, &old_ctx->uc_mcontext, 0)
+		    || __copy_to_user(&old_ctx->uc_sigmask,
+				      &current->blocked, sizeof(sigset_t))
+		    /* the next 2 things aren't strictly necessary */
+		    || __copy_to_user(&old_ctx->uc_oldsigmask,
+				      &current->blocked, sizeof(sigset_t))
+		    || __put_user(&old_ctx->uc_mcontext, &old_ctx->uc_regs))
+			return -EFAULT;
+	}
+	if (new_ctx == NULL)
+		return 0;
+	if (verify_area(VERIFY_READ, new_ctx, sizeof(*new_ctx))
+	    || __get_user(tmp, (u8 *) new_ctx)
+	    || __get_user(tmp, (u8 *) (new_ctx + 1) - 1))
+		return -EFAULT;
+
+	/*
+	 * If we get a fault copying the context into the kernel's
+	 * image of the user's registers, we can't just return -EFAULT
+	 * because the user's registers will be corrupted.  For instance
+	 * the NIP value may have been updated but not some of the
+	 * other registers.  Given that we have done the verify_area
+	 * and successfully read the first and last bytes of the region
+	 * above, this should only happen in an out-of-memory situation
+	 * or if another thread unmaps the region containing the context.
+	 * We kill the task with a SIGSEGV in this situation.
+	 */
+	if (do_setcontext(new_ctx, regs))
+		do_exit(SIGSEGV);
+	sigreturn_exit(regs);
+	/* doesn't actually return back to here */
+	return 0;
+}
+
+int sys_rt_sigreturn(int r3, int r4, int r5, int r6, int r7, int r8,
+		     struct pt_regs *regs)
+{
+	struct rt_sigframe __user *rt_sf;
+
+	rt_sf = (struct rt_sigframe __user *)
+		(regs->gpr[1] + __SIGNAL_FRAMESIZE + 16);
+	if (verify_area(VERIFY_READ, rt_sf, sizeof(struct rt_sigframe)))
+		goto bad;
+	if (do_setcontext(&rt_sf->uc, regs))
+		goto bad;
+
+	/*
+	 * It's not clear whether or why it is desirable to save the
+	 * sigaltstack setting on signal delivery and restore it on
+	 * signal return.  But other architectures do this and we have
+	 * always done it up until now so it is probably better not to
+	 * change it.  -- paulus
+	 */
+	do_sigaltstack(&rt_sf->uc.uc_stack, NULL, regs->gpr[1]);
 
 	sigreturn_exit(regs);		/* doesn't return here */
 	return 0;
 
-badframe:
-	do_exit(SIGSEGV);
-}	
+ bad:
+	force_sig(SIGSEGV, current);
+	return 0;
+}
 
 /*
- * Set up a signal frame.
+ * OK, we're invoking a handler
  */
 static void
-setup_frame(struct pt_regs *regs, struct sigregs __user *frame,
-	    unsigned long newsp)
+handle_signal(unsigned long sig, struct k_sigaction *ka,
+	      siginfo_t *info, sigset_t *oldset, struct pt_regs * regs,
+	      unsigned long newsp)
 {
-	struct sigcontext __user *sc = (struct sigcontext __user *) newsp;
+	struct sigcontext __user *sc;
+	struct sigregs __user *frame;
+	unsigned long origsp = newsp;
 
-	if (verify_area(VERIFY_WRITE, frame, sizeof(*frame)))
+	/* Set up Signal Frame */
+	newsp -= sizeof(struct sigregs);
+	frame = (struct sigregs __user *) newsp;
+
+	/* Put a sigcontext on the stack */
+	newsp -= sizeof(*sc);
+	sc = (struct sigcontext __user *) newsp;
+
+	/* create a stack frame for the caller of the handler */
+	newsp -= __SIGNAL_FRAMESIZE;
+
+	if (verify_area(VERIFY_WRITE, (void *) newsp, origsp - newsp))
 		goto badframe;
-	CHECK_FULL_REGS(regs);
-	if (regs->msr & MSR_FP)
-		giveup_fpu(current);
-	if (__copy_to_user(&frame->gp_regs, regs, GP_REGS_SIZE)
-	    || __copy_to_user(&frame->fp_regs, current->thread.fpr,
-			      ELF_NFPREG * sizeof(double))
-	    || __put_user(0x38000000UL + __NR_sigreturn, &frame->tramp[0])
-	    || __put_user(0x44000002UL, &frame->tramp[1]))   /* sc */
+
+#if _NSIG != 64
+#error "Please adjust handle_signal()"
+#endif
+	if (__put_user((unsigned long) ka->sa.sa_handler, &sc->handler)
+	    || __put_user(oldset->sig[0], &sc->oldmask)
+	    || __put_user(oldset->sig[1], &sc->_unused[3])
+	    || __put_user((struct pt_regs *)frame, &sc->regs)
+	    || __put_user(sig, &sc->signal))
 		goto badframe;
-	flush_icache_range((unsigned long) &frame->tramp[0],
-			   (unsigned long) &frame->tramp[2]);
-	current->thread.fpscr = 0;	/* turn off all fp exceptions */
 
-	newsp -= __SIGNAL_FRAMESIZE;
-	if (put_user(regs->gpr[1], (unsigned long __user *)newsp)
-	    || get_user(regs->nip, &sc->handler)
-	    || get_user(regs->gpr[3], &sc->signal))
+	if (save_user_regs(regs, &frame->mctx, __NR_sigreturn))
+		goto badframe;
+
+	if (put_user(regs->gpr[1], (unsigned long *)newsp))
 		goto badframe;
 	regs->gpr[1] = newsp;
+	regs->gpr[3] = sig;
 	regs->gpr[4] = (unsigned long) sc;
-	regs->link = (unsigned long) frame->tramp;
+	regs->nip = (unsigned long) ka->sa.sa_handler;
+	regs->link = (unsigned long) frame->mctx.tramp;
+	regs->trap = 0;
 
 	return;
 
 badframe:
 #if DEBUG_SIG
-	printk("badframe in setup_frame, regs=%p frame=%p newsp=%lx\n",
-	       regs, frame, newsp);
+	printk("badframe in handle_signal, regs=%p frame=%lx newsp=%lx\n",
+	       regs, frame, *newspp);
 #endif
-	do_exit(SIGSEGV);
+	if (sig == SIGSEGV)
+		ka->sa.sa_handler = SIG_DFL;
+	force_sig(SIGSEGV, current);
 }
 
 /*
- * OK, we're invoking a handler
+ * Do a signal return; undo the signal stack.
  */
-static void
-handle_signal(unsigned long sig, siginfo_t *info, sigset_t *oldset,
-	struct pt_regs * regs, unsigned long *newspp, unsigned long frame)
+int sys_sigreturn(int r3, int r4, int r5, int r6, int r7, int r8,
+		  struct pt_regs *regs)
 {
 	struct sigcontext __user *sc;
-	struct rt_sigframe __user *rt_sf;
-	struct k_sigaction *ka = &current->sighand->action[sig-1];
-
-	if (TRAP(regs) == 0x0C00 /* System Call! */
-	    && ((int)regs->result == -ERESTARTNOHAND ||
-		(int)regs->result == -ERESTART_RESTARTBLOCK ||
-		((int)regs->result == -ERESTARTSYS &&
-		 !(ka->sa.sa_flags & SA_RESTART)))) {
-		if ((int)regs->result == -ERESTART_RESTARTBLOCK)
-			current_thread_info()->restart_block.fn
-				= do_no_restart_syscall;
-		regs->result = -EINTR;
-		regs->gpr[3] = EINTR;
-		regs->ccr |= 0x10000000;
-	}
+	struct sigcontext sigctx;
+	struct mcontext __user *sr;
+	sigset_t set;
 
-	/* Set up Signal Frame */
-	if (ka->sa.sa_flags & SA_SIGINFO) {
-		/* Put a Real Time Context onto stack */
-		*newspp -= sizeof(*rt_sf);
-		rt_sf = (struct rt_sigframe __user *) *newspp;
-		if (verify_area(VERIFY_WRITE, rt_sf, sizeof(*rt_sf)))
-			goto badframe;
-
-		if (__put_user((unsigned long) ka->sa.sa_handler, &rt_sf->uc.uc_mcontext.handler)
-		    || __put_user(&rt_sf->info, &rt_sf->pinfo)
-		    || __put_user(&rt_sf->uc, &rt_sf->puc)
-		    /* Put the siginfo */
-		    || copy_siginfo_to_user(&rt_sf->info, info)
-		    /* Create the ucontext */
-		    || __put_user(0, &rt_sf->uc.uc_flags)
-		    || __put_user(0, &rt_sf->uc.uc_link)
-		    || __put_user(current->sas_ss_sp, &rt_sf->uc.uc_stack.ss_sp)
-		    || __put_user(sas_ss_flags(regs->gpr[1]), 
-				  &rt_sf->uc.uc_stack.ss_flags)
-		    || __put_user(current->sas_ss_size, &rt_sf->uc.uc_stack.ss_size)
-		    || __copy_to_user(&rt_sf->uc.uc_sigmask, oldset, sizeof(*oldset))
-		    /* mcontext.regs points to preamble register frame */
-		    || __put_user((struct pt_regs *)frame, &rt_sf->uc.uc_mcontext.regs)
-		    || __put_user(sig, &rt_sf->uc.uc_mcontext.signal))
-			goto badframe;
-	} else {
-		/* Put a sigcontext on the stack */
-		*newspp -= sizeof(*sc);
-		sc = (struct sigcontext __user *) *newspp;
-		if (verify_area(VERIFY_WRITE, sc, sizeof(*sc)))
-			goto badframe;
-		
-		if (__put_user((unsigned long) ka->sa.sa_handler, &sc->handler)
-		    || __put_user(oldset->sig[0], &sc->oldmask)
-#if _NSIG_WORDS > 1
-		    || __put_user(oldset->sig[1], &sc->_unused[3])
-#endif
-		    || __put_user((struct pt_regs *)frame, &sc->regs)
-		    || __put_user(sig, &sc->signal))
-			goto badframe;
-	}
+	sc = (struct sigcontext __user *)(regs->gpr[1] + __SIGNAL_FRAMESIZE);
+	if (copy_from_user(&sigctx, sc, sizeof(sigctx)))
+		goto badframe;
 
-	if (ka->sa.sa_flags & SA_ONESHOT)
-		ka->sa.sa_handler = SIG_DFL;
+	set.sig[0] = sigctx.oldmask;
+	set.sig[1] = sigctx._unused[3];
+	restore_sigmask(&set);
 
-	if (!(ka->sa.sa_flags & SA_NODEFER)) {
-		spin_lock_irq(&current->sighand->siglock);
-		sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
-		sigaddset(&current->blocked,sig);
-		recalc_sigpending();
-		spin_unlock_irq(&current->sighand->siglock);
-	}
-	return;
+	sr = (struct mcontext *) sigctx.regs;
+	if (verify_area(VERIFY_READ, sr, sizeof(*sr))
+	    || restore_user_regs(regs, sr))
+		goto badframe;
+
+	sigreturn_exit(regs);		/* doesn't return */
+	return 0;
 
 badframe:
-#if DEBUG_SIG
-	printk("badframe in handle_signal, regs=%p frame=%lx newsp=%lx\n",
-	       regs, frame, *newspp);
-	printk("sc=%p sig=%d ka=%p info=%p oldset=%p\n", sc, sig, ka, info, oldset);
-#endif
-	do_exit(SIGSEGV);
+	force_sig(SIGSEGV, current);
+	return 0;
 }
 
 /*
@@ -475,7 +547,7 @@ int do_signal(sigset_t *oldset, struct pt_regs *regs)
 	siginfo_t info;
 	struct k_sigaction *ka;
 	unsigned long frame, newsp;
-	int signr;
+	int signr, ret;
 
 	if (!oldset)
 		oldset = &current->blocked;
@@ -483,40 +555,65 @@ int do_signal(sigset_t *oldset, struct pt_regs *regs)
 	newsp = frame = 0;
 
 	signr = get_signal_to_deliver(&info, regs, NULL);
-	if (signr > 0) {
-		ka = &current->sighand->action[signr-1];
-		if ( (ka->sa.sa_flags & SA_ONSTACK)
-		     && (! on_sig_stack(regs->gpr[1])))
-			newsp = (current->sas_ss_sp + current->sas_ss_size);
-		else
-			newsp = regs->gpr[1];
-		newsp = frame = newsp - sizeof(struct sigregs);
-
-		/* Whee!  Actually deliver the signal.  */
-		handle_signal(signr, &info, oldset, regs, &newsp, frame);
-	}
 
-	if (TRAP(regs) == 0x0C00) {	/* System Call! */
-		if ((int)regs->result == -ERESTARTNOHAND ||
-		    (int)regs->result == -ERESTARTSYS ||
-		    (int)regs->result == -ERESTARTNOINTR) {
-			regs->gpr[3] = regs->orig_gpr3;
+	ka = (signr == 0)? NULL: &current->sighand->action[signr-1];
+
+	if (TRAP(regs) == 0x0C00		/* System Call! */
+	    && regs->ccr & 0x10000000		/* error signalled */
+	    && ((ret = regs->gpr[3]) == ERESTARTSYS
+		|| ret == ERESTARTNOHAND || ret == ERESTARTNOINTR
+		|| ret == ERESTART_RESTARTBLOCK)) {
+
+		if (signr > 0
+		    && (ret == ERESTARTNOHAND || ret == ERESTART_RESTARTBLOCK
+			|| (ret == ERESTARTSYS
+			    && !(ka->sa.sa_flags & SA_RESTART)))) {
+			/* make the system call return an EINTR error */
+			regs->result = -EINTR;
+			regs->gpr[3] = EINTR;
+			/* note that the cr0.SO bit is already set */
+			/* clear any restart function that was set */
+			if (ret == ERESTART_RESTARTBLOCK)
+				current_thread_info()->restart_block.fn
+					= do_no_restart_syscall;
+		} else {
 			regs->nip -= 4;	/* Back up & retry system call */
 			regs->result = 0;
-		} else if ((int)regs->result == -ERESTART_RESTARTBLOCK) {
-			regs->gpr[0] = __NR_restart_syscall;
-			regs->nip -= 4;
-			regs->result = 0;
+			regs->trap = 0;
+			if (ret == ERESTART_RESTARTBLOCK)
+				regs->gpr[0] = __NR_restart_syscall;
+			else
+				regs->gpr[3] = regs->orig_gpr3;
 		}
 	}
 
-	if (newsp == frame)
+	if (signr == 0)
 		return 0;		/* no signals delivered */
 
+	if ((ka->sa.sa_flags & SA_ONSTACK) && current->sas_ss_size
+	    && !on_sig_stack(regs->gpr[1]))
+		newsp = current->sas_ss_sp + current->sas_ss_size;
+	else
+		newsp = regs->gpr[1];
+	newsp &= ~0xfUL;
+
+	/* Whee!  Actually deliver the signal.  */
 	if (ka->sa.sa_flags & SA_SIGINFO)
-		setup_rt_frame(regs, (struct sigregs __user *) frame, newsp);
+		handle_rt_signal(signr, ka, &info, oldset, regs, newsp);
 	else
-		setup_frame(regs, (struct sigregs __user *) frame, newsp);
+		handle_signal(signr, ka, &info, oldset, regs, newsp);
+
+	if (ka->sa.sa_flags & SA_ONESHOT)
+		ka->sa.sa_handler = SIG_DFL;
+
+	if (!(ka->sa.sa_flags & SA_NODEFER)) {
+		spin_lock_irq(&current->sighand->siglock);
+		sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
+		sigaddset(&current->blocked, signr);
+		recalc_sigpending();
+		spin_unlock_irq(&current->sighand->siglock);
+	}
+
 	return 1;
 }