From 8c38b3156c90d1e1803d9f3404cfb66d963b0cfc Mon Sep 17 00:00:00 2001
From: miod <miod@openbsd.org>
Date: Wed, 11 Jan 2023 19:57:17 +0000
Subject: [PATCH] Implement X-only mappings on sun4u by not letting the dtlb
 miss handler allow ttes with the "exec only" bit; joint work with deraadt@,
 unfortunately no effect on sun4v due to the lack of software bits in ttes to
 fit an "exec only" bit.

ok deraadt@ kettenis@
---
 sys/arch/sparc64/sparc64/genassym.cf |  3 ++-
 sys/arch/sparc64/sparc64/locore.s    | 10 +++++++---
 sys/arch/sparc64/sparc64/pmap.c      | 14 +++++++++-----
 3 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/sys/arch/sparc64/sparc64/genassym.cf b/sys/arch/sparc64/sparc64/genassym.cf
index 1e389227cf4..48fd26b907f 100644
--- a/sys/arch/sparc64/sparc64/genassym.cf
+++ b/sys/arch/sparc64/sparc64/genassym.cf
@@ -1,4 +1,4 @@
-#	$OpenBSD: genassym.cf,v 1.39 2022/10/21 18:55:42 miod Exp $
+#	$OpenBSD: genassym.cf,v 1.40 2023/01/11 19:57:17 miod Exp $
 #	$NetBSD: genassym.cf,v 1.23 2001/08/08 00:09:30 eeh Exp $
 
 #
@@ -269,6 +269,7 @@ export	SUN4U_TLB_ACCESS
 export	SUN4U_TLB_MODIFY
 export	SUN4U_TLB_REAL_W
 export	SUN4U_TLB_EXEC
+export	SUN4U_TLB_EXEC_ONLY
 export	SUN4U_TLB_W
 
 export	SUN4V_TLB_ACCESS
diff --git a/sys/arch/sparc64/sparc64/locore.s b/sys/arch/sparc64/sparc64/locore.s
index be95325d5e7..891eeb2aef6 100644
--- a/sys/arch/sparc64/sparc64/locore.s
+++ b/sys/arch/sparc64/sparc64/locore.s
@@ -1,4 +1,4 @@
-/*	$OpenBSD: locore.s,v 1.197 2023/01/06 19:10:18 miod Exp $	*/
+/*	$OpenBSD: locore.s,v 1.198 2023/01/11 19:57:17 miod Exp $	*/
 /*	$NetBSD: locore.s,v 1.137 2001/08/13 06:10:10 jdolecek Exp $	*/
 
 /*
@@ -1714,11 +1714,15 @@ data_miss:
 1:
 	ldxa	[%g6] ASI_PHYS_CACHED, %g4
 	brgez,pn %g4, data_nfo				! Entry invalid?  Punt
-	 or	%g4, SUN4U_TLB_ACCESS, %g7		! Update the access bit
+	 nop
+
+	btst	SUN4U_TLB_EXEC_ONLY, %g4		! no read/write allowed?
+	bne,pn	%xcc, data_nfo				! bail
+	 nop
 	
 	btst	SUN4U_TLB_ACCESS, %g4			! Need to update access git?
 	bne,pt	%xcc, 1f
-	 nop
+	 or	%g4, SUN4U_TLB_ACCESS, %g7		! Update the access bit
 	casxa	[%g6] ASI_PHYS_CACHED, %g4, %g7		!  and write it out
 	cmp	%g4, %g7
 	bne,pn	%xcc, 1b
diff --git a/sys/arch/sparc64/sparc64/pmap.c b/sys/arch/sparc64/sparc64/pmap.c
index 2903f1a59ee..5715ab81644 100644
--- a/sys/arch/sparc64/sparc64/pmap.c
+++ b/sys/arch/sparc64/sparc64/pmap.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: pmap.c,v 1.107 2023/01/10 17:38:10 miod Exp $	*/
+/*	$OpenBSD: pmap.c,v 1.108 2023/01/11 19:57:18 miod Exp $	*/
 /*	$NetBSD: pmap.c,v 1.107 2001/08/31 16:47:41 eeh Exp $	*/
 /*
  * 
@@ -780,7 +780,6 @@ remap_data:
 		OF_exit();
 	}
 
-
 	/*
 	 * Now the kernel text segment is in its final location we can try to
 	 * find out how much memory really is free.  
@@ -1691,6 +1690,8 @@ pmap_kenter_pa(vaddr_t va, paddr_t pa, vm_prot_t prot)
 			tte.data |= SUN4U_TLB_REAL_W|SUN4U_TLB_W;
 		if (prot & PROT_EXEC)
 			tte.data |= SUN4U_TLB_EXEC;
+		if (prot == PROT_EXEC)
+			tte.data |= SUN4U_TLB_EXEC_ONLY;
 		tte.data |= SUN4U_TLB_TSB_LOCK;	/* wired */
 	}
 	KDASSERT((tte.data & TLB_NFO) == 0);
@@ -1823,6 +1824,8 @@ pmap_enter(struct pmap *pm, vaddr_t va, paddr_t pa, vm_prot_t prot, int flags)
 			tte.data |= SUN4U_TLB_REAL_W;
 		if (prot & PROT_EXEC)
 			tte.data |= SUN4U_TLB_EXEC;
+		if (prot == PROT_EXEC)
+			tte.data |= SUN4U_TLB_EXEC_ONLY;
 		if (wired)
 			tte.data |= SUN4U_TLB_TSB_LOCK;
 	}
@@ -1947,8 +1950,7 @@ pmap_protect(struct pmap *pm, vaddr_t sva, vaddr_t eva, vm_prot_t prot)
 	KDASSERT(pm != pmap_kernel() || eva < INTSTACK || sva > EINTSTACK);
 	KDASSERT(pm != pmap_kernel() || eva < kdata || sva > ekdata);
 
-	if ((prot & (PROT_WRITE | PROT_EXEC)) ==
-	    (PROT_WRITE | PROT_EXEC))
+	if ((prot & (PROT_WRITE | PROT_EXEC)) == (PROT_WRITE | PROT_EXEC))
 		return;
 
 	if (prot == PROT_NONE) {
@@ -1991,7 +1993,7 @@ pmap_protect(struct pmap *pm, vaddr_t sva, vaddr_t eva, vm_prot_t prot)
 				if ((prot & PROT_WRITE) == 0)
 					data &= ~(SUN4U_TLB_W|SUN4U_TLB_REAL_W);
 				if ((prot & PROT_EXEC) == 0)
-					data &= ~(SUN4U_TLB_EXEC);
+					data &= ~(SUN4U_TLB_EXEC | SUN4U_TLB_EXEC_ONLY);
 			}
 			KDASSERT((data & TLB_NFO) == 0);
 			if (pseg_set(pm, sva, data, 0)) {
@@ -2470,6 +2472,8 @@ pmap_page_protect(struct vm_page *pg, vm_prot_t prot)
 				clear |= SUN4U_TLB_EXEC;
 			if (PROT_EXEC == prot)
 				set |= SUN4U_TLB_EXEC_ONLY;
+			else
+				clear |= SUN4U_TLB_EXEC_ONLY;
 		}
 
 		pv = pa_to_pvh(pa);
-- 
2.20.1