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Date:      Thu, 3 Jan 2019 16:21:45 +0000 (UTC)
From:      Mark Johnston <markj@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r342734 - head/sys/riscv/riscv
Message-ID:  <201901031621.x03GLjE4042237@repo.freebsd.org>
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Author: markj
Date: Thu Jan  3 16:21:44 2019
New Revision: 342734
URL: https://svnweb.freebsd.org/changeset/base/342734

Log:
  Fix some issues with the riscv pmap_protect() implementation.
  
  - Handle VM_PROT_EXECUTE.
  - Clear PTE_D and mark the page dirty when removing write access
    from a mapping.
  - Atomically clear PTE_W to avoid clobbering a hardware PTE update.
  
  Reviewed by:	jhb, kib
  MFC after:	1 week
  Sponsored by:	The FreeBSD Foundation
  Differential Revision:	https://reviews.freebsd.org/D18719

Modified:
  head/sys/riscv/riscv/pmap.c

Modified: head/sys/riscv/riscv/pmap.c
==============================================================================
--- head/sys/riscv/riscv/pmap.c	Thu Jan  3 16:19:32 2019	(r342733)
+++ head/sys/riscv/riscv/pmap.c	Thu Jan  3 16:21:44 2019	(r342734)
@@ -1853,22 +1853,28 @@ pmap_remove_all(vm_page_t m)
 void
 pmap_protect(pmap_t pmap, vm_offset_t sva, vm_offset_t eva, vm_prot_t prot)
 {
-	vm_offset_t va_next;
 	pd_entry_t *l1, *l2;
-	pt_entry_t *l3p, l3;
-	pt_entry_t entry;
+	pt_entry_t *l3, l3e, mask;
+	vm_page_t m;
+	vm_offset_t va_next;
 
 	if ((prot & VM_PROT_READ) == VM_PROT_NONE) {
 		pmap_remove(pmap, sva, eva);
 		return;
 	}
 
-	if ((prot & VM_PROT_WRITE) == VM_PROT_WRITE)
+	if ((prot & (VM_PROT_WRITE | VM_PROT_EXECUTE)) ==
+	    (VM_PROT_WRITE | VM_PROT_EXECUTE))
 		return;
 
+	mask = 0;
+	if ((prot & VM_PROT_WRITE) == 0)
+		mask |= PTE_W | PTE_D;
+	if ((prot & VM_PROT_EXECUTE) == 0)
+		mask |= PTE_X;
+
 	PMAP_LOCK(pmap);
 	for (; sva < eva; sva = va_next) {
-
 		l1 = pmap_l1(pmap, sva);
 		if (pmap_load(l1) == 0) {
 			va_next = (sva + L1_SIZE) & ~L1_OFFSET;
@@ -1882,26 +1888,30 @@ pmap_protect(pmap_t pmap, vm_offset_t sva, vm_offset_t
 			va_next = eva;
 
 		l2 = pmap_l1_to_l2(l1, sva);
-		if (l2 == NULL)
+		if (l2 == NULL || pmap_load(l2) == 0)
 			continue;
-		if (pmap_load(l2) == 0)
-			continue;
 		if ((pmap_load(l2) & PTE_RX) != 0)
 			continue;
 
 		if (va_next > eva)
 			va_next = eva;
 
-		for (l3p = pmap_l2_to_l3(l2, sva); sva != va_next; l3p++,
+		for (l3 = pmap_l2_to_l3(l2, sva); sva != va_next; l3++,
 		    sva += L3_SIZE) {
-			l3 = pmap_load(l3p);
-			if ((l3 & PTE_V) != 0) {
-				entry = pmap_load(l3p);
-				entry &= ~PTE_W;
-				pmap_store(l3p, entry);
-				/* XXX: Use pmap_invalidate_range */
-				pmap_invalidate_page(pmap, sva);
+			l3e = pmap_load(l3);
+retry:
+			if ((l3e & PTE_V) == 0)
+				continue;
+			if ((prot & VM_PROT_WRITE) == 0 &&
+			    (l3e & (PTE_SW_MANAGED | PTE_D)) ==
+			    (PTE_SW_MANAGED | PTE_D)) {
+				m = PHYS_TO_VM_PAGE(PTE_TO_PHYS(l3e));
+				vm_page_dirty(m);
 			}
+			if (!atomic_fcmpset_long(l3, &l3e, l3e & ~mask))
+				goto retry;
+			/* XXX: Use pmap_invalidate_range */
+			pmap_invalidate_page(pmap, sva);
 		}
 	}
 	PMAP_UNLOCK(pmap);

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