From: bluhm <bluhm@openbsd.org>
Date: Thu, 20 May 2021 12:34:35 +0000 (+0000)
Subject: We changed powerpc64 to allow write access to write only mappings.
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=68e8b34d613e6f4c1e8cd29063aa3c9aa58bffe2;p=openbsd

We changed powerpc64 to allow write access to write only mappings.
Although the page table cannot prevent reads on write only pages,
the first access in trap() knows what is is.  This should be passed
to uvm_fault().  Then regress/sys/kern/fork-exit passes.  Copy the
new powerpc64 logic to powerpc.
OK tobhe@ kettenis@ deraadt@
---

diff --git a/sys/arch/powerpc/powerpc/trap.c b/sys/arch/powerpc/powerpc/trap.c
index 02d6aab22d4..3a8be7f3bc6 100644
--- a/sys/arch/powerpc/powerpc/trap.c
+++ b/sys/arch/powerpc/powerpc/trap.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: trap.c,v 1.120 2021/05/05 07:29:01 mpi Exp $	*/
+/*	$OpenBSD: trap.c,v 1.121 2021/05/20 12:34:35 bluhm Exp $	*/
 /*	$NetBSD: trap.c,v 1.3 1996/10/13 03:31:37 christos Exp $	*/
 
 /*
@@ -235,7 +235,7 @@ trap(struct trapframe *frame)
 	faultbuf *fb;
 	struct vm_map *map;
 	vaddr_t va;
-	int ftype, vftype;
+	int access_type;
 	struct sysent *callp;
 	size_t argsize;
 	register_t code, error;
@@ -278,12 +278,11 @@ trap(struct trapframe *frame)
 				return;
 		}
 		if (frame->dsisr & DSISR_STORE)
-			ftype = PROT_READ | PROT_WRITE;
+			access_type = PROT_WRITE;
 		else
-			ftype = PROT_READ;
-
-		error = uvm_fault(map, trunc_page(va), 0, ftype);
+			access_type = PROT_READ;
 
+		error = uvm_fault(map, trunc_page(va), 0, access_type);
 		if (error == 0)
 			return;
 
@@ -310,15 +309,13 @@ trap(struct trapframe *frame)
 		    uvm_map_inentry_sp, p->p_vmspace->vm_map.sserial))
 			goto out;
 
-		if (frame->dsisr & DSISR_STORE) {
-			ftype = PROT_READ | PROT_WRITE;
-			vftype = PROT_WRITE;
-		} else
-			vftype = ftype = PROT_READ;
+		if (frame->dsisr & DSISR_STORE)
+			access_type = PROT_WRITE;
+		else
+			access_type = PROT_READ;
 
 		error = uvm_fault(&p->p_vmspace->vm_map,
-		    trunc_page(frame->dar), 0, ftype);
-
+		    trunc_page(frame->dar), 0, access_type);
 		if (error == 0) {
 			uvm_grow(p, frame->dar);
 			break;
@@ -326,9 +323,9 @@ trap(struct trapframe *frame)
 
 		/*
 		 * keep this for later in case we want it later.
-		*/
+		 */
 		sv.sival_int = frame->dar;
-		trapsignal(p, SIGSEGV, vftype, SEGV_MAPERR, sv);
+		trapsignal(p, SIGSEGV, access_type, SEGV_MAPERR, sv);
 		break;
 
 	case EXC_ISI|EXC_USER:
@@ -337,10 +334,10 @@ trap(struct trapframe *frame)
 		    frame->srr0, 0, 1))
 			break;
 
-		ftype = PROT_READ | PROT_EXEC;
+		access_type = PROT_READ | PROT_EXEC;
 
 		error = uvm_fault(&p->p_vmspace->vm_map,
-		    trunc_page(frame->srr0), 0, ftype);
+		    trunc_page(frame->srr0), 0, access_type);
 
 		if (error == 0) {
 			uvm_grow(p, frame->srr0);