From: Ben Gras <ben@minix3.org>
Date: Tue, 5 Mar 2013 16:17:21 +0000 (+0100)
Subject: VM: shared memory pagefault fix
X-Git-Tag: v3.3.0~1106
X-Git-Url: http://zhaoyanbai.com/repos/%22http:/www.isc.org/icons/zlib_tech.html?a=commitdiff_plain;h=449ed1783384122c32cb8b80fef7c5f043d7df22;p=minix.git

VM: shared memory pagefault fix

	. if there is no memory there, it's not writable; this
	  check bug by the shared memory's writable() method causes
	  pagefaults not to be handled  at all in certain situations,
	  triggering an assert() in pt_writemap()
	. added some assert()s to catch this and similar situations
	  in the future

Change-Id: Ife89bfab4f9a3aa7bf4e33dfb0b13b89dcd5bb94
---

diff --git a/servers/vm/mem_anon.c b/servers/vm/mem_anon.c
index 0971708fd..55d30bc23 100644
--- a/servers/vm/mem_anon.c
+++ b/servers/vm/mem_anon.c
@@ -108,9 +108,11 @@ static int anon_sanitycheck(struct phys_region *pr, char *file, int line)
 static int anon_writable(struct phys_region *pr)
 {
 	assert(pr->ph->refcount > 0);
+	if(pr->ph->phys == MAP_NONE)
+		return 0;
 	if(pr->parent->remaps > 0)
 		return 1;
-	return pr->ph->phys != MAP_NONE && pr->ph->refcount == 1;
+	return pr->ph->refcount == 1;
 }
 
 static int anon_resize(struct vmproc *vmp, struct vir_region *vr, vir_bytes l)
diff --git a/servers/vm/region.c b/servers/vm/region.c
index 8d55fe3ae..78ad03f31 100644
--- a/servers/vm/region.c
+++ b/servers/vm/region.c
@@ -1032,9 +1032,11 @@ int write;
 
 		assert(ph);
 		assert(ph->ph);
+		assert(ph->ph->phys != MAP_NONE);
 	}
 
 	assert(ph->ph);
+	assert(ph->ph->phys != MAP_NONE);
 
 	if((r = map_ph_writept(vmp, region, ph)) != OK) {
 		printf("map_pf: writept failed\n");