vm_remap_ro

- allows shared memory to be mapped in readonly

- ben@minix3.org & tom@minix3.org

commands/service/parse.c

@@ -716,6 +716,7 @@ struct
 	{ "DELDMA",		VM_DELDMA },
 	{ "GETDMA",		VM_GETDMA },
 	{ "REMAP",		VM_REMAP },
+	{ "REMAP_RO",		VM_REMAP_RO },
 	{ "SHM_UNMAP",		VM_SHM_UNMAP },
 	{ "GETPHYS",		VM_GETPHYS },
 	{ "GETREF",		VM_GETREF },

common/include/minix/com.h

@@ -999,6 +999,7 @@
 #	define VMRE_SA			m1_p2
 #	define VMRE_RETA		m1_p3
 #	define VMRE_SIZE		m1_i3
+#	define VMRE_FLAGS		m1_i3
 
 #define VM_SHM_UNMAP		(VM_RQ_BASE+34)
 #	define VMUN_ENDPT		m2_i1
@@ -1051,8 +1052,11 @@
 #define VM_WATCH_EXIT		(VM_RQ_BASE+43)
 #	define VM_WE_EP		m1_i1
 
+#define VM_REMAP_RO		(VM_RQ_BASE+44)
+/* same args as VM_REMAP */
+
 /* Total. */
-#define NR_VM_CALLS				44
+#define NR_VM_CALLS				45
 #define VM_CALL_MASK_SIZE			BITMAP_CHUNKS(NR_VM_CALLS)
 
 /* not handled as a normal VM call, thus at the end of the reserved rage */

include/sys/mman.h

@@ -30,6 +30,8 @@ _PROTOTYPE( int minix_munmap, (void *, size_t));
 _PROTOTYPE( int minix_munmap_text, (void *, size_t));
 _PROTOTYPE( void *vm_remap, (endpoint_t d, endpoint_t s, void *da,
 				void *sa, size_t si));
+_PROTOTYPE( void *vm_remap_ro, (endpoint_t d, endpoint_t s, void *da,
+				void *sa, size_t si));
 _PROTOTYPE( int vm_unmap, (endpoint_t endpt, void *addr));
 _PROTOTYPE( unsigned long vm_getphys, (endpoint_t endpt, void *addr));
 _PROTOTYPE( u8_t vm_getrefcount, (endpoint_t endpt, void *addr));

lib/libc/posix/_mmap.c

@@ -76,6 +76,28 @@ PUBLIC void *vm_remap(endpoint_t d,
 	return (void *) m.VMRE_RETA;
 }
 
+PUBLIC void *vm_remap_ro(endpoint_t d,
+			endpoint_t s,
+			void *da,
+			void *sa,
+			size_t size)
+{
+	message m;
+	int r;
+
+	m.VMRE_D = d;
+	m.VMRE_S = s;
+	m.VMRE_DA = (char *) da;
+	m.VMRE_SA = (char *) sa;
+	m.VMRE_SIZE = size;
+
+	r = _syscall(VM_PROC_NR, VM_REMAP_RO, &m);
+	if (r != OK)
+		return MAP_FAILED;
+	return (void *) m.VMRE_RETA;
+}
+
+
 PUBLIC int vm_unmap(endpoint_t endpt, void *addr)
 {
 	message m;

lib/nbsd_libc/sys-minix/mmap.c

@@ -85,6 +85,27 @@ PUBLIC void *vm_remap(endpoint_t d,
 	return (void *) m.VMRE_RETA;
 }
 
+PUBLIC void *vm_remap_ro(endpoint_t d,
+			endpoint_t s,
+			void *da,
+			void *sa,
+			size_t size)
+{
+	message m;
+	int r;
+
+	m.VMRE_D = d;
+	m.VMRE_S = s;
+	m.VMRE_DA = (char *) da;
+	m.VMRE_SA = (char *) sa;
+	m.VMRE_SIZE = size;
+
+	r = _syscall(VM_PROC_NR, VM_REMAP_RO, &m);
+	if (r != OK)
+		return MAP_FAILED;
+	return (void *) m.VMRE_RETA;
+}
+
 PUBLIC int vm_unmap(endpoint_t endpt, void *addr)
 {
 	message m;

servers/ipc/ipc.conf

@@ -10,6 +10,7 @@ service ipc
 		;
 	vm
 		REMAP
+		REMAP_RO
 		SHM_UNMAP
 		GETPHYS
 		GETREF

servers/vm/main.c

@@ -361,6 +361,7 @@ PRIVATE int sef_cb_init_fresh(int type, sef_init_info_t *info)
 
 	/* Generic calls. */
 	CALLMAP(VM_REMAP, do_remap);
+	CALLMAP(VM_REMAP_RO, do_remap);
 	CALLMAP(VM_GETPHYS, do_get_phys);
 	CALLMAP(VM_SHM_UNMAP, do_shared_unmap);
 	CALLMAP(VM_GETREF, do_get_refcount);

servers/vm/mmap.c

@@ -231,6 +231,13 @@ PUBLIC int do_remap(message *m)
 	struct vir_region *region;
 	struct vmproc *dvmp, *svmp;
 	int r;
+	int readonly;
+
+	if(m->m_type == VM_REMAP)
+		readonly = 0;
+	else if(m->m_type == VM_REMAP_RO)
+		readonly = 1;
+	else panic("do_remap: can't be");
 
 	da = (vir_bytes) m->VMRE_DA;
 	sa = (vir_bytes) m->VMRE_SA;
@@ -275,7 +282,7 @@ PUBLIC int do_remap(message *m)
 		return EFAULT;
 	}
 
-	if ((r = map_remap(dvmp, da, size, region, &startv)) != OK)
+	if ((r = map_remap(dvmp, da, size, region, &startv, readonly)) != OK)
 		return r;
 
 	m->VMRE_RETA = (char *) arch_map2vir(dvmp, startv);

servers/vm/pagefaults.c

@@ -86,11 +86,6 @@ PUBLIC void do_pagefaults(message *m)
 	 */
 	assert(!(region->flags & VR_NOPF));
 
-	/* We do not allow shared memory to cause pagefaults.
-	 * These pages have to be pre-allocated.
-	 */
-	assert(!(region->flags & VR_SHARED));
-
 	/* If process was writing, see if it's writable. */
 	if(!(region->flags & VR_WRITABLE) && wr) {
 		printf("VM: pagefault: SIGSEGV %d ro map 0x%lx %s\n",

servers/vm/proto.h

@@ -169,7 +169,7 @@ _PROTOTYPE(struct vir_region * map_region_lookup_tag, (struct vmproc *vmp, u32_t
 _PROTOTYPE(void map_region_set_tag, (struct vir_region *vr, u32_t tag));
 _PROTOTYPE(u32_t map_region_get_tag, (struct vir_region *vr));
 _PROTOTYPE(int map_remap, (struct vmproc *dvmp, vir_bytes da, size_t size,
-	struct vir_region *region, vir_bytes *r));
+	struct vir_region *region, vir_bytes *r, int ro));
 _PROTOTYPE(int map_get_phys, (struct vmproc *vmp, vir_bytes addr, phys_bytes *r));
 _PROTOTYPE(int map_get_ref, (struct vmproc *vmp, vir_bytes addr, u8_t *cnt));
 

servers/vm/region.c

@@ -36,8 +36,9 @@ PRIVATE yielded_t *lru_youngest = NULL, *lru_oldest = NULL;
 
 /* Should a physblock be mapped writable? */
 #define WRITABLE(r, pb) \
+	(((r)->flags & VR_WRITABLE) && 			\
 		(((r)->flags & (VR_DIRECT | VR_SHARED)) ||	\
-	 (((r)->flags & VR_WRITABLE) && (pb)->refcount == 1))
+		 (pb)->refcount == 1))
 
 FORWARD _PROTOTYPE(int map_new_physblock, (struct vmproc *vmp,
 	struct vir_region *region, vir_bytes offset, vir_bytes length,
@@ -1426,6 +1427,7 @@ PRIVATE struct vir_region *map_copy_region(struct vmproc *vmp, struct vir_region
 		newvr->lower = newvr->higher = NULL;
 		newvr->phys = phavl;
 	);
+
 	physr_init(newvr->phys);
 
 	physr_start_iter_least(vr->phys, &iter);
@@ -1806,7 +1808,7 @@ PUBLIC int map_unmap_region(struct vmproc *vmp, struct vir_region *r,
  *				map_remap				  *
  *========================================================================*/
 PUBLIC int map_remap(struct vmproc *dvmp, vir_bytes da, size_t size,
-		struct vir_region *region, vir_bytes *r)
+		struct vir_region *region, vir_bytes *r, int readonly)
 {
 	struct vir_region *vr;
 	struct phys_region *ph;
@@ -1843,7 +1845,11 @@ PUBLIC int map_remap(struct vmproc *dvmp, vir_bytes da, size_t size,
 	vr->length = size;
 	vr->flags = region->flags;
 	vr->tag = VRT_NONE;
-	vr->parent = dvmp;);
+	vr->parent = dvmp;
+	  if(readonly) {
+		vr->flags &= ~VR_WRITABLE;
+	  }
+	);
 	assert(vr->flags & VR_SHARED);
 
 	region_insert(&dvmp->vm_regions_avl, vr);