base: stricter distinction between rx and rwx

This patch restricts 'Region_map::attach_executable' to create read-only
mappings, while offering the option to map the full rights using a new
'attach_rwx' method.

The 'attach_rwx' method is now used by the dynamic linker to explicitly
attach the linker area with full rwx rights. With the old page-fault
handling code, the execute flag was evaluated only for leaf dataspaces,
not for managed dataspaces while traversing region-map hierarchies.
With the new page-fault handling code, the execute bit is downgraded
to no-execute when passing a managed dataspace that is not attached
as executable.

Issue #4920

repos/base/include/region_map/region_map.h

@@ -127,11 +127,18 @@ struct Genode::Region_map : Interface
 		return attach(ds, size, offset, true, local_addr); }
 
 	/**
-	 * Shortcut for attaching a dataspace executable at a predefined local address
+	 * Shortcut for attaching a dataspace executable at local address
 	 */
 	Local_addr attach_executable(Dataspace_capability ds, addr_t local_addr,
 	                             size_t size = 0, off_t offset = 0) {
-		return attach(ds, size, offset, true, local_addr, true); }
+		return attach(ds, size, offset, true, local_addr, true, false ); }
+
+	/**
+	 * Shortcut for attaching a dataspace will full rights at local address
+	 */
+	Local_addr attach_rwx(Dataspace_capability ds, addr_t local_addr,
+	                      size_t size = 0, off_t offset = 0) {
+		return attach(ds, size, offset, true, local_addr, true, true ); }
 
 	/**
 	 * Remove region from local address space

repos/base/src/lib/ldso/include/region_map.h

@@ -57,7 +57,7 @@ class Linker::Region_map
 		Region_map(Env &env, Allocator &md_alloc, addr_t base)
 		:
 			_env(env), _range(&md_alloc),
-			_base((addr_t)_env.rm().attach_at(_rm.dataspace(), base))
+			_base((addr_t)_env.rm().attach_rwx(_rm.dataspace(), base))
 		{
 			_range.add_range(base, Pd_session::LINKER_AREA_SIZE);
 

repos/ports/src/virtualbox5/generic/sup_vmm.cc

@@ -135,8 +135,7 @@ static Sub_rm_connection &vm_memory(Genode::uint64_t vm_size = 0)
 		while (allocated < memory_size) {
 			Ram_dataspace_capability ds = genode_env().ram().alloc(alloc_size);
 
-			addr_t to = vm_memory.attach_executable(ds, memory.addr +
+			addr_t to = vm_memory.attach_rwx(ds, memory.addr + allocated - vmm_local,
-			                                            allocated - vmm_local,
 			                                 alloc_size);
 			Assert(to == vm_memory.local_addr(memory.addr + allocated - vmm_local));
 			allocated += alloc_size;

repos/ports/src/virtualbox5/mm.h

@@ -39,7 +39,7 @@ class Sub_rm_connection : private Genode::Rm_connection,
 		:
 			Rm_connection(env),
 			Genode::Region_map_client(Rm_connection::create(size)),
-			_offset(env.rm().attach(dataspace())),
+			_offset(env.rm().attach(dataspace(), 0, 0, false, nullptr, true, true)),
 			_size(size)
 		{ }
 

repos/ports/src/virtualbox5/spec/nova/sup.cc

@@ -110,8 +110,7 @@ static Sub_rm_connection &vm_memory(Genode::uint64_t vm_size = 0)
 		while (allocated < memory_size) {
 			Ram_dataspace_capability ds = genode_env().ram().alloc(alloc_size);
 
-			addr_t to = vm_memory.attach_executable(ds, memory.addr +
+			addr_t to = vm_memory.attach_rwx(ds, memory.addr + allocated - vmm_local,
-			                                            allocated - vmm_local,
 			                                 alloc_size);
 			Assert(to == vm_memory.local_addr(memory.addr + allocated - vmm_local));
 			allocated += alloc_size;

repos/ports/src/virtualbox6/sup_gmm.cc

@@ -35,7 +35,7 @@ void Sup::Gmm::_add_one_slice()
 	Ram_dataspace_capability ds = _env.ram().alloc(slice_size);
 
 	_map.connection.retry_with_upgrade(Ram_quota{8192}, Cap_quota{2}, [&] () {
-		_map.rm.attach_executable(ds, attach_base, slice_size); });
+		_map.rm.attach_rwx(ds, attach_base, slice_size); });
 
 	_slices[_slice_index(Offset{attach_base})] = ds;