libc: Add munmap support to plugin interface

With this patch, libc plugins become able to handle munmap for regions
attached by the plugin.

libports/include/libc-plugin/plugin.h

@@ -58,6 +58,7 @@ namespace Libc {
 			virtual bool supports_socket(int domain, int type, int protocol);
 			virtual bool supports_stat(const char *path);
 			virtual bool supports_unlink(const char *path);
+			virtual bool supports_mmap();
 
 			virtual File_descriptor *accept(File_descriptor *,
 			                                struct ::sockaddr *addr,
@@ -98,6 +99,7 @@ namespace Libc {
 			virtual int mkdir(const char *pathname, mode_t mode);
 			virtual void *mmap(void *addr, ::size_t length, int prot, int flags,
 			                   File_descriptor *, ::off_t offset);
+			virtual int munmap(void *addr, ::size_t length);
 			virtual File_descriptor *open(const char *pathname, int flags);
 			virtual int pipe(File_descriptor *pipefd[2]);
 			virtual ssize_t read(File_descriptor *, void *buf, ::size_t count);

libports/lib/mk/libc.mk

@@ -10,7 +10,7 @@ LIBS  += timed_semaphore cxx
 #
 # Back end
 #
-SRC_CC = atexit.cc dummies.cc rlimit.cc sysctl.cc readlink.cc munmap.cc \
+SRC_CC = atexit.cc dummies.cc rlimit.cc sysctl.cc readlink.cc \
          issetugid.cc errno.cc gai_strerror.cc clock_gettime.cc \
          gettimeofday.cc malloc.cc progname.cc fd_alloc.cc file_operations.cc \
          plugin.cc plugin_registry.cc select.cc exit.cc environ.cc nanosleep.cc \

libports/src/lib/libc/file_operations.cc

@@ -30,6 +30,7 @@
 
 /* libc-internal includes */
 #include "libc_mem_alloc.h"
+#include "libc_mmap_registry.h"
 
 using namespace Libc;
 
@@ -43,6 +44,13 @@ using namespace Libc;
 enum { INVALID_FD = -1 };
 
 
+Libc::Mmap_registry *Libc::mmap_registry()
+{
+	static Libc::Mmap_registry registry;
+	return &registry;
+}
+
+
 /***************
  ** Utilities **
  ***************/
@@ -295,17 +303,48 @@ extern "C" void *mmap(void *addr, ::size_t length, int prot, int flags,
                       int libc_fd, ::off_t offset)
 {
 	/* handle requests for anonymous memory */
-	if (!addr && libc_fd == -1)
-		return Libc::mem_alloc()->alloc(length, PAGE_SHIFT);
+	if (!addr && libc_fd == -1) {
+		PDBG("call Libc::mem_alloc()->alloc(%zd)", length);
+		void *start = Libc::mem_alloc()->alloc(length, PAGE_SHIFT);
+		mmap_registry()->insert(start, length, 0);
+		PDBG("return addr %p", start);
+		return start;
+	}
 
 	/* lookup plugin responsible for file descriptor */
 	File_descriptor *fd = libc_fd_to_fd(libc_fd, "mmap");
-	if (!fd || !fd->plugin) {
+	if (!fd || !fd->plugin || !fd->plugin->supports_mmap()) {
 		PWRN("mmap not supported for file descriptor %d", libc_fd);
 		return (void *)INVALID_FD;
 	}
 
-	return fd->plugin->mmap(addr, length, prot, flags, fd, offset);
+	void *start = fd->plugin->mmap(addr, length, prot, flags, fd, offset);
+	mmap_registry()->insert(start, length, fd->plugin);
+	return start;
+}
+
+
+extern "C" int munmap(void *start, size_t length)
+{
+	if (!mmap_registry()->is_registered(start)) {
+		PWRN("munmap: could not lookup plugin for address %p", start);
+		errno = EINVAL;
+		return -1;
+	}
+
+	/*
+	 * Lookup plugin that was used for mmap
+	 *
+	 * If the pointer is NULL, 'start' refers to an anonymous mmap.
+	 */
+	Plugin *plugin = mmap_registry()->lookup_plugin_by_addr(start);
+
+	if (!plugin) {
+		Libc::mem_alloc()->free(start);
+		return 0;
+	}
+
+	return plugin->munmap(start, length);
 }
 
 

libports/src/lib/libc/libc_mmap_registry.h

@@ -0,0 +1,108 @@
+/*
+ * \brief  Registry for keeping track of mmapped regions
+ * \author Norman Feske
+ * \date   2012-08-16
+ */
+
+#ifndef _LIBC_MMAP_REGISTRY_H_
+#define _LIBC_MMAP_REGISTRY_H_
+
+/* Genode includes */
+#include <base/lock.h>
+#include <base/env.h>
+#include <base/printf.h>
+
+/* libc-internal includes */
+#include <libc-plugin/plugin.h>
+
+/* libc includes */
+#include <errno.h>
+
+namespace Libc {
+
+	class Mmap_registry;
+
+	/**
+	 * Return singleton instance of mmap registry
+	 */
+	Mmap_registry *mmap_registry();
+}
+
+
+class Libc::Mmap_registry
+{
+	public:
+
+		struct Entry : Genode::List<Entry>::Element
+		{
+			void   * const start;
+			Plugin * const plugin;
+
+			Entry(void *start, Plugin *plugin)
+			: start(start), plugin(plugin) { }
+		};
+
+	private:
+
+		Genode::List<Mmap_registry::Entry> _list;
+
+		Genode::Lock mutable _lock;
+
+		Entry *_lookup_by_addr_unsynchronized(void * const start) const
+		{
+			Entry *curr = _list.first();
+
+			for (; curr; curr = curr->next())
+				if (curr->start == start)
+					return curr;
+
+			return 0;
+		}
+
+	public:
+
+		void insert(void *start, Genode::size_t len, Plugin *plugin)
+		{
+			Genode::Lock::Guard guard(_lock);
+
+			if (_lookup_by_addr_unsynchronized(start)) {
+				PINF("mmap region at %p is already registered", start);
+				return;
+			}
+
+			_list.insert(new (Genode::env()->heap()) Entry(start, plugin));
+		}
+
+		Plugin *lookup_plugin_by_addr(void *start) const
+		{
+			Genode::Lock::Guard guard(_lock);
+
+			Entry * const e = _lookup_by_addr_unsynchronized(start);
+			return e ? e->plugin : 0;
+		}
+
+		bool is_registered(void *start) const
+		{
+			Genode::Lock::Guard guard(_lock);
+
+			return _lookup_by_addr_unsynchronized(start) != 0;
+		}
+
+		void remove(void *start)
+		{
+			Genode::Lock::Guard guard(_lock);
+
+			Entry *e = _lookup_by_addr_unsynchronized(start);
+
+			if (!e) {
+				PWRN("lookup for address %p in in mmap registry failed", start);
+				return;
+			}
+
+			_list.remove(e);
+			destroy(Genode::env()->heap(), e);
+		}
+};
+
+
+#endif /* _LIBC_MMAP_REGISTRY_H_ */

libports/src/lib/libc/munmap.cc

@@ -1,22 +0,0 @@
-/*
- * \brief  C-library back end
- * \author Norman Feske
- * \date   2008-11-11
- */
-
-/*
- * Copyright (C) 2008-2012 Genode Labs GmbH
- *
- * This file is part of the Genode OS framework, which is distributed
- * under the terms of the GNU General Public License version 2.
- */
-
-#include <sys/mman.h>
-
-#include "libc_debug.h"
-
-extern "C" int munmap(void *start, size_t length)
-{
-	raw_write_str("munmap called, not yet implemented!\n");
-	return 0;
-}

libports/src/lib/libc/plugin.cc

@@ -110,6 +110,13 @@ bool Plugin::supports_unlink(const char*)
 	return false;
 }
 
+
+bool Plugin::supports_mmap()
+{
+	return false;
+}
+
+
 /**
  * Default implementations
  */
@@ -181,6 +188,7 @@ DUMMY(int, -1, getaddrinfo,  (const char *, const char *, const struct ::addrinf
 DUMMY(int, -1, mkdir,        (const char*, mode_t));
 DUMMY(void *, (void *)(-1), mmap, (void *addr, ::size_t length, int prot, int flags,
                                    File_descriptor *, ::off_t offset));
+DUMMY(int, -1, munmap,       (void *, ::size_t));
 DUMMY(int, -1, pipe,         (File_descriptor*[2]));
 DUMMY(int, -1, rename,       (const char *, const char *));
 DUMMY(int, -1, select,       (int, fd_set *, fd_set *, fd_set *, struct timeval *));