Mutex test progress

- Mutex test added. Forked tasks demonstrate produce/consumer using a
  shared mmap'ed page.
- Added l4lib assembler syscall
- Added forgotten SWI to mutex control offset in syscall page.
- Added mutex head initialization
- Contended child successfully sleeps in a waitqueue.

Issues:
- Somehow the child's produced page buffer is altered at about [4020] offset.
  Parent fails to validate buffer therefore.
- Need to add syncing to test so that parent does not unlock and lock again
  before child has a chance to lock buffer and produce.

tasks/test0/src/mutextest.c

@@ -0,0 +1,161 @@
+/*
+ * Tests for userspace mutexes
+ *
+ * Copyright (C) 2007-2009 Bahadir Bilgehan Balban
+ */
+#include <l4lib/arch/syslib.h>
+#include <l4lib/ipcdefs.h>
+#include <l4lib/mutex.h>
+#include <errno.h>
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <tests.h>
+
+/*
+ * This structure is placed at the head of shared memory.
+ * Tasks lock and write to rest of the page. Indicate that
+ * they have run, and the later running task tests that both
+ * processes has run and no data corruption occured on page_rest.
+ */
+struct shared_page {
+	struct l4_mutex mutex;
+	int child_has_run;
+	int parent_has_run;
+	char page_rest[];
+};
+
+static struct shared_page *shared_page;
+
+/*
+ * This test forks a parent task, creates a shared memory mapping, and makes two tasks
+ * lock and write to almost the whole page 10 times with different values, and makes
+ * the tasks test that the writes are all there without any wrong values. The amount of
+ * time spent should justify a context switch and demonstrate that lock protects the
+ * region.
+ */
+int user_mutex_test(void)
+{
+	pid_t child, parent;
+	int map_size = PAGE_SIZE;
+	int buf_size;
+	void *base;
+
+	/* Get parent pid */
+	parent = getpid();
+
+
+	/*
+	 * Create a shared anonymous memory region. This can be
+	 * accessed by both parent and child after a fork.
+	 */
+	if ((int)(base = mmap(0, map_size, PROT_READ | PROT_WRITE,
+			      MAP_SHARED | MAP_ANONYMOUS, 0, 0)) < 0) {
+		printf("%s: mmap for extended ipc buffer failed: %d\n",
+			    __FUNCTION__, (int)base);
+		goto out_err;
+	} else
+		printf("mmap: Anonymous shared buffer at %p\n", base);
+
+	shared_page = base;
+
+	/* Find the buffer size */
+	buf_size = map_size - sizeof(*shared_page);
+	printf("Total buffer size: %d\n", buf_size);
+
+	/* Initialize the mutex */
+	l4_mutex_init(&shared_page->mutex);
+
+	/* Initialize buffer with unique child value */
+	printf("Child writing:\n");
+	for (int i = 0; i < buf_size; i++) {
+		shared_page->page_rest[i] = 'c';
+		printf("%c", shared_page->page_rest[i]);
+	}
+	printf("\n\n");
+
+	/* Fork the current task */
+	if ((child = fork()) < 0) {
+		printf("%s: Fork failed with %d\n", __FUNCTION__, errno);
+		goto out_err;
+	}
+
+	if (child)
+		printf("%d: Created child with pid %d\n", getpid(), child);
+	else
+		printf("Child %d running.\n", getpid());
+
+	/* Child locks and produces */
+	if (child == 0) {
+
+		for (int i = 0; i < 5; i++) {
+			/* Lock */
+			printf("Child locking page.\n");
+			l4_mutex_lock(&shared_page->mutex);
+
+			printf("Child locked page.\n");
+			/* Get sample value */
+			char val = shared_page->page_rest[0];
+
+			/* Write a unique child value to whole buffer */
+			for (int i = 0; i < buf_size; i++) {
+				/* Check sample is same in all */
+				if (shared_page->page_rest[i] != val) {
+					printf("Sample values dont match. "
+					       "page_rest[%d] = %c, "
+					       "val = %c\n", i,
+					       shared_page->page_rest[i], val);
+					goto out_err;
+				}
+				shared_page->page_rest[i] = 'c';
+			}
+			printf("Child produced.\n");
+			/* Unlock */
+			l4_mutex_unlock(&shared_page->mutex);
+			printf("Child unlocked page.\n");
+		}
+
+	/* Parent locks and consumes */
+	} else {
+		for (int i = 0; i < 5; i++) {
+			printf("Parent locking page.\n");
+
+			/* Lock the page */
+			l4_mutex_lock(&shared_page->mutex);
+			printf("Parent locked page.\n");
+
+			printf("Parent reading:\n");
+
+			/* Test and consume the page */
+			for (int i = 0; i < buf_size; i++) {
+				printf("%c", shared_page->page_rest[i]);
+				/* Test that child has produced */
+				if (shared_page->page_rest[i] != 'c') {
+					printf("Child not produced. "
+					       "page_rest[%d] = %c, "
+					       "expected = 'c'\n",
+					       i, shared_page->page_rest[i]);
+					goto out_err;
+				}
+				/* Consume the page */
+				shared_page->page_rest[i] = 'P';
+			}
+			printf("\n\n");
+			printf("Parent consumed.\n");
+			l4_mutex_unlock(&shared_page->mutex);
+			printf("Parent unlocked page.\n");
+		}
+
+		printf("USER MUTEX TEST:    -- PASSED --\n");
+	}
+	return 0;
+
+out_err:
+	printf("USER MUTEX TEST:    -- FAILED --\n");
+	return -1;
+}
+
+
+
+
+