my solution to lab5

lab/user/init.c

@@ -0,0 +1,69 @@
+#include <inc/lib.h>
+
+struct {
+	char msg1[5000];
+	char msg2[1000];
+} data = {
+	"this is initialized data",
+	"so is this"
+};
+
+char bss[6000];
+
+int
+sum(const char *s, int n)
+{
+	int i, tot = 0;
+	for (i = 0; i < n; i++)
+		tot ^= i * s[i];
+	return tot;
+}
+
+void
+umain(int argc, char **argv)
+{
+	int i, r, x, want;
+	char args[256];
+
+	cprintf("init: running\n");
+
+	want = 0xf989e;
+	if ((x = sum((char*)&data, sizeof data)) != want)
+		cprintf("init: data is not initialized: got sum %08x wanted %08x\n",
+			x, want);
+	else
+		cprintf("init: data seems okay\n");
+	if ((x = sum(bss, sizeof bss)) != 0)
+		cprintf("bss is not initialized: wanted sum 0 got %08x\n", x);
+	else
+		cprintf("init: bss seems okay\n");
+
+	// output in one syscall per line to avoid output interleaving 
+	strcat(args, "init: args:");
+	for (i = 0; i < argc; i++) {
+		strcat(args, " '");
+		strcat(args, argv[i]);
+		strcat(args, "'");
+	}
+	cprintf("%s\n", args);
+
+	cprintf("init: running sh\n");
+
+	// being run directly from kernel, so no file descriptors open yet
+	close(0);
+	if ((r = opencons()) < 0)
+		panic("opencons: %e", r);
+	if (r != 0)
+		panic("first opencons used fd %d", r);
+	if ((r = dup(0, 1)) < 0)
+		panic("dup: %e", r);
+	while (1) {
+		cprintf("init: starting sh\n");
+		r = spawnl("/sh", "sh", (char*)0);
+		if (r < 0) {
+			cprintf("init: spawn sh: %e\n", r);
+			continue;
+		}
+		wait(r);
+	}
+}