first usable version of kernel and commands

After an year of hard work, this is a first "usable" version of Jehanne.

qa/lib/c/longjmp.c

@@ -0,0 +1,48 @@
+
+#include <u.h>
+#include <libc.h>
+
+enum {
+	Njmps = 10000
+};
+
+void foo(void);
+
+void
+main(void)
+{
+	int i, njmp;
+	int fail = 0;
+	jmp_buf label;
+
+	njmp = 0;
+	while((njmp = setjmp(label)) < Njmps)
+		longjmp(label, njmp+1);
+
+	for(i = 0; i < nelem(label); i++)
+		fprint(2, "label[%d] = %p\n", i, label[i]);
+	fprint(2, "main: %p foo: %p\n", main, foo);
+
+	if(njmp != Njmps)
+		fail++;
+	if(label[JMPBUFPC] < (uintptr_t)main)
+		fail++;
+	if(label[JMPBUFPC] > (uintptr_t)foo)
+		fail++;
+	if(label[JMPBUFSP] > (uintptr_t)&label[nelem(label)])
+		fail++;
+	if(label[JMPBUFSP] < 0x7fffffd00000)
+		fail++;
+
+	if(fail == 0){
+		print("PASS\n");
+		exits("PASS");
+	}
+	print("FAIL\n");
+	exits("FAIL");
+}
+
+void
+foo(void)
+{
+}