update to qemu v2.9.0! rand_check.c, init_forward.sh

README.md

@@ -262,6 +262,8 @@ and they will be run automatically before the login prompt.
 
 For convenience, we also setup a symlink from `S99` to `rootfs_overlay/etc/init.d/S99`.
 
+Scripts under `/etc/init.d` are run by `/etc/init.d/rcS`, which gets called by the line `::sysinit:/etc/init.d/rcS` in `/etc/inittab`.
+
 ### Custom init
 
 Is the default BusyBox `/init` too bloated for you, minimalism freak?

kernel_module/user/README.md

@@ -18,6 +18,7 @@ These programs can also be compiled and used on host.
         1.  [poweroff](poweroff.c)
         1.  [init_dev_kmsg](init_dev_kmsg.c)
     1.  [uio_read](uio_read.c)
+    1.  [rand_check](rand_check.c)
 1.  Module tests
     1.  [anonymous_inode](anonymous_inode.c)
     1.  [poll](poll.c)

kernel_module/user/rand_check.c

@@ -0,0 +1,41 @@
+/* Check if we were able to remove certain sources of randomness
+ * across boots using different techniques:
+ *
+ * - QEMU icount record replay
+ * - norandmaps boot parameter
+ *
+ * You might want to run this as the init process to further remove undeterminism. */
+
+#include <inttypes.h>
+#include <signal.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+int bss = 0;
+int data = 1;
+
+int main(__attribute__((unused)) int argc, char **argv) {
+	int i, *ip;
+	uint64_t uint64;
+	FILE *fp;
+
+	printf("time(NULL) = %ju\n", (uintmax_t)time(NULL));
+	printf("&i         = %p\n", (void *)&i);
+	printf("&argv[0]   = %p\n", (void *)&argv[0]);
+	printf("&main      = %p\n", (void *)(intptr_t)main);
+	printf("&bss       = %p\n", (void *)&bss);
+	printf("&data      = %p\n", (void *)&data);
+
+	/* malloc */
+	ip = malloc(sizeof(*ip));
+	printf("&malloc    = %p\n", (void *)ip);
+	free(ip);
+
+	/* /dev/urandom */
+	fp = fopen("/dev/urandom", "rb");
+	fread(&uint64, sizeof(uint64), 1, fp);
+	printf("/dev/urandom = %" PRIx64 "\n", uint64);
+	fclose(fp);
+}

rootfs_overlay/README.md

@@ -6,7 +6,3 @@ We use it to for things like:
 
 - customized configuration files
 - userland module test scripts
-
-Most tests correspond clearly to a given kernel module, but the following ones don't:
-
-- [gpio](gpio.sh)

rootfs_overlay/init_forward.sh

@@ -0,0 +1,6 @@
+#!/bin/sh
+# Failed attempt at debugging /init, because:
+#     init must be run as pid 1
+# Is this just a random BusyBox sanity check?
+# - https://stackoverflow.com/questions/35019995/strace-init-process-pid-1-in-linux
+/sbin/init "$@"