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From: Robert Watson <rwatson@FreeBSD.org>
Subject: PERFORCE change 219706 for review
To: Perforce Change Reviews <perforce@freebsd.org>
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http://p4web.freebsd.org/@@219706?ac=10

Change 219706 by rwatson@rwatson_svr_ctsrd_mipsbuild on 2012/11/09 19:16:20

	Add new cheritest commands: sandbox, unsandbox, and yieldtest,
	which are intended to help validate that the kernel is correctly
	preventing sandboxed userspace code from performing system calls.
	"sandboxed" in this case simply means a minor adjustment to $C0
	that won't affect actual code execution, just the kernel's
	gating of system calls.  Hopefully.

Affected files ...

.. //depot/projects/ctsrd/cheribsd/src/bin/cheritest/cheritest.c#5 edit

Differences ...

==== //depot/projects/ctsrd/cheribsd/src/bin/cheritest/cheritest.c#5 (text+ko) ====

@@ -31,8 +31,11 @@
 #include <sys/types.h>
 
 #include <machine/cheri.h>
+#include <machine/cpuregs.h>
 
+#include <err.h>
 #include <inttypes.h>
+#include <sched.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -64,7 +67,10 @@
 	fprintf(stderr, "cheritest copyregs\n");
 	fprintf(stderr, "cheritest listregs\n");
 	fprintf(stderr, "cheritest overrun\n");
+	fprintf(stderr, "cheritest sandbox\n");
 	fprintf(stderr, "cheritest sleep\n");
+	fprintf(stderr, "cheritest unsandbox\n");
+	fprintf(stderr, "cheritest yieldtest\n");
 	exit(EX_USAGE);
 }
 
@@ -86,7 +92,6 @@
 cheritest_copyregs(void)
 {
 
-	CHERI_CMOVE(1, 0);
 	CHERI_CMOVE(2, 0);
 	CHERI_CMOVE(3, 0);
 	CHERI_CMOVE(4, 0);
@@ -133,6 +138,42 @@
 	CHERI_CAPREG_PRINT(26);
 }
 
+static void
+cheritest_sandbox(void)
+{
+
+	/*
+	 * Install a limited C0 so that the kernel will no longer accept
+	 * system calls.
+	 */
+	CHERI_CSETLEN(0, 1, CHERI_CAP_USER_LENGTH - 1);
+
+}
+
+static void
+cheritest_unsandbox(void)
+{
+
+	/*
+	 * Restore a more privielged C0 so that the kernel will accept system
+	 * calls again.
+	 */
+	CHERI_CSETLEN(0, 1, CHERI_CAP_USER_LENGTH);
+}
+
+static void
+cheritest_yieldtest(void)
+{
+	int ret;
+
+	cheritest_sandbox();
+	ret = sched_yield();
+	cheritest_unsandbox();
+	if (ret)
+		err(1, "sched_yield");
+
+}
+
 int
 main(__unused int argc, __unused char *argv[])
 {
@@ -149,6 +190,9 @@
 	if (argc == 0)
 		usage();
 
+	/* Save original C0 in C1 for later use. */
+	CHERI_CMOVE(1, 0);
+
 	for (i = 0; i < argc; i++) {
 		if (strcmp(argv[0], "listregs") == 0)
 			cheritest_listregs();
@@ -156,8 +200,14 @@
 			cheritest_copyregs();
 		else if (strcmp(argv[0], "overrun") == 0)
 			cheritest_overrun();
+		else if (strcmp(argv[0], "sandbox") == 0)
+			cheritest_sandbox();
 		else if (strcmp(argv[0], "sleep") == 0)
 			sleep(10);
+		else if (strcmp(argv[0], "unsandbox") == 0)
+			cheritest_unsandbox();
+		else if (strcmp(argv[0], "yieldtest") == 0)
+			cheritest_yieldtest();
 		else
 			usage();
 	}