Add check-value support and check /proc/cmdline for cros_nodebug

Change-Id: I35158810184be03f18d98893e4dd640088384579

BUG=12904
TEST=manual

crossystem fwb_tries=1
crossystem fwb_tries?1 && echo YES || echo NO --> YES
crossystem fwb_tries?0x01 && echo YES || echo NO --> YES
crossystem fwb_tries?0 && echo YES || echo NO --> NO

crossystem fwb_tries=0
crossystem fwb_tries?0 && echo YES || echo NO --> YES
crossystem fwb_tries?1 && echo YES || echo NO --> NO
crossystem fwb_tries?0x01 && echo YES || echo NO --> NO

crossystem ecfw_act --> RW (if it's not, change RW to RO in the tests below)
crossystem ecfw_act?RW && echo YES || echo NO --> YES
crossystem ecfw_act?BOB && echo YES || echo NO --> NO

For the following tests, boot Alex with dev switch on and fwb_tries=1
Expected output of `crossystem mainfw_type mainfw_act cros_debug` under each of the following scenarios:
* Neither "cros_debug" nor" cros_nodebug" in kernel command line: normal B 1
* Kernel command line changed to include "cros_nodebug": normal B 0
* Kernel command line changed to include "cros_nodebugg": normal B 1
* Kernel command line changed to include "ccros_nodebug": normal B 1

Review URL: http://codereview.chromium.org/6665005

1 files changed, 3 insertions, 1 deletions

diff --git a/host/lib/crossystem.c b/host/lib/crossystem.c
index 17f4f505..04dc9756 100644
--- a/host/lib/crossystem.c
+++ b/host/lib/crossystem.c
@@ -473,7 +473,7 @@ int VbGetCrosDebug(void) {
     return 1;  /* Developer firmware always allows debug. */
 
   /* Normal new firmware, older ChromeOS firmware, or non-Chrome firmware.
-   * For all these cases, check /proc/cmdline for cros_debug. */
+   * For all these cases, check /proc/cmdline for cros_[no]debug. */
   f = fopen(KERNEL_CMDLINE_PATH, "rt");
   if (f) {
     if (NULL == fgets(buf, sizeof(buf), f))
@@ -483,6 +483,8 @@ int VbGetCrosDebug(void) {
   for (t = strtok_r(buf, " ", &saveptr); t; t=strtok_r(NULL, " ", &saveptr)) {
     if (0 == strcmp(t, "cros_debug"))
       return 1;
+    else if (0 == strcmp(t, "cros_nodebug"))
+      return 0;
   }
 
   /* Normal new firmware or older Chrome OS firmware allows debug if the