Add VB_INIT_OUT_ENABLE_ALTERNATE_OS flag

This adds a flag to the list of values returned by VbInit(). When
this flag is set, the BIOS may be asked to boot something other than
ChromeOS. If this requires some sort of special preparation, the BIOS
should do it.

BUG=chromium-os:22454
TEST=none

There is no test for this. It requires a change to the BIOS in order
to do anything differently, and we haven't yet decided whether the
BIOS should pay attention to it.

Change-Id: I5d89e7cd5b745ee74b8ace7fa613c0db03eebefd
Reviewed-on: https://gerrit.chromium.org/gerrit/11714
Tested-by: Bill Richardson <wfrichar@chromium.org>
Reviewed-by: Randall Spangler <rspangler@chromium.org>

firmware/include/gbb_header.h

@@ -38,9 +38,11 @@
 /* BIOS should load option ROMs from arbitrary PCI devices. We'll never enable
  * this ourselves because it executes non-verified code, but if a customer wants
  * to void their warranty and set this flag in the read-only flash, they should
- * be able to do so.
+ * be able to do so. */
- */
 #define GBB_FLAG_LOAD_OPTION_ROMS         0x00000002
+/* The factory flow may need the BIOS to boot a non-ChromeOS kernel if the
+ * dev-switch is on. This flag allows that. */
+#define GBB_FLAG_ENABLE_ALTERNATE_OS      0x00000004
 
 #ifdef __cplusplus
 extern "C" {

firmware/include/vboot_api.h

@@ -186,6 +186,8 @@ typedef struct VbCommonParams {
 #define VB_INIT_OUT_S3_DEBUG_BOOT        0x00000010
 /* BIOS should load any PCI option ROMs it finds, not just internal video */
 #define VB_INIT_OUT_ENABLE_OPROM         0x00000020
+/* BIOS may be asked to boot something other than ChromeOS */
+#define VB_INIT_OUT_ENABLE_ALTERNATE_OS  0x00000040
 
 
 /* Data only used by VbInit() */

firmware/lib/vboot_api_init.c

@@ -22,6 +22,7 @@ VbError_t VbInit(VbCommonParams* cparams, VbInitParams* iparams) {
   uint32_t recovery = VBNV_RECOVERY_NOT_REQUESTED;
   int is_s3_resume = 0;
   uint32_t s3_debug_boot = 0;
+  uint32_t user_enabled_custom_os = 0;
 
   VBDEBUG(("VbInit() input flags 0x%x\n", iparams->flags));
 
@@ -105,12 +106,27 @@ VbError_t VbInit(VbCommonParams* cparams, VbInitParams* iparams) {
     iparams->out_flags |= (VB_INIT_OUT_CLEAR_RAM |
                           VB_INIT_OUT_ENABLE_DISPLAY |
                           VB_INIT_OUT_ENABLE_USB_STORAGE);
+    /* ... which could include custom OSes */
+    VbNvGet(&vnc, VBNV_DEV_BOOT_CUSTOM, &user_enabled_custom_os);
+    if (user_enabled_custom_os)
+      iparams->out_flags |= VB_INIT_OUT_ENABLE_ALTERNATE_OS;
+  } else {
+    /* Normal mode, so disable dev_boot_* flags.  This ensures they will be
+     * initially disabled if the user later transitions back into developer
+     * mode. */
+    VbNvSet(&vnc, VBNV_DEV_BOOT_USB, 0);
+    VbNvSet(&vnc, VBNV_DEV_BOOT_CUSTOM, 0);
   }
 
   /* Allow BIOS to load arbitrary option ROMs? */
   if (gbb->flags & GBB_FLAG_LOAD_OPTION_ROMS)
     iparams->out_flags |= VB_INIT_OUT_ENABLE_OPROM;
 
+  /* The factory may need to boot custom OSes whenever the dev-switch is on */
+  if ((gbb->flags & GBB_FLAG_ENABLE_ALTERNATE_OS) &&
+      (iparams->flags & VB_INIT_FLAG_DEV_SWITCH_ON))
+    iparams->out_flags |= VB_INIT_OUT_ENABLE_ALTERNATE_OS;
+
   /* copy current recovery reason to shared data */
   shared->recovery_reason = (uint8_t)recovery;
 

firmware/lib/vboot_api_kernel.c

@@ -105,13 +105,6 @@ uint32_t VbTryLoadKernel(VbCommonParams* cparams, LoadKernelParams* p,
 
 /* Handle a normal boot. */
 VbError_t VbBootNormal(VbCommonParams* cparams, LoadKernelParams* p) {
-
-  /* Force dev_boot_* flags disabled.  This ensures they will be
-   * initially disabled if the user later transitions back into
-   * developer mode. */
-  VbNvSet(&vnc, VBNV_DEV_BOOT_USB, 0);
-  VbNvSet(&vnc, VBNV_DEV_BOOT_CUSTOM, 0);
-
   /* Boot from fixed disk only */
   return VbTryLoadKernel(cparams, p, VB_DISK_FLAG_FIXED);
 }