vboot: Add support for reading GBB flags

This change adds basic support for reading flags from GBB header
located in "GBB" section on SPI flash.

Change-Id: I35ecb5ba964511379baa4e9f458ba2e8c6b74b4e
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://review.coreboot.org/25459
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/security/vboot/Makefile.inc

@@ -23,6 +23,8 @@ postcar-y += bootmode.c
 
 verstage-generic-ccopts += -D__PRE_RAM__ -D__VERSTAGE__
 
+ramstage-y += gbb.c
+
 bootblock-y += vbnv.c
 verstage-y += vbnv.c
 romstage-y += vbnv.c

src/security/vboot/gbb.c

@@ -0,0 +1,77 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2018 Google LLC
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <commonlib/region.h>
+#include <console/console.h>
+#include <fmap.h>
+#include <gbb_header.h>
+#include <security/vboot/gbb.h>
+#include <string.h>
+
+#define GBB_FMAP_REGION_NAME	"GBB"
+
+/* Copy of GBB header read from boot media. */
+static GoogleBinaryBlockHeader gbb_header;
+
+/*
+ * Read "GBB" region from SPI flash to obtain GBB header and validate
+ * signature.
+ *
+ * Return value:
+ * Success = 0
+ * Error = 1
+ */
+static int gbb_init(void)
+{
+	static bool init_done = false;
+	struct region_device gbb_rdev;
+
+	if (init_done != false)
+		return 0;
+
+	if (fmap_locate_area_as_rdev(GBB_FMAP_REGION_NAME, &gbb_rdev))
+		return 1;
+
+	if (rdev_readat(&gbb_rdev, &gbb_header, 0,
+			sizeof(GoogleBinaryBlockHeader)) !=
+	    sizeof(GoogleBinaryBlockHeader)) {
+		printk(BIOS_ERR, "%s: Failure to read GBB header!\n", __func__);
+		return 1;
+	}
+
+	if (memcmp(gbb_header.signature, GBB_SIGNATURE, GBB_SIGNATURE_SIZE)) {
+		printk(BIOS_ERR, "%s: Signature check failed!\n", __func__);
+		return 1;
+	}
+
+	init_done = true;
+	return 0;
+}
+
+uint32_t gbb_get_flags(void)
+{
+	if (gbb_init()) {
+		printk(BIOS_ERR,
+		       "%s: Failure to initialize GBB. Returning flags as 0!\n",
+		       __func__);
+		return 0;
+	}
+	return gbb_header.flags;
+}
+
+bool gbb_is_flag_set(uint32_t flag)
+{
+	return !!(gbb_get_flags() & flag);
+}

src/security/vboot/gbb.h

@@ -0,0 +1,39 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2018 Google LLC
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef __SECURITY_VBOOT_GBB_H__
+#define __SECURITY_VBOOT_GBB_H__
+
+#include <stdint.h>
+
+/* In order to use GBB_FLAG_* macros from vboot, include gbb_header.h. */
+
+/*
+ * Read flags field from GBB header.
+ * Return value:
+ * Success: 32-bit unsigned integer representing flags field from GBB header.
+ * Error  : 0
+ */
+uint32_t gbb_get_flags(void);
+
+/*
+ * Check if given flag is set in the flags field in GBB header.
+ * Return value:
+ * true: Flag is set.
+ * false: Flag is not set or failure to read GBB flags.
+ */
+bool gbb_is_flag_set(uint32_t flag);
+
+#endif /* __SECURITY_VBOOT_GBB_H__ */