cbfs: Add metadata cache

This patch adds a new CBFS "mcache" (metadata cache) -- a memory buffer
that stores the headers of all CBFS files. Similar to the existing FMAP
cache, this cache should reduce the amount of SPI accesses we need to do
every boot: rather than having to re-read all CBFS headers from SPI
flash every time we're looking for a file, we can just walk the same
list in this in-memory copy and finally use it to directly access the
flash at the right position for the file data.

This patch adds the code to support the cache but doesn't enable it on
any platform. The next one will turn it on by default.

Change-Id: I5b1084bfdad1c6ab0ee1b143ed8dd796827f4c65
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/38423
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/security/vboot/vboot_loader.c

@@ -1,6 +1,9 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 
+#include <boot_device.h>
 #include <cbfs.h>
+#include <cbmem.h>
+#include <commonlib/bsd/cbfs_private.h>
 #include <console/console.h>
 #include <ec/google/chromeec/ec.h>
 #include <rmodule.h>
@@ -22,12 +25,27 @@ _Static_assert(!CONFIG(VBOOT_RETURN_FROM_VERSTAGE) ||
 
 int vboot_executed;
 
+static void build_rw_mcache(void)
+{
+	if (CONFIG(NO_CBFS_MCACHE))
+		return;
+
+	const struct cbfs_boot_device *cbd = vboot_get_cbfs_boot_device();
+	if (!cbd)	/* Don't build RW mcache in recovery mode. */
+		return;
+	cb_err_t err = cbfs_mcache_build(&cbd->rdev, cbd->mcache,
+					 cbd->mcache_size, NULL);
+	if (err && err != CB_CBFS_CACHE_FULL)
+		die("Failed to build RW mcache.");	/* TODO: -> recovery? */
+}
+
 void vboot_run_logic(void)
 {
 	if (verification_should_run()) {
 		/* Note: this path is not used for VBOOT_RETURN_FROM_VERSTAGE */
 		verstage_main();
 		vboot_executed = 1;
+		build_rw_mcache();
 	} else if (verstage_should_load()) {
 		struct cbfsf file;
 		struct prog verstage =
@@ -55,21 +73,29 @@ void vboot_run_logic(void)
 			return;
 
 		vboot_executed = 1;
+		build_rw_mcache();
 	}
 }
 
-int vboot_locate_cbfs(struct region_device *rdev)
+const struct cbfs_boot_device *vboot_get_cbfs_boot_device(void)
 {
-	struct vb2_context *ctx;
-
 	/* Don't honor vboot results until the vboot logic has run. */
 	if (!vboot_logic_executed())
-		return -1;
+		return NULL;
 
-	ctx = vboot_get_context();
+	static struct cbfs_boot_device cbd;
+	if (region_device_sz(&cbd.rdev))
+		return &cbd;
 
+	struct vb2_context *ctx = vboot_get_context();
 	if (ctx->flags & VB2_CONTEXT_RECOVERY_MODE)
-		return -1;
+		return NULL;
 
-	return vboot_locate_firmware(ctx, rdev);
+	boot_device_init();
+	if (vboot_locate_firmware(ctx, &cbd.rdev))
+		return NULL;
+
+	cbfs_boot_device_find_mcache(&cbd, CBMEM_ID_CBFS_RW_MCACHE);
+
+	return &cbd;
 }