Julius Werner would like Aaron Durbin and Joel Kitching to review this change.

View Change

security/vboot: Ensure firmware body size is respected again

CB:36845 simplified how coreboot finds the RW CBFS after vboot has and
eliminated a layer of caching. Unfortunately, we missed the fact that
the former cached value didn't exactly match the FMAP section... it was
in fact truncated to the data actually used by vboot. That patch
unintentionally broke this truncation which leads to performance
regressions on certain CBFS accesses.

This patch makes use of a new API function added to vboot (CL:1965920)
which we can use to retrieve the real firmware body length as before.

(Also stop making all the vb2_context pointers const. vboot generally
never marks context pointers as const in its API functions, even when
the function doesn't modify the context. Therefore constifying it inside
coreboot just makes things weird because it prevents you from calling
random API functions for no reason. If we really want const context
pointers, that's a refactoring that would have to start inside vboot
first.)

Change-Id: I167cd40cb435dbae7f09d6069c9f1ffc1d99fe13
Signed-off-by: Julius Werner <jwerner@chromium.org>
---
M src/security/vboot/common.c
M src/security/vboot/misc.h
M src/security/vboot/vboot_loader.c
M src/security/vboot/vboot_logic.c
4 files changed, 22 insertions(+), 30 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/80/37680/1

diff --git a/src/security/vboot/common.c b/src/security/vboot/common.c
index c21fe15..214f6fa 100644
--- a/src/security/vboot/common.c
+++ b/src/security/vboot/common.c
@@ -68,8 +68,7 @@
 	return vboot_ctx;
 }
 
-int vboot_locate_firmware(const struct vb2_context *ctx,
-			  struct region_device *fw)
+int vboot_locate_firmware(struct vb2_context *ctx, struct region_device *fw)
 {
 	const char *name;
 
@@ -78,7 +77,12 @@
 	else
 		name = "FW_MAIN_B";
 
-	return fmap_locate_area_as_rdev(name, fw);
+	int ret = fmap_locate_area_as_rdev(name, fw);
+	if (ret)
+		return ret;
+
+	/* Truncate area to the size that was actually signed by vboot. */
+	return rdev_chain(fw, fw, 0, vb2api_get_firmware_size(ctx));
 }
 
 static void vboot_setup_cbmem(int unused)
diff --git a/src/security/vboot/misc.h b/src/security/vboot/misc.h
index 1fda8b4..0b2c8e5 100644
--- a/src/security/vboot/misc.h
+++ b/src/security/vboot/misc.h
@@ -30,7 +30,7 @@
 /*
  * Returns 1 if firmware slot A is used, 0 if slot B is used.
  */
-static inline int vboot_is_firmware_slot_a(const struct vb2_context *ctx)
+static inline int vboot_is_firmware_slot_a(struct vb2_context *ctx)
 {
 	return !(ctx->flags & VB2_CONTEXT_FW_SLOT_B);
 }
@@ -49,8 +49,7 @@
 /*
  * Locates firmware as a region device. Returns 0 on success, -1 on failure.
  */
-int vboot_locate_firmware(const struct vb2_context *ctx,
-			  struct region_device *fw);
+int vboot_locate_firmware(struct vb2_context *ctx, struct region_device *fw);
 
 /*
  * Source: security/vboot/bootmode.c
diff --git a/src/security/vboot/vboot_loader.c b/src/security/vboot/vboot_loader.c
index 9aaaff2..b72c82b 100644
--- a/src/security/vboot/vboot_loader.c
+++ b/src/security/vboot/vboot_loader.c
@@ -72,7 +72,7 @@
 
 static int vboot_locate(struct region_device *rdev)
 {
-	const struct vb2_context *ctx;
+	struct vb2_context *ctx;
 
 	/* Don't honor vboot results until the vboot logic has run. */
 	if (!vboot_logic_executed())
diff --git a/src/security/vboot/vboot_logic.c b/src/security/vboot/vboot_logic.c
index 6c4f8fd..1d17a17 100644
--- a/src/security/vboot/vboot_logic.c
+++ b/src/security/vboot/vboot_logic.c
@@ -173,10 +173,10 @@
 }
 
 static vb2_error_t hash_body(struct vb2_context *ctx,
-			     struct region_device *fw_main)
+			     struct region_device *fw_body)
 {
 	uint64_t load_ts;
-	uint32_t expected_size;
+	uint32_t remaining;
 	uint8_t block[TODO_BLOCK_SIZE];
 	uint8_t hash_digest[VBOOT_MAX_HASH_SIZE];
 	const size_t hash_digest_sz = sizeof(hash_digest);
@@ -197,33 +197,22 @@
 	load_ts = timestamp_get();
 	timestamp_add(TS_START_HASH_BODY, load_ts);
 
-	expected_size = region_device_sz(fw_main);
+	remaining = region_device_sz(fw_body);
 	offset = 0;
 
 	/* Start the body hash */
-	rv = vb2api_init_hash(ctx, VB2_HASH_TAG_FW_BODY, &expected_size);
+	rv = vb2api_init_hash(ctx, VB2_HASH_TAG_FW_BODY);
 	if (rv)
 		return rv;
 
-	/*
-	 * Honor vboot's RW slot size. The expected size is pulled out of
-	 * the preamble and obtained through vb2api_init_hash() above. By
-	 * creating sub region the RW slot portion of the boot media is
-	 * limited.
-	 */
-	if (rdev_chain(fw_main, fw_main, 0, expected_size)) {
-		printk(BIOS_ERR, "Unable to restrict CBFS size.\n");
-		return VB2_ERROR_UNKNOWN;
-	}
-
 	/* Extend over the body */
-	while (expected_size) {
+	while (remaining) {
 		uint64_t temp_ts;
-		if (block_size > expected_size)
-			block_size = expected_size;
+		if (block_size > remaining)
+			block_size = remaining;
 
 		temp_ts = timestamp_get();
-		if (rdev_readat(fw_main, block, offset, block_size) < 0)
+		if (rdev_readat(fw_body, block, offset, block_size) < 0)
 			return VB2_ERROR_UNKNOWN;
 		load_ts += timestamp_get() - temp_ts;
 
@@ -231,7 +220,7 @@
 		if (rv)
 			return rv;
 
-		expected_size -= block_size;
+		remaining -= block_size;
 		offset += block_size;
 	}
 
@@ -309,7 +298,7 @@
 void verstage_main(void)
 {
 	struct vb2_context *ctx;
-	struct region_device fw_main;
+	struct region_device fw_body;
 	vb2_error_t rv;
 
 	timestamp_add_now(TS_START_VBOOT);
@@ -405,12 +394,12 @@
 	}
 
 	printk(BIOS_INFO, "Phase 4\n");
-	rv = vboot_locate_firmware(ctx, &fw_main);
+	rv = vboot_locate_firmware(ctx, &fw_body);
 	if (rv)
 		die_with_post_code(POST_INVALID_ROM,
 			"Failed to read FMAP to locate firmware");
 
-	rv = hash_body(ctx, &fw_main);
+	rv = hash_body(ctx, &fw_body);
 	vboot_save_data(ctx);
 	if (rv) {
 		printk(BIOS_INFO, "Reboot requested (%x)\n", rv);

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