[U-Boot] [PATCH v2] fastboot: handle flash write to GPT partition

[Steve Rae]

Implement a feature to allow fastboot to write the downloaded image
to the space reserved for the Protective MBR and the Primary GUID
Partition Table.

Signed-off-by: Steve Rae <srae at broadcom.com>
---

Changes in v2:
add validation of the GPT before writing to flash
(suggested by: Lukasz Majewski <l.majewski at samsung.com>)

 README          |  7 +++++++
 common/fb_mmc.c | 26 +++++++++++++++++++++++---
 disk/part_efi.c | 37 +++++++++++++++++++++++++++++++++++++
 include/part.h  | 10 ++++++++++
 4 files changed, 77 insertions(+), 3 deletions(-)

diff --git a/README b/README
index 4ca04d0..5f50cdd 100644
--- a/README
+++ b/README
@@ -1773,6 +1773,13 @@ The following options need to be configured:
 		regarding the non-volatile storage device. Define this to
 		the eMMC device that fastboot should use to store the image.
 
+		CONFIG_FASTBOOT_GPT_NAME
+		The fastboot "flash" command supports writing the downloaded
+		image to the Protective MBR and the Primary GUID Partition
+		Table. This occurs when the specified "partition name" on the
+		"fastboot flash" command line matches this value.
+		Default is GPT_ENTRY_NAME (currently "gpt") if undefined.
+
 - Journaling Flash filesystem support:
 		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
 		CONFIG_JFFS2_NAND_DEV
diff --git a/common/fb_mmc.c b/common/fb_mmc.c
index fb06d8a..a646a7b 100644
--- a/common/fb_mmc.c
+++ b/common/fb_mmc.c
@@ -4,12 +4,17 @@
  * SPDX-License-Identifier:	GPL-2.0+
  */
 
+#include <config.h>
 #include <common.h>
 #include <fb_mmc.h>
 #include <part.h>
 #include <aboot.h>
 #include <sparse_format.h>
 
+#ifndef CONFIG_FASTBOOT_GPT_NAME
+#define CONFIG_FASTBOOT_GPT_NAME GPT_ENTRY_NAME
+#endif
+
 /* The 64 defined bytes plus the '\0' */
 #define RESPONSE_LEN	(64 + 1)
 
@@ -62,9 +67,9 @@ static void write_raw_image(block_dev_desc_t *dev_desc, disk_partition_t *info,
 void fb_mmc_flash_write(const char *cmd, void *download_buffer,
 			unsigned int download_bytes, char *response)
 {
-	int ret;
 	block_dev_desc_t *dev_desc;
 	disk_partition_t info;
+	lbaint_t blksz;
 
 	/* initialize the response buffer */
 	response_str = response;
@@ -76,8 +81,23 @@ void fb_mmc_flash_write(const char *cmd, void *download_buffer,
 		return;
 	}
 
-	ret = get_partition_info_efi_by_name(dev_desc, cmd, &info);
-	if (ret) {
+	if (strcmp(cmd, CONFIG_FASTBOOT_GPT_NAME) == 0) {
+		printf("%s: updating GUID Partition Table (including MBR)\n",
+		       __func__);
+		/* start at Protective MBR */
+		info.start = (GPT_PRIMARY_PARTITION_TABLE_LBA - 1);
+		blksz = dev_desc->blksz;
+		info.blksz = blksz;
+		/* assume that the Partition Entry Array starts in LBA 2 */
+		info.size = (2 + (GPT_ENTRY_NUMBERS * GPT_ENTRY_SIZE) / blksz);
+
+		if (is_valid_gpt_primary(download_buffer, dev_desc->blksz)) {
+			printf("%s: invalid GPT - refusing to write to flash\n",
+			       __func__);
+			fastboot_fail("invalid GPT partition");
+			return;
+		}
+	} else if (get_partition_info_efi_by_name(dev_desc, cmd, &info)) {
 		error("cannot find partition: '%s'\n", cmd);
 		fastboot_fail("cannot find partition");
 		return;
diff --git a/disk/part_efi.c b/disk/part_efi.c
index efed58f..86cb160 100644
--- a/disk/part_efi.c
+++ b/disk/part_efi.c
@@ -455,6 +455,43 @@ err:
 	free(gpt_h);
 	return ret;
 }
+
+int is_valid_gpt_primary(void *buf, unsigned long blksz)
+{
+	int rc = 0;
+	gpt_header *gpt_h;
+	gpt_entry *gpt_e;
+	gpt_header gpt_hdr;
+	uint32_t calc_crc32;
+
+	/* GPT Header starts at "LBA[1]" in the buffer */
+	gpt_h = buf + blksz;
+	if (gpt_h->signature != cpu_to_le64(GPT_HEADER_SIGNATURE)) {
+		printf("%s: 'signature' is invalid\n", __func__);
+		rc += 1;
+	}
+
+	memcpy(&gpt_hdr, gpt_h, sizeof(gpt_header));
+	gpt_hdr.header_crc32 = 0;
+	calc_crc32 = efi_crc32((const unsigned char *)&gpt_hdr,
+			       le32_to_cpu(gpt_h->header_size));
+	if (gpt_h->header_crc32 != cpu_to_le32(calc_crc32)) {
+		printf("%s: 'header_crc32' is invalid\n", __func__);
+		rc += 1;
+	}
+
+	/* GPT Entries start at "LBA[2]" in the buffer */
+	gpt_e = buf + (2 * blksz);
+	calc_crc32 = efi_crc32((const unsigned char *)gpt_e,
+			       le32_to_cpu(gpt_h->num_partition_entries) *
+			       le32_to_cpu(gpt_h->sizeof_partition_entry));
+	if (gpt_h->partition_entry_array_crc32 != cpu_to_le32(calc_crc32)) {
+		printf("%s: 'partition_entry_array_crc32' is invalid\n",
+		       __func__);
+		rc += 1;
+	}
+	return rc;
+}
 #endif
 
 /*
diff --git a/include/part.h b/include/part.h
index a496a4a..9cfa4c9 100644
--- a/include/part.h
+++ b/include/part.h
@@ -244,6 +244,16 @@ int gpt_fill_header(block_dev_desc_t *dev_desc, gpt_header *gpt_h,
  */
 int gpt_restore(block_dev_desc_t *dev_desc, char *str_disk_guid,
 		disk_partition_t *partitions, const int parts_count);
+
+/**
+ * is_valid_gpt_primary() - Ensure that the Primary GPT information is valid
+ *
+ * @param buf - buffer which contains the Primary GPT info
+ * @param blksz -  block size (in bytes)
+ *
+ * @return - '0' on success, otherwise error
+ */
+int is_valid_gpt_primary(void *buf, unsigned long blksz);
 #endif
 
 #endif /* _PART_H */
-- 
1.8.5