[U-Boot] [PATCH v3 4/5] rename GPT partitions to detect boot failure

Lothar Waßmann
2017-06-06T08:20:41Z

Hi,

On Fri, 2 Jun 2017 19:22:33 -0700 alison at peloton-tech.com wrote:
> From: Alison Chaiken <alison@peloton-tech.com>
>
> This patch provides support in u-boot for renaming GPT
> partitions. The renaming is accomplished via a new 'gpt flip'
> command.
>
> The concept for the bootloader state machine is the following:
>
> -- u-boot renames ‘primary’ partitions as ‘candidate’ and tries
> to boot them.
> -- Linux, at boot, will rename ‘candidate’ partitions as
> ‘primary’.
> -- If u-boot sees a ‘candidate’ partition after a boot attempt,
> it tries to boot the ‘backup’ partition.
>
> Rewriting the partition table has the side-effect that all partitions
> end up with "msftdata" flag set. The reason is that partition type
> PARTITION_BASIC_DATA_GUID is hard-coded in the gpt_fill_pte()
> function. This does not appear to cause any harm.
>
> Signed-off-by: Alison Chaiken <alison@peloton-tech.com>
> ---
> cmd/Kconfig | 7 ++
> cmd/gpt.c | 199 +++++++++++++++++++++++++++++++++++++++++++++++++++++++--
> doc/README.gpt | 13 ++++
> 3 files changed, 215 insertions(+), 4 deletions(-)
>
> diff --git a/cmd/Kconfig b/cmd/Kconfig
> index 6f75b86..8b925e5 100644
> --- a/cmd/Kconfig
> +++ b/cmd/Kconfig
> @@ -593,6 +593,13 @@ config CMD_GPT
> Enable the 'gpt' command to ready and write GPT style partition
> tables.
>
> +config CMD_GPT_FLIP
> + bool "GPT flip-partitions command"
> + depends on CMD_GPT
> + help
> + Enables the 'gpt' command to write modified GPT partition
> + tables via the 'gpt flip' command.
> +
> config CMD_ARMFLASH
> #depends on FLASH_CFI_DRIVER
> bool "armflash"
> diff --git a/cmd/gpt.c b/cmd/gpt.c
> index 5c2651f..f6968de 100644
> --- a/cmd/gpt.c
> +++ b/cmd/gpt.c
> @@ -20,6 +20,7 @@
> #include <div64.h>
> #include <memalign.h>
> #include <linux/compat.h>
> +#include <linux/sizes.h>
>
> static LIST_HEAD(disk_partitions);
>
> @@ -190,16 +191,33 @@ static struct disk_part *allocate_disk_part(disk_partition_t *info, int partnum)
> return newpart;
> }
>
> +static void prettyprint_part_size(char *sizestr, unsigned long partsize,
> + unsigned long blksize)
> +{
> + unsigned long long partbytes;
> + unsigned long partmegabytes;
> +
> + partbytes = partsize * blksize;
> + partmegabytes = lldiv(partbytes, SZ_1M);
> + snprintf(sizestr, 16, "%luMiB", partmegabytes);
> +}
> +
> static void print_gpt_info(void)
> {
> struct list_head *pos;
> struct disk_part *curr;
> + char partstartstr[16];
> + char partsizestr[16];
>
> list_for_each(pos, &disk_partitions) {
> curr = list_entry(pos, struct disk_part, list);
> + prettyprint_part_size(partstartstr, (unsigned long)curr->gpt_part_info.start,
> + (unsigned long) curr->gpt_part_info.blksz);
> + prettyprint_part_size(partsizestr, (unsigned long)curr->gpt_part_info.size,
> + (unsigned long) curr->gpt_part_info.blksz);
> +
> printf("Partition %d:\n", curr->partnum);
> - printf("1st block %x, size %x\n", (unsigned)curr->gpt_part_info.start,
> - (unsigned)curr->gpt_part_info.size);
> + printf("Start %s, size %s\n", partstartstr, partsizestr);
> printf("Block size %lu, name %s\n", curr->gpt_part_info.blksz,
> curr->gpt_part_info.name);
> printf("Type %s, bootable %d\n", curr->gpt_part_info.type,
> @@ -211,6 +229,85 @@ static void print_gpt_info(void)
> }
> }
>
> +#ifdef CONFIG_CMD_GPT_FLIP
> +static int calc_parts_list_len(int numparts)
> +{
> + /*
> + * prefatory string:
> + * doc/README.GPT, suggests that
> + * int partlistlen = UUID_STR_LEN + 1 + strlen("partitions=uuid_disk=");
> + * is correct, but extract_val() expects "uuid_disk" first.
> + */
> + int partlistlen = UUID_STR_LEN + 1 + strlen("uuid_disk=");
> + /* for the comma */
> + partlistlen++;
> +
> + /* per-partition additions; numparts starts at 1, so this should be correct */
> + partlistlen += numparts * (strlen("name=,") + PART_NAME_LEN + 1);
> + /* 17 because partstr in create_gpt_partitions_list() is 16 chars */
>
NO! The size of partstr in create_gpt_partitions_list() is:
| char partstr[PART_NAME_LEN + 1];
which happens to be defined as:
--- a/include/part.h
+++ b/include/part.h
@@ -49,6 +49,7 @@ struct block_drvr {

#define PART_NAME_LEN 32
^^
#define PART_TYPE_LEN 32

> + partlistlen += numparts * (strlen("start=MiB,") + 17);
> + partlistlen += numparts * (strlen("size=MiB,") + 17);
>
Never use magic numbers in code, but use appropriate #define's!

> @@ -523,6 +625,86 @@ static int do_disk_guid(struct blk_desc *dev_desc, char * const namestr)
> return ret;
> }
>
> +#ifdef CONFIG_CMD_GPT_FLIP
> +static int do_flip_gpt_parts(struct blk_desc *dev_desc)
> +{
> + struct list_head *pos;
> + struct disk_part *curr;
> + disk_partition_t *new_partitions = NULL;
> + char disk_guid[UUID_STR_LEN + 1];
> + char *partitions_list, *str_disk_guid;
> + u8 part_count = 0;
> + int partlistlen, ret, numparts = 0;
> +
> + ret = get_disk_guid(dev_desc, disk_guid);
> + if (ret < 0)
> + return ret;
AGAIN: You are passing the return value of this function back to the
caller of the CMD handler do_gpt() which expects a return value of
CMD_RET_FAILURE or CMD_RET_SUCCESS, not an arbitrary negative value.

> +
> + numparts = get_gpt_info(dev_desc);
> + if (numparts < 0)
> + return numparts;
> + printf("Current partition table with %d partitions is:\n", numparts);
> + print_gpt_info();
> +
> + partlistlen = calc_parts_list_len(numparts);
> + partitions_list = (char *)malloc(partlistlen);
> + memset(partitions_list, '\0', partlistlen);
> +
> + ret = create_gpt_partitions_list(numparts, (const char *) disk_guid,
> + partitions_list);
> + if (ret < 0)
> + return ret;
> + debug("OLD partitions_list is %s with %d chars\n", partitions_list, strlen(partitions_list));
> +
> + ret = set_gpt_info(dev_desc, (const char *)partitions_list, &str_disk_guid,
> + &new_partitions, &part_count);
> + if (ret < 0)
> + return ret;
> +
> + list_for_each(pos, &disk_partitions) {
> + curr = list_entry(pos, struct disk_part, list);
> + if (!strcmp((char *)curr->gpt_part_info.name, "backup_kernel"))
> + strcpy((char *)curr->gpt_part_info.name, "candidate_kernel");
> + if (!strcmp((char *)curr->gpt_part_info.name, "primary_kernel"))
> + strcpy((char *)curr->gpt_part_info.name, "backup_kernel");
> + if (!strcmp((char *)curr->gpt_part_info.name, "backup_rootfs"))
> + strcpy((char *)curr->gpt_part_info.name, "candidate_rootfs");
> + if (!strcmp((char *)curr->gpt_part_info.name, "primary_rootfs"))
> + strcpy((char *)curr->gpt_part_info.name, "backup_rootfs");
> + }
> +
> + ret = create_gpt_partitions_list(numparts, (const char *) disk_guid, partitions_list);
> + if (ret < 0)
> + return ret;
> + debug("NEW partitions_list is %s with %d chars\n", partitions_list, strlen(partitions_list));
> +
> + ret = set_gpt_info(dev_desc, (const char *)partitions_list, &str_disk_guid,
> + &new_partitions, &part_count);
> + if (ret < 0)
> + return ret;
> +
> + debug("Writing new partition table\n");
> + ret = gpt_restore(dev_desc, disk_guid, new_partitions, numparts);
> + if (ret < 0) {
> + printf("Writing new partition table failed\n");
> + return ret;
> + }
> +
> + debug("Reading back new partition table\n");
> + numparts = get_gpt_info(dev_desc);
> + if (numparts < 0)
> + return numparts;
> + printf("new partition table with %d partitions is:\n", numparts);
> + print_gpt_info();
> +
> + del_gpt_info();
> + free(partitions_list);
> + free(str_disk_guid);
> + free(new_partitions);
> + return ret;
> +}
> +#endif
> +
> /**
> * do_gpt(): Perform GPT operations
> *
> @@ -565,6 +747,10 @@ static int do_gpt(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
> return do_disk_guid(blk_dev_desc, argv[4]);
> } else if (strcmp(argv[1], "read") == 0) {
> return do_get_gpt_info(blk_dev_desc);
> +#ifdef CONFIG_CMD_GPT_FLIP
> + } else if (strcmp(argv[1], "flip") == 0) {
> + return do_flip_gpt_parts(blk_dev_desc);
> +#endif
>
See my comment to your patch 1/5.

Lothar Waßmann