Re: [U-Boot] [PATCH v6 3/3] GPT: provide commands to selectively rename partitions

12 Jun 2017

      On Mon, Jun 12, 2017 at 12:45 AM, Wolfgang Denk wd@denx.de wrote:
...
Dear Alison,
In message 1497137617-772-1-git-send-email-alison@peloton-tech.com you
wrote:
...
This patch provides support in u-boot for renaming GPT
partitions.  The renaming is accomplished via new 'gpt swap'
and 'gpt rename' commands.
Thanks.
One question: can multiple GPT partitions have the same name?
The idea behind the 'swap' mode is that a storage device can have two sets
of partitions, one set all named 'primary' and one set all named 'backup'.
  The software updater in userspace can then simply rename the partitions
with sgdisk in order to pick the new image.   The swap mode changes the
whole set of labels at once, so there's little chance of being interrupted.
...
...
The 'swap' mode prints a warning if no matching partition names
are found.  If only one matching name of a provided pair is found, it
renames the matching partitions to the new name.
I see a problem here...
...

if (!strcmp(subcomm, "swap")) {

        if ((strlen(name1) > PART_NAME_LEN) || (strlen(name2) >

PART_NAME_LEN)) {
...

                printf("Names longer than %d characters are

truncated.\n", PART_NAME_LEN);
...

                return -EINVAL;

        }

        list_for_each(pos, &disk_partitions) {

                curr = list_entry(pos, struct disk_part, list);

                if (!strcmp((char *)curr->gpt_part_info.name,

name1)) {
...

                        strcpy((char *)curr->gpt_part_info.name,

name2);
...

                        changed++;

                }

                else if (!strcmp((char *)curr->gpt_part_info.name,

name2)) {
...

                        strcpy((char *)curr->gpt_part_info.name,

name1);
...

                        changed++;

                }

        }

        if (changed == 0) {

                printf("No matching partition names were

found.\n");
...

                return ret;

        }

You will never know if there really was a pair of names that was
swapped.  Just a single rename of name1->name2 _or_ of name2->name1
will make the user think everything was fine.
Point taken.   The last version I posted has two counters instead of just
changed in order to address this problem.
...
[Note: I'm in the process of relocating and will be offline for the
next 2..3. days.  Don't expect more comments from mee soon.
Sorry...]
Best regards,
Wolfgang Denk
One additional note: the last version I posted worked fine for the sandbox,
but wouldn't link for an ARM target with the Linaro toolchain, as the
linker couldn't find atoi().   I guess the libc for the x86 compiler
includes it.   To test on ARM, I copied in simple_atoi() from
lib/vsprintf.c, but assuredly that is an ugly solution.    Does anyone have
a better idea to solve this problem?
Thanks,
Alison Chaiken
Peloton Technology