On 2026-01-13 13:28:59 [+0100], Thomas Weißschuh wrote:
> --- /dev/null
> +++ b/scripts/modules-merkle-tree.c
> @@ -0,0 +1,467 @@
…
> +static void build_proof(struct mtree *mt, unsigned int n, int fd)
> +{
> + unsigned char cur[EVP_MAX_MD_SIZE];
> + unsigned char tmp[EVP_MAX_MD_SIZE];
This and a few other instances below could be optimized to avoid
hashing. I probably forgot to let you know.
->
https://git.kernel.org/pub/scm/linux/kernel/git/bigeasy/mtree-hashed-mods.git/commit/?id=10b565c123c731da37befe862de13678b7c54877
> + struct file_entry *fe, *fe_sib;
> +
> + fe = &fh_list[n];
> +
> + if ((n & 1) == 0) {
> + /* No pair, hash with itself */
> + if (n + 1 == num_files)
> + fe_sib = fe;
> + else
> + fe_sib = &fh_list[n + 1];
> + } else {
> + fe_sib = &fh_list[n - 1];
> + }
> + /* First comes the node position into the file */
> + write_be_int(fd, n);
> +
> + if ((n & 1) == 0)
> + hash_entry(fe->hash, fe_sib->hash, cur);
> + else
> + hash_entry(fe_sib->hash, fe->hash, cur);
> +
> + /* Next is the sibling hash, followed by hashes in the tree */
> + write_hash(fd, fe_sib->hash);
> +
> + for (unsigned int i = 0; i < mt->levels - 1; i++) {
> + n >>= 1;
> + if ((n & 1) == 0) {
> + void *h;
> +
> + /* No pair, hash with itself */
> + if (n + 1 == mt->entries[i])
> + h = cur;
> + else
> + h = mt->l[i][n + 1].hash;
> +
> + hash_entry(cur, h, tmp);
> + write_hash(fd, h);
> + } else {
> + hash_entry(mt->l[i][n - 1].hash, cur, tmp);
> + write_hash(fd, mt->l[i][n - 1].hash);
> + }
> + memcpy(cur, tmp, hash_size);
> + }
> +
> + /* After all that, the end hash should match the root hash */
> + if (memcmp(cur, mt->l[mt->levels - 1][0].hash, hash_size))
> + errx(1, "hash mismatch");
> +}
Sebastian
