On 2/12/26 10:32 PM, James Hilliard wrote:
On Thu, Feb 12, 2026 at 1:05 PM Marek Vasut <[email protected]> wrote:
On 2/12/26 8:52 PM, James Hilliard wrote:
On Thu, Feb 12, 2026 at 8:26 AM Marek Vasut <[email protected]> wrote:
On 2/11/26 7:06 PM, James Hilliard wrote:
+static int boot_get_fdt_fit_into_buffer(const void *src, ulong srclen,
+ ulong extra, ulong min_dstlen,
+ void **fdtdstbuf, ulong *fdtdstlenp)
+{
+ const void *fdtsrcbuf;
+ void *tmp = NULL;
+ void *dstbuf, *newdstbuf;
+ ulong dstlen, newdstlen;
+ int err;
+
+ /* Make sure the source FDT/DTO is 8-byte aligned for libfdt. */
+ fdtsrcbuf = src;
+ if (!IS_ALIGNED((uintptr_t)src, 8)) {
+ tmp = memalign(8, srclen);
+ if (!tmp)
+ return -ENOMEM;
+
+ memcpy(tmp, src, srclen);
+ fdtsrcbuf = tmp;
+ }
+
+ newdstlen = ALIGN(fdt_totalsize(fdtsrcbuf) + extra, SZ_4K);
+ min_dstlen = ALIGN(min_dstlen, SZ_4K);
+ if (newdstlen < min_dstlen)
+ newdstlen = min_dstlen;
+
+ dstbuf = *fdtdstbuf;
+ dstlen = dstbuf ? *fdtdstlenp : 0;
+
+ /*
+ * If the caller already provided a large enough writable buffer,
+ * and we're not moving the FDT, nothing to do.
+ */
+ if (dstbuf && dstlen >= newdstlen && dstbuf == fdtsrcbuf) {
Can $dstbuf ever be NULL ?
+ free(tmp);
+ return 0;
You could try something like this here, to reduce the duplicate
free(tmp) in the code:
"
err = 0;
goto exit;
...
exit:
free(tmp);
return err;
"
+ }
+
[...]
- load = (ulong)of_flat_tree;
+ len = fdt_off_dt_strings(base_buf) + fdt_size_dt_strings(base_buf);
How does this new length calculation work, can you please clarify that ?
From my understanding, that len is tracking the current packed DTB data
length (up to the end of the strings block), not the allocated buffer size. We
recompute it after each overlay so need = len + ovcopylen
CONFIG_SYS_FDT_PAD grows from real used bytes instead of
accumulated slack. This is roughly the same idea as libfdt’s internal
fdt_data_size_(), and the final returned size is still taken after fdt_pack()
with fdt_totalsize().
Ah I see, thank you for the clarification, this helped. It would be nice
to include that as code comment too.
I'll add a comment.
But don't you have to account for the FDT headers too, so wouldn't
fdt_totalsize() be more appropriate here ?
From my understanding, fdt_off_dt_strings() + fdt_size_dt_strings() is the
packed DTB data size we need for growth calculations, and it already
covers data from the blob start (so headers are implicitly accounted for
via the offset). fdt_totalsize() includes spare/free space, so using it there
would overestimate need and cause unnecessary buffer growth.
Thank you for spelling that out. Please also add that as a code comment,
this really helps understand the code.
With that in place, for V6, add my:
Reviewed-by: Marek Vasut <[email protected]>
Thank you for your hard work.
