[PATCH] boot: image-fit: Add runtime flag to always relocate overlays
Marek Vasut
marek.vasut at mailbox.org
Tue Feb 10 13:28:29 CET 2026
On 2/10/26 1:24 PM, Jamie.Gibbons at microchip.com wrote:
> Hi Marek,
>
> On Fri, 2026-02-06 at 20:06 +0100, Marek Vasut wrote:
>> EXTERNAL EMAIL: Do not click links or open attachments unless you
>> know the content is safe
>>
>> On 2/6/26 4:14 PM, Jamie Gibbons wrote:
>>> Some platforms
>>
>> All platforms, DTs and DTOs have to be 8 Byte aligned, always,
>> period.
> Thanks for your feedback. I have realised I misinterpreted Tom's
> instruction on my previous patch fix about passing a new flag.
>>
>>> require device tree overlays (DTOs) to be 8-byte aligned
>>> when applying them with libfdt. Previously, the code did not
>>> guarantee
>>> this alignment, which could result in alignment errors during
>>> overlay
>>> application.
>>> Introduce a new runtime parameter, always_relocate_overlay, to
>>> boot_get_fdt_fit(). When set, overlays are always copied to an 8-
>>> byte
>>> aligned buffer before being passed to fdt_open_into().
>>> This resolves issues with FDT overlay application on platforms that
>>> require strict alignment.
>>>
>>> Fixes: 8fbcc0e0e839 ("boot: Assure FDT is always at 8-byte aligned
>>> address")
>>>
>>> Signed-off-by: Jamie Gibbons <jamie.gibbons at microchip.com>
>>> ---
>>> boot/image-fdt.c | 2 +-
>>> boot/image-fit.c | 23 +++++++++++++++++------
>>> include/image.h | 5 ++++-
>>> 3 files changed, 22 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/boot/image-fdt.c b/boot/image-fdt.c
>>> index a3a4fb8b558..33fd4248acd 100644
>>> --- a/boot/image-fdt.c
>>> +++ b/boot/image-fdt.c
>>> @@ -431,7 +431,7 @@ static int select_fdt(struct bootm_headers
>>> *images, const char *select, u8 arch,
>>> fdt_noffset =
>>> boot_get_fdt_fit(images, fdt_addr,
>>>
>>> &fit_uname_fdt,
>>>
>>> &fit_uname_config,
>>> - arch,
>>> &load, &len);
>>> + arch,
>>> &load, &len, true);
>>
>> This flag is always true, do we actually need it ?
>>
>>> if (fdt_noffset < 0)
>>> return -ENOENT;
>>> diff --git a/boot/image-fit.c b/boot/image-fit.c
>>> index d2b0a7daccc..a3fa2a01463 100644
>>> --- a/boot/image-fit.c
>>> +++ b/boot/image-fit.c
>>> @@ -2370,7 +2370,8 @@ int boot_get_setup_fit(struct bootm_headers
>>> *images, uint8_t arch,
>>> #ifndef USE_HOSTCC
>>> int boot_get_fdt_fit(struct bootm_headers *images, ulong addr,
>>> const char **fit_unamep, const char
>>> **fit_uname_configp,
>>> - int arch, ulong *datap, ulong *lenp)
>>> + int arch, ulong *datap, ulong *lenp,
>>> + bool always_relocate_overlay)
>>> {
>>> int fdt_noffset, cfg_noffset, count;
>>> const void *fit;
>>> @@ -2492,11 +2493,21 @@ int boot_get_fdt_fit(struct bootm_headers
>>> *images, ulong addr,
>>> ov = map_sysmem(ovload, ovlen);
>>>
>>> ovcopylen = ALIGN(fdt_totalsize(ov), SZ_4K);
>>> - ovcopy = malloc(ovcopylen);
>>> - if (!ovcopy) {
>>> - printf("failed to duplicate DTO before
>>> application\n");
>>> - fdt_noffset = -ENOMEM;
>>> - goto out;
>>> + if (always_relocate_overlay) {
>>> + ovcopy = aligned_alloc(8, ovcopylen);
>>> + if (!ovcopy) {
>>> + printf("failed to allocate aligned
>>> DTO buffer\n");
>>> + fdt_noffset = -ENOMEM;
>>> + goto out;
>>> + }
>>> + memcpy(ovcopy, ov, ovlen);
>>> + } else {
>>> + ovcopy = malloc(ovcopylen);
>>> + if (!ovcopy) {
>>> + printf("failed to duplicate DTO
>>> before application\n");
>>> + fdt_noffset = -ENOMEM;
>>> + goto out;
>>> + }
>>
>> Looking at this, if the problem is $ov aligned to 4 Bytes, then $base
>> a
>> bit below could also be aligned to 4 Bytes if there are two or more
>> DTs
>> in the fitImage without external data. Can you please try the
>> attached
>> patch and see if that still works ?
>>
>> diff --git a/boot/image-fit.c b/boot/image-fit.c
>> index 3ed69b5f7bc..845e769a7e3 100644
>> --- a/boot/image-fit.c
>> +++ b/boot/image-fit.c
>> @@ -2368,6 +2368,48 @@ int boot_get_setup_fit(struct bootm_headers
>> *images, uint8_t arch,
>> }
>>
>> #ifndef USE_HOSTCC
>> +#ifdef CONFIG_OF_LIBFDT_OVERLAY
>> +static int boot_get_fdt_fit_into_buffer(ulong loadaddr, ulong
>> loadlen,
>> void **fdtdstbuf)
>> +{
>> + void *fdtsrcbuf, *map;
>> + ulong fdtdstlen;
>> + int err;
>> +
>> + map = map_sysmem(loadaddr, loadlen);
>> +
>> + /* Set up source buffer, make sure DT in the buffer is 8-
>> Bytes aligned */
>> + if (!IS_ALIGNED((uintptr_t)map, 8)) {
>> + fdtsrcbuf = aligned_alloc(8, loadlen);
>> + if (!fdtsrcbuf)
>> + return -ENOMEM;
>> + memcpy(fdtsrcbuf, map, loadlen);
>> + } else {
>> + fdtsrcbuf = map;
>> + }
>> +
>> + /* Set up destination buffer, make sure DT in the buffer is
>> 8-Bytes
>> aligned */
>> + fdtdstlen = ALIGN(fdt_totalsize(fdtsrcbuf), SZ_4K);
>> + fdtdstbuf = aligned_alloc(8, fdtdstlen);
>> + if (!fdtdstbuf) {
>> + printf("failed to duplicate DTO before
>> application\n");
>> + if (!IS_ALIGNED((uintptr_t)map, 8))
>> + free(fdtsrcbuf);
>> + return -ENOMEM;
>> + }
>> +
>> + err = fdt_open_into(fdtsrcbuf, *fdtdstbuf, fdtdstlen);
>> + if (!IS_ALIGNED((uintptr_t)map, 8))
>> + free(fdtsrcbuf);
>> + if (err < 0) {
>> + printf("failed on fdt_open_into for DTO: %s\n",
>> + fdt_strerror(err));
>> + return err;
>> + }
>> +
>> + return 0;
>> +};
>> +#endif
>> +
>> int boot_get_fdt_fit(struct bootm_headers *images, ulong addr,
>> const char **fit_unamep, const char
>> **fit_uname_configp,
>> int arch, ulong *datap, ulong *lenp)
>> @@ -2380,7 +2422,7 @@ int boot_get_fdt_fit(struct bootm_headers
>> *images,
>> ulong addr,
>> char *next_config = NULL;
>> ulong load, len;
>> #ifdef CONFIG_OF_LIBFDT_OVERLAY
>> - ulong ovload, ovlen, ovcopylen;
>> + ulong ovload, ovlen;
>> const char *uconfig;
>> const char *uname;
>> /*
>> @@ -2391,7 +2433,7 @@ int boot_get_fdt_fit(struct bootm_headers
>> *images,
>> ulong addr,
>> * Instead, let's be lazy and use void *.
>> */
>> char *of_flat_tree;
>> - void *base, *ov, *ovcopy = NULL;
>> + void *base, *ovcopy = NULL;
>> int i, err, noffset, ov_noffset;
>> #endif
>>
>> @@ -2489,17 +2531,7 @@ int boot_get_fdt_fit(struct bootm_headers
>> *images, ulong addr,
>> }
>> debug("%s loaded at 0x%08lx len=0x%08lx\n",
>> uname, ovload, ovlen);
>> - ov = map_sysmem(ovload, ovlen);
>> -
>> - ovcopylen = ALIGN(fdt_totalsize(ov), SZ_4K);
>> - ovcopy = malloc(ovcopylen);
>> - if (!ovcopy) {
>> - printf("failed to duplicate DTO before
>> application\n");
>> - fdt_noffset = -ENOMEM;
>> - goto out;
>> - }
>> -
>> - err = fdt_open_into(ov, ovcopy, ovcopylen);
>> + err = boot_get_fdt_fit_into_buffer(ovload, ovlen,
>> &ovcopy);
>> if (err < 0) {
>> printf("failed on fdt_open_into for DTO:
>> %s\n",
>> fdt_strerror(err));
>> @@ -2507,8 +2539,7 @@ int boot_get_fdt_fit(struct bootm_headers
>> *images,
>> ulong addr,
>> goto out;
>> }
>>
>> - base = map_sysmem(load, len + ovlen);
>> - err = fdt_open_into(base, base, len + ovlen);
>> + err = boot_get_fdt_fit_into_buffer(load, len + ovlen,
>> &base);
>> if (err < 0) {
>> printf("failed on fdt_open_into: %s\n",
>> fdt_strerror(err));
>> --
>> 2.51.0
> Thanks for the suggestion. I tested your patch and found that, although
> overlays are applied to aligned buffers, the CPU OPP overlay does not
> appear in the final device tree in Linux. With my previous patch above
> (the alignment fix), the OPP overlay works. It looks like the new
> buffer management breaks overlay chaining or the final DT pointer isn’t
> updated correctly, so overlays aren’t present in the running device
> tree.
> Let me know if you have suggestions for tracking the buffer or chaining
> overlays differently.
Maybe some memcpy is missing there somewhere ? Can you please have a
look and debug this a bit ?
Thank you
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