[PATCH] boot: image-fit: Add runtime flag to always relocate overlays
Jamie.Gibbons at microchip.com
Jamie.Gibbons at microchip.com
Thu Feb 12 13:50:03 CET 2026
Hi Marek, all,
On Tue, 2026-02-10 at 14:41 +0100, Marek Vasut wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you
> know the content is safe
>
> On 2/10/26 1:28 PM, Marek Vasut wrote:
> > 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 ?
>
> Also, can you reproduce this in sandbox ? Can you share such a
> reproducer ?
This patch is no longer needed as the issue this was working to fix has
been fixed by James' patch: [PATCH v4 1/1] image: fit: Apply overlays
using aligned writable FDT copies. Tested and confirmed.
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