[PATCH v2 2/2] kbuild: Use relative paths in generated .incbin directives

[Simon Glass]

Hi Rasmus,

On Fri, 27 Mar 2026 at 04:27, Rasmus Villemoes <ravi at prevas.dk> wrote:
>
> On Fri, Mar 27 2026, Rasmus Villemoes <ravi at prevas.dk> wrote:
>
> > On Thu, Mar 26 2026, Simon Glass <sjg at chromium.org> wrote:
> >
> >> The generated .S files for fonts and splash screens use .incbin with the
> >> full prerequisite path. When building with O= this bakes an absolute
> >> path into the .S file. If the build directory is later used on a
> >> different machine (e.g. in a container), the assembler cannot find the
> >> source file.
> >
> > I must be missing something, because I can't see how this can be a
> > problem, while all the other absolute paths to the source dir that go
> > into files generated in the build directory is not. For example, there's
> > a top-level "source -> /path/to/u-boot" symlink created, and as far as I
> > can tell, all the .foo.o.cmd files end up full of such references as
> > well, e.g. $BUILD/lib/.vsprintf.o.cmd contains
> >
> > source_lib/vsprintf.o := /path/to/u-boot/lib/vsprintf.c

Thanks for looking at this.

When I build outside the container and then build inside I get:
$ um -n b sandbox
buildman -L -I -w -W --boards sandbox -o /tmp/b/sandbox
$ um b sandbox
drivers/video/fonts/cantoraone_regular.S: Assembler messages:
drivers/video/fonts/cantoraone_regular.S:5: Error: file not found:
/home/sglass/files.local/u-boot/drivers/video/fonts/cantoraone_regular.ttf
make[4]: *** [scripts/Makefile.build:344:
drivers/video/fonts/cantoraone_regular.o] Error 1
drivers/video/fonts/nimbus_sans_l_regular.S: Assembler messages:
drivers/video/fonts/nimbus_sans_l_regular.S:5: Error: file not found:
/home/sglass/files.local/u-boot/drivers/video/fonts/nimbus_sans_l_regular.ttf
make[4]: *** [scripts/Makefile.build:344:
drivers/video/fonts/nimbus_sans_l_regular.o] Error 1
make[3]: *** [scripts/Makefile.build:492: drivers/video/fonts] Error 2
drivers/video/u_boot_logo.S: Assembler messages:
drivers/video/u_boot_logo.S:5: Error: file not found:
/home/sglass/files.local/u-boot/drivers/video/u_boot_logo.bmp
make[3]: *** [scripts/Makefile.build:344: drivers/video/u_boot_logo.o] Error 1
make[2]: *** [scripts/Makefile.build:492: drivers/video] Error 2
make[1]: *** [Makefile:2201: drivers] Error 2
make: *** [Makefile:189: __sub-make] Error 2
drivers/video/fonts/cantoraone_regular.S: Assembler messages:
drivers/video/fonts/cantoraone_regular.S:5: Error: file not found:
/home/sglass/files.local/u-boot/drivers/video/fonts/cantoraone_regular.ttf
make[4]: *** [scripts/Makefile.build:344:
drivers/video/fonts/cantoraone_regular.o] Error 1
drivers/video/fonts/nimbus_sans_l_regular.S: Assembler messages:
drivers/video/fonts/nimbus_sans_l_regular.S:5: Error: file not found:
/home/sglass/files.local/u-boot/drivers/video/fonts/nimbus_sans_l_regular.ttf
make[4]: *** [scripts/Makefile.build:344:
drivers/video/fonts/nimbus_sans_l_regular.o] Error 1
make[3]: *** [scripts/Makefile.build:492: drivers/video/fonts] Error 2
drivers/video/u_boot_logo.S: Assembler messages:
drivers/video/u_boot_logo.S:5: Error: file not found:
/home/sglass/files.local/u-boot/drivers/video/u_boot_logo.bmp
make[3]: *** [scripts/Makefile.build:344: drivers/video/u_boot_logo.o] Error 1
make[2]: *** [scripts/Makefile.build:492: drivers/video] Error 2
make[1]: *** [Makefile:2201: drivers] Error 2
make: *** [Makefile:189: __sub-make] Error 2

If I then do a fresh build inside the container, then build outside, I get:

$ um b sandbox
drivers/video/fonts/cantoraone_regular.S: Assembler messages:
drivers/video/fonts/cantoraone_regular.S:5: Error: file not found:
/home/ubuntu/project/drivers/video/fonts/cantoraone_regular.ttf
make[4]: *** [scripts/Makefile.build:344:
drivers/video/fonts/cantoraone_regular.o] Error 1
drivers/video/fonts/nimbus_sans_l_regular.S: Assembler messages:
drivers/video/fonts/nimbus_sans_l_regular.S:5: Error: file not found:
/home/ubuntu/project/drivers/video/fonts/nimbus_sans_l_regular.ttf
make[4]: *** [scripts/Makefile.build:344:
drivers/video/fonts/nimbus_sans_l_regular.o] Error 1
make[3]: *** [scripts/Makefile.build:492: drivers/video/fonts] Error 2
make[2]: *** [scripts/Makefile.build:492: drivers/video] Error 2
make[1]: *** [Makefile:2201: drivers] Error 2
make: *** [Makefile:189: __sub-make] Error 2
drivers/video/fonts/cantoraone_regular.S: Assembler messages:
drivers/video/fonts/cantoraone_regular.S:5: Error: file not found:
/home/ubuntu/project/drivers/video/fonts/cantoraone_regular.ttf
make[4]: *** [scripts/Makefile.build:344:
drivers/video/fonts/cantoraone_regular.o] Error 1
drivers/video/fonts/nimbus_sans_l_regular.S: Assembler messages:
drivers/video/fonts/nimbus_sans_l_regular.S:5: Error: file not found:
/home/ubuntu/project/drivers/video/fonts/nimbus_sans_l_regular.ttf
make[4]: *** [scripts/Makefile.build:344:
drivers/video/fonts/nimbus_sans_l_regular.o] Error 1
make[3]: *** [scripts/Makefile.build:492: drivers/video/fonts] Error 2
make[2]: *** [scripts/Makefile.build:492: drivers/video] Error 2
make[1]: *** [Makefile:2201: drivers] Error 2
make: *** [Makefile:189: __sub-make] Error 2

>
> OK, I can sort-of reproduce, though I don't know if what I did is
> representable for your use case. No containers involved, just moved the
> source directory.
>
>   # original source dir
>   $ cd /tmp/u-boot
>   $ make O=/tmp/build sandbox_defconfig
>   $ make O=/tmp/build -j7
>   $ cd /tmp ; mv u-boot u-boot-new ; cd u-boot-new
>   $ make O=/tmp/build -j7
>
> This breaks as you describe, but most files simply get rebuilt due to
> their .cmd files containing stale references to /tmp/u-boot/. Which
> suggests that the bug is really the lack of a .S.cmd file describing how
> the .S file was created in the first place.
>
> This seems to be a better fix, which also causes the .S files to be
> generated anew if one does some actual change to the rule:
>
> diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> index 7386353e0cc..b2441080e7e 100644
> --- a/scripts/Makefile.lib
> +++ b/scripts/Makefile.lib
> @@ -526,8 +526,8 @@ cmd_S_ttf=                                          \
>         echo '.balign 16';                              \
>  ) > $@
>
> -$(obj)/%.S: $(src)/%.ttf
> -       $(call cmd,S_ttf)
> +$(obj)/%.S: $(src)/%.ttf FORCE
> +       $(call if_changed,S_ttf)
>
>  # Splash logos
>  # ---------------------------------------------------------------------------
> @@ -547,8 +547,8 @@ cmd_S_splash=                                               \
>         echo '.balign 16';                              \
>  ) > $@
>
> -$(obj)/%.S: $(src)/%.bmp
> -       $(call cmd,S_splash)
> +$(obj)/%.S: $(src)/%.bmp FORCE
> +       $(call if_changed,S_splash)
>
>  # EFI applications
>  # A Makefile target *.efi is built as EFI application.
>
> See e.g. kernel commit a7f9241909 which did essentially the same change
> to the .dtb -> .S rule back in 2018.
>
> It still makes sense to put these rules in a u-boot specific makefile,
> but this should avoid the need for each font .o file to need those
> AFLAGS changes.

Sure, but it causes the font/logo .S files to be rebuilt on every make
invocation. How did you test this?

It would be nice to use if_changed though. It needs the .cmd file to
be loaded via -include, which only happens for files in the targets
variable. The generated .S files are never added to targets, so cmd_$@
is always empty and if_changed always rebuilds.

The kernel commit you referenced (a7f9241909) works for DTB because
.dtb.o has a compound suffix with a matching intermediate_targets
entry. We could follow the same convention, renaming to .ttf.o/.bmp.o
and adding:

targets += $(call intermediate_targets, .ttf.o, .ttf.S) \
           $(call intermediate_targets, .bmp.o, .bmp.S)

The pattern stem stays the same, so symbol names are unaffected. What
do you think?

Regards,
Simon