[U-Boot] Board-specific commands unintentionally linked into SPL?

[Tyler Olmstead]

Hi Christian,

On Thu, Jul 26, 2012 at 10:03 AM, Christian Riesch
<christian.riesch at omicron.at> wrote:
>
> [cc'd Prabhakar Lad, Tom Rini, and Scott Wood]
>
> Tyler,
>
> On Thu, Jul 26, 2012 at 5:37 PM, Tyler Olmstead
> <tyler.j.olmstead at gmail.com> wrote:
> > Hi all,
> >
> > I have encountered some issues adding a board-specific command to the
> > board file of a project I have been working on. Specifically, after
> > adding a U-Boot shell command to my board file, I have been seeing
> > link-stage failures when attempting to build SPL.
>
> It's hard to tell without having your code, but I think this problem
> was already discussed in [1]. However I do not remember how Prabhakar
> solved it in the end.

Yes, I ran into this thread while debugging the problem, which
ultimately lead me to my solution. From that same thread [1], Wolfgang
Denk writes:

<quote>
>
> *I want to add a command using U_BOOT_CMD in uboot, where SPL_BUILD is
> enabled for example for da850evm in spl frame work how can i do that *

This makes no sense. Commands can only be executed when we have full
U-Boot running (actually even only after relocation).  You cannot run
commands in the SPL.
</quote>

I understand of course why it makes no sense to have command support
in the SPL. However, the crux of this problem is that U-Boot and SPL
both link in the same board object file, so in that sense compile-time
switches wont work. From later in [1], Scott Wood writes:

<quote>
> Maybe we should poke <command.h> to nop out U_BOOT_CMD for
> CONFIG_SPL_BUILD?  OTOH, #ifndef'ing U_BOOT_CMD and the code itself
> gets us a space savings we wouldn't get otherwise (I suspect giving
> the MTD/NAND issue I've mentioned before)...

Commands should be stripped out already with the new SPL -- that's what
the (unfortunately uncommented) sed command in GEN_UBOOT appears to be
doing.

-Scott
</quote>

Unfortunately, this is incorrect. From the ld man page [2]:

-u symbol
--undefined=symbol
           Force symbol to be entered in the output file as an
undefined symbol.  Doing this may, for example, trigger linking of
additional modules from standard libraries.  -u may be repeated with
different option arguments to enter additional undefined symbols.
This option is equivalent to the "EXTERN" linker script command.

Which means that the sed command in GEN_UBOOT in the SPL makefile
actually forces the *inclusion* of the command table, and therefore
forces the resolution of any undefined symbols in the command function
(hence my problem). This same command also appears in the top-level
U-Boot makefile, and I find it likely that it was included in the SPL
makefile as the result of a copy-paste error. This problem would only
arise for commands in object files that are linked into the SPL image,
such as the board file.

-- Tyler
[2] http://unixhelp.ed.ac.uk/CGI/man-cgi?ld

>
> In [1] I suggested to put an
>
> #ifndef CONFIG_SPL_BUILD
> U_BOOT_CMD(
> ...
> );
> #endif
>
> around the command definition in the board file. But also other
> solutions were discussed in that thread, please have a look.
>
> Regards, Christian
>
> [1] http://marc.info/?t=132748548900003
>
> >
> > <snip>
> >
> > UNDEF_SYM=`arm-arago-linux-gnueabi-objdump -x
> > /home/tolmstead/tolmstead_lab-OptiPlex-380/uboot/uboot_nand/spl/arch/arm/cpu/arm926ejs/davinci/libdavinci.o
> > /home/tolmstead/tolmstead_lab-OptiPlex-380/uboot/uboot_nand/spl/arch/arm/cpu/arm926ejs/libarm926ejs.o
> > /home/tolmstead/tolmstead_lab-OptiPlex-380/uboot/uboot_nand/spl/arch/arm/lib/libarm.o
> > /home/tolmstead/tolmstead_lab-OptiPlex-380/uboot/uboot_nand/spl/board/davinci/da8xxevm/libda8xxevm.o
> > /home/tolmstead/tolmstead_lab-OptiPlex-380/uboot/uboot_nand/spl/drivers/mtd/nand/libnand.o
> > /home/tolmstead/tolmstead_lab-OptiPlex-380/uboot/uboot_nand/spl/drivers/serial/libserial.o
> > /home/tolmstead/tolmstead_lab-OptiPlex-380/uboot/uboot_nand/spl/lib/libgeneric.o
> > | sed  -n -e 's/.*\(__u_boot_cmd_.*\)/-u\1/p'|sort|uniq`; cd
> > /home/tolmstead/tolmstead_lab-OptiPlex-380/uboot/uboot_nand/spl/ &&
> > arm-arago-linux-gnueabi-ld  -T
> > /home/tolmstead/tolmstead_lab-OptiPlex-380/uboot/uboot_nand/spl/u-boot-spl.lds
> > --gc-sections -Bstatic -Ttext 0xc1080000 $UNDEF_SYM
> > arch/arm/cpu/arm926ejs/start.o --start-group
> > arch/arm/cpu/arm926ejs/davinci/libdavinci.o
> > arch/arm/cpu/arm926ejs/libarm926ejs.o arch/arm/lib/libarm.o
> > board/davinci/da8xxevm/libda8xxevm.o drivers/mtd/nand/libnand.o
> > drivers/serial/libserial.o lib/libgeneric.o --end-group
> > /home/tolmstead/tolmstead_lab-OptiPlex-380/uboot/uboot_nand/spl/arch/arm/lib/eabi_compat.o
> > -L /usr/local/ti-sdk-am180x-evm/linux-devkit/bin/../lib/gcc/arm-arago-linux-gnueabi/4.3.3
> > -lgcc -Map u-boot-spl.map -o u-boot-spl
> > board/davinci/da8xxevm/libda8xxevm.o: In function `do_mycmd':
> > /home/tolmstead/tolmstead_lab-OptiPlex-380/uboot/uboot_nand/board/davinci/da8xxevm/awpb3.c:121:
> > undefined reference to `eth_get_dev_by_index'
> > /home/tolmstead/tolmstead_lab-OptiPlex-380/uboot/uboot_nand/board/davinci/da8xxevm/awpb3.c:123:
> > undefined reference to `eth_write_hwaddr'
> > /home/tolmstead/tolmstead_lab-OptiPlex-380/uboot/uboot_nand/board/davinci/da8xxevm/awpb3.c:126:
> > undefined reference to `printf'
> > make[1]: *** [/home/tolmstead/tolmstead_lab-OptiPlex-380/uboot/uboot_nand/spl/u-boot-spl]
> > Error 1
> > make[1]: Leaving directory
> > `/home/tolmstead/tolmstead_lab-OptiPlex-380/uboot/uboot_nand/spl'
> > make: *** [spl/u-boot-spl.bin] Error 2
> >
> > </snip>
> >
> > In the output above, one can see the environment variable $UNDEF_SYM
> > being defined as the result of the following SPL makefile
> > (spl/Makefile) target:
> >
> > GEN_UBOOT = \
> >         UNDEF_SYM=`$(OBJDUMP) -x $(LIBS) | \
> >         sed  -n -e 's/.*\($(SYM_PREFIX)__u_boot_cmd_.*\)/-u\1/p'|sort|uniq`;\
> >         cd $(obj) && $(LD) $(LDFLAGS) $(LDFLAGS_$(@F)) $$UNDEF_SYM $(__START) \
> >                 --start-group $(__LIBS) --end-group $(PLATFORM_LIBS) \
> >                 -Map u-boot-spl.map -o u-boot-spl
> >
> > $(obj)u-boot-spl:       depend $(START) $(LIBS) $(obj)u-boot-spl.lds
> >         $(GEN_UBOOT)
> >
> > For my target, $UNDEF_SYM expands to the following:
> > -u__u_boot_cmd_mycmd
> >
> > As I understand it, this is to force the inclusion of the commands
> > into the command table located in the special .u_boot_cmd section so
> > that unreferenced commands are not linked out of the final U-Boot
> > binary. However, I don't think that the inclusion of commands into the
> > SPL is intended. Removing the $UNDEF_SYM variable from the SPL
> > makefile resolves my build issues. I am planning on submitting a
> > patch. Does anyone see a flaw in my thinking?
> >
> > Thanks,
> > -- Tyler
> > _______________________________________________
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