Re: [PATCH V4 1/8] spl: guard u_boot_any with X86

[Alper Nebi Yasak <alpernebiyasak@gmail.com>]

On 21/05/2022 15:05, Tom Rini wrote:
> On Sat, May 21, 2022 at 08:33:56AM +0000, Peng Fan wrote:
>>> Subject: Re: [PATCH V4 1/8] spl: guard u_boot_any with X86
>>>
>>> On Fri, May 20, 2022 at 10:10:40PM +0800, Peng Fan (OSS) wrote:
>>>
>>>> From: Peng Fan <peng.fan@nxp.com>
>>>>
>>>> set the symbol as weak not work if LTO is enabled. Since u_boot_any is
>>>> only used on X86 for now, so guard it with X86, otherwise build break
>>>> if we use BINMAN_SYMBOLS on i.MX.
>>>>
>>>> Tested-by: Tim Harvey <tharvey@gateworks.com> #imx8m[m,n,p]-venice
>>>> Signed-off-by: Peng Fan <peng.fan@nxp.com>
>>>> ---
>>>>  common/spl/spl.c     | 8 ++++++--
>>>>  common/spl/spl_ram.c | 4 ++++
>>>>  2 files changed, 10 insertions(+), 2 deletions(-)
>>>
>>> I think we long term need to figure this out and address it so LTO works.  But
>>> for now can you please guard this with a test on LTO instead, so it's clear
>>> where the problem is?
>>
>> Sorry, I could not get your point about guard with a test on LTO.
>>
>> Actually binman weak symbol will report a warning log if there is no u_boot_any
>> binman symbol. Since only X86 use it, I guard with X86.
> 
> Why are you mentioning LTO in the commit message?  When I read the
> commit message it sounds like you're saying the problem is that LTO
> doesn't like how this symbol is handled, but if LTO was disabled,
> everything would be fine.  If it's not LTO-related, please re-word the
> message instead.

It looks like we should be able to change things in common/spl/spl.c to:

    #if CONFIG_IS_ENABLED(BINMAN_SYMBOLS)
    /* See spl.h for information about this */
    binman_sym_declare_optional(ulong, u_boot_any, image_pos);
    binman_sym_declare_optional(ulong, u_boot_any, size);
    #endif

which would mark the symbol as 'weak' and turn the error into a warning
on the binman side. But that is somehow being undone by LTO.

I'm trying to build for imx8mm-beacon with that change instead of this
patch. With CONFIG_LTO=y, build fails and spl/u-boot-spl.sym has:

> 00000000007fbe28 l     O .binman_sym	0000000000000008 _binman_u_boot_any_prop_image_pos

Looks like the size symbol is optimized out. With CONFIG_LTO unset, the
build succeeds and the same file has:

> 00000000007fe90c  w    O .binman_sym	0000000000000008 _binman_u_boot_any_prop_image_pos
> 00000000007fe904  w    O .binman_sym	0000000000000008 _binman_u_boot_any_prop_size

I don't know much about linking stuff, so this is as deep as I could dig...