[PATCH 1/1] arm: cpu: armv7m: add required .type name, %function directive

[Johannes Krottmayer]

Hi Tom!

Thanks for the quick response!

On 5/7/25 18:55, Tom Rini wrote:
> On Wed, May 07, 2025 at 06:07:54AM +0000, Johannes Krottmayer wrote:
> 
>> Since GNU binutils version 2.44, assembly functions must include
>> the assembler directive .type name, %function. If not a call to
>> these functions fails with the error message 'Unknown destination
>> type (ARM/Thumb)' and the error message 'dangerous relocation:
>> unsupported relocation' at linking.
>>
>> Signed-off-by: Johannes Krottmayer <johannes at krotti42.com>
>> Cc: Tom Rini <trini at konsulko.com>
>> ---
>>   arch/arm/cpu/armv7m/start.S | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/arch/arm/cpu/armv7m/start.S b/arch/arm/cpu/armv7m/start.S
>> index 0c07f2140c7..c20f01a0aed 100644
>> --- a/arch/arm/cpu/armv7m/start.S
>> +++ b/arch/arm/cpu/armv7m/start.S
>> @@ -12,5 +12,6 @@ reset:
>>   	W(b)	_main
>>   
>>   .globl	c_runtime_cpu_setup
>> +.type c_runtime_cpu_setup, %function
>>   c_runtime_cpu_setup:
>>   	mov	pc, lr
> 
> Thanks for making the patch. There's an argument that this should use
> the ENTRY / ENDPROC macros from <linux/linkage.h> but that also shows
> that we're missing commit 5d4cae5fe2ea ("[ARM] VFP: fix section mismatch
> error") from the kernel. And so I'm fine with making a TODO to clean
> this up later if you don't want to embark on something a bit more
> complicated here.
> 

No problem for me to creating my simple patch. It's also not a problem
for me to use the required macros (ENTRY, ENDPROC). Use some similar
macros on my own projects too.

I have searched for your mentioned commit from Linux, and it's okay
when I try to add this too in further patches. For the correct
initialization from the floating point unit I must look more
precisely into the U-Boot and Linux source code.

But I have a question according the ENPROC macro:

include/linux/linkage.h (from U-Boot):
#ifndef ENDPROC
#define ENDPROC(name) \
	.type name STT_FUNC ASM_NL \
	END(name)
#endif

Especially the macro/define STT_FUNC. I have thought STT_FUNC is
%function, but haven't found these in the current U-Boot master
branch.

Simple search with grep on the shell:
"
jk at workstation:~/Projects/U-Boot/src> grep -R STT_FUNC
include/linux/linkage.h:        .type name STT_FUNC ASM_NL \
include/elf.h:#define STT_FUNC  2               /* function */
jk at workstation:~/Projects/U-Boot/src>
"

Also tried a much more comfortable search with the elixir.bootlin
identifier search. As you can see STT_FUNC is defined only in the
ELF header. 'include/linux/linkage.h' doesn't include the ELF
header. And I don't know if the value 2 for STT_FUNC is an alternative
usage from the .type directive. 'include/linux/linkage.h' includes
'asm/linkage.h'. I'm still a newbie with the U-Boot build process
and I think on build the machine dependent header will included
(arch/arm/include/linkage.h). Correct me if I'm wrong please.
Also there will be elf.h not included.

Maybe the STT_FUNC will defined in build process, but shouldn't
I find this in a specific Makefile with a simple search with grep?

By the I could change STT_FUNC to %function, but I didn't know
(not tried yet) if this has other bad effects.

Thanks in advance!

Kind regards,

Johannes