[PATCH 1/1] arm: separate .data and .text sections of EFI binaries

[Heinrich Schuchardt]

On 2/24/24 10:16, Heinrich Schuchardt wrote:
> On 2/16/24 11:35, Ilias Apalodimas wrote:
>> Hi Heinrich,
>>
>> [...]
>>
>>>          }
>>> +       .rela.dyn : { *(.rela.dyn) }
>>> +       .rela.plt : { *(.rela.plt) }
>>> +       .rela.got : { *(.rela.got) }
>>> +       .rela.data : { *(.rela.data) *(.rela.data*) }
>>
>> Why are we switching from Rel to Rela?
> 
> This was wrong.
> 
> Looking at the u-boot ELF binary we see these relocation sections:
> 
> arm: .rel.dyn
> arm64: .rela.dyn
> riscv64: .rela.dyn
> 
> In our EFI object files we currently have no relocations. This is why 
> tests did not complain.
> 
> In arch/arm/lib/reloc_arm_efi.c we handle DT_REL.
> In arch/arm/lib/reloc_aarch64_efi.c we handle DT_RELA.
> In arch/riscv/lib/reloc_riscv_efi.c we handle DT_RELA.

To be truthful our generated binaries are only usable because we have no 
relocations.

If we had relocations, copying these to the .text or .data section would 
would not work. We would have to translate them to the relocation format 
of PE files and put them into the .reloc section like EDK II does in 
BaseTools/Source/C/GenFw/Elf32Convert.c.

Best regards

Heinrich

> 
> Best regards
> 
> Heinrich
> 
>>
>>>          _etext = .;
>>>          _text_size = . - _text;
>>> -       .dynamic  : { *(.dynamic) }
>>> +       . = ALIGN(4096);
>>>          .data : {
>>>                  _data = .;
>>>                  *(.sdata)
>>> @@ -47,20 +59,19 @@ SECTIONS
>>>                  . = ALIGN(512);
>>>                  _bss_end = .;
>>>                  _edata = .;
>>> -       }
>>> -       .rel.dyn : { *(.rel.dyn) }
>>> -       .rel.plt : { *(.rel.plt) }
>>> -       .rel.got : { *(.rel.got) }
>>> -       .rel.data : { *(.rel.data) *(.rel.data*) }
>>> -       _data_size = . - _etext;
>>> +       } :data
>>> +       _data_size = _edata - _data;
>>>
>>> +       . = ALIGN(4096);
>>> +       .dynsym   : { *(.dynsym) }
>>> +       . = ALIGN(4096);
>>> +       .dynstr   : { *(.dynstr) }
>>> +       . = ALIGN(4096);
>>> +       .note.gnu.build-id : { *(.note.gnu.build-id) }
>>>          /DISCARD/ : {
>>>                  *(.rel.reloc)
>>>                  *(.eh_frame)
>>>                  *(.note.GNU-stack)
>>> -               *(.dynsym)
>>> -               *(.dynstr)
>>> -               *(.note.gnu.build-id)
>>> -               *(.comment)
>>>          }
>>> +       .comment 0 : { *(.comment) }
>>>   }
>>> -- 
>>> 2.43.0
>>>
>>
>> Cheers
>> /Ilias
>