[PATCH] bpf: Added linker support for R_BPF_64_NODYLD32.

[Cupertino Miranda]

Thanks! Committed.

Jose E. Marchesi writes:

> Hi Cuper.
> OK, thanks.
>
>> Hi Jose,
>>
>> Thanks for your review.
>> I realized I missed to update the macro for the relocation where the
>> properties like size, overflow check, (etc.) are defined.
>> I have added the comment near the relocation macro definition.
>>
>> Sending the patch for review once again.
>>
>> Regards,
>> Cupertino
>>
>> From bb8afde9a8f17d42393067c3a667bec1f08b252a Mon Sep 17 00:00:00 2001
>> From: Cupertino Miranda <cupertino.miranda@oracle.com>
>> Date: Wed, 20 Dec 2023 12:24:03 +0000
>> Subject: [PATCH] bpf: Added linker support for R_BPF_64_NODYLD32.
>>
>> This patch adds linker support to patch R_BPF_64_NODYLD32 relocations.
>> The implementation was based on comments and code in LLVM, as the GNU
>> toolchain does not uses this relocation type.
>> ---
>>  bfd/bpf-reloc.def | 17 ++++++++++-------
>>  bfd/elf64-bpf.c   |  1 +
>>  2 files changed, 11 insertions(+), 7 deletions(-)
>>
>> diff --git a/bfd/bpf-reloc.def b/bfd/bpf-reloc.def
>> index 7e7497892fa..42ba1a169ea 100644
>> --- a/bfd/bpf-reloc.def
>> +++ b/bfd/bpf-reloc.def
>> @@ -90,17 +90,20 @@
>>
>>    /* R_BPF_64_NODYLD32 is not used by GNU tools - but it is generated by LLVM.
>>       We provide an entry here so that tools like strip can safely handle BPF
>> -     binaries generated by other tools.  */
>> +     binaries generated by other tools.
>> +     R_BPF_64_NODYLD32 should be fixed at linker like a R_BPF_64_ABS32.
>> +     The difference to ABS32 is that LLVM execution engine does not resolve
>> +     R_BPF_64_NODYLD32 relocations.  */
>>    BPF_HOWTO (R_BPF_64_NODYLD32,	/* type */
>>  	 0,			/* rightshift */
>> -	 0,			/* size */
>> -	 0,			/* bitsize */
>> +	 4,			/* size */
>> +	 32,			/* bitsize */
>>  	 false,			/* pc_relative */
>>  	 0,			/* bitpos */
>> -	 complain_overflow_dont, /* complain_on_overflow */
>> +	 complain_overflow_bitfield, /* complain_on_overflow */
>>  	 bpf_elf_generic_reloc, /* special_function */
>>  	 "R_BPF_64_NODYLD32",	/* name */
>>  	 false,			/* partial_inplace */
>> -	 0,			/* src_mask */
>> -	 0,			/* dst_mask */
>> -	 false)			/* pcrel_offset */
>> +	 0xffffffff,		/* src_mask */
>> +	 0xffffffff,		/* dst_mask */
>> +	 true)			/* pcrel_offset */
>> diff --git a/bfd/elf64-bpf.c b/bfd/elf64-bpf.c
>> index c932a4024ba..0bffe2c5717 100644
>> --- a/bfd/elf64-bpf.c
>> +++ b/bfd/elf64-bpf.c
>> @@ -276,6 +276,7 @@ bpf_elf_relocate_section (bfd *output_bfd ATTRIBUTE_UNUSED,
>>            }
>>  	case R_BPF_64_ABS64:
>>  	case R_BPF_64_ABS32:
>> +	case R_BPF_64_NODYLD32:
>>  	  {
>>  	    addend = bfd_get (howto->bitsize, input_bfd, where);
>>  	    relocation += addend;