Re: [PATCH] bpf: Added linker support for R_BPF_64_NODYLD32.

["Jose E. Marchesi" <jose.marchesi@oracle.com>]

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;