Re: [PATCH bpf-next] docs/bpf: add llvm_reloc.rst to explain llvm bpf relocations

[Yonghong Song <yhs@fb.com>]

On 5/22/21 9:39 AM, Yonghong Song wrote:
> LLVM upstream commit https://reviews.llvm.org/D102712
> made some changes to bpf relocations to make them
> llvm linker lld friendly. The scope of
> existing relocations R_BPF_64_{64,32} is narrowed
> and new relocations R_BPF_64_{ABS32,ABS64,NODYLD32}
> are introduced.

Daniel, John and Lorenz,

Could you help check how the new relocation scheme
may impact you? libbpf has a similar issue and is fixed by
   https://lore.kernel.org/bpf/20210522162341.3687617-1-yhs@fb.com/
In most cases, you should just change relocation enum number,
no relocation resolution is changed.

Please let me know. Thanks!

> 
> Let us add some documentation about llvm bpf
> relocations so people can understand how to resolve
> them properly in their respective tools.
> 
> Cc: John Fastabend <john.fastabend@gmail.com>
> Cc: Lorenz Bauer <lmb@cloudflare.com>
> Signed-off-by: Yonghong Song <yhs@fb.com>
> ---
>   Documentation/bpf/index.rst      |   1 +
>   Documentation/bpf/llvm_reloc.rst | 168 +++++++++++++++++++++++++++++++
>   2 files changed, 169 insertions(+)
>   create mode 100644 Documentation/bpf/llvm_reloc.rst
> 
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