Re: [PATCH v2 dwarves 2/5] btf_encoder: Add true_signature feature support for "."-suffixed functions

Yonghong Song
2026-01-23T19:05:47Z

On 1/23/26 9:26 AM, Alan Maguire wrote:
> Currently we collate function information by name and add functions
> provided there are no inconsistencies across various representations.
>
> For true_signature support - where we wish to add the real signature
> of a function even if it differs from source level - we need to do
> a few things:
>
> 1. For "."-suffixed functions, we need to match from DWARF->ELF;
> we can do this via the address associated with the function.
> In doing this, we can then be confident that the debug info
> for foo.isra.0 is the right info for the function at that
> address.
>
> 2. When adding saved functions we need to look for such cases
> and provided they do not violate other constraints around BTF
> representation - unexpected reg usage for function, uncertain
> parameter location or ambiguous address - we add them with
> their "."-suffixed name. The latter can be used as a signal
> that the function is transformed from the original.
>
> Doing this adds 500 functions to BTF. These are traceable with
> their "."-suffix names and because we have excluded ambiguous
> address cases we know exactly which function address they refer
> to.
>
> Signed-off-by: Alan Maguire <alan.maguire@oracle.com>

Acked-by: Yonghong Song <yonghong.song@linux.dev>