[Lldb-commits] [lldb] Read and store gnu build id from loaded core file (PR #92078)

[Pavel Labath via lldb-commits]

labath wrote:

> > Can we make this less brute force? I believe searching for the Build ID Note should be a completely deterministic process, without the need for heuristics. You start with the elf header, find the program headers, iterate to find the PT_NOTE segment (there could be more of them), and iterate over the notes until you find NT_GNU_BUILD_ID. All of these things should be in the memory (=> also in the core file) and within the first 4k of the mapping. There should be no need to search through a potentially huge file mapping just to see if it contains the build id.
> 
> Yes, we can parse the program headers. That is a good idea as long as all the info we need is mapped

It should all be there. In the files I looked at, both the program headers and all the note segments are in the first page of the mapping (which is the page containing the elf header). I can't find a reference for that now but I remember reading somewhere that this was intentional (to ensure the build id survives).

BTW, we have some elf parsing code in `NativeProcessELF::GetELFImageInfoAddress()`, that you could draw inspiration from.


https://github.com/llvm/llvm-project/pull/92078