On 8/24/20 5:05 PM, Hao Luo wrote:
Yonghong, An update on this thread. I successfully reproduced this issue on a 8.2.0 gcc compiler, It looks like gcc 4.9 did not have this issue. I was also using clang which did not show this bug. It seems having a DW_AT_specification that refers to another DW_TAG_variable isn't handled in pahole. I have a (maybe hacky) pahole patch as fix and let me clean it up and post for review soon.
Sounds good. Thanks for fixing it in pahole! People may use gcc 4.9 up to gcc 10, or llvm compiler (let us say llvm10 which is the version which has CO-RE support and is recommended for compiling bpf
programs.) Once you have fix for gcc 8.2, it might be worthwhile to check a few other gcc/llvm version (at least gcc8/9/10 and llvm10) to ensure it still works. Currently, by default kernel is using DWARF2, pahole has a good support for dwarf2. I am not sure whether it supports dwarf4 well or not. But I think additional dwarf4 support, if needed, can be done a little bit later as dwarf4 is not widely used yet for kernel, I think.
Hao
