how can I get elf type using c api

[lemon0910]

I can get elf type like:

readelf -h profile

ELF Header:

Type: DYN (Position-Independent Executable file)

It's very important to convert address to symbol.

but I read c api document https://docs.rs/blazesym-c/latest/blazesym_c/fn.blaze_inspect_syms_elf.html, I don't find api to get the type of elf files

[d-e-s-o]

Can you elaborate on your workflow, what you are trying to achieve, and why the ELF type would have relevance for that?

[lemon0910]

I write a progarm like profile (https://github.com/libbpf/libbpf-bootstrap/blob/master/examples/c/profile.c).

I want to profile c++ program.

The c++ program split debuginfo from binary : objcopy --only-keep-debug my_program my_program.debug

so I need:
1, call bpf_get_stack to get stack function adress.
2, convert function address to symbol using debuginfo.

In pharse 2, different elf type like ET_DYN or ET_EXEC have different way to convert.

For ET_EXEC type, I can directly convert using blaze_symbolize_elf_virt_offsets

For ET_DYN type, I need call blaze_normalize_user_addrs before blaze_symbolize_elf_virt_offsets

[d-e-s-o]

different elf type like ET_DYN or ET_EXEC have different way to convert.

I don't believe that is true, the mechanism is the same for all types.

For ET_EXEC type, I can directly convert using blaze_symbolize_elf_virt_offsets

bpf_get_stack should report absolute addresses, so you'd need process symbolization, which also normalizes addresses, in both cases. Yes, blaze_symbolize_elf_virt_offsets may work in some cases, but it's still not right.

Split debug info support has not yet been implemented for blazesym (#60). That being said, the objcopy way you outline above is basically just producing "regular" DWARF from what I understand -- just not inside the executable file itself. So you should be able to symbolize it once #634 lands: set a custom process dispatch function and then return an ElfResolver working on my_program my_program.debug.

[danielocfb]

So you should be able to symbolize it once #634 lands: set a custom process dispatch function and then return an ElfResolver working on my_program my_program.debug.

That change has landed.

Direct debug link support is out as well: #665