Hello, We recently bumped LLVM used for bpftool compilation from 15 to 18 and our alerting system notified us about some unknown bpf programs. It turns out, the names were truncated to 15 chars, whereas before they were longer. After some investigation, I was able to see that the following code: diff --git a/src/common.c b/src/common.c index 958e92a..ac38506 100644 --- a/src/common.c +++ b/src/common.c @@ -435,7 +435,9 @@ void get_prog_full_name(const struct bpf_prog_info *prog_info, int prog_fd, if (!prog_btf) goto copy_name; + printf("[0] finfo.type_id = %x\n", finfo.type_id); func_type = btf__type_by_id(prog_btf, finfo.type_id); + printf("[1] finfo.type_id = %x\n", finfo.type_id); if (!func_type || !btf_is_func(func_type)) goto copy_name; When ran under gdb, shows: (gdb) b common.c:439 Breakpoint 1 at 0x16859: file common.c, line 439. (gdb) r 3403: tracing [0] finfo.type_id = 0 Breakpoint 1, get_prog_full_name (prog_info=0x7fffffffe160, prog_fd=3, name_buff=0x7fffffffe030 "", buff_len=128) at common.c:439 439 func_type = btf__type_by_id(prog_btf, finfo.type_id); (gdb) print finfo $1 = {insn_off = 0, type_id = 1547} Notice that finfo.type_id is printed as zero, but in gdb it is in fact 1547. Disassembly difference looks like this: - 8b 75 cc mov -0x34(%rbp),%esi - e8 47 8d 02 00 call 3f5b0 <btf__type_by_id> + 31 f6 xor %esi,%esi + e8 a9 8c 02 00 call 3f510 <btf__type_by_id> This can be avoided if one removes "const" during finfo initialization: const struct bpf_func_info finfo = {}; This seems like a pretty annoying miscompilation, and hopefully there's a way to make clang complain about this loudly, but that's outside of my expertise. There might be other places like this that we just haven't noticed yet. I can send a patch to fix this particular issue, but I'm hoping for a more comprehensive approach from people who know better. Thanks.