[BPF] Remove unused weak symbol __bpf_trap (#166003)

Nikita Popov reported an issue ([1]) where a dangling weak symbol
__bpf_trap is in the final binary and this caused libbpf failing like
below:

  $ veristat -v ./t.o
  Processing 't.o'...
  libbpf: elf: skipping unrecognized data section(4) .eh_frame
  libbpf: elf: skipping relo section(5) .rel.eh_frame for section(4) .eh_frame
  libbpf: failed to find BTF for extern '__bpf_trap': -3
  Failed to open './t.o': -3

In llvm, the dag selection phase generates __bpf_trap in code. Later the
UnreachableBlockElim pass removed __bpf_trap from the code, but
__bpf_trap symbol survives in the symbol table.

Having a dangling __bpf_trap weak symbol is not good for old kernels as
seen in the above veristat failure. Although users could use compiler
flag `-mllvm -bpf-disable-trap-unreachable` to workaround the issue,
this patch fixed the issue by removing the dangling __bpf_trap.

  [1] https://github.com/llvm/llvm-project/issues/165696

0 files changed, 0 insertions, 0 deletions