Hello,

I was wondering if BCC implements the new BPF feature (as of kernel 5.10) to allow BPF programs to utilize both BPF tail calls and BPF subprograms. This behavior is described near the end of this section of the BPF reference guide. I am interested in this functionality to extend a BPF program in order to reach the limit of 8KB of stack space.

Thanks,

Jake

On Wed, Feb 24, 2021 at 12:24 PM <jwkova@...> wrote:

Hello,

I was wondering if BCC implements the new BPF feature (as of kernel 5.10) to allow BPF programs to utilize both BPF tail calls and BPF subprograms. This behavior is described near the end of this section of the BPF reference guide. I am interested in this functionality to extend a BPF program in order to reach the limit of 8KB of stack space.

You can use bpf tail calls today. You can look at
bcc/tests/cc/test_prog_table.cc for an example. bcc does not support
subprogram yet. In the future we do plan to be more libbpf compatible
so we can use those features.
BTW, the stack limit is 512 bytes not 8KB.

Thanks,

Jake