On Fri, Aug 15, 2014 at 11:56 AM, Alexei Starovoitov <ast@xxxxxxxxxxxx> wrote: > On Fri, Aug 15, 2014 at 11:50 AM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote: >> On Aug 15, 2014 10:36 AM, "Alexei Starovoitov" <ast@xxxxxxxxxxxx> wrote: >>> >>> On Fri, Aug 15, 2014 at 10:20 AM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote: >>> > The downside of this approach is that compat support might be >>> > difficult or impossible. >>> >>> Would do you mean by compat? 32-bit programs on 64-bit kernels? >>> There is no such concept for eBPF. All eBPF programs are always >>> operating on 64-bit registers. >> >> Doesn't the eBPF program need to know sizeof(long) to read these >> fields correctly? Or am I misunderstanding what the code does? > > correct. eBPF program would be using 8-byte read on 64-bit kernel > and 4-byte read on 32-bit kernel. Same with access to ptrace fields > and pretty much all other fields in the kernel. The program will be > different on different kernels. > Say, this bpf_context struct doesn't exist at all. The programs would > still need to be different to walk in-kernel data structures... Hmm. I guess this isn't so bad. What's the actual difficulty with using u64? ISTM that, if the clang front-end can't deal with u64, there's a bigger problem. Or is it something else I don't understand. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
