On 3/1/19 12:06 PM, Daniel Borkmann wrote: > On 03/01/2019 08:19 PM, Yonghong Song wrote: >> On 3/1/19 11:10 AM, Andrii Nakryiko wrote: >>> On Fri, Mar 1, 2019 at 10:58 AM Yonghong Song <yhs@xxxxxx> wrote: >>>> On 3/1/19 10:48 AM, Andrii Nakryiko wrote: >>>>> On Fri, Mar 1, 2019 at 10:31 AM Yonghong Song <yhs@xxxxxx> wrote: >>>>>> On 2/28/19 3:18 PM, Daniel Borkmann wrote: > [...] >>>>> Would it be reasonable to just plain disable usage of uninitialized >>>>> global variables, as it kind of goes against BPF's philosophy that >>>>> everything should be written to, before can be read? So while we can >>>>> just implicitly zero-out everything beforehand, it might be a good >>>>> idea to remind and enforce that explictly? >>>> >>>> There will be a verifier error, so the program with "int g" will not >>>> run, the same as today. >>> >>> Yeah, I understand, but with pretty obscure error about not supporting >>> relocations and stuff, right? >>> >>>> >>>> We could improve by flagging the error at compiler error or libbpf time. >>> >>> So that's my point, that having compiler emit nicer error for >>> target=bpf would be nice touch to user experience :) >> >> I just removed a compiler error for static variables... >> >> I will wait for this patch lands, hear people complains (either need to >> support "int g;" or need better error messages, etc.) and then decide >> what next to do ... > > By the way, from LLVM side, do you think it makes sense for local vars > where you encode the offset into insn->imm to already encode it into > (insn+1)->imm of the ldimm64, so that loaders can just pass this offset > through instead of fixing it up like I did? I'm fine either way though, > just thought might be worth pointing out while we're at it. :) Yes, llvm can do that. Let me prototype it and will let you know if it landed in llvm trunk. > > Thanks, > Daniel >
