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. :) Thanks, Daniel
