On Tue, Aug 12, 2014 at 1:10 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote: > On Tue, Aug 12, 2014 at 1:00 PM, Alexei Starovoitov <ast@xxxxxxxxxxxx> wrote: >> On Tue, Aug 12, 2014 at 12:32 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote: >>> On Thu, Jul 24, 2014 at 12:25 PM, Alexei Starovoitov <ast@xxxxxxxxxxxx> wrote: >>>> On Thu, Jul 24, 2014 at 11:25 AM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote: >>>>> On Thu, Jul 17, 2014 at 9:20 PM, Alexei Starovoitov <ast@xxxxxxxxxxxx> wrote: >>>>>> Safety of eBPF programs is statically determined by the verifier, which detects: >>>>>> - loops >>>>>> - out of range jumps >>>>>> - unreachable instructions >>>>>> - invalid instructions >>>>>> - uninitialized register access >>>>>> - uninitialized stack access >>>>>> - misaligned stack access >>>>>> - out of range stack access >>>>>> - invalid calling convention >>>>> >>>>> Is there something that documents exactly what conditions an eBPF >>>>> program must satisfy in order to be considered valid? >>>> >>>> I did a writeup in the past on things that verifiers checks and gave it >>>> to internal folks to review. Guys have said that now they understand very >>>> well how it works, but in reality it didn't help at all to write valid programs. >>>> What worked is 'verification trace' = the instruction by instruction dump >>>> of verifier state while it's analyzing the program. >>>> I gave few simple examples of it in >>>> 'Understanding eBPF verifier messages' section: >>>> https://git.kernel.org/cgit/linux/kernel/git/ast/bpf.git/diff/Documentation/networking/filter.txt?id=b22459133b9f52d2176c8c0f8b5eb036478a40c9 >>>> Every example there is what "program must satisfy to be valid"... >>>> >>>> Therefore I'm addressing two things: >>>> 1. how verifier works and what it checks for. >>>> that is described in 'eBPF verifier' section of the doc and >>>> in 200 lines of comments inside verifier.c >>> >>> That doc is pretty good. I'll try to read it carefully soon. Sorry >>> for the huge delay here -- I've been on vacation. >> >> I've been sitting on v4 for few weeks, since it's a merge window. >> So please hold on a careful review. I'll post v4 later today. >> Mainly I've split the verifier into several patches to make it >> easier to read. >> Thanks! > > Will you be at KS / LSS / LinuxCon? I would love to, but I didn't get an invite for KS. I'll be at plumbers in October. -- 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
