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? --Andy -- Andy Lutomirski AMA Capital Management, LLC -- 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
