[llvm-dev] bpf compilation using clang

[Sameeh Jubran via llvm-dev]

Ping.
On Sun, Sep 16, 2018 at 11:30 AM Sameeh Jubran <sameeh at daynix.com> wrote:
>
> ping?
> Who is maintaining bpf compilation
> On Thu, Sep 13, 2018 at 12:58 PM Sameeh Jubran <sameeh at daynix.com> wrote:
> >
> > Hi all,
> >
> > I am trying to insert instructions into the bpf using the bpf syscall,
> > the instructions were generated using the following command line:
> >
> > clang -I ~/Builds/bpf_rss/iproute2/include -Wall -target bpf -O2
> > -emit-llvm -c upstream/qemu/hw/net/rss_tap_bpf_program.c -o - | llc
> > -march=bpf -filetype=obj -o tap_bpf_program.o
> >
> > and then were translated to bpf instructions using the BPFCparser tool
> >
> > Every time I try to insert the array of instructions the verfier fails
> > with the following error:
> >
> > back-edge from insn 363 to 364
> >
> > or something similar even though the compilation succeeds.
> >
> > I have multiple maps in my code and I translate only the code section
> > to bpf insns structure and insert it using the bpf syscall as follows:
> >
> >     memset(&attr, 0, sizeof(attr));
> >     attr.prog_type = BPF_PROG_TYPE_SOCKET_FILTER;
> >     attr.insn_cnt = ARRAY_SIZE(l3_l4_hash_insns);
> >     attr.insns = (__u64) (unsigned long) (l3_l4_hash_insns);
> >     attr.license = (__u64) (unsigned long) ("Dual BSD/GPL");
> >     attr.log_buf = (__u64) (unsigned long) (buffer);
> >     attr.log_level = 7;
> >     attr.log_size = BUFF_LEN;
> >     attr.kern_version = 0;
> >
> >     ret = sys_bpf(BPF_PROG_LOAD, &attr, sizeof(attr));
> >
> > I am not sure how to debug this error since the instructions are in
> > binary and the precompiled source code doesn't seem to contain any
> > weird loops or goto instructions...
> >
> > Is there a way to identify which line of source code is causing these errors?
> >
> > Thanks!
>
>
>
> --
> Respectfully,
> Sameeh Jubran
> Linkedin
> Software Engineer @ Daynix.



-- 
Respectfully,
Sameeh Jubran
Linkedin
Software Engineer @ Daynix.