On Wed, Sep 10, 2014 at 2:03 AM, Daniel Borkmann <dborkman@xxxxxxxxxx> wrote:
>> struct { /* anonymous struct used by BPF_PROG_LOAD command */
>> enum bpf_prog_type prog_type;
>> __u32 insn_cnt;
>> const struct bpf_insn *insns;
>> const char *license;
>> __u32 log_level; /* verbosity level of
>> eBPF verifier */
>> __u32 log_size; /* size of user buffer */
>> void *log_buf; /* user supplied buffer
>> */
>
>
> What is log buffer? Would that mean the verifier will return an error
> string if the program will not pass it, or if not, what other data?
> I think the man page is missing how to examine the returned verifier
> log buffer data.
yes. it's an error log (as text string for humans) from verifier.
It is briefly explained in the man page:
EACCES For BPF_PROG_LOAD, though program has valid instructions, it was
rejected, since it was deemed unsafe (may access disallowed mem-
ory region or uninitialized stack/register or function con-
straints don't match actual types or misaligned access). In such
case it is recommended to call bpf() again with log_level = 1
and examine log_buf for specific reason provided by verifier.
and there is a whole section about it in
Documentation/networking/filter.txt
called "Understanding eBPF verifier messages".
--
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
