Hi William,
On 04/18/2017 06:54 PM, William Tu via iovisor-dev wrote:
Hi,
I found that if the loop variable "int i" is used in the map lookup as below:
#pragma clang loop unroll(full)
for (i = 0; i < 8; ++i) {
struct bpf_flow_keys *mask;
mask = bpf_map_lookup_elem(&flow_mask, &i);
if (!mask)
break;
}
Then the compiled BPF code does not unrolled the loop, causing errors:
"back-edge from insn 240 to 219"
A workaround for that is to declare another variable "int j", then I
can pass the verifier.
#pragma clang loop unroll(full)
for (i = 0; i < 8; ++i) {
int j = i;
struct bpf_flow_keys *mask;
mask = bpf_map_lookup_elem(&flow_mask, &j); // ---> use "j"
if (!mask)
break;
}
Does anyone hit similar issue?
Yes, we hit exactly the same problem [1], at that time we thought it was
because of the missing "const" qualifier in the bpf_map_* helpers [2],
however we added it and the result was the same.
Until now we don't know what is the cause of the problem, we continue to
use that workaround.
Mauricio V,
[1]
https://lists.iovisor.org/pipermail/iovisor-dev/2016-December/000560.html
[2]
https://lists.iovisor.org/pipermail/iovisor-dev/2016-December/000559.html
Regards,
William
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