On 12/13/2016 08:38 PM, Alexei Starovoitov wrote:
On Tue, Nov 29, 2016 at 9:01 AM, Alexei Starovoitov
<alexei.starovoi...@gmail.com> wrote:
If I try to run samples/bpf/test_cls_bpf.sh the verifier will complain:
R0=imm0,min_value=0,max_value=0 R1=pkt(id=0,off=0,r=42) R2=pkt_end
112: (0f) r4 += r3
113: (0f) r1 += r4
114: (b7) r0 = 2
115: (69) r2 = *(u16 *)(r1 +2)
invalid access to packet, off=2 size=2, R1(id=3,off=0,r=0)
Now multiply 115 * 8 and convert to hex. This is address 0x398 in llvm-objdump:
; struct udphdr *udp = data + tp_off;
388: r1 += r4
390: r0 = 2
; if (udp->dest == htons(DEFAULT_PKTGEN_UDP_PORT) ||
398: r2 = *(u16 *)(r1 + 2)
3a0: if r2 == 2304 goto 16
Now it's clear which line of C code is causing the verifier to reject.
[...]
Could llvm-objdump switch line numbering for bpf same way as verifier
output, so mapping step is not really needed?
you mean that llvm-objdump to print 113,114,115 ?
I guess it's doable. Will give it a try.
Hi Daniel,
your feature request turned out to be pretty straightforward
to implement. Please pull the latest llvm and rebuild llvm-objdump.
It will be printing instruction numbers instead of absolute addresses.
No "multiply 115 * 8 and convert to hex" steps necessary anymore.
That's great to hear, thanks for following up on this. Sounds about
right to upgrade.
Thanks,
Daniel
