On 5/1/17 7:31 PM, David Miller wrote:
If the last BPF instruction before exit is a ldimm64, branches to the exit point at the wrong location. Here is what I get from test_pkt_access.c on sparc: 0000000000000000 <process>: 0: b7 00 00 00 00 00 00 02 mov r0, 2 8: 61 21 00 50 00 00 00 00 ldw r2, [r1+80] 10: 61 11 00 4c 00 00 00 00 ldw r1, [r1+76] 18: bf 41 00 00 00 00 00 00 mov r4, r1 20: 07 40 00 00 00 00 00 0e add r4, 14 28: 2d 42 00 25 00 00 00 00 jgt r4, r2, 148 <LBB0_11> ... 0000000000000148 <LBB0_11>: 148: 18 00 00 00 ff ff ff ff ldimm64 r0, 4294967295 150: 00 00 00 00 00 00 00 00 0000000000000158 <LBB0_12>: 158: 95 00 00 00 00 00 00 00 exit The offset field in the "jgt" instruction is 0x25 which multiplied by 8 is 0x128, add 0x128 to the instruction location which is 0x28, and we get 0x150, which is the second 64-bit chunk of the ldimm64 instruction.
looks fine to me. it jumps to 0x158, since offset 0 is the next insn after jump which is 0x30 That's how classic bpf defined jumps.
