Unaligned 64bit load in ubpf_vm.c @ line 444

[Alan-Jowett]

https://github.com/iovisor/ubpf/actions/runs/3223008829/jobs/5272650798#step:14:184

/Users/runner/work/ubpf/ubpf/vm/ubpf_vm.c:444:29: runtime error: load of misaligned address 0x602000000132 for type 'uint64_t' (aka 'unsigned long long'), which requires 8 byte alignment
0x602000000132: note: pointer points here
00 00 aa bb 11 22 33 44 55 66 77 88 cc dd be be be be 02 11 00 00 10 00 00 00 01 00 00 0e 00 00

        case EBPF_OP_LDXDW:
            BOUNDS_CHECK_LOAD(8);
            reg[inst.dst] = *(uint64_t *)(uintptr_t)(reg[inst.src] + inst.offset);
            break;

@matt-gretton-dann do you happen to know what processor type the CICD is running on? I haven't seen warnings like this since Itanium. Not a Mac expert myself.

[matt-gretton-dann]

@Alan-Jowett : Looking at the docs these are x86-64 machines (https://docs.github.com/en/actions/using-github-hosted-runners/about-github-hosted-runners#supported-runners-and-hardware-resources).

However, the macOS ABI seems to assume natural alignment of types, and so I wonder if ASan catches this as technically undefined behaviour.

[Alan-Jowett]

OK, that makes sense. I can update this with an alignment check and a memcpy for unaligned loads. I think:

#ifdef __APPLE__

Is the correct MacOS check.

[matt-gretton-dann]

I've also integrated a fix to this into #154.