Invalid ELF header size or alignment

[tw4452852]

A weird issue occurred today that puzzled me a lot. When I used load_file(xxx), everything worked fine. But if I used load(include_bytes!(xxx), None), it produced this error:

Error: error parsing BPF object

Caused by:
    0: error parsing ELF data
    1: Invalid ELF header size or alignment

Anyone knows why? Thanks in advance.

[ecarrara]

@tw4452852 i think you should align you array of bytes.

Zero-copy buffer mode
bpf devices may also operate in the BPF_BUFMODE_ZEROCOPY mode, in which
packet data is written directly into two user memory buffers by the ker-
nel, avoiding both system call and copying overhead. Buffers are of
fixed (and equal) size, page-aligned, and an even multiple of the page
size. The maximum zero-copy buffer size is returned by the BIOCGETZMAX
ioctl. Note that an individual packet larger than the buffer size is
necessarily truncated.
https://www.freebsd.org/cgi/man.cgi?bpf(4)

What works for me:

macro_rules! include_bytes_align_as {
    ($align_ty:ty, $path:literal) => {{
        #[repr(C)]
        pub struct AlignedAs<Align, Bytes: ?Sized> {
            pub _align: [Align; 0],
            pub bytes: Bytes,
        }

        static ALIGNED: &AlignedAs<$align_ty, [u8]> = &AlignedAs {
            _align: [],
            bytes: *include_bytes!($path),
        };

        &ALIGNED.bytes
    }};
}

static PROGRAM_DATA: &'static [u8] = include_bytes_align_as!(
    u32,
    "../../target/bpfel-unknown-none/release/libpq-tracer-bpf"
);

    // ..
    let mut bpf = Bpf::load(PROGRAM_DATA.into(), None)?;

I copied the include_bytes_align_as macro from here.

[tw4452852]

Wow, thanks @ecarrara , Now it's clear now.

[willfindlay]

Just an FYI for folks coming here from their favourite search engine: As of #76 we will have aya::include_bytes_aligned which can be used instead.