From 4df4e9c14eb1019a8c2299c48b15420ee7f20855 Mon Sep 17 00:00:00 2001
From: William Findlay <william@williamfindlay.com>
Date: Sun, 24 Oct 2021 15:56:00 -0400
Subject: [PATCH] aya: introduce include_bytes_aligned!() macro

This is a helper macro that can be used to include bytes at compile-time that can then be
used in Bpf::load(). Unlike std's include_bytes!(), this macro also ensures that the
resulting byte array is correctly aligned so that it can be parsed as an ELF binary.

Signed-off-by: William Findlay <william@williamfindlay.com>
---
 aya/src/util.rs | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/aya/src/util.rs b/aya/src/util.rs
index a3bb2aa2..0586531b 100644
--- a/aya/src/util.rs
+++ b/aya/src/util.rs
@@ -106,6 +106,40 @@ pub(crate) fn tc_handler_make(major: u32, minor: u32) -> u32 {
     (major & TC_H_MAJ_MASK) | (minor & TC_H_MIN_MASK)
 }
 
+/// Include bytes from a file for use in a subsequent [`crate::Bpf::load`].
+///
+/// This macro differs from the standard `include_bytes!` macro since it also ensures that
+/// the bytes are correctly aligned to be parsed as an ELF binary. This avoid some nasty
+/// compilation errors when the resulting byte array is not the correct alignment.
+///
+/// # Examples
+/// ```ignore
+/// use aya::{Bpf, include_bytes_aligned};
+///
+/// let mut bpf = Bpf::load(include_bytes_aligned!(
+///     "/path/to/bpf.o"
+/// ))?;
+///
+/// # Ok::<(), aya::BpfError>(())
+/// ```
+#[macro_export]
+macro_rules! include_bytes_aligned {
+    ($path:literal) => {{
+        #[repr(C)]
+        pub struct Aligned<Bytes: ?Sized> {
+            pub _align: [u32; 0],
+            pub bytes: Bytes,
+        }
+
+        static ALIGNED: &Aligned<[u8]> = &Aligned {
+            _align: [],
+            bytes: *include_bytes!($path),
+        };
+
+        &ALIGNED.bytes
+    }};
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;