From 3e48231dcb7383a50769b69b953f0ed4843bdb3b Mon Sep 17 00:00:00 2001
From: Billy McFall <22157057+Billy99@users.noreply.github.com>
Date: Thu, 25 Jul 2024 11:54:41 -0400
Subject: [PATCH] aya: adjust bpf programs for big endian

In aya/src/sys/bpf.rs, there are several simple bpf programs written as
byte arrays. These need to be adjusted to account for big endian.

Already handled in #974.

Signed-off-by: Billy McFall <22157057+Billy99@users.noreply.github.com>
---
 aya/src/sys/bpf.rs | 50 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/aya/src/sys/bpf.rs b/aya/src/sys/bpf.rs
index 1ae1dc95..3458f204 100644
--- a/aya/src/sys/bpf.rs
+++ b/aya/src/sys/bpf.rs
@@ -672,6 +672,11 @@ pub(crate) fn is_prog_name_supported() -> bool {
     });
     u.prog_name = name;
 
+    // The fields conforming an encoded basic instruction are stored in the following order:
+    //   opcode:8 src_reg:4 dst_reg:4 offset:16 imm:32   - In little-endian BPF.
+    //   opcode:8 dst_reg:4 src_reg:4 offset:16 imm:32   - In big-endian BPF.
+    // Multi-byte fields ('imm' and 'offset') are stored using endian order.
+    // https://www.kernel.org/doc/html/v6.4-rc7/bpf/instruction-set.html#instruction-encoding
     let prog: &[u8] = &[
         0xb7, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // mov64 r0 = 0
         0x95, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // exit
@@ -692,6 +697,12 @@ pub(crate) fn is_probe_read_kernel_supported() -> bool {
     let mut attr = unsafe { mem::zeroed::<bpf_attr>() };
     let u = unsafe { &mut attr.__bindgen_anon_3 };
 
+    // The fields conforming an encoded basic instruction are stored in the following order:
+    //   opcode:8 src_reg:4 dst_reg:4 offset:16 imm:32   - In little-endian BPF.
+    //   opcode:8 dst_reg:4 src_reg:4 offset:16 imm:32   - In big-endian BPF.
+    // Multi-byte fields ('imm' and 'offset') are stored using endian order.
+    // https://www.kernel.org/doc/html/v6.4-rc7/bpf/instruction-set.html#instruction-encoding
+    #[cfg(target_endian = "little")]
     let prog: &[u8] = &[
         0xbf, 0xa1, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // r1 = r10
         0x07, 0x01, 0x00, 0x00, 0xf8, 0xff, 0xff, 0xff, // r1 -= 8
@@ -700,6 +711,15 @@ pub(crate) fn is_probe_read_kernel_supported() -> bool {
         0x85, 0x00, 0x00, 0x00, 0x71, 0x00, 0x00, 0x00, // call 113
         0x95, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // exit
     ];
+    #[cfg(target_endian = "big")]
+    let prog: &[u8] = &[
+        0xbf, 0x1a, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // r1 = r10
+        0x07, 0x10, 0x00, 0x00, 0xff, 0xff, 0xff, 0xf8, // r1 -= 8
+        0xb7, 0x20, 0x00, 0x00, 0x00, 0x00, 0x00, 0x08, // r2 = 8
+        0xb7, 0x30, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // r3 = 0
+        0x85, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x71, // call 113
+        0x95, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // exit
+    ];
 
     let gpl = b"GPL\0";
     u.license = gpl.as_ptr() as u64;
@@ -716,6 +736,11 @@ pub(crate) fn is_perf_link_supported() -> bool {
     let mut attr = unsafe { mem::zeroed::<bpf_attr>() };
     let u = unsafe { &mut attr.__bindgen_anon_3 };
 
+    // The fields conforming an encoded basic instruction are stored in the following order:
+    //   opcode:8 src_reg:4 dst_reg:4 offset:16 imm:32   - In little-endian BPF.
+    //   opcode:8 dst_reg:4 src_reg:4 offset:16 imm:32   - In big-endian BPF.
+    // Multi-byte fields ('imm' and 'offset') are stored using endian order.
+    // https://www.kernel.org/doc/html/v6.4-rc7/bpf/instruction-set.html#instruction-encoding
     let prog: &[u8] = &[
         0xb7, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // mov64 r0 = 0
         0x95, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // exit
@@ -747,6 +772,12 @@ pub(crate) fn is_bpf_global_data_supported() -> bool {
     let mut attr = unsafe { mem::zeroed::<bpf_attr>() };
     let u = unsafe { &mut attr.__bindgen_anon_3 };
 
+    // The fields conforming an encoded basic instruction are stored in the following order:
+    //   opcode:8 src_reg:4 dst_reg:4 offset:16 imm:32   - In little-endian BPF.
+    //   opcode:8 dst_reg:4 src_reg:4 offset:16 imm:32   - In big-endian BPF.
+    // Multi-byte fields ('imm' and 'offset') are stored using endian order.
+    // https://www.kernel.org/doc/html/v6.4-rc7/bpf/instruction-set.html#instruction-encoding
+    #[cfg(target_endian = "little")]
     let prog: &[u8] = &[
         0x18, 0x21, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // ld_pseudo r1, 0x2, 0x0
         0x00, 0x00, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, //
@@ -754,6 +785,14 @@ pub(crate) fn is_bpf_global_data_supported() -> bool {
         0xb7, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // mov64 r0 = 0
         0x95, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // exit
     ];
+    #[cfg(target_endian = "big")]
+    let prog: &[u8] = &[
+        0x18, 0x12, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10, // ld_pseudo r1, 0x2, 0x0
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, //
+        0x7a, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x2a, // stdw [r1 + 0x0], 0x2a
+        0xb7, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // mov64 r0 = 0
+        0x95, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // exit
+    ];
 
     let mut insns = copy_instructions(prog).unwrap();
 
@@ -794,10 +833,21 @@ pub(crate) fn is_bpf_cookie_supported() -> bool {
     let mut attr = unsafe { mem::zeroed::<bpf_attr>() };
     let u = unsafe { &mut attr.__bindgen_anon_3 };
 
+    // The fields conforming an encoded basic instruction are stored in the following order:
+    //   opcode:8 src_reg:4 dst_reg:4 offset:16 imm:32   - In little-endian BPF.
+    //   opcode:8 dst_reg:4 src_reg:4 offset:16 imm:32   - In big-endian BPF.
+    // Multi-byte fields ('imm' and 'offset') are stored using endian order.
+    // https://www.kernel.org/doc/html/v6.4-rc7/bpf/instruction-set.html#instruction-encoding
+    #[cfg(target_endian = "little")]
     let prog: &[u8] = &[
         0x85, 0x00, 0x00, 0x00, 0xae, 0x00, 0x00, 0x00, // call bpf_get_attach_cookie
         0x95, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // exit
     ];
+    #[cfg(target_endian = "big")]
+    let prog: &[u8] = &[
+        0x85, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xae, // call bpf_get_attach_cookie
+        0x95, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // exit
+    ];
 
     let gpl = b"GPL\0";
     u.license = gpl.as_ptr() as u64;