From b20ad5c2437b3a7d0a8c7067f1d8b3190396afff Mon Sep 17 00:00:00 2001
From: Dave Tucker <dave@dtucker.co.uk>
Date: Mon, 27 Jun 2022 22:20:10 +0100
Subject: [PATCH] aya: Add probe for bpf_link_create for perf programs

Signed-off-by: Dave Tucker <dave@dtucker.co.uk>
---
 aya/src/bpf.rs     |  6 +++++-
 aya/src/sys/bpf.rs | 31 +++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/aya/src/bpf.rs b/aya/src/bpf.rs
index 9ac1e4df..86d476a5 100644
--- a/aya/src/bpf.rs
+++ b/aya/src/bpf.rs
@@ -31,7 +31,8 @@ use crate::{
         bpf_load_btf, bpf_map_freeze, bpf_map_update_elem_ptr, is_bpf_cookie_supported,
         is_btf_datasec_supported, is_btf_decl_tag_supported, is_btf_float_supported,
         is_btf_func_global_supported, is_btf_func_supported, is_btf_supported,
-        is_btf_type_tag_supported, is_prog_name_supported, retry_with_verifier_logs,
+        is_btf_type_tag_supported, is_perf_link_supported, is_prog_name_supported,
+        retry_with_verifier_logs,
     },
     util::{bytes_of, possible_cpus, VerifierLog, POSSIBLE_CPUS},
 };
@@ -125,6 +126,7 @@ lazy_static! {
 pub(crate) struct Features {
     pub bpf_name: bool,
     pub bpf_cookie: bool,
+    pub bpf_perf_link: bool,
     pub btf: bool,
     pub btf_func: bool,
     pub btf_func_global: bool,
@@ -139,11 +141,13 @@ impl Features {
         let mut f = Features {
             bpf_name: is_prog_name_supported(),
             bpf_cookie: is_bpf_cookie_supported(),
+            bpf_perf_link: is_perf_link_supported(),
             btf: is_btf_supported(),
             ..Default::default()
         };
         debug!("[FEAT PROBE] BPF program name support: {}", f.bpf_name);
         debug!("[FEAT PROBE] BPF cookie support: {}", f.bpf_cookie);
+        debug!("[FEAT PROBE] BPF probe link support: {}", f.bpf_perf_link);
         debug!("[FEAT PROBE] BTF support: {}", f.btf);
 
         if f.btf {
diff --git a/aya/src/sys/bpf.rs b/aya/src/sys/bpf.rs
index 1271251b..f60ba2cb 100644
--- a/aya/src/sys/bpf.rs
+++ b/aya/src/sys/bpf.rs
@@ -571,6 +571,37 @@ pub(crate) fn is_prog_name_supported() -> bool {
     }
 }
 
+pub(crate) fn is_perf_link_supported() -> bool {
+    let mut attr = unsafe { mem::zeroed::<bpf_attr>() };
+    let u = unsafe { &mut attr.__bindgen_anon_3 };
+
+    let prog: &[u8] = &[
+        0xb7, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // mov64 r0 = 0
+        0x95, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // exit
+    ];
+
+    let gpl = b"GPL\0";
+    u.license = gpl.as_ptr() as u64;
+
+    let insns = copy_instructions(prog).unwrap();
+    u.insn_cnt = insns.len() as u32;
+    u.insns = insns.as_ptr() as u64;
+    u.prog_type = bpf_prog_type::BPF_PROG_TYPE_TRACEPOINT as u32;
+
+    if let Ok(fd) = sys_bpf(bpf_cmd::BPF_PROG_LOAD, &attr) {
+        if let Err((code, _)) =
+            bpf_link_create(fd as i32, -1, bpf_attach_type::BPF_PERF_EVENT, None, 0)
+        {
+            if code == (-libc::EBADF).into() {
+                unsafe { libc::close(fd as i32) };
+                return true;
+            }
+            unsafe { libc::close(fd as i32) };
+        }
+    }
+    false
+}
+
 pub(crate) fn is_bpf_cookie_supported() -> bool {
     let mut attr = unsafe { mem::zeroed::<bpf_attr>() };
     let u = unsafe { &mut attr.__bindgen_anon_3 };