From 554702e63d7a766de65fa8a09bd98574736810a1 Mon Sep 17 00:00:00 2001
From: Luca BRUNO <lucab@lucabruno.net>
Date: Wed, 25 Jan 2023 10:04:14 +0000
Subject: [PATCH] cargo-generate: add perf_event

This adds `perf_event` program type as a template entry.
The new entry comes with a skeleton example which register
scheduled events on each CPU at 1 HZ, triggered by the kernel
(based on clock ticks). The corresponding BPF logic logs each
event, and can identify kernel tasks from userland processes.
---
 .github/workflows/ci.yml          |  9 +++++----
 cargo-generate.toml               |  1 +
 {{project-name}}-ebpf/src/main.rs | 26 ++++++++++++++++++++++++++
 {{project-name}}/src/main.rs      | 16 ++++++++++++++++
 4 files changed, 48 insertions(+), 4 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 3af968d..288e83e 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -29,14 +29,15 @@ jobs:
           - socket_filter
           - sk_msg
           - xdp
-          - classifier
           - cgroup_skb
-          - cgroup_sysctl
           - cgroup_sockopt
-          - tracepoint
+          - cgroup_sysctl
+          - classifier
           - lsm
-          - tp_btf
+          - perf_event
           - raw_tracepoint
+          - tp_btf
+          - tracepoint
 
     steps:
       - uses: actions/checkout@v2
diff --git a/cargo-generate.toml b/cargo-generate.toml
index 316ac9a..b4c4e31 100644
--- a/cargo-generate.toml
+++ b/cargo-generate.toml
@@ -15,6 +15,7 @@ choices = [
     "kprobe",
     "kretprobe",
     "lsm",
+    "perf_event",
     "raw_tracepoint",
     "sk_msg",
     "sock_ops",
diff --git a/{{project-name}}-ebpf/src/main.rs b/{{project-name}}-ebpf/src/main.rs
index eee2730..dcc9254 100644
--- a/{{project-name}}-ebpf/src/main.rs
+++ b/{{project-name}}-ebpf/src/main.rs
@@ -341,6 +341,32 @@ fn try_{{crate_name}}(ctx: RawTracePointContext) -> Result<i32, i32> {
     info!(&ctx, "tracepoint {{tracepoint_name}} called");
     Ok(0)
 }
+{%- when "perf_event" %}
+use aya_bpf::{
+    helpers::bpf_get_smp_processor_id,
+    macros::perf_event,
+    programs::PerfEventContext,
+    BpfContext,
+};
+use aya_log_ebpf::info;
+
+#[perf_event]
+pub fn {{crate_name}}(ctx: PerfEventContext) -> u32 {
+    match try_{{crate_name}}(ctx) {
+        Ok(ret) => ret,
+        Err(ret) => ret,
+    }
+}
+
+fn try_{{crate_name}}(ctx: PerfEventContext) -> Result<u32, u32> {
+    let cpu = unsafe { bpf_get_smp_processor_id() };
+    match ctx.pid() {
+        0 => info!(&ctx, "perf_event '{{crate_name}}' triggered on CPU {}, running a kernel task", cpu),
+        pid => info!(&ctx, "perf_event '{{crate_name}}' triggered on CPU {}, running PID {}", cpu, pid),
+    }
+
+    Ok(0)
+}
 {%- endcase %}
 
 #[panic_handler]
diff --git a/{{project-name}}/src/main.rs b/{{project-name}}/src/main.rs
index f7b403a..07a95fc 100644
--- a/{{project-name}}/src/main.rs
+++ b/{{project-name}}/src/main.rs
@@ -29,6 +29,9 @@ use aya::programs::CgroupSockopt;
 use aya::programs::TracePoint;
 {%- when "lsm" -%}
 use aya::{programs::Lsm, Btf};
+{%- when "perf_event" -%}
+use aya::programs::{perf_event, PerfEvent};
+use aya::util::online_cpus;
 {%- when "tp_btf" -%}
 use aya::{programs::BtfTracePoint, Btf};
 {%- when "socket_filter" -%}
@@ -164,6 +167,19 @@ async fn main() -> Result<(), anyhow::Error> {
     let cgroup = std::fs::File::open(opt.cgroup_path)?;
     program.load()?;
     program.attach(cgroup)?;
+    {%- when "perf_event" -%}
+    // This will raise scheduled events on each CPU at 1 HZ, triggered by the kernel based
+    // on clock ticks.
+    let program: &mut PerfEvent = bpf.program_mut("{{crate_name}}").unwrap().try_into()?;
+    program.load()?;
+    for cpu in online_cpus()? {
+        program.attach(
+            perf_event::PerfTypeId::Software,
+            perf_event::perf_sw_ids::PERF_COUNT_SW_CPU_CLOCK as u64,
+            perf_event::PerfEventScope::AllProcessesOneCpu { cpu },
+            perf_event::SamplePolicy::Frequency(1),
+        )?;
+    }
     {%- when "raw_tracepoint" -%}
     let program: &mut RawTracePoint = bpf.program_mut("{{crate_name}}").unwrap().try_into()?;
     program.load()?;