mirror of https://github.com/aya-rs/aya
aya+ebpf: Add integration test for reading perf_events from bpf program
Guillaume Raffin
2 years ago
parent
6cba3c5120
commit
352ec0ee90
@ -0,0 +1,56 @@
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#![no_std]
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#![no_main]
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use aya_bpf::{
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bindings::bpf_perf_event_value,
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helpers::bpf_get_smp_processor_id,
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macros::{map, perf_event},
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maps::PerfEventArray,
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programs::PerfEventContext,
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};
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#[repr(C)]
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struct EventData {
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value: u64,
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cpu_id: u32,
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tag: u8,
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}
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/// Input map: file descriptors of the perf events, obtained by calling
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/// `perf_event_open` in user space.
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#[map]
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static mut DESCRIPTORS: PerfEventArray<i32> = PerfEventArray::with_max_entries(1, 0);
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#[map]
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static mut OUTPUT: PerfEventArray<EventData> = PerfEventArray::with_max_entries(1, 0);
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#[perf_event]
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pub fn on_perf_event(ctx: PerfEventContext) -> i64 {
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match read_event(&ctx).map(|res| write_output(&ctx, res)) {
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Ok(_) => 0,
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Err(e) => e,
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}
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}
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fn read_event(ctx: &PerfEventContext) -> Result<EventData, i64> {
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// read the event value using the file descriptor in the DESCRIPTORS array
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let event: bpf_perf_event_value = unsafe { DESCRIPTORS.read_current_cpu() }?;
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let cpu_id = unsafe { bpf_get_smp_processor_id() };
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let res = EventData {
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value: event.counter,
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cpu_id,
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tag: 0xAB,
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};
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Ok(res)
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}
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fn write_output(ctx: &PerfEventContext, output: EventData) -> Result<(), i64> {
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unsafe { OUTPUT.output_current_cpu(ctx, &output) }
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}
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#[cfg(not(test))]
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#[panic_handler]
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fn panic(_info: &core::panic::PanicInfo) -> ! {
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loop {}
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}
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@ -0,0 +1,88 @@
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use std::os::fd::{AsRawFd, OwnedFd};
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use std::time::Duration;
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use aya::maps::PerfEventArray;
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use aya::programs::perf_event::{perf_event_open, PerfEventScope};
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use aya::programs::{PerfEvent, PerfTypeId, SamplePolicy};
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use aya::Bpf;
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use aya_obj::generated::{perf_hw_id, perf_sw_ids, perf_type_id};
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use bytes::BytesMut;
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use test_log::test;
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#[derive(Debug)]
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#[repr(C)]
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struct EventData {
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value: u64,
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cpu_id: u32,
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tag: u8,
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}
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#[test]
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fn perf_event_read_from_kernel() {
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// load bpf program
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let mut bpf = Bpf::load(crate::PERF_EVENTS).expect("failed to load bpf code");
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let mut descriptors = PerfEventArray::try_from(bpf.take_map("DESCRIPTORS").unwrap()).unwrap();
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let mut bpf_output = PerfEventArray::try_from(bpf.take_map("OUTPUT").unwrap()).unwrap();
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// open a perf_event
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// Beware: this returns an `OwnedFd`, which means that the file descriptor is closed at the end of the scope
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const CPU_ID: u32 = 0;
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let event_fd: OwnedFd = perf_event_open(
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perf_type_id::PERF_TYPE_HARDWARE as u32,
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perf_hw_id::PERF_COUNT_HW_CPU_CYCLES as u64,
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PerfEventScope::AllProcessesOneCpu { cpu: CPU_ID },
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None,
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None,
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0,
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)
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.unwrap();
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// pass pointer to bpf array
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descriptors.set(0, event_fd.as_raw_fd()).expect("failed to put event's fd into the map");
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// load program
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let program: &mut PerfEvent = bpf
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.program_mut("on_perf_event")
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.unwrap()
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.try_into()
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.unwrap();
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program.load().expect("the bpf program should load properly");
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// get buffer to poll the events
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const BUF_PAGE_COUNT: usize = 1;
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let mut buf = bpf_output
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.open(CPU_ID, Some(BUF_PAGE_COUNT))
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.expect("failed to open output buffer to poll events");
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// attach program
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program
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.attach(
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PerfTypeId::Software,
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perf_sw_ids::PERF_COUNT_SW_CPU_CLOCK as u64,
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PerfEventScope::AllProcessesOneCpu { cpu: CPU_ID },
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SamplePolicy::Frequency(1),
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)
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.expect("the bpf program should attach properly");
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// sleep a little bit, then poll the values from the buffer
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std::thread::sleep(Duration::from_secs(2));
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assert!(
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buf.readable(),
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"the buffer should have been filled by the bpf program"
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);
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// read the events and check that the returned data is correct
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let mut events_data: [BytesMut; BUF_PAGE_COUNT] = std::array::from_fn(|_| BytesMut::new());
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let event_stats = buf.read_events(&mut events_data).expect("failed to poll events");
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for data_buf in events_data.iter_mut().take(event_stats.read) {
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// You must ensure that the definition of the struct (here `EventData`) is the same
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// in the userspace and in the bpf program.
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let ptr = data_buf.as_ptr() as *const EventData;
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let data: EventData = unsafe { ptr.read_unaligned() };
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assert_eq!(data.cpu_id, CPU_ID, "unexpected data: {:?}", data);
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assert_eq!(data.tag, 0xAB, "unexpected data: {:?}", data);
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}
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}
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