mirror of https://github.com/aya-rs/aya
aya+ebpf: Implement read+write methods for PerfEventArray
This allow to read _and_ write a PerfEventArray, from userspace _and_ kernel.pull/649/head
Guillaume Raffin
1 year ago
parent
41351ec560
commit
0aeb379beb
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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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/// Data sent by the bpf program to userspace.
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/// This structure must be defined in the exact same way on the userspace side.
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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).and_then(|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 +1,162 @@
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use std::os::fd::OwnedFd;
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use std::time::{Duration, Instant};
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use aya::maps::perf::Events;
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use aya::maps::{AsyncPerfEventArray, PerfEventArray};
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use aya::programs::perf_event::{perf_event_open, PerfEventLinkId, PerfEventScope};
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use aya::programs::{PerfEvent, PerfTypeId, ProgramError, 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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/// Data sent by the bpf program to userspace.
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/// This structure must be defined in the exact same way on the bpf side.
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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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const CPU_ID: u32 = 0;
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const SAMPLING_FREQUENCY_HZ: u64 = 100;
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const BUF_PAGE_COUNT: usize = 2; // must be a power of two
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const WAIT_TIMEOUT: Duration = Duration::from_secs(1);
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/// Opens an hardware perf_event for testing.
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fn open_perf_event_hw() -> Result<OwnedFd, ProgramError> {
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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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}
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/// Attaches a PerfEvent bpf program to a software clock event.
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fn attach_bpf_to_clock(program: &mut PerfEvent) -> Result<PerfEventLinkId, ProgramError> {
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program.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(SAMPLING_FREQUENCY_HZ),
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)
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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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let event_fd = open_perf_event_hw().unwrap();
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// pass pointer to bpf array
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descriptors
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.set(0, &event_fd)
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.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
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.load()
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.expect("the bpf program should load properly");
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// get buffer to poll the events
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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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attach_bpf_to_clock(program).expect("the bpf program should attach properly");
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// wait for the values to be added to the buffer
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let t0 = Instant::now();
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while !buf.readable() {
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std::thread::sleep(Duration::from_millis(1000 / SAMPLING_FREQUENCY_HZ));
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assert!(
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t0.elapsed() < WAIT_TIMEOUT,
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"timeout elapsed: no data in the buffer"
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);
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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 Events { read, lost } = buf
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.read_events(&mut events_data)
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.expect("failed to poll events");
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for data_buf in events_data.iter_mut().take(read) {
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let ptr = data_buf.as_ptr() as *const EventData;
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let data @ EventData { cpu_id, tag, value } = unsafe { ptr.read_unaligned() };
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assert!(value > 0, "unexpected data: {:?}", value);
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assert_eq!(cpu_id, CPU_ID, "unexpected data: {:?}", data);
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assert_eq!(tag, 0xAB, "unexpected data: {:?}", data);
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}
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assert_eq!(lost, 0, "lost {} events", lost);
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}
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#[test(tokio::test)]
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async fn perf_event_read_from_kernel_async() {
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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 =
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AsyncPerfEventArray::try_from(bpf.take_map("DESCRIPTORS").unwrap()).unwrap();
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let mut bpf_output = AsyncPerfEventArray::try_from(bpf.take_map("OUTPUT").unwrap()).unwrap();
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// open a perf_event
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let event_fd = open_perf_event_hw().unwrap();
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// pass pointer to bpf array
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descriptors
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.set(0, &event_fd)
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.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
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.load()
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.expect("the bpf program should load properly");
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// get buffer to poll the events
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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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attach_bpf_to_clock(program).expect("the bpf program should attach properly");
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// read the events as soon as they are available
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let mut events_data: [BytesMut; BUF_PAGE_COUNT] = std::array::from_fn(|_| BytesMut::new());
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let Events { read, lost } =
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tokio::time::timeout(WAIT_TIMEOUT, buf.read_events(&mut events_data))
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.await
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.expect("timeout elapsed: no data in the buffer")
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.expect("failed to poll events");
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// check that the returned data is correct
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for data_buf in events_data.iter_mut().take(read) {
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let ptr = data_buf.as_ptr() as *const EventData;
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let data @ EventData { cpu_id, tag, value } = unsafe { ptr.read_unaligned() };
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assert!(value > 0, "unexpected data: {:?}", value);
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assert_eq!(cpu_id, CPU_ID, "unexpected data: {:?}", data);
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assert_eq!(tag, 0xAB, "unexpected data: {:?}", data);
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}
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assert_eq!(lost, 0, "lost {} events", lost)
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}
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