perf_buffer: use MMap from ring_buf

aya/src/maps/mod.rs

@@ -60,7 +60,9 @@ use std::{
 };
 
 use aya_obj::{generated::bpf_map_type, parse_map_info, EbpfSectionKind, InvalidTypeBinding};
-use libc::{getrlimit, rlim_t, rlimit, RLIMIT_MEMLOCK, RLIM_INFINITY};
+use libc::{
+    c_int, c_void, getrlimit, off_t, rlim_t, rlimit, MAP_FAILED, RLIMIT_MEMLOCK, RLIM_INFINITY,
+};
 use log::warn;
 use thiserror::Error;
 
@@ -68,7 +70,7 @@ use crate::{
     pin::PinError,
     sys::{
         bpf_create_map, bpf_get_object, bpf_map_freeze, bpf_map_get_fd_by_id, bpf_map_get_next_key,
-        bpf_map_update_elem_ptr, bpf_pin_object, SyscallError,
+        bpf_map_update_elem_ptr, bpf_pin_object, mmap, munmap, SyscallError,
     },
     util::{nr_cpus, KernelVersion},
     PinningType, Pod,
@@ -952,6 +954,62 @@ impl<T: Pod> Deref for PerCpuValues<T> {
     }
 }
 
+// MMap corresponds to a memory-mapped region.
+//
+// The data is unmapped in Drop.
+#[cfg_attr(test, derive(Debug))]
+struct MMap {
+    ptr: ptr::NonNull<c_void>,
+    len: usize,
+}
+
+// Needed because NonNull<T> is !Send and !Sync out of caution that the data
+// might be aliased unsafely.
+unsafe impl Send for MMap {}
+unsafe impl Sync for MMap {}
+
+impl MMap {
+    fn new(
+        fd: BorrowedFd<'_>,
+        len: usize,
+        prot: c_int,
+        flags: c_int,
+        offset: off_t,
+    ) -> Result<Self, SyscallError> {
+        match unsafe { mmap(ptr::null_mut(), len, prot, flags, fd, offset) } {
+            MAP_FAILED => Err(SyscallError {
+                call: "mmap",
+                io_error: io::Error::last_os_error(),
+            }),
+            ptr => {
+                let ptr = ptr::NonNull::new(ptr).ok_or(
+                    // This should never happen, but to be paranoid, and so we never need to talk
+                    // about a null pointer, we check it anyway.
+                    SyscallError {
+                        call: "mmap",
+                        io_error: io::Error::other("mmap returned null pointer"),
+                    },
+                )?;
+                Ok(Self { ptr, len })
+            }
+        }
+    }
+}
+
+impl AsRef<[u8]> for MMap {
+    fn as_ref(&self) -> &[u8] {
+        let Self { ptr, len } = self;
+        unsafe { std::slice::from_raw_parts(ptr.as_ptr().cast(), *len) }
+    }
+}
+
+impl Drop for MMap {
+    fn drop(&mut self) {
+        let Self { ptr, len } = *self;
+        unsafe { munmap(ptr.as_ptr(), len) };
+    }
+}
+
 #[cfg(test)]
 mod test_utils {
     use aya_obj::{

aya/src/maps/perf/perf_buffer.rs

@@ -1,9 +1,8 @@
 use std::{
-    ffi::c_void,
     io, mem,
     os::fd::{AsFd, BorrowedFd},
     ptr, slice,
-    sync::atomic::{self, AtomicPtr, Ordering},
+    sync::atomic::{self, Ordering},
 };
 
 use aya_obj::generated::{
@@ -12,10 +11,13 @@ use aya_obj::generated::{
     PERF_EVENT_IOC_DISABLE, PERF_EVENT_IOC_ENABLE,
 };
 use bytes::BytesMut;
-use libc::{munmap, MAP_FAILED, MAP_SHARED, PROT_READ, PROT_WRITE};
+use libc::{MAP_SHARED, PROT_READ, PROT_WRITE};
 use thiserror::Error;
 
-use crate::sys::{mmap, perf_event_ioctl, perf_event_open_bpf, SysResult};
+use crate::{
+    maps::MMap,
+    sys::{perf_event_ioctl, perf_event_open_bpf, SysResult, SyscallError},
+};
 
 /// Perf buffer error.
 #[derive(Error, Debug)]
@@ -81,9 +83,9 @@ pub struct Events {
     pub lost: usize,
 }
 
-#[derive(Debug)]
+#[cfg_attr(test, derive(Debug))]
 pub(crate) struct PerfBuffer {
-    buf: AtomicPtr<perf_event_mmap_page>,
+    mmap: MMap,
     size: usize,
     page_size: usize,
     fd: crate::MockableFd,
@@ -102,24 +104,17 @@ impl PerfBuffer {
         let fd = perf_event_open_bpf(cpu_id as i32)
             .map_err(|(_, io_error)| PerfBufferError::OpenError { io_error })?;
         let size = page_size * page_count;
-        let buf = unsafe {
+        let mmap = MMap::new(
-            mmap(
+            fd.as_fd(),
-                ptr::null_mut(),
+            size + page_size,
-                size + page_size,
+            PROT_READ | PROT_WRITE,
-                PROT_READ | PROT_WRITE,
+            MAP_SHARED,
-                MAP_SHARED,
+            0,
-                fd.as_fd(),
+        )
-                0,
+        .map_err(|SyscallError { call: _, io_error }| PerfBufferError::MMapError { io_error })?;
-            )
-        };
-        if buf == MAP_FAILED {
-            return Err(PerfBufferError::MMapError {
-                io_error: io::Error::last_os_error(),
-            });
-        }
 
         let perf_buf = Self {
-            buf: AtomicPtr::new(buf as *mut perf_event_mmap_page),
+            mmap,
             size,
             page_size,
             fd,
@@ -131,8 +126,12 @@ impl PerfBuffer {
         Ok(perf_buf)
     }
 
+    fn buf(&self) -> ptr::NonNull<perf_event_mmap_page> {
+        self.mmap.ptr.cast()
+    }
+
     pub(crate) fn readable(&self) -> bool {
-        let header = self.buf.load(Ordering::SeqCst);
+        let header = self.buf().as_ptr();
         let head = unsafe { (*header).data_head } as usize;
         let tail = unsafe { (*header).data_tail } as usize;
         head != tail
@@ -145,7 +144,7 @@ impl PerfBuffer {
         if buffers.is_empty() {
             return Err(PerfBufferError::NoBuffers);
         }
-        let header = self.buf.load(Ordering::SeqCst);
+        let header = self.buf().as_ptr();
         let base = header as usize + self.page_size;
 
         let mut events = Events { read: 0, lost: 0 };
@@ -265,13 +264,7 @@ impl AsFd for PerfBuffer {
 
 impl Drop for PerfBuffer {
     fn drop(&mut self) {
-        unsafe {
+        let _: SysResult<_> = perf_event_ioctl(self.fd.as_fd(), PERF_EVENT_IOC_DISABLE, 0);
-            let _: SysResult<_> = perf_event_ioctl(self.fd.as_fd(), PERF_EVENT_IOC_DISABLE, 0);
-            munmap(
-                self.buf.load(Ordering::SeqCst) as *mut c_void,
-                self.size + self.page_size,
-            );
-        }
     }
 }
 

aya/src/maps/ring_buf.rs

@@ -6,23 +6,18 @@
 
 use std::{
     borrow::Borrow,
-    ffi::{c_int, c_void},
     fmt::{self, Debug, Formatter},
-    io, mem,
+    mem,
     ops::Deref,
     os::fd::{AsFd as _, AsRawFd, BorrowedFd, RawFd},
-    ptr,
-    ptr::NonNull,
-    slice,
     sync::atomic::{AtomicU32, AtomicUsize, Ordering},
 };
 
 use aya_obj::generated::{BPF_RINGBUF_BUSY_BIT, BPF_RINGBUF_DISCARD_BIT, BPF_RINGBUF_HDR_SZ};
-use libc::{munmap, off_t, MAP_FAILED, MAP_SHARED, PROT_READ, PROT_WRITE};
+use libc::{MAP_SHARED, PROT_READ, PROT_WRITE};
 
 use crate::{
-    maps::{MapData, MapError},
+    maps::{MMap, MapData, MapError},
-    sys::{mmap, SyscallError},
     util::page_size,
 };
 
@@ -403,58 +398,3 @@ impl ProducerData {
         }
     }
 }
-
-// MMap corresponds to a memory-mapped region.
-//
-// The data is unmapped in Drop.
-struct MMap {
-    ptr: NonNull<c_void>,
-    len: usize,
-}
-
-// Needed because NonNull<T> is !Send and !Sync out of caution that the data
-// might be aliased unsafely.
-unsafe impl Send for MMap {}
-unsafe impl Sync for MMap {}
-
-impl MMap {
-    fn new(
-        fd: BorrowedFd<'_>,
-        len: usize,
-        prot: c_int,
-        flags: c_int,
-        offset: off_t,
-    ) -> Result<Self, MapError> {
-        match unsafe { mmap(ptr::null_mut(), len, prot, flags, fd, offset) } {
-            MAP_FAILED => Err(MapError::SyscallError(SyscallError {
-                call: "mmap",
-                io_error: io::Error::last_os_error(),
-            })),
-            ptr => Ok(Self {
-                ptr: NonNull::new(ptr).ok_or(
-                    // This should never happen, but to be paranoid, and so we never need to talk
-                    // about a null pointer, we check it anyway.
-                    MapError::SyscallError(SyscallError {
-                        call: "mmap",
-                        io_error: io::Error::other("mmap returned null pointer"),
-                    }),
-                )?,
-                len,
-            }),
-        }
-    }
-}
-
-impl AsRef<[u8]> for MMap {
-    fn as_ref(&self) -> &[u8] {
-        let Self { ptr, len } = self;
-        unsafe { slice::from_raw_parts(ptr.as_ptr().cast(), *len) }
-    }
-}
-
-impl Drop for MMap {
-    fn drop(&mut self) {
-        let Self { ptr, len } = *self;
-        unsafe { munmap(ptr.as_ptr(), len) };
-    }
-}

aya/src/sys/mod.rs

@@ -135,6 +135,15 @@ pub(crate) unsafe fn mmap(
     TEST_MMAP_RET.with(|ret| *ret.borrow())
 }
 
+#[cfg_attr(test, allow(unused_variables))]
+pub(crate) unsafe fn munmap(addr: *mut c_void, len: usize) -> c_int {
+    #[cfg(not(test))]
+    return libc::munmap(addr, len);
+
+    #[cfg(test)]
+    0
+}
+
 /// The type of eBPF statistic to enable.
 #[non_exhaustive]
 #[doc(alias = "bpf_stats_type")]

xtask/public-api/aya.txt

@@ -434,7 +434,7 @@ pub fn aya::maps::perf::AsyncPerfEventArray<T>::from(t: T) -> T
 pub struct aya::maps::perf::AsyncPerfEventArrayBuffer<T: core::borrow::BorrowMut<aya::maps::MapData>>
 impl<T: core::borrow::BorrowMut<aya::maps::MapData>> aya::maps::perf::AsyncPerfEventArrayBuffer<T>
 pub async fn aya::maps::perf::AsyncPerfEventArrayBuffer<T>::read_events(&mut self, buffers: &mut [bytes::bytes_mut::BytesMut]) -> core::result::Result<aya::maps::perf::Events, aya::maps::perf::PerfBufferError>
-impl<T> !core::marker::Freeze for aya::maps::perf::AsyncPerfEventArrayBuffer<T>
+impl<T> core::marker::Freeze for aya::maps::perf::AsyncPerfEventArrayBuffer<T>
 impl<T> core::marker::Send for aya::maps::perf::AsyncPerfEventArrayBuffer<T> where T: core::marker::Sync + core::marker::Send
 impl<T> core::marker::Sync for aya::maps::perf::AsyncPerfEventArrayBuffer<T> where T: core::marker::Sync + core::marker::Send
 impl<T> core::marker::Unpin for aya::maps::perf::AsyncPerfEventArrayBuffer<T>
@@ -533,7 +533,7 @@ impl<T: core::borrow::BorrowMut<aya::maps::MapData>> std::os::fd::owned::AsFd fo
 pub fn aya::maps::perf::PerfEventArrayBuffer<T>::as_fd(&self) -> std::os::fd::owned::BorrowedFd<'_>
 impl<T: core::borrow::BorrowMut<aya::maps::MapData>> std::os::fd::raw::AsRawFd for aya::maps::perf::PerfEventArrayBuffer<T>
 pub fn aya::maps::perf::PerfEventArrayBuffer<T>::as_raw_fd(&self) -> std::os::fd::raw::RawFd
-impl<T> !core::marker::Freeze for aya::maps::perf::PerfEventArrayBuffer<T>
+impl<T> core::marker::Freeze for aya::maps::perf::PerfEventArrayBuffer<T>
 impl<T> core::marker::Send for aya::maps::perf::PerfEventArrayBuffer<T> where T: core::marker::Sync + core::marker::Send
 impl<T> core::marker::Sync for aya::maps::perf::PerfEventArrayBuffer<T> where T: core::marker::Sync + core::marker::Send
 impl<T> core::marker::Unpin for aya::maps::perf::PerfEventArrayBuffer<T>