aya: encode perf_event ioctl contract

Enumerate the possible ioctls in an enum and bake in the knowledge that
they all return 0 on success and -1 on error.

aya/src/maps/perf/perf_buffer.rs

@@ -8,7 +8,6 @@ use std::{
 use aya_obj::generated::{
     perf_event_header, perf_event_mmap_page,
     perf_event_type::{PERF_RECORD_LOST, PERF_RECORD_SAMPLE},
-    PERF_EVENT_IOC_DISABLE, PERF_EVENT_IOC_ENABLE,
 };
 use bytes::BytesMut;
 use libc::{MAP_SHARED, PROT_READ, PROT_WRITE};
@@ -16,7 +15,7 @@ use thiserror::Error;
 
 use crate::{
     maps::MMap,
-    sys::{perf_event_ioctl, perf_event_open_bpf, SysResult, SyscallError},
+    sys::{perf_event_ioctl, perf_event_open_bpf, PerfEventIoctlRequest, SyscallError},
 };
 
 /// Perf buffer error.
@@ -120,8 +119,8 @@ impl PerfBuffer {
             fd,
         };
 
-        perf_event_ioctl(perf_buf.fd.as_fd(), PERF_EVENT_IOC_ENABLE, 0)
-            .map_err(|(_, io_error)| PerfBufferError::PerfEventEnableError { io_error })?;
+        perf_event_ioctl(perf_buf.fd.as_fd(), PerfEventIoctlRequest::Enable)
+            .map_err(|io_error| PerfBufferError::PerfEventEnableError { io_error })?;
 
         Ok(perf_buf)
     }
@@ -260,7 +259,7 @@ impl AsFd for PerfBuffer {
 
 impl Drop for PerfBuffer {
     fn drop(&mut self) {
-        let _: SysResult = perf_event_ioctl(self.fd.as_fd(), PERF_EVENT_IOC_DISABLE, 0);
+        let _: io::Result<()> = perf_event_ioctl(self.fd.as_fd(), PerfEventIoctlRequest::Disable);
     }
 }
 
@@ -289,9 +288,8 @@ mod tests {
     fn fake_mmap(buf: &mut MMappedBuf) {
         let buf: *mut _ = buf;
         override_syscall(|call| match call {
-            Syscall::PerfEventOpen { .. } | Syscall::PerfEventIoctl { .. } => {
-                Ok(crate::MockableFd::mock_signed_fd().into())
-            }
+            Syscall::PerfEventOpen { .. } => Ok(crate::MockableFd::mock_signed_fd().into()),
+            Syscall::PerfEventIoctl { .. } => Ok(0),
             call => panic!("unexpected syscall: {:?}", call),
         });
         TEST_MMAP_RET.with(|ret| *ret.borrow_mut() = buf.cast());

aya/src/programs/perf_attach.rs

@@ -1,11 +1,11 @@
 //! Perf attach links.
-use std::os::fd::{AsFd as _, AsRawFd as _, BorrowedFd, RawFd};
-
-use aya_obj::generated::{
-    bpf_attach_type::BPF_PERF_EVENT, PERF_EVENT_IOC_DISABLE, PERF_EVENT_IOC_ENABLE,
-    PERF_EVENT_IOC_SET_BPF,
+use std::{
+    io,
+    os::fd::{AsFd as _, AsRawFd as _, BorrowedFd, RawFd},
 };
 
+use aya_obj::generated::bpf_attach_type::BPF_PERF_EVENT;
+
 use crate::{
     programs::{
         id_as_key,
@@ -14,7 +14,7 @@ use crate::{
     },
     sys::{
         bpf_link_create, is_bpf_cookie_supported, perf_event_ioctl, BpfLinkCreateArgs, LinkTarget,
-        SysResult, SyscallError,
+        PerfEventIoctlRequest, SyscallError,
     },
     FEATURES,
 };
@@ -71,7 +71,7 @@ impl Link for PerfLink {
 
     fn detach(self) -> Result<(), ProgramError> {
         let Self { perf_fd, event } = self;
-        let _: SysResult = perf_event_ioctl(perf_fd.as_fd(), PERF_EVENT_IOC_DISABLE, 0);
+        let _: io::Result<()> = perf_event_ioctl(perf_fd.as_fd(), PerfEventIoctlRequest::Disable);
         if let Some(event) = event {
             let _: Result<_, _> = detach_debug_fs(event);
         }
@@ -121,13 +121,13 @@ fn perf_attach_either(
     fd: crate::MockableFd,
     event: Option<ProbeEvent>,
 ) -> Result<PerfLinkInner, ProgramError> {
-    perf_event_ioctl(fd.as_fd(), PERF_EVENT_IOC_SET_BPF, prog_fd.as_raw_fd()).map_err(
-        |(_, io_error)| SyscallError {
+    perf_event_ioctl(fd.as_fd(), PerfEventIoctlRequest::SetBpf(prog_fd)).map_err(|io_error| {
+        SyscallError {
             call: "PERF_EVENT_IOC_SET_BPF",
             io_error,
-        },
-    )?;
-    perf_event_ioctl(fd.as_fd(), PERF_EVENT_IOC_ENABLE, 0).map_err(|(_, io_error)| {
+        }
+    })?;
+    perf_event_ioctl(fd.as_fd(), PerfEventIoctlRequest::Enable).map_err(|io_error| {
         SyscallError {
             call: "PERF_EVENT_IOC_ENABLE",
             io_error,

aya/src/sys/mod.rs

@@ -9,15 +9,14 @@ mod fake;
 
 use std::{
     ffi::{c_int, c_long, c_void},
-    io, mem,
-    os::fd::{AsRawFd as _, BorrowedFd, OwnedFd},
+    io,
+    os::fd::{BorrowedFd, OwnedFd},
 };
 
 use aya_obj::generated::{bpf_attr, bpf_cmd, perf_event_attr};
 pub(crate) use bpf::*;
 #[cfg(test)]
 pub(crate) use fake::*;
-use libc::{pid_t, SYS_bpf, SYS_ioctl, SYS_perf_event_open};
 #[doc(hidden)]
 pub use netlink::netlink_set_link_up;
 pub(crate) use netlink::*;
@@ -26,6 +25,15 @@ use thiserror::Error;
 
 pub(crate) type SysResult = Result<c_long, (c_long, io::Error)>;
 
+#[cfg_attr(test, expect(dead_code))]
+#[derive(Debug)]
+pub(crate) enum PerfEventIoctlRequest<'a> {
+    Enable,
+    Disable,
+    SetBpf(BorrowedFd<'a>),
+}
+
+#[cfg_attr(test, expect(dead_code))]
 pub(crate) enum Syscall<'a> {
     Ebpf {
         cmd: bpf_cmd,
@@ -33,15 +41,14 @@ pub(crate) enum Syscall<'a> {
     },
     PerfEventOpen {
         attr: perf_event_attr,
-        pid: pid_t,
+        pid: libc::pid_t,
         cpu: i32,
         group: i32,
         flags: u32,
     },
     PerfEventIoctl {
         fd: BorrowedFd<'a>,
-        request: u32,
-        arg: c_int,
+        request: PerfEventIoctlRequest<'a>,
     },
 }
 
@@ -78,11 +85,10 @@ impl std::fmt::Debug for Syscall<'_> {
                 .field("group", group)
                 .field("flags", flags)
                 .finish(),
-            Self::PerfEventIoctl { fd, request, arg } => f
+            Self::PerfEventIoctl { fd, request } => f
                 .debug_struct("Syscall::PerfEventIoctl")
                 .field("fd", fd)
                 .field("request", request)
-                .field("arg", arg)
                 .finish(),
         }
     }
@@ -90,14 +96,16 @@ impl std::fmt::Debug for Syscall<'_> {
 
 fn syscall(call: Syscall<'_>) -> SysResult {
     #[cfg(test)]
-    return TEST_SYSCALL.with(|test_impl| unsafe { test_impl.borrow()(call) });
+    {
+        TEST_SYSCALL.with(|test_impl| unsafe { test_impl.borrow()(call) })
+    }
 
-    #[cfg_attr(test, allow(unreachable_code))]
+    #[cfg(not(test))]
     {
         let ret = unsafe {
             match call {
                 Syscall::Ebpf { cmd, attr } => {
-                    libc::syscall(SYS_bpf, cmd, attr, mem::size_of::<bpf_attr>())
+                    libc::syscall(libc::SYS_bpf, cmd, attr, std::mem::size_of::<bpf_attr>())
                 }
                 Syscall::PerfEventOpen {
                     attr,
@@ -105,9 +113,29 @@ fn syscall(call: Syscall<'_>) -> SysResult {
                     cpu,
                     group,
                     flags,
-                } => libc::syscall(SYS_perf_event_open, &attr, pid, cpu, group, flags),
-                Syscall::PerfEventIoctl { fd, request, arg } => {
-                    libc::syscall(SYS_ioctl, fd.as_raw_fd(), request, arg)
+                } => libc::syscall(libc::SYS_perf_event_open, &attr, pid, cpu, group, flags),
+                Syscall::PerfEventIoctl { fd, request } => {
+                    use std::os::fd::AsRawFd as _;
+
+                    let fd = fd.as_raw_fd();
+                    match request {
+                        PerfEventIoctlRequest::Enable => libc::syscall(
+                            libc::SYS_ioctl,
+                            fd,
+                            aya_obj::generated::PERF_EVENT_IOC_ENABLE,
+                        ),
+                        PerfEventIoctlRequest::Disable => libc::syscall(
+                            libc::SYS_ioctl,
+                            fd,
+                            aya_obj::generated::PERF_EVENT_IOC_DISABLE,
+                        ),
+                        PerfEventIoctlRequest::SetBpf(bpf_fd) => libc::syscall(
+                            libc::SYS_ioctl,
+                            fd,
+                            aya_obj::generated::PERF_EVENT_IOC_SET_BPF,
+                            bpf_fd.as_raw_fd(),
+                        ),
+                    }
                 }
             }
         };
@@ -128,11 +156,17 @@ pub(crate) unsafe fn mmap(
     fd: BorrowedFd<'_>,
     offset: libc::off_t,
 ) -> *mut c_void {
+    #[cfg(test)]
+    {
+        TEST_MMAP_RET.with(|ret| *ret.borrow())
+    }
+
     #[cfg(not(test))]
-    return libc::mmap(addr, len, prot, flags, fd.as_raw_fd(), offset);
+    {
+        use std::os::fd::AsRawFd as _;
 
-    #[cfg(test)]
-    TEST_MMAP_RET.with(|ret| *ret.borrow())
+        libc::mmap(addr, len, prot, flags, fd.as_raw_fd(), offset)
+    }
 }
 
 #[cfg_attr(test, allow(unused_variables))]

aya/src/sys/perf_event.rs

@@ -13,7 +13,7 @@ use aya_obj::generated::{
 };
 use libc::pid_t;
 
-use super::{syscall, SysResult, Syscall};
+use super::{syscall, PerfEventIoctlRequest, Syscall};
 
 #[allow(clippy::too_many_arguments)]
 pub(crate) fn perf_event_open(
@@ -104,8 +104,18 @@ pub(crate) fn perf_event_open_trace_point(
     perf_event_sys(attr, pid, cpu, PERF_FLAG_FD_CLOEXEC)
 }
 
-pub(crate) fn perf_event_ioctl(fd: BorrowedFd<'_>, request: u32, arg: c_int) -> SysResult {
-    syscall(Syscall::PerfEventIoctl { fd, request, arg })
+pub(crate) fn perf_event_ioctl(
+    fd: BorrowedFd<'_>,
+    request: PerfEventIoctlRequest<'_>,
+) -> io::Result<()> {
+    syscall(Syscall::PerfEventIoctl { fd, request })
+        .map(|code| {
+            assert_eq!(code, 0);
+        })
+        .map_err(|(code, io_error)| {
+            assert_eq!(code, -1);
+            io_error
+        })
 }
 
 fn perf_event_sys(