aya,aya-obj: cache feat probed info fields

Cached probed for ProgramInfo fields instead of exposing it through
global FEATURE. Probing occurs on cache miss, which happens when first
accessing the field, *and* if the field is 0.

aya-obj/src/obj.rs

@@ -45,8 +45,6 @@ pub struct Features {
     bpf_cookie: bool,
     cpumap_prog_id: bool,
     devmap_prog_id: bool,
-    prog_info_map_ids: bool,
-    prog_info_gpl_compatible: bool,
     btf: Option<BtfFeatures>,
 }
 
@@ -61,8 +59,6 @@ impl Features {
         bpf_cookie: bool,
         cpumap_prog_id: bool,
         devmap_prog_id: bool,
-        prog_info_map_ids: bool,
-        prog_info_gpl_compatible: bool,
         btf: Option<BtfFeatures>,
     ) -> Self {
         Self {
@@ -73,8 +69,6 @@ impl Features {
             bpf_cookie,
             cpumap_prog_id,
             devmap_prog_id,
-            prog_info_map_ids,
-            prog_info_gpl_compatible,
             btf,
         }
     }
@@ -117,16 +111,6 @@ impl Features {
         self.devmap_prog_id
     }
 
-    /// Returns whether `bpf_prog_info` supports `nr_map_ids` & `map_ids` fields.
-    pub fn prog_info_map_ids(&self) -> bool {
-        self.prog_info_map_ids
-    }
-
-    /// Returns whether `bpf_prog_info` supports `gpl_compatible` field.
-    pub fn prog_info_gpl_compatible(&self) -> bool {
-        self.prog_info_gpl_compatible
-    }
-
     /// If BTF is supported, returns which BTF features are supported.
     pub fn btf(&self) -> Option<&BtfFeatures> {
         self.btf.as_ref()

aya/src/bpf.rs

@@ -32,9 +32,9 @@ use crate::{
         bpf_load_btf, is_bpf_cookie_supported, is_bpf_global_data_supported,
         is_btf_datasec_supported, is_btf_decl_tag_supported, is_btf_enum64_supported,
         is_btf_float_supported, is_btf_func_global_supported, is_btf_func_supported,
-        is_btf_supported, is_btf_type_tag_supported, is_info_gpl_compatible_supported,
-        is_info_map_ids_supported, is_perf_link_supported, is_probe_read_kernel_supported,
-        is_prog_id_supported, is_prog_name_supported, retry_with_verifier_logs,
+        is_btf_supported, is_btf_type_tag_supported, is_perf_link_supported,
+        is_probe_read_kernel_supported, is_prog_id_supported, is_prog_name_supported,
+        retry_with_verifier_logs,
     },
     util::{bytes_of, bytes_of_slice, nr_cpus, page_size},
 };
@@ -82,8 +82,6 @@ fn detect_features() -> Features {
         is_bpf_cookie_supported(),
         is_prog_id_supported(BPF_MAP_TYPE_CPUMAP),
         is_prog_id_supported(BPF_MAP_TYPE_DEVMAP),
-        is_info_map_ids_supported(),
-        is_info_gpl_compatible_supported(),
         btf,
     );
     debug!("BPF Feature Detection: {f:#?}");

aya/src/programs/info.rs

@@ -4,6 +4,7 @@ use std::{
     ffi::CString,
     os::fd::{AsFd as _, BorrowedFd},
     path::Path,
+    sync::OnceLock,
     time::{Duration, SystemTime},
 };
 
@@ -16,7 +17,9 @@ use super::{
 use crate::{
     FEATURES,
     sys::{
-        SyscallError, bpf_get_object, bpf_prog_get_fd_by_id, bpf_prog_get_info_by_fd, iter_prog_ids,
+        SyscallError, bpf_get_object, bpf_prog_get_fd_by_id, bpf_prog_get_info_by_fd,
+        feature_probe::{is_prog_info_license_supported, is_prog_info_map_ids_supported},
+        iter_prog_ids,
     },
     util::bytes_of_bpf_name,
 };
@@ -108,13 +111,15 @@ impl ProgramInfo {
     ///
     /// Introduced in kernel v4.15.
     pub fn map_ids(&self) -> Result<Option<Vec<u32>>, ProgramError> {
-        if FEATURES.prog_info_map_ids() {
-            let mut map_ids = vec![0u32; self.0.nr_map_ids as usize];
-            bpf_prog_get_info_by_fd(self.fd()?.as_fd(), &mut map_ids)?;
-            Ok(Some(map_ids))
-        } else {
-            Ok(None)
-        }
+        static CACHE: OnceLock<bool> = OnceLock::new();
+        CACHE
+            .get_or_init(|| matches!(is_prog_info_map_ids_supported(), Ok(true)))
+            .then(|| {
+                let mut map_ids = vec![0u32; self.0.nr_map_ids as usize];
+                bpf_prog_get_info_by_fd(self.fd()?.as_fd(), &mut map_ids)?;
+                Ok(map_ids)
+            })
+            .transpose()
     }
 
     /// The name of the program as was provided when it was load. This is limited to 16 bytes.
@@ -140,8 +145,9 @@ impl ProgramInfo {
     ///
     /// Introduced in kernel v4.18.
     pub fn gpl_compatible(&self) -> Option<bool> {
-        FEATURES
-            .prog_info_gpl_compatible()
+        static CACHE: OnceLock<bool> = OnceLock::new();
+        CACHE
+            .get_or_init(|| matches!(is_prog_info_license_supported(), Ok(true)))
             .then_some(self.0.gpl_compatible() != 0)
     }
 

aya/src/sys/bpf.rs

@@ -25,7 +25,7 @@ use aya_obj::{
 use libc::{ENOENT, ENOSPC};
 
 use crate::{
-    Btf, FEATURES, Pod, VerifierLogLevel,
+    Btf, Pod, VerifierLogLevel,
     maps::{MapData, PerCpuValues},
     programs::{ProgramType, links::LinkRef},
     sys::{Syscall, SyscallError, syscall},
@@ -593,7 +593,7 @@ pub(crate) fn bpf_prog_get_info_by_fd(
     // An `E2BIG` error can occur on kernels below v4.15 when handing over a large struct where the
     // extra space is not all-zero bytes.
     bpf_obj_get_info_by_fd(fd, |info: &mut bpf_prog_info| {
-        if FEATURES.prog_info_map_ids() {
+        if !map_ids.is_empty() {
             info.nr_map_ids = map_ids.len() as _;
             info.map_ids = map_ids.as_mut_ptr() as _;
         }
@@ -808,34 +808,6 @@ where
     op(&mut attr)
 }
 
-/// Tests whether `nr_map_ids` & `map_ids` fields in `bpf_prog_info` is available.
-pub(crate) fn is_info_map_ids_supported() -> bool {
-    with_trivial_prog(ProgramType::TracePoint, |attr| {
-        let prog_fd = match bpf_prog_load(attr) {
-            Ok(fd) => fd,
-            Err(_) => return false,
-        };
-        bpf_obj_get_info_by_fd(prog_fd.as_fd(), |info: &mut bpf_prog_info| {
-            info.nr_map_ids = 1
-        })
-        .is_ok()
-    })
-}
-
-/// Tests whether `gpl_compatible` field in `bpf_prog_info` is available.
-pub(crate) fn is_info_gpl_compatible_supported() -> bool {
-    with_trivial_prog(ProgramType::TracePoint, |attr| {
-        let prog_fd = match bpf_prog_load(attr) {
-            Ok(fd) => fd,
-            Err(_) => return false,
-        };
-        if let Ok::<bpf_prog_info, _>(info) = bpf_obj_get_info_by_fd(prog_fd.as_fd(), |_| {}) {
-            return info.gpl_compatible() != 0;
-        }
-        false
-    })
-}
-
 pub(crate) fn is_probe_read_kernel_supported() -> bool {
     let mut attr = unsafe { mem::zeroed::<bpf_attr>() };
     let u = unsafe { &mut attr.__bindgen_anon_3 };
@@ -1145,7 +1117,7 @@ fn sys_bpf(cmd: bpf_cmd, attr: &mut bpf_attr) -> io::Result<i64> {
     })
 }
 
-fn unit_sys_bpf(cmd: bpf_cmd, attr: &mut bpf_attr) -> io::Result<()> {
+pub(super) fn unit_sys_bpf(cmd: bpf_cmd, attr: &mut bpf_attr) -> io::Result<()> {
     sys_bpf(cmd, attr).map(|code| assert_eq!(code, 0))
 }
 

aya/src/sys/feature_probe.rs

@@ -4,11 +4,13 @@ use std::{mem, os::fd::AsRawFd as _};
 
 use aya_obj::{
     btf::{Btf, BtfKind},
-    generated::{BPF_F_MMAPABLE, BPF_F_NO_PREALLOC, bpf_attr, bpf_cmd, bpf_map_type},
+    generated::{
+        BPF_F_MMAPABLE, BPF_F_NO_PREALLOC, bpf_attr, bpf_cmd, bpf_map_type, bpf_prog_info,
+    },
 };
 use libc::{E2BIG, EBADF, EINVAL};
 
-use super::{SyscallError, bpf_prog_load, fd_sys_bpf, with_trivial_prog};
+use super::{SyscallError, bpf_prog_load, fd_sys_bpf, unit_sys_bpf, with_trivial_prog};
 use crate::{
     MockableFd,
     maps::MapType,
@@ -26,7 +28,7 @@ use crate::{
 /// match is_program_supported(ProgramType::Xdp) {
 ///     Ok(true) => println!("XDP supported :)"),
 ///     Ok(false) => println!("XDP not supported :("),
-///     Err(err) => println!("Uh oh! Unexpected error: {:?}", err),
+///     Err(err) => println!("Uh oh! Unexpected error while probing: {:?}", err),
 /// }
 /// ```
 ///
@@ -167,7 +169,7 @@ pub fn is_program_supported(program_type: ProgramType) -> Result<bool, ProgramEr
 /// match is_map_supported(MapType::HashOfMaps) {
 ///     Ok(true) => println!("hash_of_maps supported :)"),
 ///     Ok(false) => println!("hash_of_maps not supported :("),
-///     Err(err) => println!("Uh oh! Unexpected error: {:?}", err),
+///     Err(err) => println!("Uh oh! Unexpected error while probing: {:?}", err),
 /// }
 /// ```
 ///
@@ -352,3 +354,59 @@ pub fn is_map_supported(map_type: MapType) -> Result<bool, SyscallError> {
         }),
     }
 }
+
+/// Whether `nr_map_ids` & `map_ids` fields in `bpf_prog_info` are supported.
+pub(crate) fn is_prog_info_map_ids_supported() -> Result<bool, ProgramError> {
+    let fd = with_trivial_prog(ProgramType::SocketFilter, |attr| {
+        bpf_prog_load(attr).map_err(|io_error| {
+            ProgramError::SyscallError(SyscallError {
+                call: "bpf_prog_load",
+                io_error,
+            })
+        })
+    })?;
+    // SAFETY: all-zero byte-pattern valid for `bpf_prog_info`
+    let mut info = unsafe { mem::zeroed::<bpf_prog_info>() };
+    info.nr_map_ids = 1;
+
+    probe_bpf_info(fd, info).map_err(ProgramError::from)
+}
+
+/// Tests whether `bpf_prog_info.gpl_compatible` field is supported.
+pub(crate) fn is_prog_info_license_supported() -> Result<bool, ProgramError> {
+    let fd = with_trivial_prog(ProgramType::SocketFilter, |attr| {
+        bpf_prog_load(attr).map_err(|io_error| {
+            ProgramError::SyscallError(SyscallError {
+                call: "bpf_prog_load",
+                io_error,
+            })
+        })
+    })?;
+    // SAFETY: all-zero byte-pattern valid for `bpf_prog_info`
+    let mut info = unsafe { mem::zeroed::<bpf_prog_info>() };
+    info.set_gpl_compatible(1);
+
+    probe_bpf_info(fd, info).map_err(ProgramError::from)
+}
+
+/// Probes program and map info.
+fn probe_bpf_info<T>(fd: MockableFd, info: T) -> Result<bool, SyscallError> {
+    // SAFETY: all-zero byte-pattern valid for `bpf_attr`
+    let mut attr = unsafe { mem::zeroed::<bpf_attr>() };
+    attr.info.bpf_fd = fd.as_raw_fd() as u32;
+    attr.info.info_len = mem::size_of_val(&info) as u32;
+    attr.info.info = &info as *const _ as u64;
+
+    let io_error = match unit_sys_bpf(bpf_cmd::BPF_OBJ_GET_INFO_BY_FD, &mut attr) {
+        Ok(()) => return Ok(true),
+        Err(io_error) => io_error,
+    };
+    match io_error.raw_os_error() {
+        // `E2BIG` from `bpf_check_uarg_tail_zero()`
+        Some(E2BIG) => Ok(false),
+        _ => Err(SyscallError {
+            call: "bpf_obj_get_info_by_fd",
+            io_error,
+        }),
+    }
+}

aya/src/sys/mod.rs

@@ -1,7 +1,7 @@
 //! A collection of system calls for performing eBPF related operations.
 
 mod bpf;
-mod feature_probe;
+pub(crate) mod feature_probe;
 mod netlink;
 mod perf_event;
 

test/integration-test/src/tests/info.rs

@@ -12,6 +12,7 @@ use aya::{
     Ebpf,
     maps::{Array, HashMap, IterableMap as _, MapError, MapType, loaded_maps},
     programs::{ProgramError, ProgramType, SocketFilter, TracePoint, UProbe, loaded_programs},
+    sys::{is_map_supported, is_program_supported},
     util::KernelVersion,
 };
 use libc::EINVAL;
@@ -20,7 +21,11 @@ use crate::utils::{kernel_assert, kernel_assert_eq};
 
 #[test]
 fn test_loaded_programs() {
-    // Load a program.
+    if !is_program_supported(ProgramType::SocketFilter).unwrap() {
+        eprintln!("skipping test - socket_filter program not supported");
+        return;
+    }
+
     // Since we are only testing the programs for their metadata, there is no need to "attach" them.
     let mut bpf = Ebpf::load(crate::TEST).unwrap();
     let prog: &mut UProbe = bpf.program_mut("test_uprobe").unwrap().try_into().unwrap();
@@ -33,9 +38,7 @@ fn test_loaded_programs() {
         if let ProgramError::SyscallError(err) = &err {
             // Skip entire test since feature not available
             if err.io_error.raw_os_error() == Some(EINVAL) {
-                eprintln!(
-                    "ignoring test completely as `loaded_programs()` is not available on the host"
-                );
+                eprintln!("skipping test - `loaded_programs()` not supported");
                 return;
             }
         }
@@ -71,6 +74,11 @@ fn test_loaded_programs() {
 
 #[test]
 fn test_program_info() {
+    if !is_program_supported(ProgramType::SocketFilter).unwrap() {
+        eprintln!("skipping test - socket_filter program not supported");
+        return;
+    }
+
     // Kernels below v4.15 have been observed to have `bpf_jit_enable` disabled by default.
     let _guard = ensure_sysctl_enabled("/proc/sys/net/core/bpf_jit_enable");
 
@@ -129,6 +137,11 @@ fn test_program_info() {
 
 #[test]
 fn test_loaded_at() {
+    if !is_program_supported(ProgramType::SocketFilter).unwrap() {
+        eprintln!("skipping test - socket_filter program not supported");
+        return;
+    }
+
     let mut bpf: Ebpf = Ebpf::load(crate::SIMPLE_PROG).unwrap();
     let prog: &mut SocketFilter = bpf.program_mut("simple_prog").unwrap().try_into().unwrap();
 
@@ -144,9 +157,7 @@ fn test_loaded_at() {
         let loaded_at = match prog.info().unwrap().loaded_at() {
             Some(time) => time,
             None => {
-                eprintln!(
-                    "ignoring test completely as `load_time` field of `bpf_prog_info` is not available on the host"
-                );
+                eprintln!("skipping test - `bpf_prog_info.load_time` field not supported");
                 return;
             }
         };
@@ -175,11 +186,12 @@ fn test_loaded_at() {
 
 #[test]
 fn test_prog_stats() {
-    // Test depends on whether trace point exists.
+    if !is_program_supported(ProgramType::TracePoint).unwrap() {
+        eprintln!("skipping test - tracepoint program not supported");
+        return;
+    }
     if !Path::new("/sys/kernel/debug/tracing/events/syscalls/sys_enter_bpf").exists() {
-        eprintln!(
-            "ignoring test completely as `syscalls/sys_enter_bpf` is not available on the host"
-        );
+        eprintln!("skipping test - `syscalls/sys_enter_bpf` not available");
         return;
     }
 
@@ -200,6 +212,17 @@ fn test_prog_stats() {
 
 #[test]
 fn list_loaded_maps() {
+    if !is_program_supported(ProgramType::SocketFilter).unwrap() {
+        eprintln!("skipping test - socket_filter program not supported");
+        return;
+    } else if !is_map_supported(MapType::Hash).unwrap() {
+        eprintln!("skipping test - hash map not supported");
+        return;
+    } else if !is_map_supported(MapType::Array).unwrap() {
+        eprintln!("skipping test - array map not supported");
+        return;
+    }
+
     // Load a program with maps.
     let mut bpf: Ebpf = Ebpf::load(crate::MAP_TEST).unwrap();
     let prog: &mut SocketFilter = bpf.program_mut("simple_prog").unwrap().try_into().unwrap();
@@ -210,9 +233,7 @@ fn list_loaded_maps() {
     if let Err(err) = maps.peek().unwrap() {
         if let MapError::SyscallError(err) = &err {
             if err.io_error.raw_os_error() == Some(EINVAL) {
-                eprintln!(
-                    "ignoring test completely as `loaded_maps()` is not available on the host"
-                );
+                eprintln!("skipping test - `loaded_maps()` not supported");
                 return;
             }
         }
@@ -250,6 +271,17 @@ fn list_loaded_maps() {
 
 #[test]
 fn test_map_info() {
+    if !is_program_supported(ProgramType::SocketFilter).unwrap() {
+        eprintln!("skipping test - socket_filter program not supported");
+        return;
+    } else if !is_map_supported(MapType::Hash).unwrap() {
+        eprintln!("skipping test - hash map not supported");
+        return;
+    } else if !is_map_supported(MapType::Array).unwrap() {
+        eprintln!("skipping test - array map not supported");
+        return;
+    }
+
     let mut bpf: Ebpf = Ebpf::load(crate::MAP_TEST).unwrap();
     let prog: &mut SocketFilter = bpf.program_mut("simple_prog").unwrap().try_into().unwrap();
     prog.load().unwrap();

xtask/public-api/aya-obj.txt

@@ -8678,8 +8678,6 @@ pub fn aya_obj::Features::bpf_probe_read_kernel(&self) -> bool
 pub fn aya_obj::Features::btf(&self) -> core::option::Option<&aya_obj::btf::BtfFeatures>
 pub fn aya_obj::Features::cpumap_prog_id(&self) -> bool
 pub fn aya_obj::Features::devmap_prog_id(&self) -> bool
-pub fn aya_obj::Features::prog_info_gpl_compatible(&self) -> bool
-pub fn aya_obj::Features::prog_info_map_ids(&self) -> bool
 impl core::default::Default for aya_obj::Features
 pub fn aya_obj::Features::default() -> aya_obj::Features
 impl core::fmt::Debug for aya_obj::Features
@@ -9541,8 +9539,6 @@ pub fn aya_obj::Features::bpf_probe_read_kernel(&self) -> bool
 pub fn aya_obj::Features::btf(&self) -> core::option::Option<&aya_obj::btf::BtfFeatures>
 pub fn aya_obj::Features::cpumap_prog_id(&self) -> bool
 pub fn aya_obj::Features::devmap_prog_id(&self) -> bool
-pub fn aya_obj::Features::prog_info_gpl_compatible(&self) -> bool
-pub fn aya_obj::Features::prog_info_map_ids(&self) -> bool
 impl core::default::Default for aya_obj::Features
 pub fn aya_obj::Features::default() -> aya_obj::Features
 impl core::fmt::Debug for aya_obj::Features