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fix(aya): Fix PerfEventArray resize logic

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There was a logic bug in the previously merged patch where we
set the correctly calculated max_entries size with the original.

To fix this and prevent regressions a unit test was added.
This highlighted that the original map definition needs to be
mutated in order for the max_entries change to be properly applied.

As such, this resize logic moved out of aya::sys into aya::maps

Signed-off-by: Dave Tucker <dave@dtucker.co.uk>
pull/1003/head
Dave Tucker 6 months ago committed by Michal Rostecki
parent e575712c59
commit 3d57d358e4
5 changed files with 108 additions and 26 deletions
Show Stats Download Patch File Download Diff File

3
aya/src/maps/bloom_filter.rs
Unescape Escape View File

@ -120,8 +120,7 @@ mod tests {
#[test]
fn test_try_from_wrong_map() {
// This is necessary to stop miri tripping over the PERF_EVENT_ARRAY
// logic and attempting to open a file to read number of online CPUs.
// Use any map type here other than BPF_MAP_TYPE_PERF_EVENT_ARRAY as it will trip miri
let map = new_map(test_utils::new_obj_map::<u32>(BPF_MAP_TYPE_ARRAY));
let map = Map::Array(map);

3
aya/src/maps/lpm_trie.rs
Unescape Escape View File

@ -249,8 +249,7 @@ mod tests {
#[test]
fn test_try_from_wrong_map() {
// This is necessary to stop miri tripping over the PERF_EVENT_ARRAY
// logic and attempting to open a file to read number of online CPUs.
// Use any map type here other than BPF_MAP_TYPE_PERF_EVENT_ARRAY as it will trip miri
let map = new_map(test_utils::new_obj_map::<u32>(BPF_MAP_TYPE_ARRAY));
let map = Map::Array(map);

103
aya/src/maps/mod.rs
Unescape Escape View File

@ -59,6 +59,7 @@ use std::{
ptr,
};
use aya_obj::generated::bpf_map_type;
use libc::{getrlimit, rlim_t, rlimit, RLIMIT_MEMLOCK, RLIM_INFINITY};
use log::warn;
use obj::maps::InvalidMapTypeError;
@ -172,6 +173,10 @@ pub enum MapError {
#[error("the program is not loaded")]
ProgramNotLoaded,
/// An IO error occurred
#[error(transparent)]
IoError(#[from] io::Error),
/// Syscall failed
#[error(transparent)]
SyscallError(#[from] SyscallError),
@ -550,12 +555,30 @@ pub struct MapData {
impl MapData {
/// Creates a new map with the provided `name`
pub fn create(
obj: obj::Map,
mut obj: obj::Map,
name: &str,
btf_fd: Option<BorrowedFd<'_>>,
) -> Result<Self, MapError> {
let c_name = CString::new(name).map_err(|_| MapError::InvalidName { name: name.into() })?;
// BPF_MAP_TYPE_PERF_EVENT_ARRAY's max_entries should not exceed the number of
// CPUs.
//
// By default, the newest versions of Aya, libbpf and cilium/ebpf define `max_entries` of
// `PerfEventArray` as `0`, with an intention to get it replaced with a correct value
// by the loader.
//
// We allow custom values (potentially coming either from older versions of aya-ebpf or
// programs written in C) as long as they don't exceed the number of CPUs.
//
// Otherwise, when the value is `0` or too large, we set it to the number of CPUs.
if obj.map_type() == bpf_map_type::BPF_MAP_TYPE_PERF_EVENT_ARRAY as u32 {
let ncpus = nr_cpus().map_err(MapError::IoError)? as u32;
if obj.max_entries() == 0 || obj.max_entries() > ncpus {
obj.set_max_entries(ncpus);
}
};
#[cfg(not(test))]
let kernel_version = KernelVersion::current().unwrap();
#[cfg(test)]
@ -1077,6 +1100,25 @@ mod test_utils {
symbol_index: None,
})
}
pub(super) fn new_obj_map_with_max_entries<K>(
map_type: bpf_map_type,
max_entries: u32,
) -> obj::Map {
obj::Map::Legacy(LegacyMap {
def: bpf_map_def {
map_type: map_type as u32,
key_size: std::mem::size_of::<K>() as u32,
value_size: 4,
max_entries,
..Default::default()
},
section_index: 0,
section_kind: EbpfSectionKind::Maps,
data: Vec::new(),
symbol_index: None,
})
}
}
#[cfg(test)]
@ -1150,6 +1192,65 @@ mod tests {
);
}
#[test]
#[cfg_attr(miri, ignore = "nr_cpus() opens a file on procfs that upsets miri")]
fn test_create_perf_event_array() {
override_syscall(|call| match call {
Syscall::Ebpf {
cmd: bpf_cmd::BPF_MAP_CREATE,
..
} => Ok(crate::MockableFd::mock_signed_fd().into()),
_ => Err((-1, io::Error::from_raw_os_error(EFAULT))),
});
let ncpus = nr_cpus().unwrap();
// Create with max_entries > ncpus is clamped to ncpus
assert_matches!(
MapData::create(test_utils::new_obj_map_with_max_entries::<u32>(
crate::generated::bpf_map_type::BPF_MAP_TYPE_PERF_EVENT_ARRAY,
65535,
), "foo", None),
Ok(MapData {
obj,
fd,
}) => {
assert_eq!(fd.as_fd().as_raw_fd(), crate::MockableFd::mock_signed_fd());
assert_eq!(obj.max_entries(), ncpus as u32)
}
);
// Create with max_entries = 0 is set to ncpus
assert_matches!(
MapData::create(test_utils::new_obj_map_with_max_entries::<u32>(
crate::generated::bpf_map_type::BPF_MAP_TYPE_PERF_EVENT_ARRAY,
0,
), "foo", None),
Ok(MapData {
obj,
fd,
}) => {
assert_eq!(fd.as_fd().as_raw_fd(), crate::MockableFd::mock_signed_fd());
assert_eq!(obj.max_entries(), ncpus as u32)
}
);
// Create with max_entries < ncpus is unchanged
assert_matches!(
MapData::create(test_utils::new_obj_map_with_max_entries::<u32>(
crate::generated::bpf_map_type::BPF_MAP_TYPE_PERF_EVENT_ARRAY,
1,
), "foo", None),
Ok(MapData {
obj,
fd,
}) => {
assert_eq!(fd.as_fd().as_raw_fd(), crate::MockableFd::mock_signed_fd());
assert_eq!(obj.max_entries(), 1)
}
);
}
#[test]
#[cfg_attr(
miri,

22
aya/src/sys/bpf.rs
Unescape Escape View File

@ -30,7 +30,7 @@ use crate::{
copy_instructions,
},
sys::{syscall, SysResult, Syscall, SyscallError},
util::{nr_cpus, KernelVersion},
util::KernelVersion,
Btf, Pod, VerifierLogLevel, BPF_OBJ_NAME_LEN,
};
@ -46,26 +46,6 @@ pub(crate) fn bpf_create_map(
u.map_type = def.map_type();
u.key_size = def.key_size();
u.value_size = def.value_size();
u.max_entries = def.max_entries();
// BPF_MAP_TYPE_PERF_EVENT_ARRAY's max_entries should not exceed the number of
// CPUs.
//
// By default, the newest versions of Aya, libbpf and cilium/ebpf define `max_entries` of
// `PerfEventArray` as `0`, with an intention to get it replaced with a correct value
// by the loader.
//
// We allow custom values (potentially coming either from older versions of aya-ebpf or
// programs written in C) as long as they don't exceed the number of CPUs.
//
// Otherwise, when the value is `0` or too large, we set it to the number of CPUs.
if def.map_type() == bpf_map_type::BPF_MAP_TYPE_PERF_EVENT_ARRAY as u32 {
let ncpus = nr_cpus().map_err(|e| (-1i64, e))? as u32;
if u.max_entries == 0 || u.max_entries > ncpus {
u.max_entries = ncpus;
}
};
u.max_entries = def.max_entries();
u.map_flags = def.map_flags();

3
xtask/public-api/aya.txt
Unescape Escape View File

@ -1352,6 +1352,7 @@ pub aya::maps::MapError::InvalidName::name: alloc::string::String
pub aya::maps::MapError::InvalidValueSize
pub aya::maps::MapError::InvalidValueSize::expected: usize
pub aya::maps::MapError::InvalidValueSize::size: usize
pub aya::maps::MapError::IoError(std::io::error::Error)
pub aya::maps::MapError::KeyNotFound
pub aya::maps::MapError::OutOfBounds
pub aya::maps::MapError::OutOfBounds::index: u32
@ -1372,6 +1373,8 @@ impl core::convert::From<aya::maps::MapError> for aya::programs::ProgramError
pub fn aya::programs::ProgramError::from(source: aya::maps::MapError) -> Self
impl core::convert::From<aya_obj::maps::InvalidMapTypeError> for aya::maps::MapError
pub fn aya::maps::MapError::from(e: aya_obj::maps::InvalidMapTypeError) -> Self
impl core::convert::From<std::io::error::Error> for aya::maps::MapError
pub fn aya::maps::MapError::from(source: std::io::error::Error) -> Self
impl core::error::Error for aya::maps::MapError
pub fn aya::maps::MapError::source(&self) -> core::option::Option<&(dyn core::error::Error + 'static)>
impl core::fmt::Debug for aya::maps::MapError

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