mirror of https://github.com/aya-rs/aya
aya-ebpf: Add BTF array definition
Before this change, Aya supported only legacy BPF map definitions, which are instances of the `bpf_map_def` struct and end up in the `maps` ELF section. This change introduces a BTF map definition for arrays, with custom structs indicating the metadata of the map, which end up in the `.maps` section.reviewable/pr1340/r6
Michal R
4 days ago
parent
7f65983b2f
commit
ddb30ea420
@ -0,0 +1,75 @@
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use std::borrow::Cow;
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use proc_macro2::TokenStream;
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use quote::quote;
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use syn::{ItemStatic, Result};
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use crate::args::name_arg;
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pub(crate) struct BtfMap {
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item: ItemStatic,
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name: String,
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}
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impl BtfMap {
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pub(crate) fn parse(attrs: TokenStream, item: TokenStream) -> Result<BtfMap> {
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let item: ItemStatic = syn::parse2(item)?;
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let mut args = syn::parse2(attrs)?;
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let name = name_arg(&mut args).unwrap_or_else(|| item.ident.to_string());
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Ok(BtfMap { item, name })
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}
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pub(crate) fn expand(&self) -> TokenStream {
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let section_name: Cow<'_, _> = ".maps".into();
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let name = &self.name;
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let item = &self.item;
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quote! {
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#[unsafe(link_section = #section_name)]
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#[unsafe(export_name = #name)]
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#item
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}
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}
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}
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#[cfg(test)]
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mod tests {
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use syn::parse_quote;
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use super::*;
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#[test]
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fn test_map_with_name() {
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let map = BtfMap::parse(
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parse_quote!(name = "foo"),
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parse_quote!(
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static BAR: HashMap<&'static str, u32> = HashMap::new();
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),
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)
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.unwrap();
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let expanded = map.expand();
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let expected = quote!(
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#[unsafe(link_section = ".maps")]
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#[unsafe(export_name = "foo")]
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static BAR: HashMap<&'static str, u32> = HashMap::new();
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);
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assert_eq!(expected.to_string(), expanded.to_string());
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}
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#[test]
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fn test_map_no_name() {
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let map = BtfMap::parse(
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parse_quote!(),
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parse_quote!(
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static BAR: HashMap<&'static str, u32> = HashMap::new();
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),
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)
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.unwrap();
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let expanded = map.expand();
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let expected = quote!(
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#[unsafe(link_section = ".maps")]
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#[unsafe(export_name = "BAR")]
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static BAR: HashMap<&'static str, u32> = HashMap::new();
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);
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assert_eq!(expected.to_string(), expanded.to_string());
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}
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}
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@ -0,0 +1,70 @@
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use core::{cell::UnsafeCell, ptr::NonNull};
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use crate::{
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bindings::bpf_map_type::BPF_MAP_TYPE_ARRAY, btf_map_def, cty::c_long, error::EINVAL, insert,
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lookup,
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};
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btf_map_def!(ArrayDef, BPF_MAP_TYPE_ARRAY);
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#[repr(transparent)]
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pub struct Array<T, const M: usize, const F: usize = 0>(UnsafeCell<ArrayDef<u32, T, M, F>>);
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unsafe impl<T: Sync, const M: usize, const F: usize> Sync for Array<T, M, F> {}
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impl<T, const M: usize, const F: usize> Array<T, M, F> {
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/// Creates a new [`Array`] instance with elements of type `T`, maximum
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/// capacity of `M` and additional flags `F`.
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///
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/// # Example
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///
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/// ```rust
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/// use aya_ebpf::{btf_maps::Array, macros::btf_map};
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///
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/// #[btf_map]
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/// static ARRAY: Array<u32, 10 /* max_elements */, 0> = Array::new();
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/// ```
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// BPF maps are always used as static variables, therefore this method has
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// to be `const`. `Default::default` is not const.
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#[expect(clippy::new_without_default)]
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pub const fn new() -> Self {
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Array(UnsafeCell::new(ArrayDef::new()))
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}
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#[inline(always)]
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pub fn get(&self, index: u32) -> Result<Option<&T>, c_long> {
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unsafe {
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match self.lookup(index) {
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Some(p) => {
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if p.is_aligned() {
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Ok(Some(p.as_ref()))
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} else {
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Err(-EINVAL)
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}
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}
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None => Ok(None),
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}
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}
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}
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#[inline(always)]
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pub fn get_ptr(&self, index: u32) -> Option<*const T> {
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unsafe { self.lookup(index).map(|p| p.as_ptr() as *const T) }
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}
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#[inline(always)]
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pub fn get_ptr_mut(&self, index: u32) -> Option<*mut T> {
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unsafe { self.lookup(index).map(|p| p.as_ptr()) }
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}
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#[inline(always)]
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unsafe fn lookup(&self, index: u32) -> Option<NonNull<T>> {
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lookup(self.0.get().cast(), &index)
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}
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/// Sets the value of the element at the given index.
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#[inline(always)]
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pub fn set(&self, index: u32, value: &T, flags: u64) -> Result<(), c_long> {
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insert(self.0.get().cast(), &index, value, flags)
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}
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}
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@ -0,0 +1,51 @@
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use core::marker::PhantomData;
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pub mod array;
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pub use array::Array;
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/// A marker used to remove names of annotated types in LLVM debug info and
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/// therefore also in BTF.
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#[repr(transparent)]
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pub(crate) struct AyaBtfMapMarker(PhantomData<()>);
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impl AyaBtfMapMarker {
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pub(crate) const fn new() -> Self {
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Self(PhantomData)
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}
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}
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#[macro_export]
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macro_rules! btf_map_def {
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($name:ident, $t:ident) => {
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// These fields exists only for BTF metadata exposure. None of them are
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// are actually used.
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#[expect(dead_code)]
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pub struct $name<K, V, const M: usize, const F: usize = 0> {
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r#type: *const [i32; $t as usize],
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key: *const K,
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value: *const V,
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max_entries: *const [i32; M],
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map_flags: *const [i32; F],
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// Anonymize the struct.
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_anon: $crate::btf_maps::AyaBtfMapMarker,
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}
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// BPF maps are always used as static variables, therefore this method
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// has to be `const`. `Default::default` is not const.
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#[expect(clippy::new_without_default)]
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impl<K, V, const M: usize, const F: usize> $name<K, V, M, F> {
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pub const fn new() -> $name<K, V, M, F> {
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$name {
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r#type: &[0i32; $t as usize],
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key: ::core::ptr::null(),
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value: ::core::ptr::null(),
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max_entries: &[0i32; M],
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map_flags: &[0i32; F],
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_anon: $crate::btf_maps::AyaBtfMapMarker::new(),
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}
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}
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}
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};
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}
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@ -0,0 +1,90 @@
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#![no_std]
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#![no_main]
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#[cfg(not(test))]
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extern crate ebpf_panic;
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use aya_ebpf::{
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btf_maps::Array,
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cty::c_long,
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macros::{btf_map, map, uprobe},
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maps::Array as LegacyArray,
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programs::ProbeContext,
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};
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use integration_common::array::{GET_INDEX, GET_PTR_INDEX, GET_PTR_MUT_INDEX};
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#[btf_map]
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static RESULT: Array<u32, 3 /* max_elements */, 0> = Array::new();
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#[btf_map]
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static ARRAY: Array<u32, 10 /* max_elements */, 0> = Array::new();
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#[map]
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static RESULT_LEGACY: LegacyArray<u32> = LegacyArray::with_max_entries(3, 0);
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#[map]
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static ARRAY_LEGACY: LegacyArray<u32> = LegacyArray::with_max_entries(10, 0);
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macro_rules! define_array_test {
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(
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$result_map:ident,
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$array_map:ident,
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$result_set_fn:ident,
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$set_prog:ident,
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$get_prog:ident,
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$get_ptr_prog:ident,
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$get_ptr_mut_prog:ident
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$(,)?
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) => {
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#[inline(always)]
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fn $result_set_fn(index: u32, value: u32) -> Result<(), c_long> {
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let ptr = $result_map.get_ptr_mut(index).ok_or(-1)?;
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let dst = unsafe { ptr.as_mut() };
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let dst_res = dst.ok_or(-1)?;
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*dst_res = value;
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Ok(())
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}
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#[uprobe]
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pub fn $set_prog(ctx: ProbeContext) -> Result<(), c_long> {
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let index = ctx.arg(0).ok_or(-1)?;
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let value = ctx.arg(1).ok_or(-1)?;
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$array_map.set(index, &value, 0)?;
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Ok(())
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}
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#[uprobe]
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pub fn $get_prog(ctx: ProbeContext) -> Result<(), c_long> {
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let index = ctx.arg(0).ok_or(-1)?;
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let value = $array_map.get(index)?.ok_or(-1)?;
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$result_set_fn(GET_INDEX, *value)?;
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Ok(())
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}
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#[uprobe]
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pub fn $get_ptr_prog(ctx: ProbeContext) -> Result<(), c_long> {
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let index = ctx.arg(0).ok_or(-1)?;
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let value = $array_map.get_ptr(index).ok_or(-1)?;
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$result_set_fn(GET_PTR_INDEX, unsafe { *value })?;
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Ok(())
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}
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#[uprobe]
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pub fn $get_ptr_mut_prog(ctx: ProbeContext) -> Result<(), c_long> {
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let index = ctx.arg(0).ok_or(-1)?;
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let ptr = $array_map.get_ptr_mut(index).ok_or(-1)?;
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let value = unsafe { *ptr };
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$result_set_fn(GET_PTR_MUT_INDEX, value)?;
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Ok(())
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}
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};
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}
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define_array_test!(RESULT, ARRAY, result_set, set, get, get_ptr, get_ptr_mut);
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define_array_test!(
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RESULT_LEGACY,
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ARRAY_LEGACY,
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result_set_legacy,
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set_legacy,
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get_legacy,
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get_ptr_legacy,
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get_ptr_mut_legacy,
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);
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@ -0,0 +1,88 @@
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use aya::{EbpfLoader, maps::Array, programs::UProbe};
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use integration_common::array::{GET_INDEX, GET_PTR_INDEX, GET_PTR_MUT_INDEX};
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#[unsafe(no_mangle)]
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#[inline(never)]
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pub extern "C" fn set(index: u32, value: u32) {
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std::hint::black_box((index, value));
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}
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#[unsafe(no_mangle)]
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#[inline(never)]
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pub extern "C" fn get(index: u32) {
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std::hint::black_box(index);
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}
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#[unsafe(no_mangle)]
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#[inline(never)]
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pub extern "C" fn get_ptr(index: u32) {
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std::hint::black_box(index);
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}
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#[unsafe(no_mangle)]
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#[inline(never)]
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pub extern "C" fn get_ptr_mut(index: u32) {
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std::hint::black_box(index);
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}
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#[test_log::test]
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fn test_array() {
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let mut ebpf = EbpfLoader::new().load(crate::ARRAY).unwrap();
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for (result_map, array_map, progs_and_symbols) in [
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// BTF map definitions.
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(
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"RESULT",
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"ARRAY",
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[
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("set", "set"),
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("get", "get"),
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("get_ptr", "get_ptr"),
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("get_ptr_mut", "get_ptr_mut"),
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],
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),
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// Legacy map definitions.
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(
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"RESULT_LEGACY",
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"ARRAY_LEGACY",
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[
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("set_legacy", "set"),
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("get_legacy", "get"),
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("get_ptr_legacy", "get_ptr"),
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("get_ptr_mut_legacy", "get_ptr_mut"),
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],
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),
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] {
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for (prog_name, symbol) in progs_and_symbols {
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let prog: &mut UProbe = ebpf.program_mut(prog_name).unwrap().try_into().unwrap();
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prog.load().unwrap();
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prog.attach(symbol, "/proc/self/exe", None, None).unwrap();
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}
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let result_array = ebpf.map(result_map).unwrap();
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let result_array = Array::<_, u32>::try_from(result_array).unwrap();
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let array = ebpf.map(array_map).unwrap();
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let array = Array::<_, u32>::try_from(array).unwrap();
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let seq = 0..9;
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for i in seq.clone() {
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set(i, i.pow(2));
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}
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for i in seq.clone() {
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// Assert the value returned by user-space API.
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let expected_value = i.pow(2);
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let value = array.get(&i, 0).unwrap();
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assert_eq!(value, expected_value);
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// Assert the value returned by eBPF in-kernel API.
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get(i);
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let result = result_array.get(&GET_INDEX, 0).unwrap();
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assert_eq!(result, expected_value);
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get_ptr(i);
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let result = result_array.get(&GET_PTR_INDEX, 0).unwrap();
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assert_eq!(result, expected_value);
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}
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for i in seq.clone() {
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let value = i.pow(2);
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get_ptr_mut(i);
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let result = result_array.get(&GET_PTR_MUT_INDEX, 0).unwrap();
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assert_eq!(result, value);
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}
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}
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}
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