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109 lines
3.9 KiB
Rust
109 lines
3.9 KiB
Rust
use core::{cell::UnsafeCell, hint::unreachable_unchecked, mem};
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use crate::{
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EbpfContext, bindings::bpf_map_type::BPF_MAP_TYPE_PROG_ARRAY, btf_maps::AyaBtfMapMarker,
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cty::c_long, helpers::bpf_tail_call,
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};
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#[allow(dead_code)]
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pub struct ProgramArrayDef<const M: usize, const F: usize = 0> {
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r#type: *const [i32; BPF_MAP_TYPE_PROG_ARRAY as usize],
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key_size: *const [i32; mem::size_of::<u32>()],
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value_size: *const [i32; mem::size_of::<u32>()],
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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: AyaBtfMapMarker,
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}
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/// A BPF map that stores an array of program indices for tail calling.
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///
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/// # Examples
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///
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/// ```no_run
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/// # #![expect(dead_code)]
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/// use aya_ebpf::{macros::map, maps::ProgramArray, cty::c_long};
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/// # use aya_ebpf::{programs::LsmContext};
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///
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/// #[map]
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/// static JUMP_TABLE: ProgramArray = ProgramArray::with_max_entries(16, 0);
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///
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/// # unsafe fn try_test(ctx: &LsmContext) -> Result<(), c_long> {
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/// let index: u32 = 13;
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///
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/// if let Err(e) = JUMP_TABLE.tail_call(ctx, index) {
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/// return Err(e);
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/// }
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///
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/// # Err(-1)
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/// }
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/// ```
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#[repr(transparent)]
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pub struct ProgramArray<const M: usize, const F: usize = 0>(UnsafeCell<ProgramArrayDef<M, F>>);
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unsafe impl<const M: usize, const F: usize> Sync for ProgramArray<M, F> {}
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impl<const M: usize, const F: usize> ProgramArray<M, F> {
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// Implementing `Default` makes no sense in this case. Maps are always
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// global variables, so they need to be instantiated with a `const` method.
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// The `Default::default` method is not `const`.
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#[allow(clippy::new_without_default)]
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pub const fn new() -> Self {
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Self(UnsafeCell::new(ProgramArrayDef {
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r#type: &[0i32; BPF_MAP_TYPE_PROG_ARRAY as usize] as *const _,
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key_size: &[0i32; mem::size_of::<u32>()] as *const _,
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value_size: &[0i32; mem::size_of::<u32>()] as *const _,
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max_entries: &[0i32; M] as *const _,
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map_flags: &[0i32; F] as *const _,
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_anon: AyaBtfMapMarker::new(),
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}))
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}
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/// Perform a tail call into a program indexed by this map.
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///
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/// # Safety
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///
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/// This function is inherently unsafe, since it causes control flow to jump into
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/// another eBPF program. This can have side effects, such as drop methods not being
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/// called. Note that tail calling into an eBPF program is not the same thing as
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/// a function call -- control flow never returns to the caller.
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///
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/// # Return Value
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///
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/// On success, this function **does not return** into the original program.
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/// On failure, a negative error is returned, wrapped in `Err()`.
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#[cfg(not(unstable))]
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pub unsafe fn tail_call<C: EbpfContext>(&self, ctx: &C, index: u32) -> Result<(), c_long> {
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let res = unsafe { bpf_tail_call(ctx.as_ptr(), self.0.get() as *mut _, index) };
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if res != 0 {
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Err(res)
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} else {
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unsafe { unreachable_unchecked() }
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}
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}
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/// Perform a tail call into a program indexed by this map.
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///
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/// # Safety
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///
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/// This function is inherently unsafe, since it causes control flow to jump into
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/// another eBPF program. This can have side effects, such as drop methods not being
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/// called. Note that tail calling into an eBPF program is not the same thing as
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/// a function call -- control flow never returns to the caller.
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///
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/// # Return Value
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///
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/// On success, this function **does not return** into the original program.
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/// On failure, a negative error is returned, wrapped in `Err()`.
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#[cfg(unstable)]
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pub unsafe fn tail_call<C: EbpfContext>(&self, ctx: &C, index: u32) -> Result<!, c_long> {
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let res = unsafe { bpf_tail_call(ctx.as_ptr(), self.0.get() as *mut _, index) };
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if res != 0 {
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Err(res)
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} else {
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unsafe { unreachable_unchecked() }
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}
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}
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}
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