Struct FEntry

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pub struct FEntry { /* private fields */ }

Expand description

A program that can be attached to the entry point of (almost) any kernel function.

FEntry programs are similar to kprobes, but the difference is that fentry has practically zero overhead to call before kernel function. Fentry programs can be also attached to other eBPF programs.

§Minimum kernel version

The minimum kernel version required to use this feature is 5.5.

§Examples

use aya::{Ebpf, programs::FEntry, BtfError, Btf};

let btf = Btf::from_sys_fs()?;
let program: &mut FEntry = bpf.program_mut("filename_lookup").unwrap().try_into()?;
program.load("filename_lookup", &btf)?;
program.attach()?;

Implementations§

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impl FEntry

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pub const PROGRAM_TYPE: ProgramType = ProgramType::Tracing

The type of the program according to the kernel.

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pub fn load(&mut self, fn_name: &str, btf: &Btf) -> Result<(), ProgramError>

Loads the program inside the kernel.

Loads the program so it’s executed when the kernel function fn_name is entered. The btf argument must contain the BTF info for the running kernel.

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pub fn attach(&mut self) -> Result<FEntryLinkId, ProgramError>

Attaches the program.

The returned value can be used to detach, see FEntry::detach.

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impl FEntry

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pub fn detach(&mut self, link_id: FEntryLinkId) -> Result<(), ProgramError>

Detaches the program.

See Self::attach.

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pub fn take_link( &mut self, link_id: FEntryLinkId, ) -> Result<FEntryLink, ProgramError>

Takes ownership of the link referenced by the provided link_id.

The caller takes the responsibility of managing the lifetime of the link. When the returned FEntryLink is dropped, the link will be detached.

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impl FEntry

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pub fn unload(&mut self) -> Result<(), ProgramError>

Unloads the program from the kernel.

Tracked links will be detached before unloading the program. Attachment mechanisms that do not create tracked links are not affected. Note that owned links obtained using take_link() will not be detached.

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impl FEntry

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pub fn fd(&self) -> Result<&ProgramFd, ProgramError>

Returns the file descriptor of this Program.

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impl FEntry

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pub fn pin<P: AsRef<Path>>(&mut self, path: P) -> Result<(), PinError>

Pins the program to a BPF filesystem.

When a BPF object is pinned to a BPF filesystem it will remain loaded after Aya has unloaded the program. To remove the program, the file on the BPF filesystem must be removed. Any directories in the the path provided should have been created by the caller.

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pub fn unpin(&mut self) -> Result<(), Error>

Removes the pinned link from the filesystem.

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impl FEntry

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pub fn from_pin<P: AsRef<Path>>(path: P) -> Result<Self, ProgramError>

Creates a program from a pinned entry on a bpffs.

Existing links will not be populated. To work with existing links you should use crate::programs::links::PinnedLink.

On drop, any managed links are detached and the program is unloaded. This will not result in the program being unloaded from the kernel if it is still pinned.

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impl FEntry

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pub unsafe fn from_program_info( info: ProgramInfo, name: Cow<'static, str>, ) -> Result<Self, ProgramError>

Constructs an instance of a Self from a ProgramInfo.

This allows the caller to get a handle to an already loaded program from the kernel without having to load it again.

§Errors

If the program type reported by the kernel does not match Self::PROGRAM_TYPE.
If the file descriptor of the program cannot be cloned.

§Safety

The runtime type of this program, as used by the kernel, is overloaded. We assert the program type matches the runtime type but we’re unable to perform further checks. Therefore, the caller must ensure that the program type is correct or the behavior is undefined.

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