mirror of https://github.com/aya-rs/aya
aya: Implement USDT probes
Signed-off-by: Dave Tucker <dave@dtucker.co.uk>pull/329/merge^2
Dave Tucker
3 years ago
parent
eb05c18140
commit
11b8dda719
@ -0,0 +1,474 @@
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//! User statically-defined tracepoints.
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use aya_common::{UsdtSpec, USDT_MAX_SPEC_COUNT};
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use libc::pid_t;
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use object::{elf::*, read::elf::*, Endianness};
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use std::{
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collections::{HashMap, VecDeque},
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convert::TryInto,
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ffi::CStr,
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fs,
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io::{self, BufRead, Cursor, Read},
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mem,
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path::{Path, PathBuf},
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sync::Arc,
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};
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use thiserror::Error;
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use crate::{
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generated::{bpf_prog_type::BPF_PROG_TYPE_KPROBE, BPF_NOEXIST},
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maps::{MapError, MapRefMut},
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programs::{
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define_link_wrapper, load_program,
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perf_attach::{perf_attach, PerfLinkIdInner, PerfLinkInner},
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probe::create_as_probe,
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utils::{LD_SO_CACHE, LD_SO_CACHE_FILE},
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Link, ProbeKind, ProgramData, ProgramError,
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},
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Pod, FEATURES,
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};
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use crate::programs::utils::{ProcMap, ProcMapError};
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unsafe impl Pod for UsdtSpec {}
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/// Name of the map used for USDT specs.
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pub const USDT_SPEC_MAP: &str = "__bpf_usdt_specs";
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/// Name of the map used for USDT to IP mappings.
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pub const USDT_IP_TO_SPEC_MAP: &str = "__bpf_usdt_ip_to_spec_id";
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/// A user statically-defined tracepoint
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#[derive(Debug)]
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#[doc(alias = "BPF_PROG_TYPE_KPROBE")]
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pub struct Usdt {
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pub(crate) data: ProgramData<UsdtLink>,
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}
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impl Usdt {
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/// Loads the program inside the kernel.
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pub fn load(&mut self) -> Result<(), ProgramError> {
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load_program(BPF_PROG_TYPE_KPROBE, &mut self.data)
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}
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/// Attaches the program.
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///
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/// Attaches the uprobe to the tracepoint `tp_provider`/`tp_name` defined in the `target`.
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/// If `pid` is not `None`, the program executes only when the target
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/// function is executed by the given `pid`.
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///
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/// The `target` argument can be an absolute path to a binary or library, or
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/// a library name (eg: `"libc"`).
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///
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/// The returned value can be used to detach, see [Usdt::detach].
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pub fn attach<T: AsRef<Path>>(
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&mut self,
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mut spec_map: crate::maps::Array<MapRefMut, UsdtSpec>,
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mut ip_to_spec_map: crate::maps::HashMap<MapRefMut, i64, u32>,
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tp_provider: &str,
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tp_name: &str,
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target: T,
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pid: Option<pid_t>,
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) -> Result<UsdtLinkId, ProgramError> {
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let target = target.as_ref();
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let target_str = &*target.as_os_str().to_string_lossy();
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let mut path = if let Some(pid) = pid {
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let proc_map_libs =
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ProcMap::new(pid).map_err(|e| UsdtError::ProcMapError { pid, source: e })?;
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proc_map_libs
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.find_by_name(target_str)
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.map_err(|io_error| UsdtError::FileError {
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filename: format!("/proc/{}/maps", pid),
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io_error,
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})?
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} else {
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None
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};
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if path.is_none() {
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path = if target.is_absolute() {
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Some(target_str)
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} else {
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let cache = LD_SO_CACHE
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.as_ref()
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.map_err(|error| UsdtError::InvalidLdSoCache {
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io_error: error.clone(),
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})?;
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cache.resolve(target_str)
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}
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.map(String::from)
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};
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let path = path.ok_or(UsdtError::InvalidTarget {
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path: target.to_owned(),
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})?;
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let tracepoints = collect_usdts(&path, tp_provider, tp_name, pid)?;
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let mut perf_links = vec![];
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let mut spec_ids = VecDeque::with_capacity(USDT_MAX_SPEC_COUNT as usize);
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for i in 0..USDT_MAX_SPEC_COUNT {
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spec_ids.push_back(i)
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}
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let mut spec_id_map = HashMap::new();
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for t in tracepoints {
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let id = if spec_id_map.contains_key(&t.args) {
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*(spec_id_map.get(&t.args).unwrap())
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} else {
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let id = spec_ids.pop_front().unwrap();
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spec_id_map.insert(t.args.clone(), id);
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spec_map.set(id, t.spec, 0)?;
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id
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};
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let mut cookie = Some(id as u64);
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if !FEATURES.bpf_cookie {
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cookie.take();
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if let Err(MapError::SyscallError { call, io_error }) =
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ip_to_spec_map.insert(t.abs_ip.try_into().unwrap(), id, BPF_NOEXIST.into())
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{
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if io_error.raw_os_error().unwrap() != (-libc::EEXIST) {
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return Err(ProgramError::MapError(MapError::SyscallError {
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call,
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io_error,
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}));
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}
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}
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}
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let fd = create_as_probe(ProbeKind::UProbe, &path, t.rel_ip, pid, Some(t.sem_off))?;
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let link = perf_attach(self.data.fd_or_err()?, fd, cookie)?;
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perf_links.push(link);
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}
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let link = UsdtLink(MultiPerfLink { perf_links });
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self.data.links.insert(link)
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}
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/// Detaches the program.
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///
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/// See [UProbe::attach].
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pub fn detach(&mut self, link_id: UsdtLinkId) -> Result<(), ProgramError> {
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self.data.links.remove(link_id)
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}
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/// Takes ownership of the link referenced by the provided link_id.
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///
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/// The link will be detached on `Drop` and the caller is now responsible
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/// for managing its lifetime.
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pub fn take_link(&mut self, link_id: UsdtLinkId) -> Result<UsdtLink, ProgramError> {
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self.data.take_link(link_id)
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}
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}
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/// The identifer of a MultiPerfLink.
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#[derive(Debug, Hash, Eq, PartialEq)]
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pub struct MultiPerfLinkId(Vec<PerfLinkIdInner>);
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/// The attachment type of USDT programs.
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#[derive(Debug)]
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pub struct MultiPerfLink {
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perf_links: Vec<PerfLinkInner>,
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}
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impl Link for MultiPerfLink {
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type Id = MultiPerfLinkId;
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fn id(&self) -> Self::Id {
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let ids = self.perf_links.iter().map(|p| p.id()).collect();
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MultiPerfLinkId(ids)
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}
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fn detach(self) -> Result<(), ProgramError> {
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for l in self.perf_links {
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l.detach()?;
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}
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Ok(())
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}
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}
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define_link_wrapper!(
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/// The link used by [Usdt] programs.
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UsdtLink,
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/// The type returned by [Usdt::attach]. Can be passed to [Usdt::detach].
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UsdtLinkId,
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MultiPerfLink,
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MultiPerfLinkId
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);
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/// The type returned when attaching an [`UProbe`] fails.
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#[derive(Debug, Error)]
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pub enum UsdtError {
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/// There was an error parsing `/etc/ld.so.cache`.
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#[error("error reading `{}` file", LD_SO_CACHE_FILE)]
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InvalidLdSoCache {
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/// the original [`io::Error`]
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#[source]
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io_error: Arc<io::Error>,
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},
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/// The target program could not be found.
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#[error("could not resolve uprobe target `{path}`")]
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InvalidTarget {
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/// path to target
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path: PathBuf,
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},
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/// There was an error resolving the target symbol.
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#[error("error resolving symbol")]
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SymbolError {
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/// symbol name
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symbol: String,
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/// the original error
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#[source]
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error: Box<dyn std::error::Error + Send + Sync>,
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},
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/// There was an error accessing `filename`.
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#[error("`{filename}`")]
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FileError {
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/// The file name
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filename: String,
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/// The [`io::Error`] returned from the file operation
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#[source]
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io_error: io::Error,
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},
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/// There was en error resolving a path
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#[error("error fetching libs for {pid}")]
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ProcMapError {
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/// The pid
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pid: i32,
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/// The [`ProcMapError`] that caused the error
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#[source]
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source: ProcMapError,
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},
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/// Unsupported file type
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#[error("unsupported file type")]
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Unsupported,
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/// An [`io::Error`]
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#[error("io error")]
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Io(#[from] io::Error),
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/// An [`object::Error`]
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#[error("error parsing ELF")]
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Object(#[from] object::Error),
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/// Can't find matching offset in shard libs
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#[error("can't find matching offset in shared libs")]
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OffsetError,
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/// Section is not executable
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#[error("section is not executable")]
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NoExec,
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/// Segment is not found
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#[error("segment not found")]
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SegmentNotFound,
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/// BPF Cookies are not supported
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#[error("bpf cookies are required to support attachment without a pid")]
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NoCookie,
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}
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fn collect_usdts(
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path: &str,
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provider: &str,
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name: &str,
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pid: Option<pid_t>,
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) -> Result<Vec<UsdtTarget>, UsdtError> {
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let file = fs::read(path)?;
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let data = &*file;
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if let Ok(elf) = object::elf::FileHeader32::parse(data) {
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if mem::size_of::<usize>() != 4 {
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return Err(UsdtError::Unsupported);
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}
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return collect_usdts_from_elf(elf, data, provider, name, pid);
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} else if let Ok(elf) = object::elf::FileHeader64::parse(data) {
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if mem::size_of::<usize>() != 8 {
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return Err(UsdtError::Unsupported);
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}
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return collect_usdts_from_elf(elf, data, provider, name, pid);
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}
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Err(UsdtError::Unsupported)
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}
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fn collect_usdts_from_elf<Elf: FileHeader<Endian = Endianness>>(
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elf: &Elf,
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data: &[u8],
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provider: &str,
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name: &str,
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pid: Option<pid_t>,
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) -> Result<Vec<UsdtTarget>, UsdtError> {
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let endian = elf.endian()?;
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let sections = elf.sections(endian, data)?;
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let program_headers = elf.program_headers(endian, data)?;
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let mut results = vec![];
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let mut base_addr: Option<u64> = None;
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if let Some((_, base_section)) = sections.section_by_name(endian, b".stapsdt.base") {
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base_addr = Some(base_section.sh_addr(endian).into())
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};
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if let Some((_, notes_section)) = sections.section_by_name(endian, b".note.stapsdt") {
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if let Some(mut notes) = notes_section.notes(endian, data)? {
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while let Ok(Some(note)) = notes.next() {
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if note.name() != b"stapsdt" {
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continue;
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}
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if note.n_type(endian) != 3 {
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continue;
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}
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let note_data = note.desc();
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let n = UsdtNote::parse(endian, note_data)?;
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if n.provider != provider || n.name != name {
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continue;
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}
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let mut abs_ip = n.loc_addr;
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if let Some(addr) = base_addr {
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abs_ip += addr - n.base_addr;
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}
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let seg = find_segment_by_address::<Elf>(program_headers, endian, abs_ip)
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.ok_or(UsdtError::SegmentNotFound)?;
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if seg.p_flags(endian) & PF_X == 0 {
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return Err(UsdtError::NoExec);
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}
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let rel_ip = abs_ip - seg.p_vaddr(endian).into() + seg.p_offset(endian).into();
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// If attaching to a sharef library and bpf cookies are not supported.
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// Abs address of attach points are required
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if elf.e_type(endian) == ET_DYN && !FEATURES.bpf_cookie {
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if pid.is_none() {
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return Err(UsdtError::NoCookie);
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}
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let proc_map_libs =
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ProcMap::new(pid.unwrap()).map_err(|e| UsdtError::ProcMapError {
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pid: pid.unwrap(),
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source: e,
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})?;
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let res = proc_map_libs
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.find_by_offset(rel_ip)
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.ok_or(UsdtError::OffsetError)?;
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abs_ip = res.address - res.offset + rel_ip;
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}
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let mut sem_off = 0;
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if n.sem_addr != 0x0 {
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// semaphore refcnt support was in 4.20, which is min supported version so we assume its supported
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let seg = find_segment_by_address::<Elf>(program_headers, endian, n.sem_addr)
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.ok_or(UsdtError::SegmentNotFound)?;
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if seg.p_flags(endian) & PF_X == 0 {
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return Err(UsdtError::NoExec);
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}
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sem_off = n.sem_addr - seg.p_vaddr(endian).into() + seg.p_offset(endian).into();
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}
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let spec = n.args.parse().unwrap();
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results.push(UsdtTarget {
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abs_ip,
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rel_ip,
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sem_off,
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args: n.args,
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spec,
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})
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}
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}
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}
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Ok(results)
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}
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fn find_segment_by_address<Elf: FileHeader<Endian = Endianness>>(
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program_headers: &[Elf::ProgramHeader],
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endian: Endianness,
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addr: u64,
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) -> Option<&Elf::ProgramHeader> {
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program_headers.iter().find(|&header| {
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header.p_vaddr(endian).into() < addr
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&& addr < (header.p_vaddr(endian).into() + header.p_memsz(endian).into())
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})
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}
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#[derive(Debug)]
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pub(crate) struct UsdtTarget {
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abs_ip: u64,
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rel_ip: u64,
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sem_off: u64,
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args: String,
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spec: UsdtSpec,
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}
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#[derive(Debug)]
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pub(crate) struct UsdtNote {
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loc_addr: u64,
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base_addr: u64,
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sem_addr: u64,
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provider: String,
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name: String,
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args: String,
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}
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impl UsdtNote {
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pub(crate) fn parse(endianness: Endianness, data: &[u8]) -> Result<UsdtNote, UsdtError> {
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let mut cursor = Cursor::new(data);
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let read_u64 = |cursor: &mut Cursor<_>| -> Result<u64, io::Error> {
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let mut buf = [0u8; mem::size_of::<u64>()];
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cursor.read_exact(&mut buf)?;
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match endianness {
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Endianness::Big => Ok(u64::from_be_bytes(buf)),
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Endianness::Little => Ok(u64::from_le_bytes(buf)),
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}
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};
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let read_string = |cursor: &mut Cursor<_>| -> Result<String, io::Error> {
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let mut buf = vec![];
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cursor.read_until(b'\0', &mut buf)?;
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Ok(CStr::from_bytes_with_nul(&buf)
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.unwrap()
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.to_string_lossy()
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.to_string())
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};
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let loc_addr = read_u64(&mut cursor)?;
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let base_addr = read_u64(&mut cursor)?;
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let sem_addr = read_u64(&mut cursor)?;
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let provider = read_string(&mut cursor)?;
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let name = read_string(&mut cursor)?;
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let args = read_string(&mut cursor)?;
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let res = UsdtNote {
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loc_addr,
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base_addr,
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sem_addr,
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provider,
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name,
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args,
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};
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Ok(res)
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}
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}
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#[cfg(test)]
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mod test {
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use super::*;
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#[test]
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fn test_parse_stapsdt() {
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/*
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/usr/bin/mariadb: file format elf64-x86-64
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Contents of section .note.stapsdt:
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0000 08000000 34000000 03000000 73746170 ....4.......stap
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0010 73647400 34a10d00 00000000 382e3600 sdt.4.......8.6.
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0020 00000000 00000000 00000000 6c696267 ............libg
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0030 63630075 6e77696e 64003840 25726469 cc.unwind.8@%rdi
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0040 20384025 72736900 8@%rsi
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*/
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let data: &[u8] = &[
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0x34, 0xa1, 0x0d, 0x00, 0x00, 0x00, 0x00, 0x00, 0x38, 0x2e, 0x36, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x6c, 0x69, 0x62, 0x67,
|
||||
0x63, 0x63, 0x00, 0x75, 0x6e, 0x77, 0x69, 0x6e, 0x64, 0x00, 0x38, 0x40, 0x25, 0x72,
|
||||
0x64, 0x69, 0x20, 0x38, 0x40, 0x25, 0x72, 0x73, 0x69, 0x00,
|
||||
];
|
||||
let n = UsdtNote::parse(Endianness::Little, data).unwrap();
|
||||
assert_eq!(n.loc_addr, 0xda134);
|
||||
assert_eq!(n.base_addr, 0x362e38);
|
||||
assert_eq!(n.sem_addr, 0x0);
|
||||
assert_eq!(n.provider, "libgcc");
|
||||
assert_eq!(n.name, "unwind");
|
||||
assert_eq!(n.args, "8@%rdi 8@%rsi");
|
||||
}
|
||||
}
|
||||
Loading…
Reference in New Issue