Ignore relocation of maps that should be ignored.

This makes it possible to have bytecode with unsupported map types such as BPF_MAP_TYPE_RINGBUF on a target kernel that doesn't have that map type

aya-obj/src/btf/btf.rs

@@ -416,6 +416,20 @@ impl Btf {
         self.string_at(ty.name_offset()).ok().map(String::from)
     }
 
+    /// Returns a type id matching the type name
+    pub fn id_by_type_name(&self, name: &str) -> Result<u32, BtfError> {
+        for (type_id, ty) in self.types().enumerate() {
+            if self.type_name(ty)? == name {
+                return Ok(type_id as u32);
+            }
+            continue;
+        }
+
+        Err(BtfError::UnknownBtfTypeName {
+            type_name: name.to_owned(),
+        })
+    }
+
     /// Returns a type id matching the type name and [BtfKind]
     pub fn id_by_type_name_kind(&self, name: &str, kind: BtfKind) -> Result<u32, BtfError> {
         for (type_id, ty) in self.types().enumerate() {

aya-obj/src/obj.rs

@@ -8,6 +8,7 @@ use alloc::{
     vec::Vec,
 };
 use core::{ffi::CStr, mem, ptr, slice::from_raw_parts_mut, str::FromStr};
+use std::println;
 
 use log::debug;
 use object::{

aya-obj/src/relocation.rs

@@ -2,6 +2,7 @@
 
 use alloc::{borrow::ToOwned, collections::BTreeMap, string::String};
 use core::mem;
+use std::println;
 
 use log::debug;
 use object::{SectionIndex, SymbolKind};
@@ -108,9 +109,20 @@ impl Object {
         &mut self,
         maps: I,
         text_sections: &HashSet<usize>,
+        ignored_maps: &HashMap<String, Map>,
     ) -> Result<(), EbpfRelocationError> {
         let mut maps_by_section = HashMap::new();
         let mut maps_by_symbol = HashMap::new();
+        let mut ignored_by_section = HashSet::new();
+        let mut ignored_by_symbol = HashSet::new();
+
+        for (name, map) in ignored_maps {
+            ignored_by_section.insert(map.section_index());
+            if let Some(index) = map.symbol_index() {
+                ignored_by_symbol.insert(index);
+            }
+        }
+
         for (name, fd, map) in maps {
             maps_by_section.insert(map.section_index(), (name, fd, map));
             if let Some(index) = map.symbol_index() {
@@ -127,6 +139,8 @@ impl Object {
                     &maps_by_symbol,
                     &self.symbol_table,
                     text_sections,
+                    &ignored_by_section,
+                    &ignored_by_symbol,
                 )
                 .map_err(|error| EbpfRelocationError {
                     function: function.name.clone(),
@@ -176,6 +190,7 @@ impl Object {
     }
 }
 
+#[allow(clippy::too_many_arguments)]
 fn relocate_maps<'a, I: Iterator<Item = &'a Relocation>>(
     fun: &mut Function,
     relocations: I,
@@ -183,6 +198,8 @@ fn relocate_maps<'a, I: Iterator<Item = &'a Relocation>>(
     maps_by_symbol: &HashMap<usize, (&str, std::os::fd::RawFd, &Map)>,
     symbol_table: &HashMap<usize, Symbol>,
     text_sections: &HashSet<usize>,
+    ignored_by_section: &HashSet<usize>,
+    ignored_by_symbol: &HashSet<usize>,
 ) -> Result<(), RelocationError> {
     let section_offset = fun.section_offset;
     let instructions = &mut fun.instructions;
@@ -212,6 +229,7 @@ fn relocate_maps<'a, I: Iterator<Item = &'a Relocation>>(
                 index: rel.symbol_index,
             })?;
 
+
         let Some(section_index) = sym.section_index else {
             // this is not a map relocation
             continue;
@@ -222,7 +240,9 @@ fn relocate_maps<'a, I: Iterator<Item = &'a Relocation>>(
             continue;
         }
 
-        let (_name, fd, map) = if let Some(m) = maps_by_symbol.get(&rel.symbol_index) {
+        let (_name, fd, map) = if ignored_by_symbol.contains(&rel.symbol_index) {
+            continue
+        } else if let Some(m) = maps_by_symbol.get(&rel.symbol_index) {
             let map = &m.2;
             debug!(
                 "relocating map by symbol index {:?}, kind {:?} at insn {ins_index} in section {}",
@@ -232,6 +252,8 @@ fn relocate_maps<'a, I: Iterator<Item = &'a Relocation>>(
             );
             debug_assert_eq!(map.symbol_index().unwrap(), rel.symbol_index);
             m
+        } else if ignored_by_section.contains(&section_index) {
+            continue
         } else {
             let Some(m) = maps_by_section.get(&section_index) else {
                 debug!("failed relocating map by section index {}", section_index);
@@ -580,6 +602,8 @@ mod test {
             &maps_by_symbol,
             &symbol_table,
             &HashSet::new(),
+            &HashSet::new(),
+            &HashSet::new(),
         )
         .unwrap();
 
@@ -636,6 +660,8 @@ mod test {
             &maps_by_symbol,
             &symbol_table,
             &HashSet::new(),
+            &HashSet::new(),
+            &HashSet::new(),
         )
         .unwrap();
 
@@ -675,6 +701,8 @@ mod test {
             &maps_by_symbol,
             &symbol_table,
             &HashSet::new(),
+            &HashSet::new(),
+            &HashSet::new(),
         )
         .unwrap();
 
@@ -731,6 +759,8 @@ mod test {
             &maps_by_symbol,
             &symbol_table,
             &HashSet::new(),
+            &HashSet::new(),
+            &HashSet::new(),
         )
         .unwrap();
 

aya/src/bpf.rs

@@ -3,7 +3,7 @@ use std::{
     collections::{HashMap, HashSet},
     fs, io,
     os::{
-        fd::{AsFd as _, AsRawFd as _, OwnedFd},
+        fd::{AsFd as _, AsRawFd as _, FromRawFd, OwnedFd},
         raw::c_int,
     },
     path::{Path, PathBuf},
@@ -21,10 +21,10 @@ use thiserror::Error;
 
 use crate::{
     generated::{
-        bpf_map_type, bpf_map_type::*, AYA_PERF_EVENT_IOC_DISABLE, AYA_PERF_EVENT_IOC_ENABLE,
+        bpf_map_type::{self, *}, AYA_PERF_EVENT_IOC_DISABLE, AYA_PERF_EVENT_IOC_ENABLE,
         AYA_PERF_EVENT_IOC_SET_BPF,
     },
-    maps::{Map, MapData, MapError},
+    maps::{Map, MapData, MapError, MapFd},
     obj::{
         btf::{Btf, BtfError},
         Object, ParseError, ProgramSection,
@@ -137,6 +137,7 @@ pub struct EbpfLoader<'a> {
     extensions: HashSet<&'a str>,
     verifier_log_level: VerifierLogLevel,
     allow_unsupported_maps: bool,
+    deactivate_maps: HashSet<bpf_map_type>,
 }
 
 /// Builder style API for advanced loading of eBPF programs.
@@ -175,6 +176,7 @@ impl<'a> EbpfLoader<'a> {
             extensions: HashSet::new(),
             verifier_log_level: VerifierLogLevel::default(),
             allow_unsupported_maps: false,
+            deactivate_maps: HashSet::new(),
         }
     }
 
@@ -224,6 +226,12 @@ impl<'a> EbpfLoader<'a> {
         self
     }
 
+    /// Documentaaaaaaaaaaaaation
+    pub fn deactivate_maps(&mut self, set: HashSet<bpf_map_type>) -> &mut Self {
+        self.deactivate_maps = set;
+        self
+    }
+
     /// Sets the base directory path for pinned maps.
     ///
     /// Pinned maps will be loaded from `path/MAP_NAME`.
@@ -394,9 +402,9 @@ impl<'a> EbpfLoader<'a> {
             extensions,
             verifier_log_level,
             allow_unsupported_maps,
+            deactivate_maps,
         } = self;
         let mut obj = Object::parse(data)?;
-        obj.patch_map_data(globals.clone())?;
 
         let btf_fd = if let Some(features) = &FEATURES.btf() {
             if let Some(btf) = obj.fixup_and_sanitize_btf(features)? {
@@ -459,12 +467,20 @@ impl<'a> EbpfLoader<'a> {
             obj.relocate_btf(btf)?;
         }
         let mut maps = HashMap::new();
+        let mut ignored_maps = HashMap::new();
+
         for (name, mut obj) in obj.maps.drain() {
             if let (false, EbpfSectionKind::Bss | EbpfSectionKind::Data | EbpfSectionKind::Rodata) =
                 (FEATURES.bpf_global_data(), obj.section_kind())
             {
                 continue;
             }
+
+            if deactivate_maps.contains(&obj.map_type().try_into().map_err(|_| EbpfError::MapError(MapError::InvalidMapType { map_type: obj.map_type() }))?) {
+                ignored_maps.insert(name, obj);
+                continue;
+            }
+
             let num_cpus = || -> Result<u32, EbpfError> {
                 Ok(possible_cpus()
                     .map_err(|error| EbpfError::FileError {
@@ -498,7 +514,7 @@ impl<'a> EbpfLoader<'a> {
                 PinningType::ByName => {
                     // pin maps in /sys/fs/bpf by default to align with libbpf
                     // behavior https://github.com/libbpf/libbpf/blob/v1.2.2/src/libbpf.c#L2161.
-                    let path = map_pin_path
+                    let path: &Path = map_pin_path
                     .as_deref()
                     .unwrap_or_else(|| Path::new("/sys/fs/bpf"));
 
@@ -508,7 +524,6 @@ impl<'a> EbpfLoader<'a> {
             map.finalize()?;
             maps.insert(name, map);
         }
-
         let text_sections = obj
             .functions
             .keys()
@@ -519,6 +534,7 @@ impl<'a> EbpfLoader<'a> {
             maps.iter()
                 .map(|(s, data)| (s.as_str(), data.fd().as_fd().as_raw_fd(), data.obj())),
             &text_sections,
+            &ignored_maps,
         )?;
         obj.relocate_calls(&text_sections)?;
         obj.sanitize_functions(&FEATURES);