feat(aya): Implement Maps/Arrays of Maps

This commit implements the Array of Maps and Hash of Maps to eBPF.

Signed-off-by: Dave Tucker <[email protected]>

aya-obj/src/btf/btf.rs

@@ -155,6 +155,10 @@ pub enum BtfError {
     /// unable to get symbol name
     #[error("Unable to get symbol name")]
     InvalidSymbolName,
+
+    /// an error occurred while parsing a the BTF data
+    #[error("BTF error: {0}")]
+    BtfError(String),
 }
 
 /// Available BTF features
@@ -591,14 +595,6 @@ impl Btf {
                         for e in entries.iter_mut() {
                             if let BtfType::Var(var) = types.type_by_id(e.btf_type)? {
                                 let var_name = self.string_at(var.name_offset)?;
-                                if var.linkage == VarLinkage::Static {
-                                    debug!(
-                                        "{} {}: VAR {}: fixup not required",
-                                        kind, name, var_name
-                                    );
-                                    continue;
-                                }
-
                                 let offset = match symbol_offsets.get(var_name.as_ref()) {
                                     Some(offset) => offset,
                                     None => {
@@ -612,6 +608,14 @@ impl Btf {
                                     "{} {}: VAR {}: fixup offset {}",
                                     kind, name, var_name, offset
                                 );
+
+                                if var.linkage == VarLinkage::Static {
+                                    debug!(
+                                        "{} {}: VAR {}: linkage fixup not required",
+                                        kind, name, var_name
+                                    );
+                                    continue;
+                                }
                             } else {
                                 return Err(BtfError::InvalidDatasec);
                             }

aya-obj/src/lib.rs

@@ -42,7 +42,7 @@
 //! #[cfg(not(feature = "std"))]
 //! let text_sections = hashbrown::HashSet::new();
 //! object.relocate_calls(&text_sections).unwrap();
-//! object.relocate_maps(std::iter::empty(), &text_sections).unwrap();
+//! object.relocate_map_references(std::iter::empty(), &text_sections).unwrap();
 //!
 //! // Run with rbpf
 //! let function = object.functions.get(&object.programs["prog_name"].function_key()).unwrap();

aya-obj/src/maps.rs

@@ -1,6 +1,6 @@
 //! Map struct and type bindings.
 
-use alloc::vec::Vec;
+use alloc::{collections::BTreeMap, vec::Vec};
 use core::mem;
 
 use crate::{EbpfSectionKind, InvalidTypeBinding};
@@ -248,6 +248,64 @@ impl Map {
             Map::Btf(m) => Some(m.symbol_index),
         }
     }
+
+    /// Sets the inner map definition, in case of a map of maps
+    pub fn set_legacy_inner(&mut self, inner_def: &Map) {
+        match self {
+            Map::Legacy(m) => {
+                if let Map::Legacy(inner_def) = inner_def {
+                    m.inner_def = Some(inner_def.def);
+                } else {
+                    panic!("inner map is not a legacy map");
+                }
+            }
+            Map::Btf(_) => panic!("inner map already set"),
+        }
+    }
+
+    /// Returns the inner map definition, in case of a map of maps
+    pub fn inner(&self) -> Option<Map> {
+        match self {
+            Map::Legacy(m) => m.inner_def.as_ref().map(|inner_def| {
+                Map::Legacy(LegacyMap {
+                    def: *inner_def,
+                    inner_def: None,
+                    section_index: m.section_index,
+                    section_kind: m.section_kind,
+                    symbol_index: m.symbol_index,
+                    data: Vec::new(),
+                    initial_slots: BTreeMap::new(),
+                })
+            }),
+            Map::Btf(m) => m.inner_def.as_ref().map(|inner_def| {
+                Map::Btf(BtfMap {
+                    def: *inner_def,
+                    inner_def: None,
+                    section_index: m.section_index,
+                    symbol_index: m.symbol_index,
+                    data: Vec::new(),
+                    initial_slots: BTreeMap::new(),
+                })
+            }),
+        }
+    }
+
+    /// Places the file descriptor of an inner map into the initial slots of a
+    /// map-of-maps. The map is placed at the given index.
+    pub(crate) fn set_initial_map_fd(&mut self, index: usize, inner_map_fd: i32) -> bool {
+        match self {
+            Map::Legacy(m) => m.initial_slots.insert(index, inner_map_fd).is_none(),
+            Map::Btf(m) => m.initial_slots.insert(index, inner_map_fd).is_none(),
+        }
+    }
+
+    /// Returns the initial slots of a map-of-maps
+    pub fn initial_map_fds(&self) -> &BTreeMap<usize, i32> {
+        match self {
+            Map::Legacy(m) => &m.initial_slots,
+            Map::Btf(m) => &m.initial_slots,
+        }
+    }
 }
 
 /// A map declared with legacy BPF map declaration style, most likely from a `maps` section.
@@ -258,6 +316,8 @@ impl Map {
 pub struct LegacyMap {
     /// The definition of the map
     pub def: bpf_map_def,
+    /// The defintion of the inner map, in case of a map of maps
+    pub inner_def: Option<bpf_map_def>,
     /// The section index
     pub section_index: usize,
     /// The section kind
@@ -270,14 +330,20 @@ pub struct LegacyMap {
     pub symbol_index: Option<usize>,
     /// The map data
     pub data: Vec<u8>,
+    /// The initial slots of a map-of-maps
+    pub initial_slots: BTreeMap<usize, i32>,
 }
 
 /// A BTF-defined map, most likely from a `.maps` section.
 #[derive(Debug, Clone)]
 pub struct BtfMap {
     /// The definition of the map
     pub def: BtfMapDef,
+    /// The defintion of the inner map, in case of a map of maps
+    pub inner_def: Option<BtfMapDef>,
     pub(crate) section_index: usize,
     pub(crate) symbol_index: usize,
     pub(crate) data: Vec<u8>,
+    /// The initial slots of a map-of-maps
+    pub initial_slots: BTreeMap<usize, i32>,
 }