wip: bpftool but with aya

Signed-off-by: Dave Tucker <dave@dtucker.co.uk>

aya-obj/src/btf/btf.rs

@@ -46,6 +46,11 @@ pub enum BtfError {
     #[error("error parsing BTF header")]
     InvalidHeader,
 
+    /// Invalid ELF data
+    #[cfg(feature = "std")]
+    #[error("error parsing ELF")]
+    Elf,
+
     /// invalid BTF type info segment
     #[error("invalid BTF type info segment")]
     InvalidTypeInfo,
@@ -276,7 +281,8 @@ impl Btf {
         self.types.types.len() < 2
     }
 
-    pub(crate) fn types(&self) -> impl Iterator<Item = &BtfType> {
+    /// Iterates over the BTF types.
+    pub fn types(&self) -> impl Iterator<Item = &BtfType> {
         self.types.types.iter()
     }
 
@@ -307,7 +313,7 @@ impl Btf {
 
     /// Loads BTF metadata from the given `path`.
     #[cfg(feature = "std")]
-    pub fn parse_file<P: AsRef<std::path::Path>>(
+    pub(crate) fn parse_file<P: AsRef<std::path::Path>>(
         path: P,
         endianness: Endianness,
     ) -> Result<Btf, BtfError> {
@@ -322,6 +328,26 @@ impl Btf {
         )
     }
 
+    /// Loads BTF metadata from an ELF section.
+    #[cfg(feature = "std")]
+    pub fn parse_elf_file<P: AsRef<std::path::Path>>(
+        path: P,
+        endianness: Endianness,
+    ) -> Result<Btf, BtfError> {
+        use object::{Object, ObjectSection};
+        let path = path.as_ref();
+        let bin_data = std::fs::read(path).map_err(|e| BtfError::FileError {
+            path: path.to_owned(),
+            error: e,
+        })?;
+        let obj_file = object::File::parse(&*bin_data).map_err(|_| BtfError::Elf)?;
+        let section = obj_file
+            .section_by_name(".BTF")
+            .ok_or_else(|| BtfError::InvalidHeader)?;
+        let data = section.data().map_err(|_| BtfError::InvalidHeader)?;
+        Btf::parse(data, endianness)
+    }
+
     /// Parses BTF from binary data of the given endianness
     pub fn parse(data: &[u8], endianness: Endianness) -> Result<Btf, BtfError> {
         if data.len() < mem::size_of::<btf_header>() {
@@ -374,7 +400,8 @@ impl Btf {
         Ok(types)
     }
 
-    pub(crate) fn string_at(&self, offset: u32) -> Result<Cow<'_, str>, BtfError> {
+    /// Returns the string at the given offset within the BTF metadata.
+    pub fn string_at(&self, offset: u32) -> Result<Cow<'_, str>, BtfError> {
         let btf_header {
             hdr_len,
             mut str_off,
@@ -400,7 +427,8 @@ impl Btf {
         Ok(s.to_string_lossy())
     }
 
-    pub(crate) fn type_by_id(&self, type_id: u32) -> Result<&BtfType, BtfError> {
+    /// Returns the BtfType at the given type id.
+    pub fn type_by_id(&self, type_id: u32) -> Result<&BtfType, BtfError> {
         self.types.type_by_id(type_id)
     }
 

aya-obj/src/btf/types.rs

@@ -82,6 +82,10 @@ impl Const {
             btf_type,
         }
     }
+    /// The target type of the const.
+    pub fn btf_type(&self) -> u32 {
+        self.btf_type
+    }
 }
 
 #[repr(C)]
@@ -104,6 +108,11 @@ impl Volatile {
     pub(crate) fn type_info_size(&self) -> usize {
         mem::size_of::<Self>()
     }
+
+    /// The target type of the volatile.
+    pub fn btf_type(&self) -> u32 {
+        self.btf_type
+    }
 }
 
 #[derive(Clone, Debug)]
@@ -125,6 +134,11 @@ impl Restrict {
     pub(crate) fn type_info_size(&self) -> usize {
         mem::size_of::<Self>()
     }
+
+    /// The target type of the restrict.
+    pub fn btf_type(&self) -> u32 {
+        self.btf_type
+    }
 }
 
 #[repr(C)]
@@ -156,6 +170,11 @@ impl Ptr {
             btf_type,
         }
     }
+
+    /// The target type of the pointer.
+    pub fn btf_type(&self) -> u32 {
+        self.btf_type
+    }
 }
 
 #[repr(C)]
@@ -187,6 +206,11 @@ impl Typedef {
             btf_type,
         }
     }
+
+    /// The target type of the typedef.
+    pub fn btf_type(&self) -> u32 {
+        self.btf_type
+    }
 }
 
 #[repr(C)]
@@ -276,6 +300,11 @@ impl Func {
     pub(crate) fn set_linkage(&mut self, linkage: FuncLinkage) {
         self.info = (self.info & 0xFFFF0000) | (linkage as u32) & 0xFFFF;
     }
+
+    /// The target type of the func.
+    pub fn btf_type(&self) -> u32 {
+        self.btf_type
+    }
 }
 
 #[repr(C)]
@@ -378,17 +407,23 @@ impl Int {
         }
     }
 
-    pub(crate) fn encoding(&self) -> IntEncoding {
+    /// The integer size.
+    pub fn size(&self) -> u32 {
+        self.size
+    }
+
+    /// The integer encoding.
+    pub fn encoding(&self) -> IntEncoding {
         ((self.data & 0x0f000000) >> 24).into()
     }
 
-    pub(crate) fn offset(&self) -> u32 {
+    /// The offset of the integer.
+    pub fn offset(&self) -> u32 {
         (self.data & 0x00ff0000) >> 16
     }
 
-    // TODO: Remove directive this when this crate is pub
-    #[cfg(test)]
-    pub(crate) fn bits(&self) -> u32 {
+    /// The size of the integer in bits.
+    pub fn bits(&self) -> u32 {
         self.data & 0x000000ff
     }
 }
@@ -563,15 +598,27 @@ impl Enum64 {
         }
     }
 }
-
+/// A member of a struct or union.
 #[repr(C)]
 #[derive(Clone, Debug)]
-pub(crate) struct BtfMember {
+pub struct BtfMember {
     pub(crate) name_offset: u32,
     pub(crate) btf_type: u32,
     pub(crate) offset: u32,
 }
 
+impl BtfMember {
+    /// The offset of the members name in the BTF string section.
+    pub fn name_offset(&self) -> u32 {
+        self.name_offset
+    }
+
+    /// The type of the member.
+    pub fn btf_type(&self) -> u32 {
+        self.btf_type
+    }
+}
+
 #[repr(C)]
 #[derive(Clone, Debug)]
 pub struct Struct {
@@ -632,7 +679,8 @@ impl Struct {
         }
     }
 
-    pub(crate) fn member_bit_offset(&self, member: &BtfMember) -> usize {
+    /// The offset of the member within the struct or union.
+    pub fn member_bit_offset(&self, member: &BtfMember) -> usize {
         let k_flag = self.info >> 31 == 1;
         let bit_offset = if k_flag {
             member.offset & 0xFFFFFF
@@ -649,6 +697,21 @@ impl Struct {
 
         size as usize
     }
+
+    /// The size of the struct.
+    pub fn size(&self) -> u32 {
+        self.size
+    }
+
+    /// Vlen
+    pub fn vlen(&self) -> usize {
+        type_vlen(self.info)
+    }
+
+    /// The members of the struct.
+    pub fn members(&self) -> &[BtfMember] {
+        &self.members
+    }
 }
 
 #[repr(C)]
@@ -771,6 +834,14 @@ impl Array {
         mem::size_of::<Self>()
     }
 
+    pub fn index_type(&self) -> u32 {
+        self.array.index_type
+    }
+
+    pub fn len(&self) -> u32 {
+        self.array.len
+    }
+
     #[cfg(test)]
     pub(crate) fn new(name_offset: u32, element_type: u32, index_type: u32, len: u32) -> Self {
         let info = (BtfKind::Array as u32) << 24;
@@ -790,8 +861,24 @@ impl Array {
 #[repr(C)]
 #[derive(Clone, Debug)]
 pub struct BtfParam {
-    pub name_offset: u32,
-    pub btf_type: u32,
+    pub(crate) name_offset: u32,
+    pub(crate) btf_type: u32,
+}
+
+impl BtfParam {
+    pub fn new(name_offset: u32, btf_type: u32) -> Self {
+        Self {
+            name_offset,
+            btf_type,
+        }
+    }
+
+    pub fn name_offset(&self) -> u32 {
+        self.name_offset
+    }
+    pub fn btf_type(&self) -> u32 {
+        self.btf_type
+    }
 }
 
 #[repr(C)]
@@ -836,6 +923,18 @@ impl FuncProto {
         mem::size_of::<Fwd>() + mem::size_of::<BtfParam>() * self.params.len()
     }
 
+    pub fn return_type(&self) -> u32 {
+        self.return_type
+    }
+
+    pub fn vlen(&self) -> usize {
+        type_vlen(self.info)
+    }
+
+    pub fn params(&self) -> &[BtfParam] {
+        &self.params
+    }
+
     pub fn new(params: Vec<BtfParam>, return_type: u32) -> Self {
         let mut info = (BtfKind::FuncProto as u32) << 24;
         info |= (params.len() as u32) & 0xFFFF;
@@ -911,14 +1010,43 @@ impl Var {
             linkage,
         }
     }
+
+    pub fn btf_type(&self) -> u32 {
+        self.btf_type
+    }
+
+    pub fn linkage(&self) -> &VarLinkage {
+        &self.linkage
+    }
 }
 
 #[repr(C)]
 #[derive(Clone, Debug)]
 pub struct DataSecEntry {
-    pub btf_type: u32,
-    pub offset: u32,
-    pub size: u32,
+    pub(crate) btf_type: u32,
+    pub(crate) offset: u32,
+    pub(crate) size: u32,
+}
+
+impl DataSecEntry {
+    pub fn new(btf_type: u32, offset: u32, size: u32) -> Self {
+        Self {
+            btf_type,
+            offset,
+            size,
+        }
+    }
+    pub fn btf_type(&self) -> u32 {
+        self.btf_type
+    }
+
+    pub fn offset(&self) -> u32 {
+        self.offset
+    }
+
+    pub fn size(&self) -> u32 {
+        self.size
+    }
 }
 
 #[repr(C)]
@@ -980,6 +1108,18 @@ impl DataSec {
             entries,
         }
     }
+
+    pub fn size(&self) -> u32 {
+        self.size
+    }
+
+    pub fn vlen(&self) -> usize {
+        type_vlen(self.info)
+    }
+
+    pub fn entries(&self) -> &[DataSecEntry] {
+        &self.entries
+    }
 }
 
 #[repr(C)]
@@ -1337,7 +1477,8 @@ impl BtfType {
         }
     }
 
-    pub(crate) fn name_offset(&self) -> u32 {
+    /// Returns the name offset of the BTF type.
+    pub fn name_offset(&self) -> u32 {
         match self {
             BtfType::Unknown => 0,
             BtfType::Fwd(t) => t.name_offset,
@@ -1362,7 +1503,8 @@ impl BtfType {
         }
     }
 
-    pub(crate) fn kind(&self) -> BtfKind {
+    /// Returns the kind of the BTF type.
+    pub fn kind(&self) -> BtfKind {
         match self {
             BtfType::Unknown => BtfKind::Unknown,
             BtfType::Fwd(t) => t.kind(),

aya-tool/Cargo.toml

@@ -9,8 +9,10 @@ homepage.workspace = true
 edition.workspace = true
 
 [dependencies]
+aya-obj = { version = "0.1.0", path = "../aya-obj", features = ["std"] }
 bindgen = { workspace = true, default-features = true }
 clap = { workspace = true, default-features = true, features = ["derive"] }
 anyhow = { workspace = true, default-features = true }
 thiserror = { workspace = true }
 tempfile = { workspace = true }
+object = { workspace = true }

aya-tool/src/bin/aya-tool.rs

@@ -1,5 +1,6 @@
 use std::{path::PathBuf, process::exit};
 
+use aya_tool::btf::print_btf;
 use aya_tool::generate::{generate, InputFile};
 use clap::Parser;
 
@@ -23,6 +24,12 @@ enum Command {
         #[clap(last = true, action)]
         bindgen_args: Vec<String>,
     },
+    /// Pretty print an ELF file's BTF
+    #[clap(name = "print-btf", action)]
+    PrintBtf {
+        /// The ELF file to print BTF for
+        target: PathBuf,
+    },
 }
 
 fn main() {
@@ -48,6 +55,9 @@ fn try_main() -> Result<(), anyhow::Error> {
             };
             println!("{bindings}");
         }
+        Command::PrintBtf { target } => {
+            print_btf(target)?;
+        }
     };
 
     Ok(())

aya-tool/src/btf.rs

@@ -0,0 +1,119 @@
+use aya_obj::btf::{Btf, BtfType, IntEncoding, VarLinkage};
+use object::Endianness;
+
+use std::{fmt::Write, path::Path};
+
+pub fn print_btf<P: AsRef<Path>>(path: P) -> anyhow::Result<()> {
+    let btf = Btf::parse_elf_file(path, Endianness::default())?;
+    for (i, t) in btf.types().enumerate().skip(1) {
+        let kind = t.kind();
+        let name = if t.name_offset() > 0 {
+            format!(
+                "'{}'",
+                btf.string_at(t.name_offset())
+                    .unwrap_or(std::borrow::Cow::Borrowed(""))
+            )
+        } else {
+            "''".to_owned()
+        };
+        let info = match t {
+            BtfType::Unknown => "".to_string(),
+            BtfType::Fwd(_) => "type_id=0".to_string(),
+            BtfType::Const(ty) => format!("type_id={}", ty.btf_type()),
+            BtfType::Volatile(ty) => format!("type_id={}", ty.btf_type()),
+            BtfType::Restrict(ty) => format!("type_id={}", ty.btf_type()),
+            BtfType::Ptr(ty) => format!("type_id={}", ty.btf_type()),
+            BtfType::Typedef(ty) => format!("type_id={}", ty.btf_type()),
+            BtfType::Func(ty) => format!("type_id={}", ty.btf_type()),
+            BtfType::Int(i) => {
+                let encoding = match i.encoding() {
+                    IntEncoding::Signed => "(signed)",
+                    IntEncoding::Char => "(char)",
+                    IntEncoding::Bool => "(bool)",
+                    IntEncoding::None => "(none)",
+                    IntEncoding::Unknown => "(unknown)",
+                };
+                format!(
+                    "size={} bits_offset={} nr_bits={} encoding={}",
+                    i.size(),
+                    i.offset(),
+                    i.bits(),
+                    encoding,
+                )
+            }
+            BtfType::Float(_) => todo!(),
+            BtfType::Enum(_) => todo!(),
+            BtfType::Array(ty) => {
+                format!(
+                    "type_id=0 index_type_id={} nr_elems={}",
+                    ty.index_type(),
+                    ty.len()
+                )
+            }
+            BtfType::Struct(ty) => {
+                let size = ty.size();
+                let vlen = ty.vlen();
+                let mut out = format!("size={} vlen={}", size, vlen,);
+                for m in ty.members() {
+                    let name = btf
+                        .string_at(m.name_offset())
+                        .unwrap_or(std::borrow::Cow::Borrowed(""));
+                    let type_id = m.btf_type();
+                    let offset = ty.member_bit_offset(m);
+                    write!(out, "\n\t'{name}' type_id={type_id} bits_offset={offset}")?;
+                }
+                out
+            }
+            BtfType::Union(_) => todo!(),
+            BtfType::FuncProto(ty) => {
+                let ret_type_id = ty.return_type();
+                let vlen = ty.vlen();
+                let mut out = format!("ret_type_id={ret_type_id} vlen={vlen}");
+                for p in ty.params() {
+                    let name = btf
+                        .string_at(p.name_offset())
+                        .unwrap_or(std::borrow::Cow::Borrowed(""));
+                    let type_id = p.btf_type();
+                    write!(out, "\n\t'{name}' type_id={type_id}")?;
+                }
+                out
+            }
+            BtfType::Var(ty) => {
+                let type_id = ty.btf_type();
+                let linkage = match ty.linkage() {
+                    VarLinkage::Static => "static".to_owned(),
+                    VarLinkage::Global => "global".to_owned(),
+                    VarLinkage::Extern => "extern".to_owned(),
+                    VarLinkage::Unknown => "unknown".to_owned(),
+                };
+                format!("type_id={type_id} linkage={linkage}")
+            }
+            BtfType::DataSec(ty) => {
+                let size = ty.size();
+                let vlen = ty.vlen();
+                let mut out = format!("size={size} vlen={vlen}");
+                for entry in ty.entries() {
+                    let points_to = btf.type_by_id(entry.btf_type()).unwrap();
+                    let name = btf
+                        .string_at(points_to.name_offset())
+                        .unwrap_or(std::borrow::Cow::Borrowed(""));
+                    write!(
+                        out,
+                        "\n\ttype_id={} offset={} size={} ({} '{}')",
+                        entry.btf_type(),
+                        entry.offset(),
+                        entry.size(),
+                        points_to.kind(),
+                        name
+                    )?;
+                }
+                out
+            }
+            BtfType::DeclTag(_) => unimplemented!("decl tag formatting not implemented"),
+            BtfType::TypeTag(_) => unimplemented!("type tag formatting not implemented"),
+            BtfType::Enum64(_) => unimplemented!("enum64 formatting not implemented"),
+        };
+        println!("[{i}] {kind} {name} {info}");
+    }
+    Ok(())
+}

aya-tool/src/lib.rs

@@ -5,6 +5,7 @@ use std::{
 };
 
 pub mod bindgen;
+pub mod btf;
 pub mod generate;
 pub mod rustfmt;
 

aya/src/sys/bpf.rs

@@ -849,14 +849,8 @@ pub(crate) fn is_btf_func_supported() -> bool {
     let a_name = btf.add_string("a");
     let b_name = btf.add_string("b");
     let params = vec![
-        BtfParam {
-            name_offset: a_name,
-            btf_type: int_type_id,
-        },
-        BtfParam {
-            name_offset: b_name,
-            btf_type: int_type_id,
-        },
+        BtfParam::new(a_name, int_type_id),
+        BtfParam::new(b_name, int_type_id),
     ];
     let func_proto = BtfType::FuncProto(FuncProto::new(params, int_type_id));
     let func_proto_type_id = btf.add_type(func_proto);
@@ -879,14 +873,8 @@ pub(crate) fn is_btf_func_global_supported() -> bool {
     let a_name = btf.add_string("a");
     let b_name = btf.add_string("b");
     let params = vec![
-        BtfParam {
-            name_offset: a_name,
-            btf_type: int_type_id,
-        },
-        BtfParam {
-            name_offset: b_name,
-            btf_type: int_type_id,
-        },
+        BtfParam::new(a_name, int_type_id),
+        BtfParam::new(b_name, int_type_id),
     ];
     let func_proto = BtfType::FuncProto(FuncProto::new(params, int_type_id));
     let func_proto_type_id = btf.add_type(func_proto);
@@ -911,11 +899,7 @@ pub(crate) fn is_btf_datasec_supported() -> bool {
     let var_type_id = btf.add_type(var_type);
 
     let name_offset = btf.add_string(".data");
-    let variables = vec![DataSecEntry {
-        btf_type: var_type_id,
-        offset: 0,
-        size: 4,
-    }];
+    let variables = vec![DataSecEntry::new(var_type_id, 0, 4)];
     let datasec_type = BtfType::DataSec(DataSec::new(name_offset, variables, 4));
     btf.add_type(datasec_type);