wip: elf packing

Cargo.lock

@@ -2,6 +2,23 @@
 # It is not intended for manual editing.
 version = 3
 
+[[package]]
+name = "adler"
+version = "1.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f26201604c87b1e01bd3d98f8d5d9a8fcbb815e8cedb41ffccbeb4bf593a35fe"
+
+[[package]]
+name = "ahash"
+version = "0.7.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fcb51a0695d8f838b1ee009b3fbf66bda078cd64590202a864a8f3e8c4315c47"
+dependencies = [
+ "getrandom",
+ "once_cell",
+ "version_check",
+]
+
 [[package]]
 name = "aho-corasick"
 version = "0.7.18"
@@ -131,6 +148,7 @@ dependencies = [
  "libc",
  "log",
  "nix",
+ "object",
  "serde",
  "serde_json",
  "tempfile",
@@ -147,6 +165,15 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "crc32fast"
+version = "1.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b540bd8bc810d3885c6ea91e2018302f68baba2129ab3e88f32389ee9370880d"
+dependencies = [
+ "cfg-if",
+]
+
 [[package]]
 name = "criterion"
 version = "0.3.5"
@@ -284,6 +311,29 @@ dependencies = [
  "instant",
 ]
 
+[[package]]
+name = "flate2"
+version = "1.0.23"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b39522e96686d38f4bc984b9198e3a0613264abaebaff2c5c918bfa6b6da09af"
+dependencies = [
+ "cfg-if",
+ "crc32fast",
+ "libc",
+ "miniz_oxide",
+]
+
+[[package]]
+name = "getrandom"
+version = "0.2.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d39cd93900197114fa1fcb7ae84ca742095eed9442088988ae74fa744e930e77"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "wasi",
+]
+
 [[package]]
 name = "half"
 version = "1.8.2"
@@ -295,6 +345,9 @@ name = "hashbrown"
 version = "0.11.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ab5ef0d4909ef3724cc8cce6ccc8572c5c817592e9285f5464f8e86f8bd3726e"
+dependencies = [
+ "ahash",
+]
 
 [[package]]
 name = "hermit-abi"
@@ -405,6 +458,15 @@ dependencies = [
  "autocfg",
 ]
 
+[[package]]
+name = "miniz_oxide"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d2b29bd4bc3f33391105ebee3589c19197c4271e3e5a9ec9bfe8127eeff8f082"
+dependencies = [
+ "adler",
+]
+
 [[package]]
 name = "nix"
 version = "0.23.1"
@@ -437,6 +499,25 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "object"
+version = "0.28.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "40bec70ba014595f99f7aa110b84331ffe1ee9aece7fe6f387cc7e3ecda4d456"
+dependencies = [
+ "crc32fast",
+ "flate2",
+ "hashbrown",
+ "indexmap",
+ "memchr",
+]
+
+[[package]]
+name = "once_cell"
+version = "1.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "87f3e037eac156d1775da914196f0f37741a274155e34a0b7e427c35d2a2ecb9"
+
 [[package]]
 name = "oorandom"
 version = "11.1.3"
@@ -735,6 +816,12 @@ version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8ccb82d61f80a663efe1f787a51b16b5a51e3314d6ac365b08639f52387b33f3"
 
+[[package]]
+name = "version_check"
+version = "0.9.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "49874b5167b65d7193b8aba1567f5c7d93d001cafc34600cee003eda787e483f"
+
 [[package]]
 name = "walkdir"
 version = "2.3.2"
@@ -746,6 +833,12 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "wasi"
+version = "0.10.2+wasi-snapshot-preview1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fd6fbd9a79829dd1ad0cc20627bf1ed606756a7f77edff7b66b7064f9cb327c6"
+
 [[package]]
 name = "wasm-bindgen"
 version = "0.2.79"

Cargo.toml

@@ -22,6 +22,7 @@ nix = "0.23.1"
 
 close_fds = "0.3.2"
 tempfile = "3.3"
+object = { version = "0.28", features = ["write_core"] }
 
 [dev-dependencies]
 criterion = "0.3"

src/error.rs

@@ -18,13 +18,22 @@ pub enum Error {
     #[error("bincode: {0}")]
     Bincode(#[from] bincode::Error),
 
+    #[error("elf: read: {0}")]
+    ElfRead(#[from] object::read::Error),
+
+    #[error("elf: write: {0}")]
+    ElfWrite(#[from] object::write::Error),
+
     #[error("bad pipe specification: a pipe must have exactly one reader and one writer: {0}")]
     BadPipe(String),
 
     #[error("bad socket specification: a socket must have exactly one reader and one writer: {0}")]
     BadFileSocket(String),
 
-    #[error("bad specification type: only .json files are supported")]
+    #[error("no specification provided")]
+    NoSpecification,
+
+    #[error("bad specification type: only json files are supported")]
     BadSpecType,
 
     #[error("bad trigger argument: this entrypoint is not triggered by something with arguments")]

src/lib.rs

@@ -2,6 +2,7 @@ use log::{debug, info};
 
 pub mod clone;
 mod error;
+mod pack;
 mod spawner;
 mod specification;
 mod void;
@@ -18,7 +19,6 @@ use std::path::Path;
 use nix::fcntl::OFlag;
 use nix::sys::socket;
 use nix::unistd;
-
 pub struct PackArgs<'a> {
     pub spec: &'a Path,
     pub binary: &'a Path,
@@ -26,16 +26,14 @@ pub struct PackArgs<'a> {
 }
 
 pub fn pack(args: &PackArgs) -> Result<()> {
-    let spec: Specification = if args.spec.ends_with(".json") {
+    let spec: Specification = if args.spec.extension().map(|e| e == "json") == Some(true) {
         let f = std::fs::File::open(args.spec)?;
         Ok(serde_json::from_reader(f)?)
     } else {
         Err(Error::BadSpecType)
     }?;
 
-    let spec_bin = bincode::serialize(&spec)?;
-
-    Ok(())
+    pack::pack_binary(args.binary, &spec, args.output)
 }
 
 pub struct RunArgs<'a> {
@@ -56,7 +54,12 @@ pub fn run(args: &RunArgs) -> Result<()> {
             Err(Error::BadSpecType)
         }
     } else {
-        unimplemented!("reading spec from the elf is unimplemented")
+        let spec = pack::extract_specification(args.binary)?;
+        if let Some(s) = spec {
+            Ok(s)
+        } else {
+            Err(Error::NoSpecification)
+        }
     }?;
 
     debug!("specification read: {:?}", &spec);

src/pack.rs

@@ -0,0 +1,75 @@
+use crate::{Result, Specification};
+
+use std::fs::File;
+use std::path::Path;
+
+use bincode::Options;
+use object::endian::Endianness;
+use object::read::ReadCache;
+use object::read::{Object, ObjectSection};
+use object::write::{StandardSegment, StreamingBuffer};
+use object::SectionKind;
+
+const SPECIFICATION_SECTION_NAME: &str = "void_specification";
+
+pub(crate) fn pack_binary(binary: &Path, spec: &Specification, output: &Path) -> Result<()> {
+    let binary = File::open(binary)?;
+    let binary = ReadCache::new(binary);
+
+    let output = File::create(output)?;
+    let mut output = StreamingBuffer::new(output);
+
+    let input_object = object::File::parse(&binary)?;
+
+    let format = input_object.format();
+    let architecture = input_object.architecture();
+    let endianness = if input_object.is_little_endian() {
+        Endianness::Little
+    } else {
+        Endianness::Big
+    };
+
+    let mut output_object = object::write::Object::new(format, architecture, endianness);
+
+    for input_section in input_object.sections() {
+        let output_section = output_object.add_section(
+            input_section.segment_name_bytes()?.unwrap_or(&[]).to_vec(),
+            input_section.name_bytes()?.to_vec(),
+            input_section.kind(),
+        );
+
+        output_object.set_section_data(output_section, input_section.data()?, 0);
+    }
+
+    let spec_section = output_object.add_section(
+        output_object.segment_name(StandardSegment::Debug).to_vec(),
+        SPECIFICATION_SECTION_NAME.to_string().into(),
+        SectionKind::Other,
+    );
+
+    let spec = bincode_options().serialize(spec)?;
+    output_object.set_section_data(spec_section, spec, 0);
+
+    output_object.emit(&mut output)?;
+    Ok(())
+}
+
+pub(crate) fn extract_specification(binary: &Path) -> Result<Option<Specification>> {
+    let binary = File::open(binary)?;
+    let binary = ReadCache::new(binary);
+    let input_object = object::File::parse(&binary)?;
+
+    let spec_section = if let Some(s) = input_object.section_by_name(SPECIFICATION_SECTION_NAME) {
+        s
+    } else {
+        return Ok(None);
+    };
+
+    let spec_data = spec_section.data()?;
+
+    Ok(Some(bincode_options().deserialize(spec_data)?))
+}
+
+fn bincode_options() -> impl bincode::Options {
+    bincode::DefaultOptions::new()
+}