From d39ebb5b51a9f5d3395364c905a4281683bc1e17 Mon Sep 17 00:00:00 2001
From: Robbert van der Helm <mail@robbertvanderhelm.nl>
Date: Sat, 26 Feb 2022 19:58:30 +0100
Subject: [PATCH] Add a bundler module for parsing exported symbols

We can use this to detect which plugin formats are supported by a
plugin. Otherwise the bundler would be very awkward to use when
supporting multiple formats.
---
 Cargo.lock           | 38 ++++++++++++++++++++++++++++++++++++++
 xtask/Cargo.toml     |  1 +
 xtask/src/main.rs    |  2 ++
 xtask/src/symbols.rs | 31 +++++++++++++++++++++++++++++++
 4 files changed, 72 insertions(+)
 create mode 100644 xtask/src/symbols.rs

diff --git a/Cargo.lock b/Cargo.lock
index 9032c87c..52ff918f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -400,6 +400,17 @@ dependencies = [
  "xml-rs",
 ]
 
+[[package]]
+name = "goblin"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c955ab4e0ad8c843ea653a3d143048b87490d9be56bd7132a435c2407846ac8f"
+dependencies = [
+ "log",
+ "plain",
+ "scroll",
+]
+
 [[package]]
 name = "itoa"
 version = "1.0.1"
@@ -665,6 +676,12 @@ version = "0.3.24"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "58893f751c9b0412871a09abd62ecd2a00298c6c83befa223ef98c52aef40cbe"
 
+[[package]]
+name = "plain"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b4596b6d070b27117e987119b4dac604f3c58cfb0b191112e24771b2faeac1a6"
+
 [[package]]
 name = "proc-macro2"
 version = "1.0.36"
@@ -728,6 +745,26 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d29ab0c6d3fc0ee92fe66e2d99f700eab17a8d57d1c1d3b748380fb20baa78cd"
 
+[[package]]
+name = "scroll"
+version = "0.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "04c565b551bafbef4157586fa379538366e4385d42082f255bfd96e4fe8519da"
+dependencies = [
+ "scroll_derive",
+]
+
+[[package]]
+name = "scroll_derive"
+version = "0.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bdbda6ac5cd1321e724fa9cee216f3a61885889b896f073b8f82322789c5250e"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "serde"
 version = "1.0.136"
@@ -1118,6 +1155,7 @@ name = "xtask"
 version = "0.1.0"
 dependencies = [
  "anyhow",
+ "goblin",
  "serde",
  "toml",
 ]
diff --git a/xtask/Cargo.toml b/xtask/Cargo.toml
index e27edc69..aa943fc5 100644
--- a/xtask/Cargo.toml
+++ b/xtask/Cargo.toml
@@ -7,5 +7,6 @@ license = "ISC"
 
 [dependencies]
 anyhow = "1.0"
+goblin = "0.5"
 serde = { version = "1.0", features = ["derive"] }
 toml = "0.5"
diff --git a/xtask/src/main.rs b/xtask/src/main.rs
index 9dda1610..7c26728e 100644
--- a/xtask/src/main.rs
+++ b/xtask/src/main.rs
@@ -5,6 +5,8 @@ use std::fs;
 use std::path::Path;
 use std::process::Command;
 
+mod symbols;
+
 const USAGE_STRING: &str =
     "Usage: cargo xtask bundle <package> [--release] [--target <triple>] [--bundle-vst3]";
 
diff --git a/xtask/src/symbols.rs b/xtask/src/symbols.rs
new file mode 100644
index 00000000..f1cec36f
--- /dev/null
+++ b/xtask/src/symbols.rs
@@ -0,0 +1,31 @@
+use anyhow::{bail, Context, Result};
+use std::fs;
+use std::path::Path;
+
+/// Check whether a binary exports the specified symbol. Used to detect the plugin formats supported
+/// by a plugin library. Returns an error if the binary cuuld not be read. This function will also
+/// parse non-native binaries.
+pub fn exported<P: AsRef<Path>>(binary: P, symbol: &str) -> Result<bool> {
+    // Parsing the raw binary instead of relying on nm-like tools makes cross compiling a bit easier
+    let bytes = fs::read(&binary)
+        .with_context(|| format!("Could not read '{}'", binary.as_ref().display()))?;
+    match goblin::Object::parse(&bytes)? {
+        goblin::Object::Elf(obj) => Ok(obj.dynsyms.iter().any(|sym| {
+            !sym.is_import()
+                && sym.is_function()
+                && obj.dynstrtab.get_at(sym.st_name) == Some(symbol)
+        })),
+        goblin::Object::Mach(obj) => {
+            let obj = match obj {
+                goblin::mach::Mach::Fat(arches) => arches
+                    .get(0)
+                    .context("Fat Mach-O binary without any binaries")?,
+                goblin::mach::Mach::Binary(obj) => obj,
+            };
+
+            Ok(obj.exports()?.into_iter().any(|sym| sym.name == symbol))
+        }
+        goblin::Object::PE(obj) => Ok(obj.exports.iter().any(|sym| sym.name == Some(symbol))),
+        obj => bail!("Unsupported object type: {:?}", obj),
+    }
+}