bindings/rust/libflashrom-sys: Create thin rust bindgen binding

Use bindgen to create a rust library that calls into libflashrom using
FFI.

BUG=b:230545739
BRANCH=None
TEST=cargo test

Change-Id: I36ba70de2bca8f83d2fdd6fd4c9b7c28a11624ee
Signed-off-by: Evan Benn <evanbenn@chromium.org>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/65280
Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
Reviewed-by: Peter Marheine <pmarheine@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

.gitattributes

@@ -1,5 +1,7 @@
 .gitattributes export-ignore
 .gitignore export-ignore
+/bindings export-ignore
+/bindings/** export-ignore
 /util/getrevision.sh export-ignore
 /util/git-hooks export-ignore
 /util/git-hooks/** export-ignore

.gitignore

@@ -16,3 +16,5 @@
 /util/ich_descriptors_tool/ich_descriptors_tool.exe
 /util/ich_descriptors_tool/.dep
 /util/ich_descriptors_tool/.obj
+
+target/

bindings/rust/libflashrom-sys/.cargo/config.toml

@@ -0,0 +1,2 @@
+[env]
+RUST_TEST_THREADS = "1"

bindings/rust/libflashrom-sys/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "libflashrom-sys"
+version = "0.1.0"
+links = "flashrom"
+build = "build.rs"
+edition = "2021"
+
+[build-dependencies]
+pkg-config = "0.3.19"
+bindgen = "0.59.2"

bindings/rust/libflashrom-sys/build.rs

@@ -0,0 +1,32 @@
+fn main() {
+    pkg_config::probe_library("flashrom").unwrap();
+    let bindings = bindgen::Builder::default()
+        .header("../../../include/libflashrom.h")
+        // Tell cargo to invalidate the built crate whenever any of the
+        // included header files changed.
+        .parse_callbacks(Box::new(bindgen::CargoCallbacks))
+        // only generate the flashrom functions and used types.
+        .allowlist_function("flashrom_.*")
+        // newtype enums provide type checking without the UB potential of rust enums.
+        .default_enum_style(bindgen::EnumVariation::NewType { is_bitfield: false })
+        // We use constified enum for flashrom_log_level to allow '<' comparison.
+        .constified_enum("flashrom_log_level")
+        .prepend_enum_name(false)
+        .derive_copy(false)
+        .must_use_type("flashrom_wp_result")
+        // Avoid some va_list related functionality that is not easy to use in rust.
+        .blocklist_function("flashrom_set_log_callback")
+        .blocklist_type("flashrom_log_callback")
+        .blocklist_type("va_list")
+        .blocklist_type("__builtin_va_list")
+        .blocklist_type("__va_list_tag")
+        .size_t_is_usize(true)
+        .generate()
+        .expect("Unable to generate bindings");
+
+    // Write the bindings to the $OUT_DIR/bindings.rs file.
+    let out_path = std::path::PathBuf::from(std::env::var("OUT_DIR").unwrap());
+    bindings
+        .write_to_file(out_path.join("bindings.rs"))
+        .expect("Couldn't write bindings!");
+}

bindings/rust/libflashrom-sys/src/lib.rs

@@ -0,0 +1,5 @@
+#![allow(non_upper_case_globals)]
+#![allow(non_camel_case_types)]
+#![allow(non_snake_case)]
+#![allow(deref_nullptr)]
+include!(concat!(env!("OUT_DIR"), "/bindings.rs"));