[PATCH 2/4] rust: add reproducibility patch to eliminate host leakage

[Alexander Kanavin <alex.kanavin@gmail.com>]

From: Alexander Kanavin <alex@linutronix.de>

[YOCTO #15185]

Signed-off-by: Alexander Kanavin <alex@linutronix.de>
---
 ...te-host-information-into-compilation.patch | 51 +++++++++++++++++++
 meta/recipes-devtools/rust/rust-source.inc    |  1 +
 2 files changed, 52 insertions(+)
 create mode 100644 meta/recipes-devtools/rust/files/0001-cargo-do-not-write-host-information-into-compilation.patch

diff --git a/meta/recipes-devtools/rust/files/0001-cargo-do-not-write-host-information-into-compilation.patch b/meta/recipes-devtools/rust/files/0001-cargo-do-not-write-host-information-into-compilation.patch
new file mode 100644
index 00000000000..a6ee8676058
--- /dev/null
+++ b/meta/recipes-devtools/rust/files/0001-cargo-do-not-write-host-information-into-compilation.patch
@@ -0,0 +1,51 @@
+From 065d7c263091118437465d714d8a29dbb6296921 Mon Sep 17 00:00:00 2001
+From: Alexander Kanavin <alex@linutronix.de>
+Date: Mon, 13 May 2024 14:57:54 +0200
+Subject: [PATCH] cargo: do not write host information into compilation unit
+ hashes
+
+This breaks reproducibility in cross-builds where the cross-target
+can be the same, but build hosts are different, as seen with
+"rustc --version -v":
+...
+host: x86_64-unknown-linux-gnu
+
+vs.
+
+host: aarch64-unknown-linux-gnu
+
+This can possibly be improved by only hashing host info if the build
+is a native one (e.g. there's no --target option passed to cargo
+invocation) but I'm not sure how.
+
+Upstream-Status: Inappropriate [reported at https://github.com/rust-lang/cargo/issues/13922]
+Signed-off-by: Alexander Kanavin <alex@linutronix.de>
+---
+ .../src/cargo/core/compiler/context/compilation_files.rs      | 4 ++--
+ 1 file changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/src/tools/cargo/src/cargo/core/compiler/context/compilation_files.rs b/src/tools/cargo/src/cargo/core/compiler/context/compilation_files.rs
+index d83dbf10c..b2ad8d9f3 100644
+--- a/src/tools/cargo/src/cargo/core/compiler/context/compilation_files.rs
++++ b/src/tools/cargo/src/cargo/core/compiler/context/compilation_files.rs
+@@ -652,7 +652,7 @@ fn hash_rustc_version(bcx: &BuildContext<'_, '_>, hasher: &mut StableHasher) {
+     if vers.pre.is_empty() || bcx.config.cli_unstable().separate_nightlies {
+         // For stable, keep the artifacts separate. This helps if someone is
+         // testing multiple versions, to avoid recompiles.
+-        bcx.rustc().verbose_version.hash(hasher);
++        //bcx.rustc().verbose_version.hash(hasher);
+         return;
+     }
+     // On "nightly"/"beta"/"dev"/etc, keep each "channel" separate. Don't hash
+@@ -665,7 +665,7 @@ fn hash_rustc_version(bcx: &BuildContext<'_, '_>, hasher: &mut StableHasher) {
+     // Keep "host" since some people switch hosts to implicitly change
+     // targets, (like gnu vs musl or gnu vs msvc). In the future, we may want
+     // to consider hashing `unit.kind.short_name()` instead.
+-    bcx.rustc().host.hash(hasher);
++    //bcx.rustc().host.hash(hasher);
+     // None of the other lines are important. Currently they are:
+     // binary: rustc  <-- or "rustdoc"
+     // commit-hash: 38114ff16e7856f98b2b4be7ab4cd29b38bed59a
+-- 
+2.39.2
+
diff --git a/meta/recipes-devtools/rust/rust-source.inc b/meta/recipes-devtools/rust/rust-source.inc
index c83c8ec3a39..20ef5e82bc4 100644
--- a/meta/recipes-devtools/rust/rust-source.inc
+++ b/meta/recipes-devtools/rust/rust-source.inc
@@ -12,6 +12,7 @@ SRC_URI += "https://static.rust-lang.org/dist/rustc-${RUST_VERSION}-src.tar.xz;n
             file://target-build-value.patch;patchdir=${RUSTSRC} \
             file://0001-Handle-vendored-sources-when-remapping-paths.patch;patchdir=${RUSTSRC} \
             file://repro-issue-fix-with-v175.patch;patchdir=${RUSTSRC} \
+            file://0001-cargo-do-not-write-host-information-into-compilation.patch;patchdir=${RUSTSRC} \
 "
 SRC_URI[rust.sha256sum] = "4526f786d673e4859ff2afa0bab2ba13c918b796519a25c1acce06dba9542340"
 
-- 
2.39.2