4 files changed, 144 insertions, 0 deletions
diff --git a/nixpkgs/pkgs/build-support/rust/sysroot/Cargo.lock b/nixpkgs/pkgs/build-support/rust/sysroot/Cargo.lock
new file mode 100644
index 000000000000..d9b0c25d02f2
--- /dev/null
+++ b/nixpkgs/pkgs/build-support/rust/sysroot/Cargo.lock
@@ -0,0 +1,44 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "alloc"
+version = "0.0.0"
+dependencies = [
+ "compiler_builtins",
+ "core",
+]
+
+[[package]]
+name = "compiler_builtins"
+version = "0.1.87"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f867ce54c09855ccd135ad4a50c777182a0c7af5ff20a8f537617bd648b10d50"
+dependencies = [
+ "rustc-std-workspace-core",
+]
+
+[[package]]
+name = "core"
+version = "0.0.0"
+
+[[package]]
+name = "nixpkgs-sysroot-stub-crate"
+version = "0.0.0"
+dependencies = [
+ "alloc",
+ "compiler_builtins",
+ "core",
+]
+
+[[package]]
+name = "rustc-std-workspace-core"
+version = "1.99.0"
+dependencies = [
+ "core",
+]
+
+[[patch.unused]]
+name = "rustc-std-workspace-alloc"
+version = "1.99.0"
diff --git a/nixpkgs/pkgs/build-support/rust/sysroot/cargo.py b/nixpkgs/pkgs/build-support/rust/sysroot/cargo.py
new file mode 100644
index 000000000000..9d970eff79e8
--- /dev/null
+++ b/nixpkgs/pkgs/build-support/rust/sysroot/cargo.py
@@ -0,0 +1,47 @@
+import os
+import toml
+
+rust_src = os.environ['RUSTC_SRC']
+orig_cargo = os.environ['ORIG_CARGO'] if 'ORIG_CARGO' in os.environ else None
+
+base = {
+  'package': {
+    'name': 'nixpkgs-sysroot-stub-crate',
+    'version': '0.0.0',
+    'authors': ['The Rust Project Developers'],
+    'edition': '2018',
+  },
+  'dependencies': {
+    'compiler_builtins': {
+      'version': '0.1.0',
+      'features': ['rustc-dep-of-std', 'mem'],
+    },
+    'core': {
+      'path': os.path.join(rust_src, 'core'),
+    },
+    'alloc': {
+      'path': os.path.join(rust_src, 'alloc'),
+    },
+  },
+  'patch': {
+    'crates-io': {
+      'rustc-std-workspace-core': {
+        'path': os.path.join(rust_src, 'rustc-std-workspace-core'),
+      },
+      'rustc-std-workspace-alloc': {
+        'path': os.path.join(rust_src, 'rustc-std-workspace-alloc'),
+      },
+    },
+  },
+}
+
+if orig_cargo is not None:
+  with open(orig_cargo, 'r') as f:
+    src = toml.loads(f.read())
+    if 'profile' in src:
+      base['profile'] = src['profile']
+
+out = toml.dumps(base)
+
+with open('Cargo.toml', 'x') as f:
+  f.write(out)
diff --git a/nixpkgs/pkgs/build-support/rust/sysroot/src.nix b/nixpkgs/pkgs/build-support/rust/sysroot/src.nix
new file mode 100644
index 000000000000..664702e82c31
--- /dev/null
+++ b/nixpkgs/pkgs/build-support/rust/sysroot/src.nix
@@ -0,0 +1,26 @@
+{ lib, stdenv, rustPlatform, buildPackages
+, originalCargoToml ? null
+}:
+
+stdenv.mkDerivation {
+  name = "cargo-src";
+  preferLocalBuild = true;
+
+  unpackPhase = "true";
+  dontConfigure = true;
+  dontBuild = true;
+
+  installPhase = ''
+    export RUSTC_SRC=${rustPlatform.rustLibSrc.override { }}
+  ''
+  + lib.optionalString (originalCargoToml != null) ''
+    export ORIG_CARGO=${originalCargoToml}
+  ''
+  + ''
+    ${buildPackages.python3.withPackages (ps: with ps; [ toml ])}/bin/python3 ${./cargo.py}
+    mkdir -p $out/src
+    echo '#![no_std]' > $out/src/lib.rs
+    cp Cargo.toml $out/Cargo.toml
+    cp ${./Cargo.lock} $out/Cargo.lock
+  '';
+}
diff --git a/nixpkgs/pkgs/build-support/rust/sysroot/update-lockfile.sh b/nixpkgs/pkgs/build-support/rust/sysroot/update-lockfile.sh
new file mode 100755
index 000000000000..d0596d1e5a62
--- /dev/null
+++ b/nixpkgs/pkgs/build-support/rust/sysroot/update-lockfile.sh
@@ -0,0 +1,27 @@
+#!/usr/bin/env nix-shell
+#!nix-shell -i bash -p python3 python3.pkgs.toml cargo
+
+set -eu pipefile
+
+HERE=$(readlink -e $(dirname "${BASH_SOURCE[0]}"))
+NIXPKGS_ROOT="$HERE/../../../.."
+
+# https://unix.stackexchange.com/a/84980/390173
+tempdir=$(mktemp -d 2>/dev/null || mktemp -d -t 'update-lockfile')
+cd "$tempdir"
+mkdir -p src
+touch src/lib.rs
+
+RUSTC_SRC=$(nix-build "${NIXPKGS_ROOT}" -A pkgs.rustPlatform.rustLibSrc --no-out-link)
+
+ln -s $RUSTC_SRC/{core,alloc} ./
+
+export RUSTC_SRC
+python3 "$HERE/cargo.py"
+
+export RUSTC_BOOTSTRAP=1
+cargo generate-lockfile
+
+cp Cargo.lock "$HERE"
+
+rm -rf "$tempdir"