--- /dev/null
+++ bazel/rules_rust/freebsd_local_toolchain.patch
@@ -0,0 +1,99 @@
+diff --git crate_universe/private/generate_utils.bzl crate_universe/private/generate_utils.bzl
+--- crate_universe/private/generate_utils.bzl
++++ crate_universe/private/generate_utils.bzl
+@@ -388,6 +388,11 @@
+             else:
+                 return True
+ 
++    # The digest of the lockfile includes the cargo and rustc versions. Allow
++    # using the lockfile as is with a different (e.g. local) toolchain.
++    if repository_ctx.os.environ.get("CARGO_BAZEL_SKIP_DIGEST_CHECK", "0") == "1":
++        return not lockfile_path
++
+     # If a deterministic lockfile was not added then always repin
+     if not lockfile_path:
+         return True
+diff --git rust/private/repository_utils.bzl rust/private/repository_utils.bzl
+--- rust/private/repository_utils.bzl
++++ rust/private/repository_utils.bzl
+@@ -872,6 +872,68 @@
+ 
+     return archive_path, ""
+ 
++# Files of a locally installed Rust (e.g. ${LOCALBASE} with lang/rust on
++# FreeBSD), per tool archive, which has the same layout.
++_LOCAL_TOOL_FILES = {
++    "cargo": ["bin/cargo"],
++    "clippy": ["bin/cargo-clippy", "bin/clippy-driver"],
++    "llvm-tools": [],
++    "rust-std": ["lib/rustlib/{triple}/lib"],
++    "rustc": [
++        "bin/rustc",
++        "bin/rustdoc",
++        "lib/librustc_driver-*",
++        "lib/rustlib/{triple}/bin",
++        "lib/rustlib/{triple}/codegen-backends",
++    ],
++    "rustc-dev": [],
++    "rustfmt": ["bin/cargo-fmt", "bin/rustfmt"],
++}
++
++def _link_local_tool(ctx, prefix, tool_name, target_triple):
++    """Symlinks the files of a tool from a local Rust installation.
++
++    Args:
++        ctx (repository_ctx): A repository_ctx.
++        prefix (str): The prefix of the local Rust installation.
++        tool_name (str): The name of the tool per the archive naming.
++        target_triple (struct): The rust-style target triple of the tool.
++    """
++    if tool_name not in _LOCAL_TOOL_FILES:
++        fail("Tool {} is not supported with RULES_RUST_LOCAL_TOOLCHAIN".format(tool_name))
++    if not ctx.path("{}/lib/rustlib/{}".format(prefix, target_triple.str)).exists:
++        fail("Target {} is not installed in {}".format(target_triple.str, prefix))
++
++    todo = []
++    for pattern in _LOCAL_TOOL_FILES[tool_name]:
++        rel = pattern.format(triple = target_triple.str)
++        if rel.endswith("*"):
++            directory, _, file_prefix = rel[:-1].rpartition("/")
++            for child in ctx.path("{}/{}".format(prefix, directory)).readdir():
++                if child.basename.startswith(file_prefix):
++                    todo.append((child, "{}/{}".format(directory, child.basename)))
++        elif ctx.path("{}/{}".format(prefix, rel)).exists:
++            todo.append((ctx.path("{}/{}".format(prefix, rel)), rel))
++
++    # Starlark has no recursion or while loops.
++    for _ in range(100000):
++        if not todo:
++            break
++        src, dest = todo.pop()
++        if src.is_dir:
++            for child in src.readdir():
++                todo.append((child, "{}/{}".format(dest, child.basename)))
++        else:
++            ctx.symlink(src, dest)
++
++    # The llvm-tools component is not part of a regular Rust installation.
++    if tool_name == "llvm-tools":
++        binary_ext = system_to_binary_ext(target_triple.system)
++        for tool in ["llvm-cov", "llvm-profdata"]:
++            path = "lib/rustlib/{}/bin/{}{}".format(target_triple.str, tool, binary_ext)
++            if not ctx.path(path).exists:
++                ctx.file(path, "#!/bin/sh\necho \"{} is not available\" >&2\nexit 1\n".format(tool), executable = True)
++
+ def load_arbitrary_tool(
+         ctx,
+         tool_name,
+@@ -911,6 +973,11 @@
+         Dict[str, str]: A mapping of the tool name to it's sha256 value if the requested tool does not have
+             enough information in the repository_ctx to be reproducible.
+     """
++    local_prefix = ctx.os.environ.get("RULES_RUST_LOCAL_TOOLCHAIN", "")
++    if local_prefix:
++        _link_local_tool(ctx, local_prefix, tool_name, target_triple)
++        return {}
++
+     check_version_valid(version, iso_date, param_prefix = tool_name + "_")
+ 
+     # View the indices mentioned in the docstring to find the tool_suburl for a given