[PATCH 6.18 685/752] rust: kbuild: pass `-Zunstable-options` for Rust 1.95.0

Sasha Levin
2026-02-28T17:58:21Z

From: Miguel Ojeda <ojeda@kernel.org>

[ Upstream commit 0a9be83e57de0d0ca8ca4ec610bc344f17a8e5e7 ]

Custom target specifications are unstable, but starting with Rust 1.95.0,
`rustc` requires to explicitly pass `-Zunstable-options` to use them [1]:

error: error loading target specification: custom targets are unstable and require `-Zunstable-options`
|
= help: run `rustc --print target-list` for a list of built-in targets

David (Rust compiler team lead), writes:

"We're destabilising custom targets to allow us to move forward with
build-std without accidentally exposing functionality that we'd like
to revisit prior to committing to. I'll start a thread on Zulip to
discuss with the RfL team how we can come up with an alternative
for them."

Thus pass it.

Cc: David Wood <david@davidtw.co>
Cc: Wesley Wiser <wwiser@gmail.com>
Cc: stable@vger.kernel.org # Needed in 6.12.y and later (Rust is pinned in older LTSs).
Link: https://github.com/rust-lang/rust/pull/151534 [1]
Reviewed-by: Gary Guo <gary@garyguo.net>
Tested-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260206204535.39431-1-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
rust/Makefile | 3 +++
1 file changed, 3 insertions(+)

diff --git a/rust/Makefile b/rust/Makefile
index 7842ad0a4ea72..d4618f646b05b 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -437,6 +437,8 @@ $(obj)/$(libpin_init_internal_name): private rustc_target_flags = --cfg kernel
$(obj)/$(libpin_init_internal_name): $(src)/pin-init/internal/src/lib.rs FORCE
+$(call if_changed_dep,rustc_procmacro)

+# `rustc` requires `-Zunstable-options` to use custom target specifications
+# since Rust 1.95.0 (https://github.com/rust-lang/rust/pull/151534).
quiet_cmd_rustc_library = $(if $(skip_clippy),RUSTC,$(RUSTC_OR_CLIPPY_QUIET)) L $@
cmd_rustc_library = \
OBJTREE=$(abspath $(objtree)) \
@@ -447,6 +449,7 @@ quiet_cmd_rustc_library = $(if $(skip_clippy),RUSTC,$(RUSTC_OR_CLIPPY_QUIET)) L
--crate-type rlib -L$(objtree)/$(obj) \
--crate-name $(patsubst %.o,%,$(notdir $@)) $< \
--sysroot=/dev/null \
+ -Zunstable-options \
$(if $(rustc_objcopy),;$(OBJCOPY) $(rustc_objcopy) $@) \
$(cmd_objtool)

--
2.51.0