FAILED: patch "[PATCH] rust: kbuild: treat `build_error` and `rustdoc` as kernel" failed to apply to 6.12-stable tree

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 16c43a56b79e2c3220b043236369a129d508c65a
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025110816-catalog-residency-716f@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 16c43a56b79e2c3220b043236369a129d508c65a Mon Sep 17 00:00:00 2001
From: Miguel Ojeda <[email protected]>
Date: Sun, 2 Nov 2025 22:28:52 +0100
Subject: [PATCH] rust: kbuild: treat build_error and rustdoc as kernel
objects

Even if normally build_error isn't a kernel object, it should still be treated as such so that we pass the same flags. Similarly, rustdoc targets are never kernel objects, but we need to treat them as such.

Otherwise, starting with Rust 1.91.0 (released 2025-10-30), rustc will complain about missing sanitizer flags since -Zsanitizer is a target modifier too [1]:

error: mixing -Zsanitizer will cause an ABI mismatch in crate build_error
--> rust/build_error.rs:3:1
|
3 | //! Build-time error.
| ^
|
= help: the -Zsanitizer flag modifies the ABI so Rust crates compiled with different values of this flag cannot be used together safely = note: unset -Zsanitizer in this crate is incompatible with -Zsanitizer=kernel-address in dependency core
= help: set -Zsanitizer=kernel-address in this crate or unset -Zsanitizer in core
= help: if you are sure this will not cause problems, you may use -Cunsafe-allow-abi-mismatch=sanitizer to silence this error

Thus explicitly mark them as kernel objects.

index 23c7ae905bd2..a9fb9354b659 100644
@@ -127,9 +127,14 @@ rustdoc-core: private rustc_target_flags = --edition=$(core-edition) $(core-cfgs
 rustdoc-core: $(RUST_LIB_SRC)/core/src/lib.rs rustdoc-clean FORCE
 	+$(call if_changed,rustdoc)
 
+# Even if `rustdoc` targets are not kernel objects, they should still be
+# treated as such so that we pass the same flags. Otherwise, for instance,
+# `rustdoc` will complain about missing sanitizer flags causing an ABI mismatch.
+rustdoc-compiler_builtins: private is-kernel-object := y
 rustdoc-compiler_builtins: $(src)/compiler_builtins.rs rustdoc-core FORCE
 	+$(call if_changed,rustdoc)
 
+rustdoc-ffi: private is-kernel-object := y
 rustdoc-ffi: $(src)/ffi.rs rustdoc-core FORCE
 	+$(call if_changed,rustdoc)
 

@@ -147,6 +152,7 @@ rustdoc-pin_init: $(src)/pin-init/src/lib.rs rustdoc-pin_init_internal \
     rustdoc-macros FORCE
 	+$(call if_changed,rustdoc)
 
+rustdoc-kernel: private is-kernel-object := y
 rustdoc-kernel: private rustc_target_flags = --extern ffi --extern pin_init \
     --extern build_error --extern macros \
     --extern bindings --extern uapi

@@ -522,6 +528,10 @@ $(obj)/pin_init.o: $(src)/pin-init/src/lib.rs $(obj)/compiler_builtins.o \
     $(obj)/$(libpin_init_internal_name) $(obj)/$(libmacros_name) FORCE
 	+$(call if_changed_rule,rustc_library)
 
+# Even if normally `build_error` is not a kernel object, it should still be
+# treated as such so that we pass the same flags. Otherwise, for instance,
+# `rustc` will complain about missing sanitizer flags causing an ABI mismatch.
+$(obj)/build_error.o: private is-kernel-object := y
 $(obj)/build_error.o: private skip_gendwarfksyms = 1
 $(obj)/build_error.o: $(src)/build_error.rs $(obj)/compiler_builtins.o FORCE
 	+$(call if_changed_rule,rustc_library)

From: Miguel Ojeda <[email protected]>

[ Upstream commit 16c43a56b79e2c3220b043236369a129d508c65a ]

Even if normally build_error isn't a kernel object, it should still be treated as such so that we pass the same flags. Similarly, rustdoc targets are never kernel objects, but we need to treat them as such.

Otherwise, starting with Rust 1.91.0 (released 2025-10-30), rustc will complain about missing sanitizer flags since -Zsanitizer is a target modifier too [1]:

error: mixing -Zsanitizer will cause an ABI mismatch in crate build_error
--> rust/build_error.rs:3:1
|
3 | //! Build-time error.
| ^
|
= help: the -Zsanitizer flag modifies the ABI so Rust crates compiled with different values of this flag cannot be used together safely = note: unset -Zsanitizer in this crate is incompatible with -Zsanitizer=kernel-address in dependency core
= help: set -Zsanitizer=kernel-address in this crate or unset -Zsanitizer in core
= help: if you are sure this will not cause problems, you may use -Cunsafe-allow-abi-mismatch=sanitizer to silence this error

Thus explicitly mark them as kernel objects.

---
 rust/Makefile | 10 ++++++++++
 1 file changed, 10 insertions(+)

index 07c13100000cd..6bcc478900af2 100644
@@ -107,12 +107,18 @@ rustdoc-core: private rustc_target_flags = --edition=$(core-edition) $(core-cfgs
 rustdoc-core: $(RUST_LIB_SRC)/core/src/lib.rs rustdoc-clean FORCE
 	+$(call if_changed,rustdoc)
 
+# Even if `rustdoc` targets are not kernel objects, they should still be
+# treated as such so that we pass the same flags. Otherwise, for instance,
+# `rustdoc` will complain about missing sanitizer flags causing an ABI mismatch.
+rustdoc-compiler_builtins: private is-kernel-object := y
 rustdoc-compiler_builtins: $(src)/compiler_builtins.rs rustdoc-core FORCE
 	+$(call if_changed,rustdoc)
 
+rustdoc-ffi: private is-kernel-object := y
 rustdoc-ffi: $(src)/ffi.rs rustdoc-core FORCE
 	+$(call if_changed,rustdoc)
 
+rustdoc-kernel: private is-kernel-object := y
 rustdoc-kernel: private rustc_target_flags = --extern ffi \
     --extern build_error --extern macros=$(objtree)/$(obj)/libmacros.so \
     --extern bindings --extern uapi

@@ -433,6 +439,10 @@ $(obj)/compiler_builtins.o: private rustc_objcopy = -w -W '__*'
 $(obj)/compiler_builtins.o: $(src)/compiler_builtins.rs $(obj)/core.o FORCE
 	+$(call if_changed_rule,rustc_library)
 
+# Even if normally `build_error` is not a kernel object, it should still be
+# treated as such so that we pass the same flags. Otherwise, for instance,
+# `rustc` will complain about missing sanitizer flags causing an ABI mismatch.
+$(obj)/build_error.o: private is-kernel-object := y
 $(obj)/build_error.o: $(src)/build_error.rs $(obj)/compiler_builtins.o FORCE
 	+$(call if_changed_rule,rustc_library)
 

2.51.0

Sasha's sibling resolution looks fine, thanks!

Cheers,
Miguel

Just in case this was missed, I think this one and the related one weren't picked up for 6.12.58-rc2.

Should I do something?

Thanks!

Cheers,
Miguel

No, I just didn't get the chance to pick up backports for 6.12 and older just yet, I wanted to push out what we had already. My queue is big, due to travel at the moment, sorry.

greg "what day/timezone/continent is it now?" k-h