[PATCH v3] rust: remove spurious compiler_builtins dependents

[PATCH v3] rust: remove spurious compiler_builtins dependents

[Tamir Duberstein]

The dependency on `compiler_builtins.o` was first added in commit
2f7ab1267dc9 ("Kbuild: add Rust support") to `alloc` which matches the
standard library[0] but was copied to other targets in:
- commit ecaa6ddff2fd ("rust: add `build_error` crate")
- commit d072acda4862 ("rust: use custom FFI integer types")
- commit 4e1746656839 ("rust: uapi: Add UAPI crate")
- commit d7659acca7a3 ("rust: add pin-init crate build infrastructure")

The alloc crate was removed in commit 392e34b6bc22 ("kbuild: rust:
remove the `alloc` crate and `GlobalAlloc`"). As far as I can tell none
of the other dependencies are required; it is only required that
compiler_builtins be linked into the rust-enabled kernel. In the
standard library, compiler_builtins is a dependency of std[1].

Remove these dependency edges. Add a dependency edge from
`compiler_builtins` to `core` to `scripts/generate_rust_analyzer.py` to
match `rust/Makefile`. This has been incorrect since commit 8c4555ccc55c
("scripts: add `generate_rust_analyzer.py`")

Link: https://github.com/rust-lang/rust/blob/f820b75feef00654924c9351a2faca8d34818339/library/alloc/Cargo.toml#L19 [0]
Link: https://github.com/rust-lang/rust/blob/f820b75feef00654924c9351a2faca8d34818339/library/std/Cargo.toml#L21 [1]
Link: https://rust-for-linux.zulipchat.com/#narrow/channel/288089-General/topic/rust-analyzer.20improvements/near/510200959
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
---
Changes in v3:
- Fix typo in commit message (fas -> far).
- Link to v2: https://lore.kernel.org/r/20250524-rust-remove-compiler-builtins-deps-v2-1-4fc2ff489391@gmail.com

Changes in v2:
- Rebase on rust-fixes to include "scripts: generate_rust_analyzer: Add
  ffi crate".
- Link to v1: https://lore.kernel.org/r/20250408-rust-remove-compiler-builtins-deps-v1-1-4fda4f187190@gmail.com
---
 rust/Makefile                     | 6 +++---
 scripts/generate_rust_analyzer.py | 6 +++---
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/rust/Makefile b/rust/Makefile
index 27dec7904c3a..5a6a381bc23d 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -505,16 +505,16 @@ $(obj)/compiler_builtins.o: $(src)/compiler_builtins.rs $(obj)/core.o FORCE
 $(obj)/pin_init.o: private skip_gendwarfksyms = 1
 $(obj)/pin_init.o: private rustc_target_flags = --extern pin_init_internal \
     --extern macros --cfg kernel
-$(obj)/pin_init.o: $(src)/pin-init/src/lib.rs $(obj)/compiler_builtins.o \
+$(obj)/pin_init.o: $(src)/pin-init/src/lib.rs \
     $(obj)/$(libpin_init_internal_name) $(obj)/$(libmacros_name) FORCE
 	+$(call if_changed_rule,rustc_library)
 
 $(obj)/build_error.o: private skip_gendwarfksyms = 1
-$(obj)/build_error.o: $(src)/build_error.rs $(obj)/compiler_builtins.o FORCE
+$(obj)/build_error.o: $(src)/build_error.rs FORCE
 	+$(call if_changed_rule,rustc_library)
 
 $(obj)/ffi.o: private skip_gendwarfksyms = 1
-$(obj)/ffi.o: $(src)/ffi.rs $(obj)/compiler_builtins.o FORCE
+$(obj)/ffi.o: $(src)/ffi.rs FORCE
 	+$(call if_changed_rule,rustc_library)
 
 $(obj)/bindings.o: private rustc_target_flags = --extern ffi
diff --git a/scripts/generate_rust_analyzer.py b/scripts/generate_rust_analyzer.py
index 7c3ea2b55041..cab9a80bed49 100755
--- a/scripts/generate_rust_analyzer.py
+++ b/scripts/generate_rust_analyzer.py
@@ -83,7 +83,7 @@ def generate_crates(srctree, objtree, sysroot_src, external_src, cfgs, core_edit
     append_crate(
         "compiler_builtins",
         srctree / "rust" / "compiler_builtins.rs",
-        [],
+        ["core"],
     )
 
     append_crate(
@@ -96,7 +96,7 @@ def generate_crates(srctree, objtree, sysroot_src, external_src, cfgs, core_edit
     append_crate(
         "build_error",
         srctree / "rust" / "build_error.rs",
-        ["core", "compiler_builtins"],
+        ["core"],
     )
 
     append_crate(
@@ -117,7 +117,7 @@ def generate_crates(srctree, objtree, sysroot_src, external_src, cfgs, core_edit
     append_crate(
         "ffi",
         srctree / "rust" / "ffi.rs",
-        ["core", "compiler_builtins"],
+        ["core"],
     )
 
     def append_crate_with_generated(

---
base-commit: cc84ef3b88f407e8bd5a5f7b6906d1e69851c856
change-id: 20250408-rust-remove-compiler-builtins-deps-1f061024dfce

Best regards,
--  
Tamir Duberstein <tamird@gmail.com>

Re: [PATCH v3] rust: remove spurious compiler_builtins dependents

[kernel test robot]

Hi Tamir,

kernel test robot noticed the following build errors:

[auto build test ERROR on cc84ef3b88f407e8bd5a5f7b6906d1e69851c856]

url:    https://github.com/intel-lab-lkp/linux/commits/Tamir-Duberstein/rust-remove-spurious-compiler_builtins-dependents/20250721-012236
base:   cc84ef3b88f407e8bd5a5f7b6906d1e69851c856
patch link:    https://lore.kernel.org/r/20250720-rust-remove-compiler-builtins-deps-v3-1-0df3a493973f%40gmail.com
patch subject: [PATCH v3] rust: remove spurious compiler_builtins dependents
config: x86_64-rhel-9.4-rust (https://download.01.org/0day-ci/archive/20250721/202507211312.M1fkG8v8-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
rustc: rustc 1.88.0 (6b00bc388 2025-06-23)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250721/202507211312.M1fkG8v8-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202507211312.M1fkG8v8-lkp@intel.com/

All errors (new ones prefixed by >>):

>> error[E0463]: can't find crate for `core`
   |
   = note: the `target` target may not be installed
   = help: consider downloading the target with `rustup target add target`
   = help: consider building the standard library from source with `cargo build -Zbuild-std`
--
   For more information about this error, try `rustc --explain E0463`.
   make[3]: *** [rust/Makefile:514: rust/build_error.o] Error 1
>> error[E0463]: can't find crate for `core`
   |
   = note: the `target` target may not be installed
   = help: consider downloading the target with `rustup target add target`
   = help: consider building the standard library from source with `cargo build -Zbuild-std`
--
   For more information about this error, try `rustc --explain E0463`.
   make[3]: *** [rust/Makefile:518: rust/ffi.o] Error 1
>> error[E0463]: can't find crate for `core`
   |
   = note: the `target` target may not be installed
   = help: consider downloading the target with `rustup target add target`
   = help: consider building the standard library from source with `cargo build -Zbuild-std`

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH v3] rust: remove spurious compiler_builtins dependents

[Alice Ryhl]

On Sun, Jul 20, 2025 at 01:20:40PM -0400, Tamir Duberstein wrote:
> The dependency on `compiler_builtins.o` was first added in commit
> 2f7ab1267dc9 ("Kbuild: add Rust support") to `alloc` which matches the
> standard library[0] but was copied to other targets in:
> - commit ecaa6ddff2fd ("rust: add `build_error` crate")
> - commit d072acda4862 ("rust: use custom FFI integer types")
> - commit 4e1746656839 ("rust: uapi: Add UAPI crate")
> - commit d7659acca7a3 ("rust: add pin-init crate build infrastructure")
> 
> The alloc crate was removed in commit 392e34b6bc22 ("kbuild: rust:
> remove the `alloc` crate and `GlobalAlloc`"). As far as I can tell none
> of the other dependencies are required; it is only required that
> compiler_builtins be linked into the rust-enabled kernel. In the
> standard library, compiler_builtins is a dependency of std[1].
> 
> Remove these dependency edges. Add a dependency edge from
> `compiler_builtins` to `core` to `scripts/generate_rust_analyzer.py` to
> match `rust/Makefile`. This has been incorrect since commit 8c4555ccc55c
> ("scripts: add `generate_rust_analyzer.py`")
> 
> Link: https://github.com/rust-lang/rust/blob/f820b75feef00654924c9351a2faca8d34818339/library/alloc/Cargo.toml#L19 [0]
> Link: https://github.com/rust-lang/rust/blob/f820b75feef00654924c9351a2faca8d34818339/library/std/Cargo.toml#L21 [1]
> Link: https://rust-for-linux.zulipchat.com/#narrow/channel/288089-General/topic/rust-analyzer.20improvements/near/510200959
> Signed-off-by: Tamir Duberstein <tamird@gmail.com>

Reviewed-by: Alice Ryhl <aliceryhl@google.com>

Re: [PATCH v3] rust: remove spurious compiler_builtins dependents

[Miguel Ojeda]

On Sun, Jul 20, 2025 at 7:20 PM Tamir Duberstein <tamird@gmail.com> wrote:
>
> Remove these dependency edges.

I should have replied in previous versions: this is wrong -- the 3
changes each individually break the build.

I guess that you are not cleaning everything in your tests before
testing the build.

Cheers,
Miguel

Re: [PATCH v3] rust: remove spurious compiler_builtins dependents

[Tamir Duberstein]

On Mon, Jul 21, 2025 at 8:25 AM Miguel Ojeda
<miguel.ojeda.sandonis@gmail.com> wrote:
>
> On Sun, Jul 20, 2025 at 7:20 PM Tamir Duberstein <tamird@gmail.com> wrote:
> >
> > Remove these dependency edges.
>
> I should have replied in previous versions: this is wrong -- the 3
> changes each individually break the build.
>
> I guess that you are not cleaning everything in your tests before
> testing the build.

You're absolutely right, this patch is incorrect. I was indeed not
blowing away build artifcats.

Thanks Miguel.

Re: [PATCH v3] rust: remove spurious compiler_builtins dependents

[Benno Lossin]

On Wed Jul 23, 2025 at 5:18 PM CEST, Tamir Duberstein wrote:
> On Mon, Jul 21, 2025 at 8:25 AM Miguel Ojeda
> <miguel.ojeda.sandonis@gmail.com> wrote:
>>
>> On Sun, Jul 20, 2025 at 7:20 PM Tamir Duberstein <tamird@gmail.com> wrote:
>> >
>> > Remove these dependency edges.
>>
>> I should have replied in previous versions: this is wrong -- the 3
>> changes each individually break the build.
>>
>> I guess that you are not cleaning everything in your tests before
>> testing the build.
>
> You're absolutely right, this patch is incorrect. I was indeed not
> blowing away build artifcats.

So is the `compiler_builtins` dependency correct for all crates?

---
Cheers,
Benno

Re: [PATCH v3] rust: remove spurious compiler_builtins dependents

[Tamir Duberstein]

On Wed, Jul 23, 2025 at 3:53 PM Benno Lossin <lossin@kernel.org> wrote:
>
> On Wed Jul 23, 2025 at 5:18 PM CEST, Tamir Duberstein wrote:
> > On Mon, Jul 21, 2025 at 8:25 AM Miguel Ojeda
> > <miguel.ojeda.sandonis@gmail.com> wrote:
> >>
> >> On Sun, Jul 20, 2025 at 7:20 PM Tamir Duberstein <tamird@gmail.com> wrote:
> >> >
> >> > Remove these dependency edges.
> >>
> >> I should have replied in previous versions: this is wrong -- the 3
> >> changes each individually break the build.
> >>
> >> I guess that you are not cleaning everything in your tests before
> >> testing the build.
> >
> > You're absolutely right, this patch is incorrect. I was indeed not
> > blowing away build artifcats.
>
> So is the `compiler_builtins` dependency correct for all crates?

Looks that way to me.