[PATCH v3 0/6] Rust: support `CPU_MITIGATIONS` and enable `objtool`

[PATCH v3 0/6] Rust: support `CPU_MITIGATIONS` and enable `objtool`

[Miguel Ojeda]

Hi,

This is just v2 with the helper function suggested by Peter.

I dropped Benno's and Alice's Tested-bys from the modified patch, just
in case, but the logic should be equivalent.

Cheers,
Miguel

v3:
  - Added `is_rust_noreturn()` helper function (Peter).
  - Reworded a couple bits.

v2: https://lore.kernel.org/rust-for-linux/20240724161501.1319115-1-ojeda@kernel.org/
v1: https://lore.kernel.org/rust-for-linux/20231023174449.251550-1-ojeda@kernel.org/

Miguel Ojeda (6):
  rust: module: add static pointer to `{init,cleanup}_module()`
  x86/rust: support MITIGATION_RETPOLINE
  x86/rust: support MITIGATION_RETHUNK
  x86/rust: support MITIGATION_SLS
  objtool/rust: list `noreturn` Rust functions
  objtool/kbuild/rust: enable objtool for Rust

 arch/x86/Makefile               |  7 ++++-
 rust/Makefile                   | 22 +++++++++------
 rust/macros/module.rs           | 12 +++++++++
 scripts/Makefile.build          |  9 +++++--
 scripts/generate_rust_target.rs | 15 +++++++++++
 tools/objtool/check.c           | 48 ++++++++++++++++++++++++++++++++-
 tools/objtool/noreturns.h       |  2 ++
 7 files changed, 103 insertions(+), 12 deletions(-)


base-commit: b1263411112305acf2af728728591465becb45b0
--
2.45.2

[PATCH v3 6/6] objtool/kbuild/rust: enable objtool for Rust

[Miguel Ojeda]

Now that we should be `objtool`-warning free, enable `objtool` for
Rust too.

Before this patch series, we were already getting warnings under e.g. IBT
builds, since those would see Rust code via `vmlinux.o`.

Tested-by: Alice Ryhl <aliceryhl@google.com>
Tested-by: Benno Lossin <benno.lossin@proton.me>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
 rust/Makefile          | 22 ++++++++++++++--------
 scripts/Makefile.build |  9 +++++++--
 2 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/rust/Makefile b/rust/Makefile
index bf05e65365da..1756238b641d 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -344,7 +344,8 @@ 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 \
-	$(if $(rustc_objcopy),;$(OBJCOPY) $(rustc_objcopy) $@)
+	$(if $(rustc_objcopy),;$(OBJCOPY) $(rustc_objcopy) $@) \
+	$(cmd_objtool)
 
 rust-analyzer:
 	$(Q)$(srctree)/scripts/generate_rust_analyzer.py \
@@ -366,44 +367,49 @@ ifneq ($(or $(CONFIG_ARM64),$(and $(CONFIG_RISCV),$(CONFIG_64BIT))),)
 		__ashlti3 __lshrti3
 endif
 
+define rule_rustc_library
+	$(call cmd_and_fixdep,rustc_library)
+	$(call cmd,gen_objtooldep)
+endef
+
 $(obj)/core.o: private skip_clippy = 1
 $(obj)/core.o: private skip_flags = -Wunreachable_pub
 $(obj)/core.o: private rustc_objcopy = $(foreach sym,$(redirect-intrinsics),--redefine-sym $(sym)=__rust$(sym))
 $(obj)/core.o: private rustc_target_flags = $(core-cfgs)
 $(obj)/core.o: $(RUST_LIB_SRC)/core/src/lib.rs FORCE
-	+$(call if_changed_dep,rustc_library)
+	+$(call if_changed_rule,rustc_library)
 ifdef CONFIG_X86_64
 $(obj)/core.o: scripts/target.json
 endif
 
 $(obj)/compiler_builtins.o: private rustc_objcopy = -w -W '__*'
 $(obj)/compiler_builtins.o: $(src)/compiler_builtins.rs $(obj)/core.o FORCE
-	+$(call if_changed_dep,rustc_library)
+	+$(call if_changed_rule,rustc_library)
 
 $(obj)/alloc.o: private skip_clippy = 1
 $(obj)/alloc.o: private skip_flags = -Wunreachable_pub
 $(obj)/alloc.o: private rustc_target_flags = $(alloc-cfgs)
 $(obj)/alloc.o: $(RUST_LIB_SRC)/alloc/src/lib.rs $(obj)/compiler_builtins.o FORCE
-	+$(call if_changed_dep,rustc_library)
+	+$(call if_changed_rule,rustc_library)
 
 $(obj)/build_error.o: $(src)/build_error.rs $(obj)/compiler_builtins.o FORCE
-	+$(call if_changed_dep,rustc_library)
+	+$(call if_changed_rule,rustc_library)
 
 $(obj)/bindings.o: $(src)/bindings/lib.rs \
     $(obj)/compiler_builtins.o \
     $(obj)/bindings/bindings_generated.rs \
     $(obj)/bindings/bindings_helpers_generated.rs FORCE
-	+$(call if_changed_dep,rustc_library)
+	+$(call if_changed_rule,rustc_library)
 
 $(obj)/uapi.o: $(src)/uapi/lib.rs \
     $(obj)/compiler_builtins.o \
     $(obj)/uapi/uapi_generated.rs FORCE
-	+$(call if_changed_dep,rustc_library)
+	+$(call if_changed_rule,rustc_library)
 
 $(obj)/kernel.o: private rustc_target_flags = --extern alloc \
     --extern build_error --extern macros --extern bindings --extern uapi
 $(obj)/kernel.o: $(src)/kernel/lib.rs $(obj)/alloc.o $(obj)/build_error.o \
     $(obj)/libmacros.so $(obj)/bindings.o $(obj)/uapi.o FORCE
-	+$(call if_changed_dep,rustc_library)
+	+$(call if_changed_rule,rustc_library)
 
 endif # CONFIG_RUST
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index efacca63c897..72b1232b1f7d 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -288,10 +288,15 @@ rust_common_cmd = \
 # would not match each other.
 
 quiet_cmd_rustc_o_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@
-      cmd_rustc_o_rs = $(rust_common_cmd) --emit=obj=$@ $<
+      cmd_rustc_o_rs = $(rust_common_cmd) --emit=obj=$@ $< $(cmd_objtool)
+
+define rule_rustc_o_rs
+	$(call cmd_and_fixdep,rustc_o_rs)
+	$(call cmd,gen_objtooldep)
+endef
 
 $(obj)/%.o: $(obj)/%.rs FORCE
-	+$(call if_changed_dep,rustc_o_rs)
+	+$(call if_changed_rule,rustc_o_rs)
 
 quiet_cmd_rustc_rsi_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@
       cmd_rustc_rsi_rs = \
-- 
2.45.2

Re: [PATCH v3 0/6] Rust: support `CPU_MITIGATIONS` and enable `objtool`

[Benno Lossin]

On 25.07.24 20:33, Miguel Ojeda wrote:
> Hi,
> 
> This is just v2 with the helper function suggested by Peter.
> 
> I dropped Benno's and Alice's Tested-bys from the modified patch, just
> in case, but the logic should be equivalent.

I re-ran my tests and the results are the same as with v1.

Tested-by: Benno Lossin <benno.lossin@proton.me>

---
Cheers,
Benno

> Cheers,
> Miguel
> 
> v3:
>   - Added `is_rust_noreturn()` helper function (Peter).
>   - Reworded a couple bits.
> 
> v2: https://lore.kernel.org/rust-for-linux/20240724161501.1319115-1-ojeda@kernel.org/
> v1: https://lore.kernel.org/rust-for-linux/20231023174449.251550-1-ojeda@kernel.org/
> 
> Miguel Ojeda (6):
>   rust: module: add static pointer to `{init,cleanup}_module()`
>   x86/rust: support MITIGATION_RETPOLINE
>   x86/rust: support MITIGATION_RETHUNK
>   x86/rust: support MITIGATION_SLS
>   objtool/rust: list `noreturn` Rust functions
>   objtool/kbuild/rust: enable objtool for Rust
> 
>  arch/x86/Makefile               |  7 ++++-
>  rust/Makefile                   | 22 +++++++++------
>  rust/macros/module.rs           | 12 +++++++++
>  scripts/Makefile.build          |  9 +++++--
>  scripts/generate_rust_target.rs | 15 +++++++++++
>  tools/objtool/check.c           | 48 ++++++++++++++++++++++++++++++++-
>  tools/objtool/noreturns.h       |  2 ++
>  7 files changed, 103 insertions(+), 12 deletions(-)
> 
> 
> base-commit: b1263411112305acf2af728728591465becb45b0
> --
> 2.45.2

Re: [PATCH v3 0/6] Rust: support `CPU_MITIGATIONS` and enable `objtool`

[Miguel Ojeda]

On Thu, Jul 25, 2024 at 8:35 PM Miguel Ojeda <ojeda@kernel.org> wrote:
>
> Miguel Ojeda (6):
>   rust: module: add static pointer to `{init,cleanup}_module()`
>   x86/rust: support MITIGATION_RETPOLINE
>   x86/rust: support MITIGATION_RETHUNK
>   x86/rust: support MITIGATION_SLS
>   objtool/rust: list `noreturn` Rust functions
>   objtool/kbuild/rust: enable objtool for Rust
>
>  arch/x86/Makefile               |  7 ++++-
>  rust/Makefile                   | 22 +++++++++------
>  rust/macros/module.rs           | 12 +++++++++
>  scripts/Makefile.build          |  9 +++++--
>  scripts/generate_rust_target.rs | 15 +++++++++++
>  tools/objtool/check.c           | 48 ++++++++++++++++++++++++++++++++-
>  tools/objtool/noreturns.h       |  2 ++
>  7 files changed, 103 insertions(+), 12 deletions(-)

Applied to `rust-next` -- thanks everyone!

In the `noreturn` patch:

    [ Kees agrees this should be automated and Peter says:

        So it would be fairly simple to make objtool consume a magic section
        emitted by the compiler.. I think we've asked the compiler folks
        for that at some point even, but I don't have clear recollections.

      We will ask upstream Rust about it. And if they agree, then perhaps
      we can get Clang/GCC to implement something similar too -- for this
      sort of thing we can take advantage of the shorter cycles of `rustc`
      as well as their unstable features concept to experiment.

      Gary proposed using DWARF (though it would need to be available), and
      wrote a proof of concept script using the `object` and `gimli` crates:
      https://gist.github.com/nbdd0121/449692570622c2f46a29ad9f47c3379a

        - Miguel ]

    [ Added `len_mismatch_fail` symbol for new `kernel` crate code merged
      since then as well as 3 more `core::panicking` symbols that appear
      in `RUST_DEBUG_ASSERTIONS=y` builds.  - Miguel ]

Cheers,
Miguel