Re: [PATCH v4] rust: Makefile: bound rustdoc workaround to affected versions

Re: [PATCH v4] rust: Makefile: bound rustdoc workaround to affected versions

[Nathan Chancellor]

On Wed, Feb 04, 2026 at 08:48:43AM +0900, HeeSu Kim wrote:
> The `-Cunsafe-allow-abi-mismatch=fixed-x18` workaround was added to
> handle a rustdoc bug where target modifiers were not properly saved [1].
> 
> This bug was fixed in Rust 1.90.0 [2]. Restrict the workaround to only
> apply for Rust 1.88.x and 1.89.x versions that are affected by the
> bug, preserving ABI compatibility checks on newer compiler versions.
> 
> Add `rustc-max-version` macro to `scripts/Makefile.compiler` for
> version upper bound checks, mirroring the existing `rustc-min-version`.
> 
> Link: https://github.com/rust-lang/rust/issues/144521 [1]
> Link: https://github.com/rust-lang/rust/pull/144523 [2]
> Suggested-by: Gary Guo <gary@garyguo.net>
> Link: https://lore.kernel.org/rust-for-linux/DG4JM9PU51M0.1YRGM9HVTY24U@garyguo.net/
> Suggested-by: Miguel Ojeda <ojeda@kernel.org>
> Link: https://lore.kernel.org/rust-for-linux/CANiq72n39eU9WE=Yh0_yJzmqMxo=QAaU2pN0UqP9jZ7bT7rhgA@mail.gmail.com/
> Cc: stable@vger.kernel.org # Useful in 6.18.y and later.
> Signed-off-by: HeeSu Kim <mlksvender@gmail.com>

Acked-by: Nathan Chancellor <nathan@kernel.org>

I assume Miguel will pick this up.

> ---
> Changes in v4:
> - Add rustc-max-version macro for cleaner version bounds
> - Use rustc-max-version instead of test-lt for readability
> 
> Changes in v3:
> - Remove Fixes: tag (this is a feature, not a fix)
> - Use full URLs with Link: tags instead of GitHub-style references
> - Add Link: to lore.kernel.org for Suggested-by attribution
> - Add Cc: stable for potential backporting to 6.18.y
> 
> Changes in v2:
> - Change approach: bound to affected Rust versions instead of ARM64-only
>   (the flag is simply ignored on non-ARM64 architectures)
> 
>  rust/Makefile             | 3 ++-
>  scripts/Makefile.compiler | 4 ++++
>  2 files changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/rust/Makefile b/rust/Makefile
> index 5c0155b83454..1e8a75bc2878 100644
> --- a/rust/Makefile
> +++ b/rust/Makefile
> @@ -136,7 +136,8 @@ pin_init-flags := \
>  
>  # `rustdoc` did not save the target modifiers, thus workaround for
>  # the time being (https://github.com/rust-lang/rust/issues/144521).
> -rustdoc_modifiers_workaround := $(if $(call rustc-min-version,108800),-Cunsafe-allow-abi-mismatch=fixed-x18)
> +# The bug was fixed in Rust 1.90.0, so only apply for 1.88.x and 1.89.x.
> +rustdoc_modifiers_workaround := $(if $(call rustc-min-version,108800),$(if $(call rustc-max-version,108999),-Cunsafe-allow-abi-mismatch=fixed-x18))
>  
>  # Similarly, for doctests (https://github.com/rust-lang/rust/issues/146465).
>  doctests_modifiers_workaround := $(rustdoc_modifiers_workaround)$(if $(call rustc-min-version,109100),$(comma)sanitizer)
> diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
> index ef91910de265..85268f6f1494 100644
> --- a/scripts/Makefile.compiler
> +++ b/scripts/Makefile.compiler
> @@ -71,6 +71,10 @@ clang-min-version = $(call test-ge, $(CONFIG_CLANG_VERSION), $1)
>  # Usage: rustc-$(call rustc-min-version, 108500) += -Cfoo
>  rustc-min-version = $(call test-ge, $(CONFIG_RUSTC_VERSION), $1)
>  
> +# rustc-max-version
> +# Usage: rustc-$(call rustc-max-version, 109000) += -Cfoo
> +rustc-max-version = $(call test-le, $(CONFIG_RUSTC_VERSION), $1)

Minor meta comment: It is generally perferred to add a macro like this
in a separate change to make it easier to backport if it is needed in
the future.

>  # ld-option
>  # Usage: KBUILD_LDFLAGS += $(call ld-option, -X, -Y)
>  ld-option = $(call try-run, $(LD) $(KBUILD_LDFLAGS) $(1) -v,$(1),$(2),$(3))
> -- 
> 2.52.0
> 

[PATCH v4] rust: Makefile: bound rustdoc workaround to affected versions

[HeeSu Kim]

The `-Cunsafe-allow-abi-mismatch=fixed-x18` workaround was added to
handle a rustdoc bug where target modifiers were not properly saved [1].

This bug was fixed in Rust 1.90.0 [2]. Restrict the workaround to only
apply for Rust 1.88.x and 1.89.x versions that are affected by the
bug, preserving ABI compatibility checks on newer compiler versions.

Add `rustc-max-version` macro to `scripts/Makefile.compiler` for
version upper bound checks, mirroring the existing `rustc-min-version`.

Link: https://github.com/rust-lang/rust/issues/144521 [1]
Link: https://github.com/rust-lang/rust/pull/144523 [2]
Suggested-by: Gary Guo <gary@garyguo.net>
Link: https://lore.kernel.org/rust-for-linux/DG4JM9PU51M0.1YRGM9HVTY24U@garyguo.net/
Suggested-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://lore.kernel.org/rust-for-linux/CANiq72n39eU9WE=Yh0_yJzmqMxo=QAaU2pN0UqP9jZ7bT7rhgA@mail.gmail.com/
Cc: stable@vger.kernel.org # Useful in 6.18.y and later.
Signed-off-by: HeeSu Kim <mlksvender@gmail.com>
---
Changes in v4:
- Add rustc-max-version macro for cleaner version bounds
- Use rustc-max-version instead of test-lt for readability

Changes in v3:
- Remove Fixes: tag (this is a feature, not a fix)
- Use full URLs with Link: tags instead of GitHub-style references
- Add Link: to lore.kernel.org for Suggested-by attribution
- Add Cc: stable for potential backporting to 6.18.y

Changes in v2:
- Change approach: bound to affected Rust versions instead of ARM64-only
  (the flag is simply ignored on non-ARM64 architectures)

 rust/Makefile             | 3 ++-
 scripts/Makefile.compiler | 4 ++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/rust/Makefile b/rust/Makefile
index 5c0155b83454..1e8a75bc2878 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -136,7 +136,8 @@ pin_init-flags := \
 
 # `rustdoc` did not save the target modifiers, thus workaround for
 # the time being (https://github.com/rust-lang/rust/issues/144521).
-rustdoc_modifiers_workaround := $(if $(call rustc-min-version,108800),-Cunsafe-allow-abi-mismatch=fixed-x18)
+# The bug was fixed in Rust 1.90.0, so only apply for 1.88.x and 1.89.x.
+rustdoc_modifiers_workaround := $(if $(call rustc-min-version,108800),$(if $(call rustc-max-version,108999),-Cunsafe-allow-abi-mismatch=fixed-x18))
 
 # Similarly, for doctests (https://github.com/rust-lang/rust/issues/146465).
 doctests_modifiers_workaround := $(rustdoc_modifiers_workaround)$(if $(call rustc-min-version,109100),$(comma)sanitizer)
diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
index ef91910de265..85268f6f1494 100644
--- a/scripts/Makefile.compiler
+++ b/scripts/Makefile.compiler
@@ -71,6 +71,10 @@ clang-min-version = $(call test-ge, $(CONFIG_CLANG_VERSION), $1)
 # Usage: rustc-$(call rustc-min-version, 108500) += -Cfoo
 rustc-min-version = $(call test-ge, $(CONFIG_RUSTC_VERSION), $1)
 
+# rustc-max-version
+# Usage: rustc-$(call rustc-max-version, 109000) += -Cfoo
+rustc-max-version = $(call test-le, $(CONFIG_RUSTC_VERSION), $1)
+
 # ld-option
 # Usage: KBUILD_LDFLAGS += $(call ld-option, -X, -Y)
 ld-option = $(call try-run, $(LD) $(KBUILD_LDFLAGS) $(1) -v,$(1),$(2),$(3))
-- 
2.52.0

[PATCH v5 1/2] kbuild: add rustc-max-version macro

[HeeSu Kim]

Add `rustc-max-version` macro to `scripts/Makefile.compiler` for
version upper bound checks, mirroring the existing `rustc-min-version`.

This will be used to bound workarounds to specific compiler version
ranges.

Suggested-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://lore.kernel.org/rust-for-linux/CANiq72n39eU9WE=Yh0_yJzmqMxo=QAaU2pN0UqP9jZ7bT7rhgA@mail.gmail.com/
Acked-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: HeeSu Kim <mlksvender@gmail.com>
---
Changes in v5:
- Split rustc-max-version macro into separate patch for easier backporting
  (was part of the workaround patch in v4)

 scripts/Makefile.compiler | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
index ef91910de265..85268f6f1494 100644
--- a/scripts/Makefile.compiler
+++ b/scripts/Makefile.compiler
@@ -71,6 +71,10 @@ clang-min-version = $(call test-ge, $(CONFIG_CLANG_VERSION), $1)
 # Usage: rustc-$(call rustc-min-version, 108500) += -Cfoo
 rustc-min-version = $(call test-ge, $(CONFIG_RUSTC_VERSION), $1)
 
+# rustc-max-version
+# Usage: rustc-$(call rustc-max-version, 109000) += -Cfoo
+rustc-max-version = $(call test-le, $(CONFIG_RUSTC_VERSION), $1)
+
 # ld-option
 # Usage: KBUILD_LDFLAGS += $(call ld-option, -X, -Y)
 ld-option = $(call try-run, $(LD) $(KBUILD_LDFLAGS) $(1) -v,$(1),$(2),$(3))
-- 
2.52.0

[PATCH v5 2/2] rust: Makefile: bound rustdoc workaround to affected versions

[HeeSu Kim]

The `-Cunsafe-allow-abi-mismatch=fixed-x18` workaround was added to
handle a rustdoc bug where target modifiers were not properly saved [1].

This bug was fixed in Rust 1.90.0 [2]. Restrict the workaround to only
apply for Rust 1.88.x and 1.89.x versions that are affected by the
bug, preserving ABI compatibility checks on newer compiler versions.

Link: https://github.com/rust-lang/rust/issues/144521 [1]
Link: https://github.com/rust-lang/rust/pull/144523 [2]
Suggested-by: Gary Guo <gary@garyguo.net>
Link: https://lore.kernel.org/rust-for-linux/DG4JM9PU51M0.1YRGM9HVTY24U@garyguo.net/
Cc: stable@vger.kernel.org # Useful in 6.18.y and later.
Acked-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: HeeSu Kim <mlksvender@gmail.com>
---
Changes in v5:
- Split rustc-max-version macro into separate patch for easier backporting

Changes in v4:
- Add rustc-max-version macro for cleaner version bounds
- Use rustc-max-version instead of test-lt for readability

Changes in v3:
- Remove Fixes: tag (this is a feature, not a fix)
- Use full URLs with Link: tags instead of GitHub-style references
- Add Link: to lore.kernel.org for Suggested-by attribution
- Add Cc: stable for potential backporting to 6.18.y

Changes in v2:
- Change approach: bound to affected Rust versions instead of ARM64-only
  (the flag is simply ignored on non-ARM64 architectures)

 rust/Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/rust/Makefile b/rust/Makefile
index 5c0155b83454..1e8a75bc2878 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -136,7 +136,8 @@ pin_init-flags := \
 
 # `rustdoc` did not save the target modifiers, thus workaround for
 # the time being (https://github.com/rust-lang/rust/issues/144521).
-rustdoc_modifiers_workaround := $(if $(call rustc-min-version,108800),-Cunsafe-allow-abi-mismatch=fixed-x18)
+# The bug was fixed in Rust 1.90.0, so only apply for 1.88.x and 1.89.x.
+rustdoc_modifiers_workaround := $(if $(call rustc-min-version,108800),$(if $(call rustc-max-version,108999),-Cunsafe-allow-abi-mismatch=fixed-x18))
 
 # Similarly, for doctests (https://github.com/rust-lang/rust/issues/146465).
 doctests_modifiers_workaround := $(rustdoc_modifiers_workaround)$(if $(call rustc-min-version,109100),$(comma)sanitizer)
-- 
2.52.0

Re: [PATCH v5 1/2] kbuild: add rustc-max-version macro

[Nicolas Schier]

On Thu, Feb 05, 2026 at 10:18:14PM +0900, HeeSu Kim wrote:
> Add `rustc-max-version` macro to `scripts/Makefile.compiler` for
> version upper bound checks, mirroring the existing `rustc-min-version`.
> 
> This will be used to bound workarounds to specific compiler version
> ranges.
> 
> Suggested-by: Miguel Ojeda <ojeda@kernel.org>
> Link: https://lore.kernel.org/rust-for-linux/CANiq72n39eU9WE=Yh0_yJzmqMxo=QAaU2pN0UqP9jZ7bT7rhgA@mail.gmail.com/
> Acked-by: Nathan Chancellor <nathan@kernel.org>
> Signed-off-by: HeeSu Kim <mlksvender@gmail.com>
> ---
> Changes in v5:
> - Split rustc-max-version macro into separate patch for easier backporting
>   (was part of the workaround patch in v4)
> 
>  scripts/Makefile.compiler | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
> index ef91910de265..85268f6f1494 100644
> --- a/scripts/Makefile.compiler
> +++ b/scripts/Makefile.compiler
> @@ -71,6 +71,10 @@ clang-min-version = $(call test-ge, $(CONFIG_CLANG_VERSION), $1)
>  # Usage: rustc-$(call rustc-min-version, 108500) += -Cfoo
>  rustc-min-version = $(call test-ge, $(CONFIG_RUSTC_VERSION), $1)
>  
> +# rustc-max-version
> +# Usage: rustc-$(call rustc-max-version, 109000) += -Cfoo
> +rustc-max-version = $(call test-le, $(CONFIG_RUSTC_VERSION), $1)
> +

Acked-by: Nicolas Schier <nsc@kernel.org>



(nit-picking; not crucial for this very patch set)

For readability, a less-than version check might be easier to read; and
that would probably better match the suggested version range check:

    rustc-lt-version = $(if $(call rustc-min-version, $(1)),,y)
    rustc-version-range = $(and $(call rustc-lt-version,$(2)), $(call rustc-min-version,$(1)))

so that the actual version check could become

    # The bug was fixed in Rust 1.90.0, so only apply for 1.88.x to < 1.90.0
    rustdoc_modifiers_workaround := $(if $(call rustc-version-range, 108800, 109000), \
    		-Cunsafe-allow-abi-mismatch=fixed-x18)

or:

    ifeq ($(call rustc-version-range, 108800, 109000),y)
    rustdoc_modifiers_workaround := -Cunsafe-allow-abi-mismatch=fixed-x18
    endif


-- 
Nicolas

Re: [PATCH v5 1/2] kbuild: add rustc-max-version macro

[Miguel Ojeda]

On Thu, Feb 5, 2026 at 4:55 PM Nicolas Schier <nsc@kernel.org> wrote:
>
> For readability, a less-than version check might be easier to read; and
> that would probably better match the suggested version range check:
>
>     rustc-lt-version = $(if $(call rustc-min-version, $(1)),,y)
>     rustc-version-range = $(and $(call rustc-lt-version,$(2)), $(call rustc-min-version,$(1)))
>
> so that the actual version check could become
>
>     # The bug was fixed in Rust 1.90.0, so only apply for 1.88.x to < 1.90.0
>     rustdoc_modifiers_workaround := $(if $(call rustc-version-range, 108800, 109000), \
>                 -Cunsafe-allow-abi-mismatch=fixed-x18)
>
> or:
>
>     ifeq ($(call rustc-version-range, 108800, 109000),y)
>     rustdoc_modifiers_workaround := -Cunsafe-allow-abi-mismatch=fixed-x18
>     endif

Yeah, exactly, I think the range check looks simpler for readers.

I would say let's do it as an improvement on top, and to simplify the
delta needed later on and to avoid the `99`, I will change the patch
on apply to be `rustc-lt-version`.

If no one shouts, I will do that, keeping the Acked-bys. Then we can
easily add the range check on top.

Thanks!

Cheers,
Miguel

Re: [PATCH v5 2/2] rust: Makefile: bound rustdoc workaround to affected versions

[Miguel Ojeda]

On Thu, Feb 5, 2026 at 5:18 AM HeeSu Kim <mlksvender@gmail.com> wrote:
>
>  # Similarly, for doctests (https://github.com/rust-lang/rust/issues/146465).
>  doctests_modifiers_workaround := $(rustdoc_modifiers_workaround)$(if $(call rustc-min-version,109100),$(comma)sanitizer)

So I was merrily going to apply this, but sadly, this is not so
simple: the patch doesn't work because the doctests (the variable
quoted above, no the one that the patch modifies) need to take into
account the other one, which appends the sanitizer case using a comma.

For instance, for Rust 1.94.0, this would expand to just `,sanitizer`.

And it is not as simple as adding the flag there -- please see what I
wrote in commit fad472efab0a ("rust: kbuild: workaround `rustdoc`
doctests modifier bug"):

    By the way, the `-Cunsafe-allow-abi-mismatch` flag overwrites previous
    ones rather than appending, so it needs to be all done in the same flag.
    Moreover, unknown modifiers are rejected, and thus we have to gate based
    on the version too.

I would suggest we take the chance to introduce the range version
check, and also to gate the doctests check up to 1.92, since it should
be fixed in that version.

And perhaps it is simpler if we split (expand) the cases explicitly
version by version for each variable using conditionals with the
version check. That is way more verbose, but it is way easier to see
what is going on in each case and to later on remove the cases when we
upgrade etc.:

    ifeq ($(call rustc-version-range,108800,109000),y)
    rustdoc_modifiers_workaround := -Cunsafe-allow-abi-mismatch=fixed-x18
    doctests_modifiers_workaround := -Cunsafe-allow-abi-mismatch=fixed-x18
    else ifeq ($(call rustc-version-range,109000,109100),y)
    doctests_modifiers_workaround := -Cunsafe-allow-abi-mismatch=fixed-x18
    else ifeq ($(call rustc-version-range,109100,109200),y)
    doctests_modifiers_workaround :=
-Cunsafe-allow-abi-mismatch=fixed-x18,sanitizer
    endif

Cheers,
Miguel