Re: [PATCH v2] rust: Makefile: bound rustdoc workaround to affected versions

Re: [PATCH v2] rust: Makefile: bound rustdoc workaround to affected versions

[Miguel Ojeda]

On Mon, Feb 2, 2026 at 4:21 PM HeeSu Kim <mlksvender@gmail.com> wrote:
>
> This bug was fixed in Rust 1.90.0 (rust-lang/rust#144523). Restrict

Normally these references should be full links (i.e. a tag), since we
do not have "autolinking" like GitHub e.g.

  Link: https://........ [1]

Then you can use [1] above instead of the parenthesis.

> are affected by the bug, avoiding unnecessary flags on newer compiler

To clarify a bit: avoiding the flags is good, but I think avoiding the
skipping of the checks that the flag does is what is more important
(i.e. if it were just the former advantage, I would say it is not
worth the complexity of the added tests).

> Suggested-by: Gary Guo <gary@garyguo.net>

This is very minor and it is fine without a change, but for
completeness: for Suggested-by we generally add a Link: after that
tag, i.e. to lore.kernel.org to the message where Gary suggested it in
this case.

> Fixes: abbf9a449441 ("rust: workaround `rustdoc` target modifiers bug")

I think this is not really a fix anymore, i.e. nothing is broken, and
instead it is more of a feature, as far as I understand: avoiding to
skip the silencing of the checks.

If you added the tag to suggest that the patch should be backported to
stable kernels, then in these cases an explicit Cc: stable@ may be
added, mentioning the versions where this should go, e.g. in this
case:

  Cc: stable@vger.kernel.org # Useful in 6.18.y and later.

(I used "Useful" instead of my usual "Needed" since it is not critical
to backport -- but please correct me if I am wrong).

By the way, I wonder if we would want at least a `rustc-max-version`
function or instead a range-based one for this sort of test. It is not
a blocker for this patch, but we may want to limit other workarounds
too (e.g. the one below this one).

Cc'ing Kbuild since I don't recall we have that for C compilers, so
there may be a reason for that.

Thanks for the patch!

Cheers,
Miguel

Re: [PATCH v2] rust: Makefile: bound rustdoc workaround to affected versions

[Nathan Chancellor]

On Mon, Feb 02, 2026 at 05:00:59PM +0100, Miguel Ojeda wrote:
> By the way, I wonder if we would want at least a `rustc-max-version`
> function or instead a range-based one for this sort of test. It is not
> a blocker for this patch, but we may want to limit other workarounds
> too (e.g. the one below this one).
> 
> Cc'ing Kbuild since I don't recall we have that for C compilers, so
> there may be a reason for that.

I don't think there is any particular reason for this. It is probably
more that for C, we generally prefer feature or bug checks in Kconfig to
catch problems or enable features for both compilers when they are
detected or we do the version checks with the actual operators from
Kconfig rather than doing something in Kbuild.

Both a "max" version and a range-based macro make sense to me since the
range-based one could just use the min max macros under the hood.

In lieu of a separate macro, couldn't this still use 'rustc-min-version'
for both parts if it was willing to unwrap the nested ifs (which I find
kind of unreadable in their current form):

  # The bug was fixed in Rust 1.90.0, so only apply for 1.88.x and 1.89.x.
  ifeq ($(call rustc-min-version,108800)_$(call rustc-min-version,109000),y_)
  rustdoc_modifiers_workaround := -Cunsafe-allow-abi-mismatch=fixed-x18
  endif

Cheers,
Nathan

[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

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 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 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

[PATCH v6 0/2] rust: Makefile: bound rustdoc workaround to affected versions

[HeeSu Kim]

This series bounds the `-Cunsafe-allow-abi-mismatch=fixed-x18` workaround
in `rust/Makefile` to the compiler versions that are actually affected by
the rustdoc (#144521, fixed in 1.90.0) and doctests (#146465, fixed in
1.92.0) target-modifier bugs, so that ABI compatibility checks run again
on newer toolchains.

Changes since v5 [1] [2]:
 - Patch 1/2 is v5 1/2 renamed from `rustc-max-version` to
   `rustc-lt-version` per Miguel's plan to rename on apply [3] and to
   avoid the `99` form. Nathan's [4] and Nicolas' [5] Acked-bys from
   v5 1/2 are carried over as Miguel indicated they would be preserved
   through the rename.
 - Patch 2/2 reworks v5 2/2 to fix the doctests case that Miguel
   pointed out [6]: the v5 form reused `$(rustdoc_modifiers_workaround)`
   as a prefix, so on rustc >= 1.91 the doctests variable expanded to
   a stray `,sanitizer`. Use Miguel's suggested explicit
   `ifeq`/`else ifeq` layout with `rustc-min-version` +
   `rustc-lt-version` combined inline, so each affected range is
   visible on its own line.

The `rustc-version-range` macro Miguel mentioned as an "improvement on
top" [3] is intentionally left out of this series; I will send it as a
separate follow-up patch once this lands, as Miguel suggested.

Tested by building `make rustdoc` and `make rusttest` on rustc 1.93.0:
both succeed with the workaround disabled (empty expansion), confirming
the bugs really are fixed in 1.92+ and no regressions are introduced.
Macro expansion was also spot-checked across simulated rustc versions
1.87 through 1.93 to verify each range matches the expected flag value.

[1] https://lore.kernel.org/rust-for-linux/20260205131522.2942928-1-mlksvender@gmail.com/
[2] https://lore.kernel.org/rust-for-linux/20260205131815.2943152-2-mlksvender@gmail.com/
[3] https://lore.kernel.org/rust-for-linux/CANiq72n-z0v_deUVPWeg1h0c6KQ+r6xfNDf72o29_0yy6KbqGA@mail.gmail.com/
[4] https://lore.kernel.org/rust-for-linux/20260203221224.GA2703490@ax162/
[5] https://lore.kernel.org/rust-for-linux/aYS9bRugxr1rUvA3@levanger/
[6] https://lore.kernel.org/rust-for-linux/CANiq72nnuKJaKrxrut6+noR13PUiSoWWyyp-pGx-fe_2O6ayFA@mail.gmail.com/

HeeSu Kim (2):
  kbuild: add rustc-lt-version macro
  rust: Makefile: bound rustdoc workaround to affected versions

 rust/Makefile             | 18 ++++++++++++------
 scripts/Makefile.compiler |  4 ++++
 2 files changed, 16 insertions(+), 6 deletions(-)

-- 
2.52.0

[PATCH v6 1/2] kbuild: add rustc-lt-version macro

[HeeSu Kim]

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

Use a non-inclusive (less-than) comparison so that callers can express
clean version boundaries such as `109000` (Rust 1.90.0) rather than
`108999`, which is also easier to remove once the toolchain minimum
version is bumped past the bound.

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

Originally posted as `rustc-max-version` in v5 [1]; renamed to
`rustc-lt-version` on this respin per Miguel's direction to simplify
the delta and avoid the `99` form [2].

[1] https://lore.kernel.org/rust-for-linux/20260205131522.2942928-1-mlksvender@gmail.com/
[2] https://lore.kernel.org/rust-for-linux/CANiq72n-z0v_deUVPWeg1h0c6KQ+r6xfNDf72o29_0yy6KbqGA@mail.gmail.com/

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>
Acked-by: Nicolas Schier <nsc@kernel.org>
Signed-off-by: HeeSu Kim <mlksvender@gmail.com>
---
 scripts/Makefile.compiler | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
index ef91910de265..fd039e228800 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-lt-version
+# Usage: rustc-$(call rustc-lt-version, 109000) += -Cfoo
+rustc-lt-version = $(if $(call rustc-min-version,$1),,y)
+
 # 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 v6 1/2] kbuild: add rustc-lt-version macro

[HeeSu Kim]

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

Use a non-inclusive (less-than) comparison so that callers can express
clean version boundaries such as `109000` (Rust 1.90.0) rather than
`108999`, which is also easier to remove once the toolchain minimum
version is bumped past the bound.

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

Originally posted as `rustc-max-version` in v5 [1]; renamed to
`rustc-lt-version` on this respin per Miguel's direction to simplify
the delta and avoid the `99` form [2].

[1] https://lore.kernel.org/rust-for-linux/20260205131522.2942928-1-mlksvender@gmail.com/
[2] https://lore.kernel.org/rust-for-linux/CANiq72n-z0v_deUVPWeg1h0c6KQ+r6xfNDf72o29_0yy6KbqGA@mail.gmail.com/

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>
Acked-by: Nicolas Schier <nsc@kernel.org>
Signed-off-by: HeeSu Kim <mlksvender@gmail.com>
---
 scripts/Makefile.compiler | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
index ef91910de265..fd039e228800 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-lt-version
+# Usage: rustc-$(call rustc-lt-version, 109000) += -Cfoo
+rustc-lt-version = $(if $(call rustc-min-version,$1),,y)
+
 # 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 v6 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].
An analogous workaround for doctests was added later [2]; since Rust
1.91.0 the `sanitizer` modifier is also appended.

The rustdoc bug is fixed in Rust 1.90.0 [3] and the doctests one is
fixed in Rust 1.92.0, so restrict each workaround to the compiler
versions that are actually affected, letting ABI compatibility checks
run again on newer compilers.

Split the cases into explicit version ranges using
`rustc-min-version` + `rustc-lt-version` combined inline: the rustdoc
workaround applies to 1.88.x and 1.89.x, the doctests workaround to
1.88.x through 1.91.x, and the `sanitizer` modifier is only added
from 1.91.x onwards (when rustc started recognizing it). This layout
makes it easy to drop each entry as the minimum toolchain version is
bumped past the affected range.

[1] https://github.com/rust-lang/rust/issues/144521
[2] https://github.com/rust-lang/rust/issues/146465
[3] https://github.com/rust-lang/rust/pull/144523

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/CANiq72nnuKJaKrxrut6+noR13PUiSoWWyyp-pGx-fe_2O6ayFA@mail.gmail.com/
Cc: stable@vger.kernel.org # Useful in 6.18.y and later.
Signed-off-by: HeeSu Kim <mlksvender@gmail.com>
---
 rust/Makefile | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/rust/Makefile b/rust/Makefile
index 5c0155b83454..14acc9c57c60 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -134,12 +134,18 @@ pin_init-flags := \
     --extern macros \
     $(call cfgs-to-flags,$(pin_init-cfgs))
 
-# `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)
-
-# 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)
+# `rustdoc` did not save the target modifiers
+# (https://github.com/rust-lang/rust/issues/144521, fixed in Rust 1.90.0).
+# Similarly, for doctests
+# (https://github.com/rust-lang/rust/issues/146465, fixed in Rust 1.92.0).
+ifeq ($(and $(call rustc-min-version,108800),$(call rustc-lt-version,109000)),y)
+rustdoc_modifiers_workaround := -Cunsafe-allow-abi-mismatch=fixed-x18
+doctests_modifiers_workaround := -Cunsafe-allow-abi-mismatch=fixed-x18
+else ifeq ($(and $(call rustc-min-version,109000),$(call rustc-lt-version,109100)),y)
+doctests_modifiers_workaround := -Cunsafe-allow-abi-mismatch=fixed-x18
+else ifeq ($(and $(call rustc-min-version,109100),$(call rustc-lt-version,109200)),y)
+doctests_modifiers_workaround := -Cunsafe-allow-abi-mismatch=fixed-x18,sanitizer
+endif
 
 # `rustc` recognizes `--remap-path-prefix` since 1.26.0, but `rustdoc` only
 # since Rust 1.81.0. Moreover, `rustdoc` ICEs on out-of-tree builds since Rust
-- 
2.52.0

[PATCH v6 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].
An analogous workaround for doctests was added later [2]; since Rust
1.91.0 the `sanitizer` modifier is also appended.

The rustdoc bug is fixed in Rust 1.90.0 [3] and the doctests one is
fixed in Rust 1.92.0, so restrict each workaround to the compiler
versions that are actually affected, letting ABI compatibility checks
run again on newer compilers.

Split the cases into explicit version ranges using
`rustc-min-version` + `rustc-lt-version` combined inline: the rustdoc
workaround applies to 1.88.x and 1.89.x, the doctests workaround to
1.88.x through 1.91.x, and the `sanitizer` modifier is only added
from 1.91.x onwards (when rustc started recognizing it). This layout
makes it easy to drop each entry as the minimum toolchain version is
bumped past the affected range.

[1] https://github.com/rust-lang/rust/issues/144521
[2] https://github.com/rust-lang/rust/issues/146465
[3] https://github.com/rust-lang/rust/pull/144523

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/CANiq72nnuKJaKrxrut6+noR13PUiSoWWyyp-pGx-fe_2O6ayFA@mail.gmail.com/
Cc: stable@vger.kernel.org # Useful in 6.18.y and later.
Signed-off-by: HeeSu Kim <mlksvender@gmail.com>
---
 rust/Makefile | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/rust/Makefile b/rust/Makefile
index 5c0155b83454..14acc9c57c60 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -134,12 +134,18 @@ pin_init-flags := \
     --extern macros \
     $(call cfgs-to-flags,$(pin_init-cfgs))
 
-# `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)
-
-# 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)
+# `rustdoc` did not save the target modifiers
+# (https://github.com/rust-lang/rust/issues/144521, fixed in Rust 1.90.0).
+# Similarly, for doctests
+# (https://github.com/rust-lang/rust/issues/146465, fixed in Rust 1.92.0).
+ifeq ($(and $(call rustc-min-version,108800),$(call rustc-lt-version,109000)),y)
+rustdoc_modifiers_workaround := -Cunsafe-allow-abi-mismatch=fixed-x18
+doctests_modifiers_workaround := -Cunsafe-allow-abi-mismatch=fixed-x18
+else ifeq ($(and $(call rustc-min-version,109000),$(call rustc-lt-version,109100)),y)
+doctests_modifiers_workaround := -Cunsafe-allow-abi-mismatch=fixed-x18
+else ifeq ($(and $(call rustc-min-version,109100),$(call rustc-lt-version,109200)),y)
+doctests_modifiers_workaround := -Cunsafe-allow-abi-mismatch=fixed-x18,sanitizer
+endif
 
 # `rustc` recognizes `--remap-path-prefix` since 1.26.0, but `rustdoc` only
 # since Rust 1.81.0. Moreover, `rustdoc` ICEs on out-of-tree builds since Rust
-- 
2.52.0

[PATCH v6 0/2] rust: Makefile: bound rustdoc workaround to affected versions

[HeeSu Kim]

This series bounds the `-Cunsafe-allow-abi-mismatch=fixed-x18` workaround
in `rust/Makefile` to the compiler versions that are actually affected by
the rustdoc (#144521, fixed in 1.90.0) and doctests (#146465, fixed in
1.92.0) target-modifier bugs, so that ABI compatibility checks run again
on newer toolchains.

Changes since v5 [1] [2]:
 - Patch 1/2 is v5 1/2 renamed from `rustc-max-version` to
   `rustc-lt-version` per Miguel's plan to rename on apply [3] and to
   avoid the `99` form. Nathan's [4] and Nicolas' [5] Acked-bys from
   v5 1/2 are carried over as Miguel indicated they would be preserved
   through the rename.
 - Patch 2/2 reworks v5 2/2 to fix the doctests case that Miguel
   pointed out [6]: the v5 form reused `$(rustdoc_modifiers_workaround)`
   as a prefix, so on rustc >= 1.91 the doctests variable expanded to
   a stray `,sanitizer`. Use Miguel's suggested explicit
   `ifeq`/`else ifeq` layout with `rustc-min-version` +
   `rustc-lt-version` combined inline, so each affected range is
   visible on its own line.

The `rustc-version-range` macro Miguel mentioned as an "improvement on
top" [3] is intentionally left out of this series; I will send it as a
separate follow-up patch once this lands, as Miguel suggested.

Tested by building `make rustdoc` and `make rusttest` on rustc 1.93.0:
both succeed with the workaround disabled (empty expansion), confirming
the bugs really are fixed in 1.92+ and no regressions are introduced.
Macro expansion was also spot-checked across simulated rustc versions
1.87 through 1.93 to verify each range matches the expected flag value.

[1] https://lore.kernel.org/rust-for-linux/20260205131522.2942928-1-mlksvender@gmail.com/
[2] https://lore.kernel.org/rust-for-linux/20260205131815.2943152-2-mlksvender@gmail.com/
[3] https://lore.kernel.org/rust-for-linux/CANiq72n-z0v_deUVPWeg1h0c6KQ+r6xfNDf72o29_0yy6KbqGA@mail.gmail.com/
[4] https://lore.kernel.org/rust-for-linux/20260203221224.GA2703490@ax162/
[5] https://lore.kernel.org/rust-for-linux/aYS9bRugxr1rUvA3@levanger/
[6] https://lore.kernel.org/rust-for-linux/CANiq72nnuKJaKrxrut6+noR13PUiSoWWyyp-pGx-fe_2O6ayFA@mail.gmail.com/

HeeSu Kim (2):
  kbuild: add rustc-lt-version macro
  rust: Makefile: bound rustdoc workaround to affected versions

 rust/Makefile             | 18 ++++++++++++------
 scripts/Makefile.compiler |  4 ++++
 2 files changed, 16 insertions(+), 6 deletions(-)

-- 
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 v2] rust: Makefile: bound rustdoc workaround to affected versions

[HeeSu Kim]

On Mon, 3 Feb 2026, Miguel Ojeda wrote:
> On Mon, Feb 3, 2025 at 1:09 AM HeeSu Kim <mlksvender@gmail.com> wrote:
> >
> > The `-Cunsafe-allow-abi-mismatch=fixed-x18` workaround was added to
> > handle a rustdoc bug (rust-lang/rust#144521) where target modifiers
> > were not properly saved.
> >
> > This bug was fixed in Rust 1.90.0 (rust-lang/rust#144523). Restrict
>
> We tend to use `Link:` tags for these. Typically we write a line like:
>
>     Link: https://github.com/rust-lang/rust/issues/144521
>
> If you want to reference it inline, you can also just put the full URL.
>
> > Suggested-by: Gary Guo <gary@garyguo.net>
>
> Please add a `Link:` tag after this one pointing to his message.
>
> > Fixes: abbf9a449441 ("rust: workaround `rustdoc` target modifiers bug")
>
> I am not so sure this is a fix -- after all, when you use `1.88` or
> `1.89`, nothing would change. So it is more of a feature? i.e. the
> ability to use `1.90`.
>
> But I guess it could also be understood as "we should have applied
> this only for affected versions to begin with", but then it would be
> from a "code documentation" perspective, which is fine, but it is not
> something that e.g. we would need to backport. So I am leaning towards
> not having a `Fixes:` here.
>
> And this has another issue (though a different patch): the `sanitizer`
> modifier.
>
> By the way, I wonder if we would want at least a `rustc-max-version`
> (or an `-until` variant, or whatever) so that we can easily express
> that range in a single call, and document the bounds together (I could
> imagine that we could end up with a few of these over time, and then
> they start to shift versions, they get spread across lines, etc.).
>
> Perhaps the Kbuild maintainers can comment on whether that would be a
> good idea or whether they already have something.
>
> Cheers,
> Miguel

Thanks for the detailed feedback.

For v3, I will:
- Use full Link: tags for GitHub references instead of shorthand
- Add Link: tag after Suggested-by pointing to Gary's lore message
- Remove the Fixes: tag
- Add Cc: stable@vger.kernel.org # Useful in 6.18.y and later.

Regarding rustc-max-version, it would be useful for reading the code.
I'll wait for Kbuild maintainers' reply.

Best regards,
HeeSu Kim

[PATCH v3] 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.
Signed-off-by: HeeSu Kim <mlksvender@gmail.com>
---
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..55e2dc865207 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 $(call test-lt,$(CONFIG_RUSTC_VERSION),109000),-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 v2] rust: Makefile: bound rustdoc workaround to affected versions

[Gary Guo]

On Mon Feb 2, 2026 at 4:00 PM GMT, Miguel Ojeda wrote:
> On Mon, Feb 2, 2026 at 4:21 PM HeeSu Kim <mlksvender@gmail.com> wrote:
>>
>> This bug was fixed in Rust 1.90.0 (rust-lang/rust#144523). Restrict
>
> Normally these references should be full links (i.e. a tag), since we
> do not have "autolinking" like GitHub e.g.
>
>   Link: https://........ [1]
>
> Then you can use [1] above instead of the parenthesis.
>
>> are affected by the bug, avoiding unnecessary flags on newer compiler
>
> To clarify a bit: avoiding the flags is good, but I think avoiding the
> skipping of the checks that the flag does is what is more important
> (i.e. if it were just the former advantage, I would say it is not
> worth the complexity of the added tests).

I think skipping workarounds when possible is in general good, as it serves a
good reference that it can be removed whenever the toolchain minimum version is
bumped above that (and with the help with LKP, it means that it's also been
actually widely tested that the workaround is indeed not necessary).

Best,
Gary