From 4a44b17406cb5a93f90af3df9392b3a45eb336fb Mon Sep 17 00:00:00 2001 From: Alice Ryhl Date: Thu, 7 May 2026 11:14:42 +0000 Subject: rust: kasan/kbuild: fix rustc-option when cross-compiling The Makefile version of rustc-option currently checks whether the option exists for the host target instead of the target actually being compiled for. It was done this way in commit 46e24a545cdb ("rust: kasan/kbuild: fix missing flags on first build") to avoid a circular dependency on target.json. However, because of this, rustc-option currently does not function when cross-compiling from x86_64 to aarch64 if CONFIG_SHADOW_CALL_STACK is enabled. This is because KBUILD_RUSTFLAGS contains -Zfixed-x18 under this configuration. Since that flag does not exist on the host target, rustc-option runs into a compilation failure every time, leading to all flags being rejected as unsupported. To fix this, update rustc-option to pass a --target parameter so that the host target is not used. For targets using target.json, use a built-in target that is as close as possible to the target created with target.json to avoid the circular dependency on target.json. One scenario where this causes a boot failure: * Cross-compiled from x86_64 to aarch64. * With CONFIG_SHADOW_CALL_STACK=y * With CONFIG_KASAN_SW_TAGS=y * With CONFIG_KASAN_INLINE=n Then the resulting kernel image will fail to boot when it first calls into Rust code with a crash along the lines of "Unable to handle kernel paging request at virtual address 0ffffffc08541796". This is because the call threshold is not specified, so rustc will inline kasan operations, but the kasan shadow offset is not specified, which leads to the inlined kasan instructions being incorrect. Note that the -Zsanitizer=kernel-hwaddress parameter itself does not lead to a rustc-option failure despite being aarch64-specific because RUSTFLAGS_KASAN has not yet been added to KBUILD_RUSTFLAGS when rustc-option is evaluated by the kasan Makefile. Cc: stable@vger.kernel.org Fixes: 46e24a545cdb ("rust: kasan/kbuild: fix missing flags on first build") Signed-off-by: Alice Ryhl Link: https://patch.msgid.link/20260507-rustc-option-cross-v2-1-2f650a49c2b5@google.com [ Edited slightly: - Reset variable to avoid using the environment. - Use a simply expanded variable flavor for simplicity. - Export variable so that behavior in sub-`make`s is consistent. This matches other variables. - Miguel ] Signed-off-by: Miguel Ojeda --- scripts/Makefile.compiler | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'scripts') diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler index ef91910de265..06bbe29c846c 100644 --- a/scripts/Makefile.compiler +++ b/scripts/Makefile.compiler @@ -80,7 +80,7 @@ ld-option = $(call try-run, $(LD) $(KBUILD_LDFLAGS) $(1) -v,$(1),$(2),$(3)) # TODO: remove RUSTC_BOOTSTRAP=1 when we raise the minimum GNU Make version to 4.4 __rustc-option = $(call try-run,\ echo '$(pound)![allow(missing_docs)]$(pound)![feature(no_core)]$(pound)![no_core]' | RUSTC_BOOTSTRAP=1\ - $(1) --sysroot=/dev/null $(filter-out --sysroot=/dev/null --target=%,$(2)) $(3)\ + $(1) --sysroot=/dev/null $(KBUILD_RUSTFLAGS_OPTION_CHKS) $(filter-out --sysroot=/dev/null --target=%target.json,$(2)) $(3)\ --crate-type=rlib --out-dir=$(TMPOUT) --emit=obj=- - >/dev/null,$(3),$(4)) # rustc-option -- cgit v1.2.3 From 905b06d32a52afe32fcf5f30cf298c9ea6359f11 Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Sat, 30 May 2026 13:49:25 +0200 Subject: rust: x86: support Rust >= 1.98.0 target spec Starting with Rust 1.98.0 (expected 2026-08-20), the target spec will not support `x86-softfloat` anymore [1]. Instead, `softfloat` should be used, which is an alias. Otherwise, one gets: error: error loading target specification: rustc-abi: invalid rustc abi: 'x86-softfloat'. allowed values: 'x86-sse2', 'softfloat' at line 3 column 32 | = help: run `rustc --print target-list` for a list of built-in targets Thus conditionally use one or the other depending on the version. The alias has existed since Rust 1.95.0 (released 2026-04-16) [2], but use the newer version instead to avoid changing how the build works for existing compilers, at least until more testing takes place. Cc: Ralf Jung Cc: stable@vger.kernel.org # Needed in 6.12.y and later (Rust is pinned in older LTSs). Link: https://github.com/rust-lang/rust/pull/157151 [1] Link: https://github.com/rust-lang/rust/pull/151154 [2] Reviewed-by: Alice Ryhl Link: https://patch.msgid.link/20260530114925.260754-1-ojeda@kernel.org Signed-off-by: Miguel Ojeda --- scripts/generate_rust_target.rs | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'scripts') diff --git a/scripts/generate_rust_target.rs b/scripts/generate_rust_target.rs index 38b3416bb979..16f7e855e012 100644 --- a/scripts/generate_rust_target.rs +++ b/scripts/generate_rust_target.rs @@ -196,7 +196,9 @@ fn main() { } } else if cfg.has("X86_64") { ts.push("arch", "x86_64"); - if cfg.rustc_version_atleast(1, 86, 0) { + if cfg.rustc_version_atleast(1, 98, 0) { + ts.push("rustc-abi", "softfloat"); + } else if cfg.rustc_version_atleast(1, 86, 0) { ts.push("rustc-abi", "x86-softfloat"); } ts.push( @@ -236,7 +238,9 @@ fn main() { panic!("32-bit x86 only works under UML"); } ts.push("arch", "x86"); - if cfg.rustc_version_atleast(1, 86, 0) { + if cfg.rustc_version_atleast(1, 98, 0) { + ts.push("rustc-abi", "softfloat"); + } else if cfg.rustc_version_atleast(1, 86, 0) { ts.push("rustc-abi", "x86-softfloat"); } ts.push( -- cgit v1.2.3