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 <post@ralfj.de>
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
Link: https://github.com/rust-lang/rust/pull/151154
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://patch.msgid.link/20260530114925.260754-1-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

diff --git a/scripts/generate_rust_target.rs b/scripts/generate_rust_target.rs
index 38b3416bb9799e201b7cdc666a801f4494ecbcb1..16f7e855e012a497cdc65085aa31e3e2ad5a14bf 100644 (file)
--- 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(