Turn it on when available if CONFIG_HAVE_FENTRY=y.

Rust support was added in 1.98.0 with support for x86 and s390x targets.

Signed-off-by: Paul Murphy <murp@redhat.com>
---
 Makefile                        | 2 ++
 scripts/generate_rust_target.rs | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/Makefile b/Makefile
index bfb47ad8cb9a..bdfe93702a33 100644
--- a/Makefile
+++ b/Makefile
@@ -1053,10 +1053,12 @@ ifdef CONFIG_HAVE_FENTRY
     CC_FLAGS_FTRACE	+= -mfentry
     CC_FLAGS_USING	+= -DCC_USING_FENTRY
   endif
+  RUSTFLAGS_FTRACE := $(if $(call rustc-min-version,109800),-Zinstrument-mcount=fentry,)
 endif
 export CC_FLAGS_FTRACE
 KBUILD_CFLAGS	+= $(CC_FLAGS_FTRACE) $(CC_FLAGS_USING)
 KBUILD_AFLAGS	+= $(CC_FLAGS_USING)
+KBUILD_RUSTFLAGS += $(RUSTFLAGS_FTRACE)
 endif
 
 # We trigger additional mismatches with less inlining
diff --git a/scripts/generate_rust_target.rs b/scripts/generate_rust_target.rs
index 3bf296581a88..eb80a06d50d3 100644
--- a/scripts/generate_rust_target.rs
+++ b/scripts/generate_rust_target.rs
@@ -198,6 +198,7 @@ fn main() {
         ts.push("arch", "x86_64");
         if cfg.rustc_version_atleast(1, 98, 0) {
             ts.push("rustc-abi", "softfloat");
+            ts.push("supports-fentry", true);
         } else if cfg.rustc_version_atleast(1, 86, 0) {
             ts.push("rustc-abi", "x86-softfloat");
         }
@@ -240,6 +241,7 @@ fn main() {
         ts.push("arch", "x86");
         if cfg.rustc_version_atleast(1, 98, 0) {
             ts.push("rustc-abi", "softfloat");
+            ts.push("supports-fentry", true);
         } else if cfg.rustc_version_atleast(1, 86, 0) {
             ts.push("rustc-abi", "x86-softfloat");
         }

base-commit: 7059bdf4f04a3e14f4fafb3ac35fdca913e3e21a
-- 
2.55.0

On Fri, Jul 24, 2026 at 7:01 PM Paul Murphy <murp@redhat.com> wrote:
>
> Rust support was added in 1.98.0 with support for x86 and s390x targets.

"will be added"? i.e. it is not released, but I guess you mean it is
unusual to drop from beta.

Link: https://github.com/rust-lang/rust/pull/152122
Link: https://github.com/rust-lang/rust/pull/158036

Cheers,
Miguel