[PATCH v3 7/7] arm64: ftrace: Allow CALL_OPS on kCFI kernels built with Rust
flat view
WARM3d
REVIEWED: 3 (1M)
From: Jose Fernandez (Anthropic) <hidden>
Date: 2026-10-29 16:57:51
Also in:
bpf, linux-arm-kernel, lkml
Subsystem:
arm64 port (aarch64 architecture), rust, the rest · Maintainers:
Catalin Marinas, Will Deacon, Miguel Ojeda, Linus Torvalds
Status: Reviewed.
Revision v3 (3 revisions archived); 3 review trailers.
Revisions (3)
- rfc
- v2 [diff against previous]
- v3 current [diff against previous]
Pass -Zpatchable-function-entry=M,M,.discard.patchable_function_entries to rustc when CFI and CALL_OPS are both enabled, so Rust functions get the same prefix NOPs as C functions. The section argument needs Rust 1.98 [1]. Probe for it, and let ARM64_CFI_PERMITS_CALL_OPS accept RUST=y when the probe passes. Filter -fpatchable-function-entry out of bindgen's C flags on every architecture, not only on arm64 with CFI, since removing the flag does not change the ABI. [1] https://github.com/rust-lang/rust/pull/157445 Suggested-by: Ben Cressey <redacted> Reviewed-by: Ben Cressey <redacted> Reviewed-by: Florent Revest (Anthropic) <redacted> Acked-by: Alexei Starovoitov <ast@kernel.org> Assisted-by: LLM Signed-off-by: Jose Fernandez (Anthropic) <redacted> --- arch/arm64/Kconfig | 7 ++++++- arch/arm64/Makefile | 3 +++ rust/Makefile | 7 ++++++- 3 files changed, 15 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index e8cb44d881d0..e64d053e1854 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig@@ -277,11 +277,16 @@ config CC_HAS_PATCHABLE_FUNCTION_ENTRY_SECTION # https://github.com/llvm/llvm-project/pull/131230 def_bool $(cc-option,-fpatchable-function-entry=1$(comma)1$(comma).discard.patchable_function_entries) +config RUSTC_HAS_PATCHABLE_FUNCTION_ENTRY_SECTION + # The section argument needs Rust 1.98.0 or later: + # https://github.com/rust-lang/rust/pull/157445 + def_bool $(rustc-option,-Zpatchable-function-entry=1$(comma)1$(comma).discard.patchable_function_entries) + config ARM64_CFI_PERMITS_CALL_OPS def_bool y depends on CFI depends on CC_HAS_PATCHABLE_FUNCTION_ENTRY_SECTION - depends on !RUST + depends on !RUST || RUSTC_HAS_PATCHABLE_FUNCTION_ENTRY_SECTION config ARM64_FUNCTION_PREFIX_NOPS int
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 9fbfe5ab3724..b47733b585b5 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile@@ -147,6 +147,9 @@ ifeq ($(CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS),y) -DCC_USING_PATCHABLE_FUNCTION_PREFIX=$(prefix_nops) KBUILD_CFLAGS += $(CFI_PREFIX_CFLAGS) export CFI_PREFIX_CFLAGS + # Rust functions are not patched by ftrace, but they are called indirectly + # from C and make indirect calls themselves, so they need the same prefix. + KBUILD_RUSTFLAGS += -Zpatchable-function-entry=$(prefix_nops),$(prefix_nops),.discard.patchable_function_entries endif else ifeq ($(CONFIG_DYNAMIC_FTRACE_WITH_ARGS),y) KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY
diff --git a/rust/Makefile b/rust/Makefile
index 0ac9ab28cc2b..686964c826f7 100644
--- a/rust/Makefile
+++ b/rust/Makefile@@ -511,7 +511,12 @@ endif # prototypes for functions like `memcpy` -- if this flag is not passed, # `bindgen`-generated prototypes use `c_ulong` or `c_uint` depending on # architecture instead of generating `usize`. -bindgen_c_flags_final = $(bindgen_c_flags_lto) -fno-builtin -D__BINDGEN__ +# +# Do not pass -fpatchable-function-entry to bindgen: its libclang may not +# support the section argument (Clang >= 21), and removing the flag does not +# change the ABI. +bindgen_c_flags_final = $(filter-out -fpatchable-function-entry=%, \ + $(bindgen_c_flags_lto)) -fno-builtin -D__BINDGEN__ # `--rust-target` points to our minimum supported Rust version. quiet_cmd_bindgen = BINDGEN $@
--
2.54.0