kbuild: rust: keep Rust objects out of Clang LTO with inline helpersgrafted

Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit
`objtool` errors such as:

    vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a:
    can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd

The reason is that in such builds, the Clang invocation that compiles
the combined Rust plus helpers bitcode emits LLVM bitcode (again) --
the final code generation happens in the linker's LTO step, which the
`-mllvm` trap options passed to Clang do not reach.

This, in turn, means that unreachable traps are missing, and the
impossible paths do not merely fallthrough to the next symbol, but past
the end of their own section, since LTO builds place each function in
its own section.

Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always
emits machine code directly, with the traps in place.

Assisted-by: LLM
Cc: Gary Guo <gary@garyguo.net>
Cc: Boqun Feng <boqun@kernel.org>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Matthew Maurer <mmaurer@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust")
Acked-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 310 insertions, 0 deletions

diff --git a/lib/crypto/Kconfig b/lib/crypto/Kconfig
new file mode 100644
index 000000000..56f308dd0
--- /dev/null
+++ b/lib/crypto/Kconfig
@@ -0,0 +1,310 @@
+# SPDX-License-Identifier: GPL-2.0
+
+config CRYPTO_HASH_INFO
+	bool
+
+config CRYPTO_LIB_UTILS
+	tristate
+
+config CRYPTO_LIB_AES
+	tristate
+	# Select dependencies of modes that are part of libaes.
+	select CRYPTO_LIB_GF128HASH if CRYPTO_LIB_AES_GCM != n
+	select CRYPTO_LIB_UTILS
+
+config CRYPTO_LIB_AES_ARCH
+	bool
+	depends on CRYPTO_LIB_AES && !UML && !KMSAN
+	default y if ARM
+	default y if ARM64
+	default y if PPC && (SPE || (PPC64 && VSX))
+	default y if RISCV && 64BIT && TOOLCHAIN_HAS_VECTOR_CRYPTO && \
+		     RISCV_EFFICIENT_VECTOR_UNALIGNED_ACCESS
+	default y if S390
+	default y if SPARC64
+	default y if X86
+
+config CRYPTO_LIB_AESCFB
+	tristate
+	select CRYPTO_LIB_AES
+	select CRYPTO_LIB_UTILS
+
+config CRYPTO_LIB_AES_CBC
+	tristate
+	select CRYPTO_LIB_AES
+	help
+	  The AES-CBC and AES-CBC-CTS library functions.
+
+config CRYPTO_LIB_AES_CBC_MACS
+	tristate
+	select CRYPTO_LIB_AES
+	help
+	  The AES-CMAC, AES-XCBC-MAC, and AES-CBC-MAC library functions.  Select
+	  this if your module uses any of the functions from
+	  <crypto/aes-cbc-macs.h>.
+
+config CRYPTO_LIB_AES_CCM
+	tristate
+	select CRYPTO_LIB_AES
+	select CRYPTO_LIB_AES_CBC_MACS
+	select CRYPTO_LIB_AES_CTR
+	help
+	  The AES-CCM library functions.
+
+config CRYPTO_LIB_AES_CTR
+	tristate
+	select CRYPTO_LIB_AES
+	help
+	  The AES-CTR and AES-XCTR library functions.
+
+config CRYPTO_LIB_AES_ECB
+	tristate
+	select CRYPTO_LIB_AES
+	help
+	  The AES-ECB library functions.
+
+config CRYPTO_LIB_AES_GCM
+	tristate
+	select CRYPTO_LIB_AES
+	select CRYPTO_LIB_AES_CTR
+	help
+	  The AES-GCM library functions.
+
+config CRYPTO_LIB_AES_XTS
+	tristate
+	select CRYPTO_LIB_AES
+	help
+	  The AES-XTS library functions.
+
+config CRYPTO_LIB_ARC4
+	tristate
+
+config CRYPTO_LIB_GF128MUL
+	tristate
+
+config CRYPTO_LIB_BLAKE2B
+	tristate
+	help
+	  The BLAKE2b library functions.  Select this if your module uses any of
+	  the functions from <crypto/blake2b.h>.
+
+config CRYPTO_LIB_BLAKE2B_ARCH
+	bool
+	depends on CRYPTO_LIB_BLAKE2B && !UML
+	default y if ARM && KERNEL_MODE_NEON
+
+# BLAKE2s support is always built-in, so there's no CRYPTO_LIB_BLAKE2S option.
+
+config CRYPTO_LIB_BLAKE2S_ARCH
+	bool
+	depends on !UML
+	default y if ARM
+	default y if X86_64
+
+config CRYPTO_LIB_CHACHA
+	tristate
+	select CRYPTO_LIB_UTILS
+	help
+	  Enable the ChaCha library interface.  Select this if your module uses
+	  chacha_crypt() or hchacha_block().
+
+config CRYPTO_LIB_CHACHA_ARCH
+	bool
+	depends on CRYPTO_LIB_CHACHA && !UML && !KMSAN
+	default y if ARM
+	default y if ARM64
+	default y if MIPS && CPU_MIPS32_R2
+	default y if PPC64 && CPU_LITTLE_ENDIAN && VSX
+	default y if RISCV && 64BIT && TOOLCHAIN_HAS_VECTOR_CRYPTO && \
+		     RISCV_EFFICIENT_VECTOR_UNALIGNED_ACCESS
+	default y if S390
+	default y if X86_64
+
+config CRYPTO_LIB_CURVE25519
+	tristate
+	select CRYPTO_LIB_UTILS
+	help
+	  The Curve25519 library functions.  Select this if your module uses any
+	  of the functions from <crypto/curve25519.h>.
+
+config CRYPTO_LIB_CURVE25519_ARCH
+	bool
+	depends on CRYPTO_LIB_CURVE25519 && !UML && !KMSAN
+	default y if ARM && KERNEL_MODE_NEON && !CPU_BIG_ENDIAN
+	default y if PPC64 && CPU_LITTLE_ENDIAN
+	default y if X86_64
+
+config CRYPTO_LIB_CURVE25519_GENERIC
+	bool
+	depends on CRYPTO_LIB_CURVE25519
+	default y if !CRYPTO_LIB_CURVE25519_ARCH || ARM || X86_64
+
+config CRYPTO_LIB_DES
+	tristate
+
+config CRYPTO_LIB_GF128HASH
+	tristate
+	help
+	  The GHASH and POLYVAL library functions.  Select this if your module
+	  uses any of the functions from <crypto/gf128hash.h>.
+
+config CRYPTO_LIB_GF128HASH_ARCH
+	bool
+	depends on CRYPTO_LIB_GF128HASH && !UML
+	default y if ARM && KERNEL_MODE_NEON
+	default y if ARM64
+	default y if PPC64 && VSX
+	default y if RISCV && 64BIT && TOOLCHAIN_HAS_VECTOR_CRYPTO && \
+		     RISCV_EFFICIENT_VECTOR_UNALIGNED_ACCESS
+	default y if S390
+	default y if X86_64
+
+config CRYPTO_LIB_MD5
+	tristate
+	help
+	  The MD5 and HMAC-MD5 library functions.  Select this if your module
+	  uses any of the functions from <crypto/md5.h>.
+
+config CRYPTO_LIB_MLDSA
+	tristate
+	select CRYPTO_LIB_SHA3
+	help
+	  The ML-DSA library functions.  Select this if your module uses any of
+	  the functions from <crypto/mldsa.h>.
+
+config CRYPTO_LIB_NH
+	tristate
+	help
+	  Implementation of the NH almost-universal hash function, specifically
+	  the variant of NH used in Adiantum.
+
+config CRYPTO_LIB_NH_ARCH
+	bool
+	depends on CRYPTO_LIB_NH && !UML && !KMSAN
+	default y if ARM && KERNEL_MODE_NEON
+	default y if ARM64
+	default y if X86_64
+
+config CRYPTO_LIB_POLY1305
+	tristate
+	help
+	  The Poly1305 library functions.  Select this if your module uses any
+	  of the functions from <crypto/poly1305.h>.
+
+config CRYPTO_LIB_POLY1305_ARCH
+	bool
+	depends on CRYPTO_LIB_POLY1305 && !UML && !KMSAN
+	default y if ARM
+	default y if ARM64
+	default y if MIPS
+	# The PPC64 code needs to be fixed to work in softirq context.
+	default y if PPC64 && CPU_LITTLE_ENDIAN && VSX && BROKEN
+	default y if RISCV
+	default y if X86_64
+
+# This symbol controls the inclusion of the Poly1305 generic code.  This differs
+# from most of the other algorithms, which handle the generic code
+# "automatically" via __maybe_unused.  This is needed so that the Adiantum code,
+# which calls the poly1305_core_*() functions directly, can enable them.
+config CRYPTO_LIB_POLY1305_GENERIC
+	bool
+	depends on CRYPTO_LIB_POLY1305
+	# Enable if there's no arch impl or the arch impl requires the generic
+	# impl as a fallback.  (Or if selected explicitly.)
+	default y if !CRYPTO_LIB_POLY1305_ARCH || PPC64
+
+config CRYPTO_LIB_POLY1305_RSIZE
+	int
+	default 2 if MIPS || RISCV
+	default 11 if X86_64
+	default 9 if ARM || ARM64
+	default 1
+
+config CRYPTO_LIB_CHACHA20POLY1305
+	tristate
+	select CRYPTO_LIB_CHACHA
+	select CRYPTO_LIB_POLY1305
+	select CRYPTO_LIB_UTILS
+
+config CRYPTO_LIB_SHA1
+	tristate
+	help
+	  The SHA-1 and HMAC-SHA1 library functions.  Select this if your module
+	  uses any of the functions from <crypto/sha1.h>.
+
+config CRYPTO_LIB_SHA1_ARCH
+	bool
+	depends on CRYPTO_LIB_SHA1 && !UML
+	default y if ARM
+	default y if ARM64
+	default y if MIPS && CPU_CAVIUM_OCTEON
+	default y if PPC
+	default y if S390
+	default y if SPARC64
+	default y if X86_64
+
+config CRYPTO_LIB_SHA256
+	tristate
+	help
+	  The SHA-224, SHA-256, HMAC-SHA224, and HMAC-SHA256 library functions.
+	  Select this if your module uses any of these functions from
+	  <crypto/sha2.h>.
+
+config CRYPTO_LIB_SHA256_ARCH
+	bool
+	depends on CRYPTO_LIB_SHA256 && !UML
+	default y if ARM && !CPU_V7M
+	default y if ARM64
+	default y if MIPS && CPU_CAVIUM_OCTEON
+	default y if PPC && SPE
+	default y if RISCV && 64BIT && TOOLCHAIN_HAS_VECTOR_CRYPTO && \
+		     RISCV_EFFICIENT_VECTOR_UNALIGNED_ACCESS
+	default y if S390
+	default y if SPARC64
+	default y if X86_64
+
+config CRYPTO_LIB_SHA512
+	tristate
+	help
+	  The SHA-384, SHA-512, HMAC-SHA384, and HMAC-SHA512 library functions.
+	  Select this if your module uses any of these functions from
+	  <crypto/sha2.h>.
+
+config CRYPTO_LIB_SHA512_ARCH
+	bool
+	depends on CRYPTO_LIB_SHA512 && !UML
+	default y if ARM && !CPU_V7M
+	default y if ARM64
+	default y if MIPS && CPU_CAVIUM_OCTEON
+	default y if RISCV && 64BIT && TOOLCHAIN_HAS_VECTOR_CRYPTO && \
+		     RISCV_EFFICIENT_VECTOR_UNALIGNED_ACCESS
+	default y if S390
+	default y if SPARC64
+	default y if X86_64
+
+config CRYPTO_LIB_SHA3
+	tristate
+	select CRYPTO_LIB_UTILS
+	help
+	  The SHA3 library functions.  Select this if your module uses any of
+	  the functions from <crypto/sha3.h>.
+
+config CRYPTO_LIB_SHA3_ARCH
+	bool
+	depends on CRYPTO_LIB_SHA3 && !UML
+	default y if ARM64
+	default y if S390
+
+config CRYPTO_LIB_SM3
+	tristate
+	help
+	  The SM3 library functions.  Select this if your module uses any of the
+	  functions from <crypto/sm3.h>.
+
+config CRYPTO_LIB_SM3_ARCH
+	bool
+	depends on CRYPTO_LIB_SM3 && !UML
+	default y if ARM64
+	default y if RISCV && 64BIT && TOOLCHAIN_HAS_VECTOR_CRYPTO && \
+		     RISCV_EFFICIENT_VECTOR_UNALIGNED_ACCESS
+	default y if X86_64