From 5febf432df1cfa5b25d99b54c32103fafbdd0eb9 Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Sun, 16 Aug 2026 15:32:33 +0200 Subject: kbuild: rust: keep Rust objects out of Clang LTO with inline helpers 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 Cc: Boqun Feng Cc: Alice Ryhl Cc: Matthew Maurer Cc: Josh Poimboeuf Cc: Peter Zijlstra Cc: stable@vger.kernel.org Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust") Acked-by: Gary Guo Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org Signed-off-by: Miguel Ojeda --- include/crypto/chacha.h | 102 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 102 insertions(+) create mode 100644 include/crypto/chacha.h (limited to 'include/crypto/chacha.h') diff --git a/include/crypto/chacha.h b/include/crypto/chacha.h new file mode 100644 index 000000000..1cc301a48 --- /dev/null +++ b/include/crypto/chacha.h @@ -0,0 +1,102 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Common values and helper functions for the ChaCha and XChaCha stream ciphers. + * + * XChaCha extends ChaCha's nonce to 192 bits, while provably retaining ChaCha's + * security. Here they share the same key size, tfm context, and setkey + * function; only their IV size and encrypt/decrypt function differ. + * + * The ChaCha paper specifies 20, 12, and 8-round variants. In general, it is + * recommended to use the 20-round variant ChaCha20. However, the other + * variants can be needed in some performance-sensitive scenarios. The generic + * ChaCha code currently allows only the 20 and 12-round variants. + */ + +#ifndef _CRYPTO_CHACHA_H +#define _CRYPTO_CHACHA_H + +#include +#include +#include + +/* 32-bit stream position, then 96-bit nonce (RFC7539 convention) */ +#define CHACHA_IV_SIZE 16 + +#define CHACHA_KEY_SIZE 32 +#define CHACHA_BLOCK_SIZE 64 +#define CHACHAPOLY_IV_SIZE 12 + +#define CHACHA_KEY_WORDS 8 +#define CHACHA_STATE_WORDS 16 +#define HCHACHA_OUT_WORDS 8 + +/* 192-bit nonce, then 64-bit stream position */ +#define XCHACHA_IV_SIZE 32 + +struct chacha_state { + u32 x[CHACHA_STATE_WORDS]; +}; + +void chacha_block_generic(struct chacha_state *state, + u8 out[at_least CHACHA_BLOCK_SIZE], int nrounds); +static inline void chacha20_block(struct chacha_state *state, + u8 out[at_least CHACHA_BLOCK_SIZE]) +{ + chacha_block_generic(state, out, 20); +} + +void hchacha_block_generic(const struct chacha_state *state, + u32 out[at_least HCHACHA_OUT_WORDS], int nrounds); + +void hchacha_block(const struct chacha_state *state, + u32 out[at_least HCHACHA_OUT_WORDS], int nrounds); + +enum chacha_constants { /* expand 32-byte k */ + CHACHA_CONSTANT_EXPA = 0x61707865U, + CHACHA_CONSTANT_ND_3 = 0x3320646eU, + CHACHA_CONSTANT_2_BY = 0x79622d32U, + CHACHA_CONSTANT_TE_K = 0x6b206574U +}; + +static inline void chacha_init_consts(struct chacha_state *state) +{ + state->x[0] = CHACHA_CONSTANT_EXPA; + state->x[1] = CHACHA_CONSTANT_ND_3; + state->x[2] = CHACHA_CONSTANT_2_BY; + state->x[3] = CHACHA_CONSTANT_TE_K; +} + +static inline void chacha_init(struct chacha_state *state, + const u32 key[at_least CHACHA_KEY_WORDS], + const u8 iv[at_least CHACHA_IV_SIZE]) +{ + chacha_init_consts(state); + state->x[4] = key[0]; + state->x[5] = key[1]; + state->x[6] = key[2]; + state->x[7] = key[3]; + state->x[8] = key[4]; + state->x[9] = key[5]; + state->x[10] = key[6]; + state->x[11] = key[7]; + state->x[12] = get_unaligned_le32(iv + 0); + state->x[13] = get_unaligned_le32(iv + 4); + state->x[14] = get_unaligned_le32(iv + 8); + state->x[15] = get_unaligned_le32(iv + 12); +} + +void chacha_crypt(struct chacha_state *state, u8 *dst, const u8 *src, + unsigned int bytes, int nrounds); + +static inline void chacha20_crypt(struct chacha_state *state, + u8 *dst, const u8 *src, unsigned int bytes) +{ + chacha_crypt(state, dst, src, bytes, 20); +} + +static inline void chacha_zeroize_state(struct chacha_state *state) +{ + memzero_explicit(state, sizeof(*state)); +} + +#endif /* _CRYPTO_CHACHA_H */ -- cgit v1.3.1