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 --- lib/ts_fsm.c | 338 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 338 insertions(+) create mode 100644 lib/ts_fsm.c (limited to 'lib/ts_fsm.c') diff --git a/lib/ts_fsm.c b/lib/ts_fsm.c new file mode 100644 index 000000000..053615f4f --- /dev/null +++ b/lib/ts_fsm.c @@ -0,0 +1,338 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * lib/ts_fsm.c A naive finite state machine text search approach + * + * Authors: Thomas Graf + * + * ========================================================================== + * + * A finite state machine consists of n states (struct ts_fsm_token) + * representing the pattern as a finite automaton. The data is read + * sequentially on an octet basis. Every state token specifies the number + * of recurrences and the type of value accepted which can be either a + * specific character or ctype based set of characters. The available + * type of recurrences include 1, (0|1), [0 n], and [1 n]. + * + * The algorithm differs between strict/non-strict mode specifying + * whether the pattern has to start at the first octet. Strict mode + * is enabled by default and can be disabled by inserting + * TS_FSM_HEAD_IGNORE as the first token in the chain. + * + * The runtime performance of the algorithm should be around O(n), + * however while in strict mode the average runtime can be better. + */ + +#include +#include +#include +#include +#include +#include + +struct ts_fsm +{ + unsigned int ntokens; + struct ts_fsm_token tokens[]; +}; + +/* other values derived from ctype.h */ +#define _A 0x100 /* ascii */ +#define _W 0x200 /* wildcard */ + +/* Map to _ctype flags and some magic numbers */ +static const u16 token_map[TS_FSM_TYPE_MAX+1] = { + [TS_FSM_SPECIFIC] = 0, + [TS_FSM_WILDCARD] = _W, + [TS_FSM_CNTRL] = _C, + [TS_FSM_LOWER] = _L, + [TS_FSM_UPPER] = _U, + [TS_FSM_PUNCT] = _P, + [TS_FSM_SPACE] = _S, + [TS_FSM_DIGIT] = _D, + [TS_FSM_XDIGIT] = _D | _X, + [TS_FSM_ALPHA] = _U | _L, + [TS_FSM_ALNUM] = _U | _L | _D, + [TS_FSM_PRINT] = _P | _U | _L | _D | _SP, + [TS_FSM_GRAPH] = _P | _U | _L | _D, + [TS_FSM_ASCII] = _A, +}; + +static const u16 token_lookup_tbl[256] = { +_W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 0- 3 */ +_W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 4- 7 */ +_W|_A|_C, _W|_A|_C|_S, _W|_A|_C|_S, _W|_A|_C|_S, /* 8- 11 */ +_W|_A|_C|_S, _W|_A|_C|_S, _W|_A|_C, _W|_A|_C, /* 12- 15 */ +_W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 16- 19 */ +_W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 20- 23 */ +_W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 24- 27 */ +_W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 28- 31 */ +_W|_A|_S|_SP, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 32- 35 */ +_W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 36- 39 */ +_W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 40- 43 */ +_W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 44- 47 */ +_W|_A|_D, _W|_A|_D, _W|_A|_D, _W|_A|_D, /* 48- 51 */ +_W|_A|_D, _W|_A|_D, _W|_A|_D, _W|_A|_D, /* 52- 55 */ +_W|_A|_D, _W|_A|_D, _W|_A|_P, _W|_A|_P, /* 56- 59 */ +_W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 60- 63 */ +_W|_A|_P, _W|_A|_U|_X, _W|_A|_U|_X, _W|_A|_U|_X, /* 64- 67 */ +_W|_A|_U|_X, _W|_A|_U|_X, _W|_A|_U|_X, _W|_A|_U, /* 68- 71 */ +_W|_A|_U, _W|_A|_U, _W|_A|_U, _W|_A|_U, /* 72- 75 */ +_W|_A|_U, _W|_A|_U, _W|_A|_U, _W|_A|_U, /* 76- 79 */ +_W|_A|_U, _W|_A|_U, _W|_A|_U, _W|_A|_U, /* 80- 83 */ +_W|_A|_U, _W|_A|_U, _W|_A|_U, _W|_A|_U, /* 84- 87 */ +_W|_A|_U, _W|_A|_U, _W|_A|_U, _W|_A|_P, /* 88- 91 */ +_W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 92- 95 */ +_W|_A|_P, _W|_A|_L|_X, _W|_A|_L|_X, _W|_A|_L|_X, /* 96- 99 */ +_W|_A|_L|_X, _W|_A|_L|_X, _W|_A|_L|_X, _W|_A|_L, /* 100-103 */ +_W|_A|_L, _W|_A|_L, _W|_A|_L, _W|_A|_L, /* 104-107 */ +_W|_A|_L, _W|_A|_L, _W|_A|_L, _W|_A|_L, /* 108-111 */ +_W|_A|_L, _W|_A|_L, _W|_A|_L, _W|_A|_L, /* 112-115 */ +_W|_A|_L, _W|_A|_L, _W|_A|_L, _W|_A|_L, /* 116-119 */ +_W|_A|_L, _W|_A|_L, _W|_A|_L, _W|_A|_P, /* 120-123 */ +_W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_C, /* 124-127 */ +_W, _W, _W, _W, /* 128-131 */ +_W, _W, _W, _W, /* 132-135 */ +_W, _W, _W, _W, /* 136-139 */ +_W, _W, _W, _W, /* 140-143 */ +_W, _W, _W, _W, /* 144-147 */ +_W, _W, _W, _W, /* 148-151 */ +_W, _W, _W, _W, /* 152-155 */ +_W, _W, _W, _W, /* 156-159 */ +_W|_S|_SP, _W|_P, _W|_P, _W|_P, /* 160-163 */ +_W|_P, _W|_P, _W|_P, _W|_P, /* 164-167 */ +_W|_P, _W|_P, _W|_P, _W|_P, /* 168-171 */ +_W|_P, _W|_P, _W|_P, _W|_P, /* 172-175 */ +_W|_P, _W|_P, _W|_P, _W|_P, /* 176-179 */ +_W|_P, _W|_P, _W|_P, _W|_P, /* 180-183 */ +_W|_P, _W|_P, _W|_P, _W|_P, /* 184-187 */ +_W|_P, _W|_P, _W|_P, _W|_P, /* 188-191 */ +_W|_U, _W|_U, _W|_U, _W|_U, /* 192-195 */ +_W|_U, _W|_U, _W|_U, _W|_U, /* 196-199 */ +_W|_U, _W|_U, _W|_U, _W|_U, /* 200-203 */ +_W|_U, _W|_U, _W|_U, _W|_U, /* 204-207 */ +_W|_U, _W|_U, _W|_U, _W|_U, /* 208-211 */ +_W|_U, _W|_U, _W|_U, _W|_P, /* 212-215 */ +_W|_U, _W|_U, _W|_U, _W|_U, /* 216-219 */ +_W|_U, _W|_U, _W|_U, _W|_L, /* 220-223 */ +_W|_L, _W|_L, _W|_L, _W|_L, /* 224-227 */ +_W|_L, _W|_L, _W|_L, _W|_L, /* 228-231 */ +_W|_L, _W|_L, _W|_L, _W|_L, /* 232-235 */ +_W|_L, _W|_L, _W|_L, _W|_L, /* 236-239 */ +_W|_L, _W|_L, _W|_L, _W|_L, /* 240-243 */ +_W|_L, _W|_L, _W|_L, _W|_P, /* 244-247 */ +_W|_L, _W|_L, _W|_L, _W|_L, /* 248-251 */ +_W|_L, _W|_L, _W|_L, _W|_L}; /* 252-255 */ + +static inline int match_token(struct ts_fsm_token *t, u8 d) +{ + if (t->type) + return (token_lookup_tbl[d] & t->type) != 0; + else + return t->value == d; +} + +static unsigned int fsm_find(struct ts_config *conf, struct ts_state *state) +{ + struct ts_fsm *fsm = ts_config_priv(conf); + struct ts_fsm_token *cur = NULL, *next; + unsigned int match_start, block_idx = 0, tok_idx; + unsigned block_len = 0, strict, consumed = state->offset; + const u8 *data; + +#define GET_NEXT_BLOCK() \ +({ consumed += block_idx; \ + block_idx = 0; \ + block_len = conf->get_next_block(consumed, &data, conf, state); }) + +#define TOKEN_MISMATCH() \ + do { \ + if (strict) \ + goto no_match; \ + block_idx++; \ + goto startover; \ + } while(0) + +#define end_of_data() unlikely(block_idx >= block_len && !GET_NEXT_BLOCK()) + + if (end_of_data()) + goto no_match; + + strict = fsm->tokens[0].recur != TS_FSM_HEAD_IGNORE; + +startover: + match_start = consumed + block_idx; + + for (tok_idx = 0; tok_idx < fsm->ntokens; tok_idx++) { + cur = &fsm->tokens[tok_idx]; + + if (likely(tok_idx < (fsm->ntokens - 1))) + next = &fsm->tokens[tok_idx + 1]; + else + next = NULL; + + switch (cur->recur) { + case TS_FSM_SINGLE: + if (end_of_data()) + goto no_match; + + if (!match_token(cur, data[block_idx])) + TOKEN_MISMATCH(); + break; + + case TS_FSM_PERHAPS: + if (end_of_data() || + !match_token(cur, data[block_idx])) + continue; + break; + + case TS_FSM_MULTI: + if (end_of_data()) + goto no_match; + + if (!match_token(cur, data[block_idx])) + TOKEN_MISMATCH(); + + block_idx++; + fallthrough; + + case TS_FSM_ANY: + if (next == NULL) + goto found_match; + + if (end_of_data()) + continue; + + while (!match_token(next, data[block_idx])) { + if (!match_token(cur, data[block_idx])) + TOKEN_MISMATCH(); + block_idx++; + if (end_of_data()) + goto no_match; + } + continue; + + /* + * Optimization: Prefer small local loop over jumping + * back and forth until garbage at head is munched. + */ + case TS_FSM_HEAD_IGNORE: + if (end_of_data()) + continue; + + while (!match_token(next, data[block_idx])) { + /* + * Special case, don't start over upon + * a mismatch, give the user the + * chance to specify the type of data + * allowed to be ignored. + */ + if (!match_token(cur, data[block_idx])) + goto no_match; + + block_idx++; + if (end_of_data()) + goto no_match; + } + + match_start = consumed + block_idx; + continue; + } + + block_idx++; + } + + if (end_of_data()) + goto found_match; + +no_match: + return UINT_MAX; + +found_match: + state->offset = consumed + block_idx; + return match_start; +} + +static struct ts_config *fsm_init(const void *pattern, unsigned int len, + gfp_t gfp_mask, int flags) +{ + int i, err = -EINVAL; + struct ts_config *conf; + struct ts_fsm *fsm; + struct ts_fsm_token *tokens = (struct ts_fsm_token *) pattern; + unsigned int ntokens = len / sizeof(*tokens); + size_t priv_size = sizeof(*fsm) + len; + + if (len % sizeof(struct ts_fsm_token) || ntokens < 1) + goto errout; + + if (flags & TS_IGNORECASE) + goto errout; + + for (i = 0; i < ntokens; i++) { + struct ts_fsm_token *t = &tokens[i]; + + if (t->type > TS_FSM_TYPE_MAX || t->recur > TS_FSM_RECUR_MAX) + goto errout; + + if (t->recur == TS_FSM_HEAD_IGNORE && + (i != 0 || i == (ntokens - 1))) + goto errout; + } + + conf = alloc_ts_config(priv_size, gfp_mask); + if (IS_ERR(conf)) + return conf; + + conf->flags = flags; + fsm = ts_config_priv(conf); + fsm->ntokens = ntokens; + memcpy(fsm->tokens, pattern, len); + + for (i = 0; i < fsm->ntokens; i++) { + struct ts_fsm_token *t = &fsm->tokens[i]; + t->type = token_map[t->type]; + } + + return conf; + +errout: + return ERR_PTR(err); +} + +static void *fsm_get_pattern(struct ts_config *conf) +{ + struct ts_fsm *fsm = ts_config_priv(conf); + return fsm->tokens; +} + +static unsigned int fsm_get_pattern_len(struct ts_config *conf) +{ + struct ts_fsm *fsm = ts_config_priv(conf); + return fsm->ntokens * sizeof(struct ts_fsm_token); +} + +static struct ts_ops fsm_ops = { + .name = "fsm", + .find = fsm_find, + .init = fsm_init, + .get_pattern = fsm_get_pattern, + .get_pattern_len = fsm_get_pattern_len, + .owner = THIS_MODULE, + .list = LIST_HEAD_INIT(fsm_ops.list) +}; + +static int __init init_fsm(void) +{ + return textsearch_register(&fsm_ops); +} + +static void __exit exit_fsm(void) +{ + textsearch_unregister(&fsm_ops); +} + +MODULE_DESCRIPTION("naive finite state machine text search"); +MODULE_LICENSE("GPL"); + +module_init(init_fsm); +module_exit(exit_fsm); -- cgit v1.3.1