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linux-next/lib/ts_fsm.c
Gustavo A. R. Silva 842ae1f52b lib/ts_fsm.c: replace zero-length array with flexible-array member 
The current codebase makes use of the zero-length array language extension
to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning in
case the flexible array does not occur last in the structure, which will
help us prevent some kind of undefined behavior bugs from being
inadvertenly introduced[3] to the codebase from now on.

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 7649773293 ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20200211205813.GA25602@embeddedor
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-04-07 10:43:43 -07:00

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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* lib/ts_fsm.c A naive finite state machine text search approach
*
* Authors: Thomas Graf <tgraf@suug.ch>
*
* ==========================================================================
*
* 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 <linux/module.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/ctype.h>
#include <linux/textsearch.h>
#include <linux/textsearch_fsm.h>
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++;
/* fall through */
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_LICENSE("GPL");
module_init(init_fsm);
module_exit(exit_fsm);
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