From 4617721c502b2ddaa4e324e86da4997edf738fa5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 2 Sep 2026 09:55:01 -0400 Subject: ftrace: Synchronize the initialization of ftrace_ops There's some internal state that ftrace_ops needs to have set, but since it can be declared outside of the ftrace.c code, it calls ftrace_ops_init() on the ops in every global function. The issue is that if two tasks call it on the same ops at the same time it is possible to have the initialization of one corrupt the initialization of the other call. Create a ops_mutex to use to synchronize every initialization of the ftrace_ops. The mutex is taken within checking the ftrace_ops flag that states it was initializied but the flag is checked again after the mutex has been taken. Checking first outside the mutex allows it to shortcut having to take the mutex. But then the check needs to be done again after the mute is taken in case of races. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock") Reported-by: sashiko-bot@kernel.org Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/ Signed-off-by: Steven Rostedt --- lib/crc/crc8.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 87 insertions(+) create mode 100644 lib/crc/crc8.c (limited to 'lib/crc/crc8.c') diff --git a/lib/crc/crc8.c b/lib/crc/crc8.c new file mode 100644 index 000000000..329c52158 --- /dev/null +++ b/lib/crc/crc8.c @@ -0,0 +1,87 @@ +/* + * Copyright (c) 2011 Broadcom Corporation + * + * Permission to use, copy, modify, and/or distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY + * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION + * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN + * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include +#include +#include +#include + +/** + * crc8_populate_msb - fill crc table for given polynomial in reverse bit order. + * + * @table: table to be filled. + * @polynomial: polynomial for which table is to be filled. + */ +void crc8_populate_msb(u8 table[CRC8_TABLE_SIZE], u8 polynomial) +{ + int i, j; + const u8 msbit = 0x80; + u8 t = msbit; + + table[0] = 0; + + for (i = 1; i < CRC8_TABLE_SIZE; i *= 2) { + t = (t << 1) ^ (t & msbit ? polynomial : 0); + for (j = 0; j < i; j++) + table[i+j] = table[j] ^ t; + } +} +EXPORT_SYMBOL(crc8_populate_msb); + +/** + * crc8_populate_lsb - fill crc table for given polynomial in regular bit order. + * + * @table: table to be filled. + * @polynomial: polynomial for which table is to be filled. + */ +void crc8_populate_lsb(u8 table[CRC8_TABLE_SIZE], u8 polynomial) +{ + int i, j; + u8 t = 1; + + table[0] = 0; + + for (i = (CRC8_TABLE_SIZE >> 1); i; i >>= 1) { + t = (t >> 1) ^ (t & 1 ? polynomial : 0); + for (j = 0; j < CRC8_TABLE_SIZE; j += 2*i) + table[i+j] = table[j] ^ t; + } +} +EXPORT_SYMBOL(crc8_populate_lsb); + +/** + * crc8 - calculate a crc8 over the given input data. + * + * @table: crc table used for calculation. + * @pdata: pointer to data buffer. + * @nbytes: number of bytes in data buffer. + * @crc: previous returned crc8 value. + */ +u8 crc8(const u8 table[CRC8_TABLE_SIZE], const u8 *pdata, size_t nbytes, u8 crc) +{ + /* loop over the buffer data */ + while (nbytes-- > 0) + crc = table[(crc ^ *pdata++) & 0xff]; + + return crc; +} +EXPORT_SYMBOL(crc8); + +MODULE_DESCRIPTION("CRC8 (by Williams, Ross N.) function"); +MODULE_AUTHOR("Broadcom Corporation"); +MODULE_LICENSE("Dual BSD/GPL"); -- cgit v1.3.1