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/crc7.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 73 insertions(+) create mode 100644 lib/crc/crc7.c (limited to 'lib/crc/crc7.c') diff --git a/lib/crc/crc7.c b/lib/crc/crc7.c new file mode 100644 index 000000000..46b95d7ac --- /dev/null +++ b/lib/crc/crc7.c @@ -0,0 +1,73 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * crc7.c + */ + +#include +#include +#include +#include + +/* + * Table for CRC-7 (polynomial x^7 + x^3 + 1). + * This is a big-endian CRC (msbit is highest power of x), + * aligned so the msbit of the byte is the x^6 coefficient + * and the lsbit is not used. + */ +static const u8 crc7_be_syndrome_table[256] = { + 0x00, 0x12, 0x24, 0x36, 0x48, 0x5a, 0x6c, 0x7e, + 0x90, 0x82, 0xb4, 0xa6, 0xd8, 0xca, 0xfc, 0xee, + 0x32, 0x20, 0x16, 0x04, 0x7a, 0x68, 0x5e, 0x4c, + 0xa2, 0xb0, 0x86, 0x94, 0xea, 0xf8, 0xce, 0xdc, + 0x64, 0x76, 0x40, 0x52, 0x2c, 0x3e, 0x08, 0x1a, + 0xf4, 0xe6, 0xd0, 0xc2, 0xbc, 0xae, 0x98, 0x8a, + 0x56, 0x44, 0x72, 0x60, 0x1e, 0x0c, 0x3a, 0x28, + 0xc6, 0xd4, 0xe2, 0xf0, 0x8e, 0x9c, 0xaa, 0xb8, + 0xc8, 0xda, 0xec, 0xfe, 0x80, 0x92, 0xa4, 0xb6, + 0x58, 0x4a, 0x7c, 0x6e, 0x10, 0x02, 0x34, 0x26, + 0xfa, 0xe8, 0xde, 0xcc, 0xb2, 0xa0, 0x96, 0x84, + 0x6a, 0x78, 0x4e, 0x5c, 0x22, 0x30, 0x06, 0x14, + 0xac, 0xbe, 0x88, 0x9a, 0xe4, 0xf6, 0xc0, 0xd2, + 0x3c, 0x2e, 0x18, 0x0a, 0x74, 0x66, 0x50, 0x42, + 0x9e, 0x8c, 0xba, 0xa8, 0xd6, 0xc4, 0xf2, 0xe0, + 0x0e, 0x1c, 0x2a, 0x38, 0x46, 0x54, 0x62, 0x70, + 0x82, 0x90, 0xa6, 0xb4, 0xca, 0xd8, 0xee, 0xfc, + 0x12, 0x00, 0x36, 0x24, 0x5a, 0x48, 0x7e, 0x6c, + 0xb0, 0xa2, 0x94, 0x86, 0xf8, 0xea, 0xdc, 0xce, + 0x20, 0x32, 0x04, 0x16, 0x68, 0x7a, 0x4c, 0x5e, + 0xe6, 0xf4, 0xc2, 0xd0, 0xae, 0xbc, 0x8a, 0x98, + 0x76, 0x64, 0x52, 0x40, 0x3e, 0x2c, 0x1a, 0x08, + 0xd4, 0xc6, 0xf0, 0xe2, 0x9c, 0x8e, 0xb8, 0xaa, + 0x44, 0x56, 0x60, 0x72, 0x0c, 0x1e, 0x28, 0x3a, + 0x4a, 0x58, 0x6e, 0x7c, 0x02, 0x10, 0x26, 0x34, + 0xda, 0xc8, 0xfe, 0xec, 0x92, 0x80, 0xb6, 0xa4, + 0x78, 0x6a, 0x5c, 0x4e, 0x30, 0x22, 0x14, 0x06, + 0xe8, 0xfa, 0xcc, 0xde, 0xa0, 0xb2, 0x84, 0x96, + 0x2e, 0x3c, 0x0a, 0x18, 0x66, 0x74, 0x42, 0x50, + 0xbe, 0xac, 0x9a, 0x88, 0xf6, 0xe4, 0xd2, 0xc0, + 0x1c, 0x0e, 0x38, 0x2a, 0x54, 0x46, 0x70, 0x62, + 0x8c, 0x9e, 0xa8, 0xba, 0xc4, 0xd6, 0xe0, 0xf2 +}; + +/** + * crc7_be - update the CRC7 for the data buffer + * @crc: previous CRC7 value + * @buffer: data pointer + * @len: number of bytes in the buffer + * Context: any + * + * Returns the updated CRC7 value. + * The CRC7 is left-aligned in the byte (the lsbit is always 0), as that + * makes the computation easier, and all callers want it in that form. + * + */ +u8 crc7_be(u8 crc, const u8 *buffer, size_t len) +{ + while (len--) + crc = crc7_be_syndrome_table[crc ^ *buffer++]; + return crc; +} +EXPORT_SYMBOL(crc7_be); + +MODULE_DESCRIPTION("CRC7 calculations"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1