From 034dd340b08be1f2f0477ad16131d609f9dbd53c Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sun, 30 Aug 2026 09:22:00 -0700 Subject: Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing fixes from Steven Rostedt: - Fix error output of boot instance creation failure Currently if a boot instance creation fails, instead of printing out the name of the instance that failed, it prints "(null)". That is because it prints "cur_str" that had already been processed by strsep(). Print the saved name instead. While at it, print the error code of the failure. - Fix use-after-free for same named historgrams Histograms can be named so that they can be used in multiple events. But if the named histogram has a variable attached, the second event that uses the named histogram which duplicates it and needs to free the original after duplication leaves the old variable in place and still visible. If another histogram uses than variable, it will use the stale one which will try to reference the freed duplicate histogram and crash the kernel. Free the duplicate variables along with the duplicated histogram data. - Check return value of kthread_run() in event self test The events self tests uses a kthread for testing but does not check if it succeeded in creating a kthread. If the kthread creation were to fail, the code will still try to call kthread_stop() on the error returned. - Fix race between reading trace_pipe and updating subbuffer size If a user is reading the trace_pipe file at the same time they update the ring buffer sub-buffer size, can cause the trace_pipe read to read stale data. Add trace_access_lock() around updating the ring buffer sub-buffer size. - Fix eventfs_inode on failure path in creation of the events directory In the creation of the "events" directory, if after allocating the eventfs_inode a failure is detected, it calls cleanup_ei() which calls free_ei(). The free_ei() will test if eventfs_inode being freed has no children. It is a bug if it does. But on the failure case of the creation of the "events" directory, the children lists have not yet been initialized and the free will trigger a warning because list_empty() on an uninitialized list returns false. Move the initialization into init_ei() where it makes more sense and makes sure that a created eventfs_inode has its lists initialized upon creation. - Check return value of kthread_run() in ftrace direct sample code The sample code that shows how to use the ftrace direct calls does not test the return of kthread_run() to see if it succeeds. Return a failure if the kthread_run() doesn't succeed. - Clear user events state on fork in case of alloc failure On fork, the child gets a pointer to the parent's user events state. It makes a copy of it then updates the child's pointer to it. But if the allocation fails, the duplication function leaves the child with a pointer to its parent's descriptor. When the child cleans up its data, it will free the parent's descriptor while the parent is still using it. In the duplication function, set the child's user_event_mm to NULL before testing if the allocation succeeded, and when it exits it will not free the parent's descriptor. - Fix retry exhaustion in simple ring buffer reader swap simple_ring_buffer_swap_reader_page() starts with retry set to 8 and post-decrements it only after a failed link replacement. On the final attempt, a successful replacement leaves retry at zero, while a failed replacement leaves it at -1. But the check for success expects the retry value to be non-zero and exits with an error on zero. This is the opposite result. Fix it. - Fail nicely when the remote swap_reader_page() returns an error Currently, if the swap_reader_page() of a remote buffer fails, it triggers a WARN_ON_ONCE() and continues normally. Instead, have it exit with an error and a pr_warn() print instead of a full WARNING. * tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: ring-buffer: Stop remote reader update when page swap fails tracing: Fix retry exhaustion in simple ring buffer reader swap tracing/user_events: Clear copied tracing state before fork duplication samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify eventfs: Initialize ei->children and ei->list in init_ei() tracing: Fix use-after-free in trace_pipe read on sub-buffer order change tracing: Fix crash passing ERR_PTR to kthread_stop() tracing: Fix use-after-free with same-name named triggers tracing: Fix logged instance name on creation failure --- scripts/gen-crc-consts.py | 291 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 291 insertions(+) create mode 100755 scripts/gen-crc-consts.py (limited to 'scripts/gen-crc-consts.py') diff --git a/scripts/gen-crc-consts.py b/scripts/gen-crc-consts.py new file mode 100755 index 000000000..f9b44fc3a --- /dev/null +++ b/scripts/gen-crc-consts.py @@ -0,0 +1,291 @@ +#!/usr/bin/env python3 +# SPDX-License-Identifier: GPL-2.0-or-later +# +# Script that generates constants for computing the given CRC variant(s). +# +# Copyright 2025 Google LLC +# +# Author: Eric Biggers + +import sys + +# XOR (add) an iterable of polynomials. +def xor(iterable): + res = 0 + for val in iterable: + res ^= val + return res + +# Multiply two polynomials. +def clmul(a, b): + return xor(a << i for i in range(b.bit_length()) if (b & (1 << i)) != 0) + +# Polynomial division floor(a / b). +def div(a, b): + q = 0 + while a.bit_length() >= b.bit_length(): + q ^= 1 << (a.bit_length() - b.bit_length()) + a ^= b << (a.bit_length() - b.bit_length()) + return q + +# Reduce the polynomial 'a' modulo the polynomial 'b'. +def reduce(a, b): + return a ^ clmul(div(a, b), b) + +# Reflect the bits of a polynomial. +def bitreflect(poly, num_bits): + assert poly.bit_length() <= num_bits + return xor(((poly >> i) & 1) << (num_bits - 1 - i) for i in range(num_bits)) + +# Format a polynomial as hex. Bit-reflect it if the CRC is lsb-first. +def fmt_poly(variant, poly, num_bits): + if variant.lsb: + poly = bitreflect(poly, num_bits) + return f'0x{poly:0{2*num_bits//8}x}' + +# Print a pair of 64-bit polynomial multipliers. They are always passed in the +# order [HI64_TERMS, LO64_TERMS] but will be printed in the appropriate order. +def print_mult_pair(variant, mults): + mults = list(mults if variant.lsb else reversed(mults)) + terms = ['HI64_TERMS', 'LO64_TERMS'] if variant.lsb else ['LO64_TERMS', 'HI64_TERMS'] + for i in range(2): + print(f'\t\t{fmt_poly(variant, mults[i]["val"], 64)},\t/* {terms[i]}: {mults[i]["desc"]} */') + +# Pretty-print a polynomial. +def pprint_poly(prefix, poly): + terms = [f'x^{i}' for i in reversed(range(poly.bit_length())) + if (poly & (1 << i)) != 0] + j = 0 + while j < len(terms): + s = prefix + terms[j] + (' +' if j < len(terms) - 1 else '') + j += 1 + while j < len(terms) and len(s) < 73: + s += ' ' + terms[j] + (' +' if j < len(terms) - 1 else '') + j += 1 + print(s) + prefix = ' * ' + (' ' * (len(prefix) - 3)) + +# Print a comment describing constants generated for the given CRC variant. +def print_header(variant, what): + print('/*') + s = f'{"least" if variant.lsb else "most"}-significant-bit-first CRC-{variant.bits}' + print(f' * {what} generated for {s} using') + pprint_poly(' * G(x) = ', variant.G) + print(' */') + +class CrcVariant: + def __init__(self, bits, generator_poly, bit_order): + self.bits = bits + if bit_order not in ['lsb', 'msb']: + raise ValueError('Invalid value for bit_order') + self.lsb = bit_order == 'lsb' + self.name = f'crc{bits}_{bit_order}_0x{generator_poly:0{(2*bits+7)//8}x}' + if self.lsb: + generator_poly = bitreflect(generator_poly, bits) + self.G = generator_poly ^ (1 << bits) + +# Generate tables for CRC computation using the "slice-by-N" method. +# N=1 corresponds to the traditional byte-at-a-time table. +def gen_slicebyN_tables(variants, n): + for v in variants: + print('') + print_header(v, f'Slice-by-{n} CRC table') + print(f'static const u{v.bits} __maybe_unused {v.name}_table[{256*n}] = {{') + s = '' + for i in range(256 * n): + # The i'th table entry is the CRC of the message consisting of byte + # i % 256 followed by i // 256 zero bytes. + poly = (bitreflect(i % 256, 8) if v.lsb else i % 256) << (v.bits + 8*(i//256)) + next_entry = fmt_poly(v, reduce(poly, v.G), v.bits) + ',' + if len(s + next_entry) > 71: + print(f'\t{s}') + s = '' + s += (' ' if s else '') + next_entry + if s: + print(f'\t{s}') + print('};') + +def print_riscv_const(v, bits_per_long, name, val, desc): + print(f'\t.{name} = {fmt_poly(v, val, bits_per_long)}, /* {desc} */') + +def do_gen_riscv_clmul_consts(v, bits_per_long): + (G, n, lsb) = (v.G, v.bits, v.lsb) + + pow_of_x = 3 * bits_per_long - (1 if lsb else 0) + print_riscv_const(v, bits_per_long, 'fold_across_2_longs_const_hi', + reduce(1 << pow_of_x, G), f'x^{pow_of_x} mod G') + pow_of_x = 2 * bits_per_long - (1 if lsb else 0) + print_riscv_const(v, bits_per_long, 'fold_across_2_longs_const_lo', + reduce(1 << pow_of_x, G), f'x^{pow_of_x} mod G') + + pow_of_x = bits_per_long - 1 + n + print_riscv_const(v, bits_per_long, 'barrett_reduction_const_1', + div(1 << pow_of_x, G), f'floor(x^{pow_of_x} / G)') + + val = G - (1 << n) + desc = f'G - x^{n}' + if lsb: + val <<= bits_per_long - n + desc = f'({desc}) * x^{bits_per_long - n}' + print_riscv_const(v, bits_per_long, 'barrett_reduction_const_2', val, desc) + +def gen_riscv_clmul_consts(variants): + print('') + print('struct crc_clmul_consts {'); + print('\tunsigned long fold_across_2_longs_const_hi;'); + print('\tunsigned long fold_across_2_longs_const_lo;'); + print('\tunsigned long barrett_reduction_const_1;'); + print('\tunsigned long barrett_reduction_const_2;'); + print('};'); + for v in variants: + print(''); + if v.bits > 32: + print_header(v, 'Constants') + print('#ifdef CONFIG_64BIT') + print(f'static const struct crc_clmul_consts {v.name}_consts __maybe_unused = {{') + do_gen_riscv_clmul_consts(v, 64) + print('};') + print('#endif') + else: + print_header(v, 'Constants') + print(f'static const struct crc_clmul_consts {v.name}_consts __maybe_unused = {{') + print('#ifdef CONFIG_64BIT') + do_gen_riscv_clmul_consts(v, 64) + print('#else') + do_gen_riscv_clmul_consts(v, 32) + print('#endif') + print('};') + +# Generate constants for carryless multiplication based CRC computation. +def gen_x86_pclmul_consts(variants): + # These are the distances, in bits, to generate folding constants for. + FOLD_DISTANCES = [2048, 1024, 512, 256, 128] + + for v in variants: + (G, n, lsb) = (v.G, v.bits, v.lsb) + print('') + print_header(v, 'CRC folding constants') + print('static const struct {') + if not lsb: + print('\tu8 bswap_mask[16];') + for i in FOLD_DISTANCES: + print(f'\tu64 fold_across_{i}_bits_consts[2];') + print('\tu8 shuf_table[48];') + print('\tu64 barrett_reduction_consts[2];') + print(f'}} {v.name}_consts ____cacheline_aligned __maybe_unused = {{') + + # Byte-reflection mask, needed for msb-first CRCs + if not lsb: + print('\t.bswap_mask = {' + ', '.join(str(i) for i in reversed(range(16))) + '},') + + # Fold constants for all distances down to 128 bits + for i in FOLD_DISTANCES: + print(f'\t.fold_across_{i}_bits_consts = {{') + # Given 64x64 => 128 bit carryless multiplication instructions, two + # 64-bit fold constants are needed per "fold distance" i: one for + # HI64_TERMS that is basically x^(i+64) mod G and one for LO64_TERMS + # that is basically x^i mod G. The exact values however undergo a + # couple adjustments, described below. + mults = [] + for j in [64, 0]: + pow_of_x = i + j + if lsb: + # Each 64x64 => 128 bit carryless multiplication instruction + # actually generates a 127-bit product in physical bits 0 + # through 126, which in the lsb-first case represent the + # coefficients of x^1 through x^127, not x^0 through x^126. + # Thus in the lsb-first case, each such instruction + # implicitly adds an extra factor of x. The below removes a + # factor of x from each constant to compensate for this. + # For n < 64 the x could be removed from either the reduced + # part or unreduced part, but for n == 64 the reduced part + # is the only option. Just always use the reduced part. + pow_of_x -= 1 + # Make a factor of x^(64-n) be applied unreduced rather than + # reduced, to cause the product to use only the x^(64-n) and + # higher terms and always be zero in the lower terms. Usually + # this makes no difference as it does not affect the product's + # congruence class mod G and the constant remains 64-bit, but + # part of the final reduction from 128 bits does rely on this + # property when it reuses one of the constants. + pow_of_x -= 64 - n + mults.append({ 'val': reduce(1 << pow_of_x, G) << (64 - n), + 'desc': f'(x^{pow_of_x} mod G) * x^{64-n}' }) + print_mult_pair(v, mults) + print('\t},') + + # Shuffle table for handling 1..15 bytes at end + print('\t.shuf_table = {') + print('\t\t' + (16*'-1, ').rstrip()) + print('\t\t' + ''.join(f'{i:2}, ' for i in range(16)).rstrip()) + print('\t\t' + (16*'-1, ').rstrip()) + print('\t},') + + # Barrett reduction constants for reducing 128 bits to the final CRC + print('\t.barrett_reduction_consts = {') + mults = [] + + val = div(1 << (63+n), G) + desc = f'floor(x^{63+n} / G)' + if not lsb: + val = (val << 1) - (1 << 64) + desc = f'({desc} * x) - x^64' + mults.append({ 'val': val, 'desc': desc }) + + val = G - (1 << n) + desc = f'G - x^{n}' + if lsb and n == 64: + assert (val & 1) != 0 # The x^0 term should always be nonzero. + val >>= 1 + desc = f'({desc} - x^0) / x' + else: + pow_of_x = 64 - n - (1 if lsb else 0) + val <<= pow_of_x + desc = f'({desc}) * x^{pow_of_x}' + mults.append({ 'val': val, 'desc': desc }) + + print_mult_pair(v, mults) + print('\t},') + + print('};') + +def parse_crc_variants(vars_string): + variants = [] + for var_string in vars_string.split(','): + bits, bit_order, generator_poly = var_string.split('_') + assert bits.startswith('crc') + bits = int(bits.removeprefix('crc')) + assert generator_poly.startswith('0x') + generator_poly = generator_poly.removeprefix('0x') + assert len(generator_poly) % 2 == 0 + generator_poly = int(generator_poly, 16) + variants.append(CrcVariant(bits, generator_poly, bit_order)) + return variants + +if len(sys.argv) != 3: + sys.stderr.write(f'Usage: {sys.argv[0]} CONSTS_TYPE[,CONSTS_TYPE]... CRC_VARIANT[,CRC_VARIANT]...\n') + sys.stderr.write(' CONSTS_TYPE can be sliceby[1-8], riscv_clmul, or x86_pclmul\n') + sys.stderr.write(' CRC_VARIANT is crc${num_bits}_${bit_order}_${generator_poly_as_hex}\n') + sys.stderr.write(' E.g. crc16_msb_0x8bb7 or crc32_lsb_0xedb88320\n') + sys.stderr.write(' Polynomial must use the given bit_order and exclude x^{num_bits}\n') + sys.exit(1) + +print('/* SPDX-License-Identifier: GPL-2.0-or-later */') +print('/*') +print(' * CRC constants generated by:') +print(' *') +print(f' *\t{sys.argv[0]} {" ".join(sys.argv[1:])}') +print(' *') +print(' * Do not edit manually.') +print(' */') +consts_types = sys.argv[1].split(',') +variants = parse_crc_variants(sys.argv[2]) +for consts_type in consts_types: + if consts_type.startswith('sliceby'): + gen_slicebyN_tables(variants, int(consts_type.removeprefix('sliceby'))) + elif consts_type == 'riscv_clmul': + gen_riscv_clmul_consts(variants) + elif consts_type == 'x86_pclmul': + gen_x86_pclmul_consts(variants) + else: + raise ValueError(f'Unknown consts_type: {consts_type}') -- cgit v1.3.1