Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

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

1 files changed, 291 insertions, 0 deletions

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 <ebiggers@google.com>
+
+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}')