[PATCH 2/2] lib/crc32: remove other generic implementations

Eric Biggers
2025-01-23T21:33:07Z

From: Eric Biggers <ebiggers@google.com>

Now that we've standardized on the byte-by-byte implementation of CRC32
as the only generic implementation (see previous commit for the
rationale), remove the code for the other implementations.

Tested with crc_kunit.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
lib/Kconfig | 4 -
lib/crc32.c | 225 ++-----------------------------------------
lib/crc32defs.h | 59 ------------
lib/gen_crc32table.c | 113 ++++++----------------
4 files changed, 40 insertions(+), 361 deletions(-)
delete mode 100644 lib/crc32defs.h

diff --git a/lib/Kconfig b/lib/Kconfig
index e08b26e8e03f..dccb61b7d698 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -187,11 +187,10 @@ config CRC_ITU_T

config CRC32
tristate "CRC32/CRC32c functions"
default y
select BITREVERSE
- select CRC32_SARWATE
help
This option is provided for the case where no in-kernel-tree
modules require CRC32/CRC32c functions, but a module built outside
the kernel tree does. Such modules that use library CRC32/CRC32c
functions require M here.
@@ -201,13 +200,10 @@ config ARCH_HAS_CRC32

config CRC32_ARCH
tristate
default CRC32 if ARCH_HAS_CRC32 && CRC_OPTIMIZATIONS

-config CRC32_SARWATE
- bool
-
config CRC64
tristate "CRC64 functions"
help
This option is provided for the case where no in-kernel-tree
modules require CRC64 functions, but a module built outside
diff --git a/lib/crc32.c b/lib/crc32.c
index 47151624332e..ede6131f66fc 100644
--- a/lib/crc32.c
+++ b/lib/crc32.c
@@ -28,182 +28,31 @@

#include <linux/crc32.h>
#include <linux/crc32poly.h>
#include <linux/module.h>
#include <linux/types.h>
-#include <linux/sched.h>
-#include "crc32defs.h"
-
-#if CRC_LE_BITS > 8
-# define tole(x) ((__force u32) cpu_to_le32(x))
-#else
-# define tole(x) (x)
-#endif
-
-#if CRC_BE_BITS > 8
-# define tobe(x) ((__force u32) cpu_to_be32(x))
-#else
-# define tobe(x) (x)
-#endif

#include "crc32table.h"

MODULE_AUTHOR("Matt Domsch <Matt_Domsch@dell.com>");
MODULE_DESCRIPTION("Various CRC32 calculations");
MODULE_LICENSE("GPL");

-#if CRC_LE_BITS > 8 || CRC_BE_BITS > 8
-
-/* implements slicing-by-4 or slicing-by-8 algorithm */
-static inline u32 __pure
-crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 (*tab)[256])
-{
-# ifdef __LITTLE_ENDIAN
-# define DO_CRC(x) crc = t0[(crc ^ (x)) & 255] ^ (crc >> 8)
-# define DO_CRC4 (t3[(q) & 255] ^ t2[(q >> 8) & 255] ^ \
- t1[(q >> 16) & 255] ^ t0[(q >> 24) & 255])
-# define DO_CRC8 (t7[(q) & 255] ^ t6[(q >> 8) & 255] ^ \
- t5[(q >> 16) & 255] ^ t4[(q >> 24) & 255])
-# else
-# define DO_CRC(x) crc = t0[((crc >> 24) ^ (x)) & 255] ^ (crc << 8)
-# define DO_CRC4 (t0[(q) & 255] ^ t1[(q >> 8) & 255] ^ \
- t2[(q >> 16) & 255] ^ t3[(q >> 24) & 255])
-# define DO_CRC8 (t4[(q) & 255] ^ t5[(q >> 8) & 255] ^ \
- t6[(q >> 16) & 255] ^ t7[(q >> 24) & 255])
-# endif
- const u32 *b;
- size_t rem_len;
-# ifdef CONFIG_X86
- size_t i;
-# endif
- const u32 *t0=tab[0], *t1=tab[1], *t2=tab[2], *t3=tab[3];
-# if CRC_LE_BITS != 32
- const u32 *t4 = tab[4], *t5 = tab[5], *t6 = tab[6], *t7 = tab[7];
-# endif
- u32 q;
-
- /* Align it */
- if (unlikely((long)buf & 3 && len)) {
- do {
- DO_CRC(*buf++);
- } while ((--len) && ((long)buf)&3);
- }
-
-# if CRC_LE_BITS == 32
- rem_len = len & 3;
- len = len >> 2;
-# else
- rem_len = len & 7;
- len = len >> 3;
-# endif
-
- b = (const u32 *)buf;
-# ifdef CONFIG_X86
- --b;
- for (i = 0; i < len; i++) {
-# else
- for (--b; len; --len) {
-# endif
- q = crc ^ *++b; /* use pre increment for speed */
-# if CRC_LE_BITS == 32
- crc = DO_CRC4;
-# else
- crc = DO_CRC8;
- q = *++b;
- crc ^= DO_CRC4;
-# endif
- }
- len = rem_len;
- /* And the last few bytes */
- if (len) {
- u8 *p = (u8 *)(b + 1) - 1;
-# ifdef CONFIG_X86
- for (i = 0; i < len; i++)
- DO_CRC(*++p); /* use pre increment for speed */
-# else
- do {
- DO_CRC(*++p); /* use pre increment for speed */
- } while (--len);
-# endif
- }
- return crc;
-#undef DO_CRC
-#undef DO_CRC4
-#undef DO_CRC8
-}
-#endif
-
-
-/**
- * crc32_le_generic() - Calculate bitwise little-endian Ethernet AUTODIN II
- * CRC32/CRC32C
- * @crc: seed value for computation. ~0 for Ethernet, sometimes 0 for other
- * uses, or the previous crc32/crc32c value if computing incrementally.
- * @p: pointer to buffer over which CRC32/CRC32C is run
- * @len: length of buffer @p
- * @tab: little-endian Ethernet table
- * @polynomial: CRC32/CRC32c LE polynomial
- */
-static inline u32 __pure crc32_le_generic(u32 crc, unsigned char const *p,
- size_t len, const u32 (*tab)[256],
- u32 polynomial)
+u32 __pure crc32_le_base(u32 crc, const u8 *p, size_t len)
{
-#if CRC_LE_BITS == 1
- int i;
- while (len--) {
- crc ^= *p++;
- for (i = 0; i < 8; i++)
- crc = (crc >> 1) ^ ((crc & 1) ? polynomial : 0);
- }
-# elif CRC_LE_BITS == 2
- while (len--) {
- crc ^= *p++;
- crc = (crc >> 2) ^ tab[0][crc & 3];
- crc = (crc >> 2) ^ tab[0][crc & 3];
- crc = (crc >> 2) ^ tab[0][crc & 3];
- crc = (crc >> 2) ^ tab[0][crc & 3];
- }
-# elif CRC_LE_BITS == 4
- while (len--) {
- crc ^= *p++;
- crc = (crc >> 4) ^ tab[0][crc & 15];
- crc = (crc >> 4) ^ tab[0][crc & 15];
- }
-# elif CRC_LE_BITS == 8
- /* aka Sarwate algorithm */
- while (len--) {
- crc ^= *p++;
- crc = (crc >> 8) ^ tab[0][crc & 255];
- }
-# else
- crc = (__force u32) __cpu_to_le32(crc);
- crc = crc32_body(crc, p, len, tab);
- crc = __le32_to_cpu((__force __le32)crc);
-#endif
+ while (len--)
+ crc = (crc >> 8) ^ crc32table_le[(crc & 255) ^ *p++];
return crc;
}
+EXPORT_SYMBOL(crc32_le_base);

-#if CRC_LE_BITS == 1
-u32 __pure crc32_le_base(u32 crc, const u8 *p, size_t len)
-{
- return crc32_le_generic(crc, p, len, NULL, CRC32_POLY_LE);
-}
-u32 __pure crc32c_le_base(u32 crc, const u8 *p, size_t len)
-{
- return crc32_le_generic(crc, p, len, NULL, CRC32C_POLY_LE);
-}
-#else
-u32 __pure crc32_le_base(u32 crc, const u8 *p, size_t len)
-{
- return crc32_le_generic(crc, p, len, crc32table_le, CRC32_POLY_LE);
-}
u32 __pure crc32c_le_base(u32 crc, const u8 *p, size_t len)
{
- return crc32_le_generic(crc, p, len, crc32ctable_le, CRC32C_POLY_LE);
+ while (len--)
+ crc = (crc >> 8) ^ crc32ctable_le[(crc & 255) ^ *p++];
+ return crc;
}
-#endif
-EXPORT_SYMBOL(crc32_le_base);
EXPORT_SYMBOL(crc32c_le_base);

/*
* This multiplies the polynomials x and y modulo the given modulus.
* This follows the "little-endian" CRC convention that the lsbit
@@ -275,66 +124,12 @@ u32 __attribute_const__ __crc32c_le_shift(u32 crc, size_t len)
return crc32_generic_shift(crc, len, CRC32C_POLY_LE);
}
EXPORT_SYMBOL(crc32_le_shift);
EXPORT_SYMBOL(__crc32c_le_shift);

-/**
- * crc32_be_generic() - Calculate bitwise big-endian Ethernet AUTODIN II CRC32
- * @crc: seed value for computation. ~0 for Ethernet, sometimes 0 for
- * other uses, or the previous crc32 value if computing incrementally.
- * @p: pointer to buffer over which CRC32 is run
- * @len: length of buffer @p
- * @tab: big-endian Ethernet table
- * @polynomial: CRC32 BE polynomial
- */
-static inline u32 __pure crc32_be_generic(u32 crc, unsigned char const *p,
- size_t len, const u32 (*tab)[256],
- u32 polynomial)
-{
-#if CRC_BE_BITS == 1
- int i;
- while (len--) {
- crc ^= *p++ << 24;
- for (i = 0; i < 8; i++)
- crc =
- (crc << 1) ^ ((crc & 0x80000000) ? polynomial :
- 0);
- }
-# elif CRC_BE_BITS == 2
- while (len--) {
- crc ^= *p++ << 24;
- crc = (crc << 2) ^ tab[0][crc >> 30];
- crc = (crc << 2) ^ tab[0][crc >> 30];
- crc = (crc << 2) ^ tab[0][crc >> 30];
- crc = (crc << 2) ^ tab[0][crc >> 30];
- }
-# elif CRC_BE_BITS == 4
- while (len--) {
- crc ^= *p++ << 24;
- crc = (crc << 4) ^ tab[0][crc >> 28];
- crc = (crc << 4) ^ tab[0][crc >> 28];
- }
-# elif CRC_BE_BITS == 8
- while (len--) {
- crc ^= *p++ << 24;
- crc = (crc << 8) ^ tab[0][crc >> 24];
- }
-# else
- crc = (__force u32) __cpu_to_be32(crc);
- crc = crc32_body(crc, p, len, tab);
- crc = __be32_to_cpu((__force __be32)crc);
-# endif
- return crc;
-}
-
-#if CRC_BE_BITS == 1
-u32 __pure crc32_be_base(u32 crc, const u8 *p, size_t len)
-{
- return crc32_be_generic(crc, p, len, NULL, CRC32_POLY_BE);
-}
-#else
u32 __pure crc32_be_base(u32 crc, const u8 *p, size_t len)
{
- return crc32_be_generic(crc, p, len, crc32table_be, CRC32_POLY_BE);
+ while (len--)
+ crc = (crc << 8) ^ crc32table_be[(crc >> 24) ^ *p++];
+ return crc;
}
-#endif
EXPORT_SYMBOL(crc32_be_base);
diff --git a/lib/crc32defs.h b/lib/crc32defs.h
deleted file mode 100644
index 0c8fb5923e7e..000000000000
--- a/lib/crc32defs.h
+++ /dev/null
@@ -1,59 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-
-/* Try to choose an implementation variant via Kconfig */
-#ifdef CONFIG_CRC32_SLICEBY8
-# define CRC_LE_BITS 64
-# define CRC_BE_BITS 64
-#endif
-#ifdef CONFIG_CRC32_SLICEBY4
-# define CRC_LE_BITS 32
-# define CRC_BE_BITS 32
-#endif
-#ifdef CONFIG_CRC32_SARWATE
-# define CRC_LE_BITS 8
-# define CRC_BE_BITS 8
-#endif
-#ifdef CONFIG_CRC32_BIT
-# define CRC_LE_BITS 1
-# define CRC_BE_BITS 1
-#endif
-
-/*
- * How many bits at a time to use. Valid values are 1, 2, 4, 8, 32 and 64.
- * For less performance-sensitive, use 4 or 8 to save table size.
- * For larger systems choose same as CPU architecture as default.
- * This works well on X86_64, SPARC64 systems. This may require some
- * elaboration after experiments with other architectures.
- */
-#ifndef CRC_LE_BITS
-# ifdef CONFIG_64BIT
-# define CRC_LE_BITS 64
-# else
-# define CRC_LE_BITS 32
-# endif
-#endif
-#ifndef CRC_BE_BITS
-# ifdef CONFIG_64BIT
-# define CRC_BE_BITS 64
-# else
-# define CRC_BE_BITS 32
-# endif
-#endif
-
-/*
- * Little-endian CRC computation. Used with serial bit streams sent
- * lsbit-first. Be sure to use cpu_to_le32() to append the computed CRC.
- */
-#if CRC_LE_BITS > 64 || CRC_LE_BITS < 1 || CRC_LE_BITS == 16 || \
- CRC_LE_BITS & CRC_LE_BITS-1
-# error "CRC_LE_BITS must be one of {1, 2, 4, 8, 32, 64}"
-#endif
-
-/*
- * Big-endian CRC computation. Used with serial bit streams sent
- * msbit-first. Be sure to use cpu_to_be32() to append the computed CRC.
- */
-#if CRC_BE_BITS > 64 || CRC_BE_BITS < 1 || CRC_BE_BITS == 16 || \
- CRC_BE_BITS & CRC_BE_BITS-1
-# error "CRC_BE_BITS must be one of {1, 2, 4, 8, 32, 64}"
-#endif
diff --git a/lib/gen_crc32table.c b/lib/gen_crc32table.c
index f755b997b967..6d03425b849e 100644
--- a/lib/gen_crc32table.c
+++ b/lib/gen_crc32table.c
@@ -1,60 +1,33 @@
// SPDX-License-Identifier: GPL-2.0
#include <stdio.h>
#include "../include/linux/crc32poly.h"
#include "../include/generated/autoconf.h"
-#include "crc32defs.h"
#include <inttypes.h>

-#define ENTRIES_PER_LINE 4
-
-#if CRC_LE_BITS > 8
-# define LE_TABLE_ROWS (CRC_LE_BITS/8)
-# define LE_TABLE_SIZE 256
-#else
-# define LE_TABLE_ROWS 1
-# define LE_TABLE_SIZE (1 << CRC_LE_BITS)
-#endif
-
-#if CRC_BE_BITS > 8
-# define BE_TABLE_ROWS (CRC_BE_BITS/8)
-# define BE_TABLE_SIZE 256
-#else
-# define BE_TABLE_ROWS 1
-# define BE_TABLE_SIZE (1 << CRC_BE_BITS)
-#endif
-
-static uint32_t crc32table_le[LE_TABLE_ROWS][256];
-static uint32_t crc32table_be[BE_TABLE_ROWS][256];
-static uint32_t crc32ctable_le[LE_TABLE_ROWS][256];
+static uint32_t crc32table_le[256];
+static uint32_t crc32table_be[256];
+static uint32_t crc32ctable_le[256];

/**
* crc32init_le() - allocate and initialize LE table data
*
* crc is the crc of the byte i; other entries are filled in based on the
* fact that crctable[i^j] = crctable[i] ^ crctable[j].
*
*/
-static void crc32init_le_generic(const uint32_t polynomial,
- uint32_t (*tab)[256])
+static void crc32init_le_generic(const uint32_t polynomial, uint32_t tab[256])
{
unsigned i, j;
uint32_t crc = 1;

- tab[0][0] = 0;
+ tab[0] = 0;

- for (i = LE_TABLE_SIZE >> 1; i; i >>= 1) {
+ for (i = 128; i; i >>= 1) {
crc = (crc >> 1) ^ ((crc & 1) ? polynomial : 0);
- for (j = 0; j < LE_TABLE_SIZE; j += 2 * i)
- tab[0][i + j] = crc ^ tab[0][j];
- }
- for (i = 0; i < LE_TABLE_SIZE; i++) {
- crc = tab[0][i];
- for (j = 1; j < LE_TABLE_ROWS; j++) {
- crc = tab[0][crc & 0xff] ^ (crc >> 8);
- tab[j][i] = crc;
- }
+ for (j = 0; j < 256; j += 2 * i)
+ tab[i + j] = crc ^ tab[j];
}
}

static void crc32init_le(void)
{
@@ -72,71 +45,45 @@ static void crc32cinit_le(void)
static void crc32init_be(void)
{
unsigned i, j;
uint32_t crc = 0x80000000;

- crc32table_be[0][0] = 0;
+ crc32table_be[0] = 0;

- for (i = 1; i < BE_TABLE_SIZE; i <<= 1) {
+ for (i = 1; i < 256; i <<= 1) {
crc = (crc << 1) ^ ((crc & 0x80000000) ? CRC32_POLY_BE : 0);
for (j = 0; j < i; j++)
- crc32table_be[0][i + j] = crc ^ crc32table_be[0][j];
- }
- for (i = 0; i < BE_TABLE_SIZE; i++) {
- crc = crc32table_be[0][i];
- for (j = 1; j < BE_TABLE_ROWS; j++) {
- crc = crc32table_be[0][(crc >> 24) & 0xff] ^ (crc << 8);
- crc32table_be[j][i] = crc;
- }
+ crc32table_be[i + j] = crc ^ crc32table_be[j];
}
}

-static void output_table(uint32_t (*table)[256], int rows, int len, char *trans)
+static void output_table(const uint32_t table[256])
{
- int i, j;
-
- for (j = 0 ; j < rows; j++) {
- printf("{");
- for (i = 0; i < len - 1; i++) {
- if (i % ENTRIES_PER_LINE == 0)
- printf("\n");
- printf("%s(0x%8.8xL), ", trans, table[j][i]);
- }
- printf("%s(0x%8.8xL)},\n", trans, table[j][len - 1]);
+ int i;
+
+ for (i = 0; i < 256; i += 4) {
+ printf("\t0x%08x, 0x%08x, 0x%08x, 0x%08x,\n",
+ table[i], table[i + 1], table[i + 2], table[i + 3]);
}
}

int main(int argc, char** argv)
{
printf("/* this file is generated - do not edit */\n\n");

- if (CRC_LE_BITS > 1) {
- crc32init_le();
- printf("static const u32 ____cacheline_aligned "
- "crc32table_le[%d][%d] = {",
- LE_TABLE_ROWS, LE_TABLE_SIZE);
- output_table(crc32table_le, LE_TABLE_ROWS,
- LE_TABLE_SIZE, "tole");
- printf("};\n");
- }
+ crc32init_le();
+ printf("static const u32 ____cacheline_aligned crc32table_le[256] = {\n");
+ output_table(crc32table_le);
+ printf("};\n");

- if (CRC_BE_BITS > 1) {
- crc32init_be();
- printf("static const u32 ____cacheline_aligned "
- "crc32table_be[%d][%d] = {",
- BE_TABLE_ROWS, BE_TABLE_SIZE);
- output_table(crc32table_be, LE_TABLE_ROWS,
- BE_TABLE_SIZE, "tobe");
- printf("};\n");
- }
- if (CRC_LE_BITS > 1) {
- crc32cinit_le();
- printf("static const u32 ____cacheline_aligned "
- "crc32ctable_le[%d][%d] = {",
- LE_TABLE_ROWS, LE_TABLE_SIZE);
- output_table(crc32ctable_le, LE_TABLE_ROWS,
- LE_TABLE_SIZE, "tole");
- printf("};\n");
- }
+ crc32init_be();
+ printf("static const u32 ____cacheline_aligned crc32table_be[256] = {\n");
+ output_table(crc32table_be);
+ printf("};\n");
+
+ crc32cinit_le();
+ printf("static const u32 ____cacheline_aligned crc32ctable_le[256] = {\n");
+ output_table(crc32ctable_le);
+ printf("};\n");

return 0;
}
--
2.48.1