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lib/crc32: remove other generic implementations
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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.

Link: https://lore.kernel.org/r/20250123212904.118683-3-ebiggers@kernel.org
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
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Eric Biggers committed Jan 29, 2025
1 parent b0430f3 commit 5e3c1c4
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Showing 4 changed files with 40 additions and 361 deletions.
4 changes: 0 additions & 4 deletions lib/Kconfig
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Original file line number Diff line number Diff line change
Expand Up @@ -189,7 +189,6 @@ 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
Expand All @@ -203,9 +202,6 @@ config CRC32_ARCH
tristate
default CRC32 if ARCH_HAS_CRC32 && CRC_OPTIMIZATIONS

config CRC32_SARWATE
bool

config CRC64
tristate "CRC64 functions"
help
Expand Down
225 changes: 10 additions & 215 deletions lib/crc32.c
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Original file line number Diff line number Diff line change
Expand Up @@ -30,178 +30,27 @@
#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);

/*
Expand Down Expand Up @@ -277,64 +126,10 @@ u32 __attribute_const__ __crc32c_le_shift(u32 crc, size_t len)
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);
59 changes: 0 additions & 59 deletions lib/crc32defs.h
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