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crc32: bolt on crc32c
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Reuse the existing crc32 code to stamp out a crc32c implementation.

Signed-off-by: Darrick J. Wong <[email protected]>
Cc: Herbert Xu <[email protected]>
Cc: Bob Pearson <[email protected]>
Cc: Randy Dunlap <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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@torvalds
Darrick J. Wong authored and torvalds committed Mar 23, 2012
1 parent 78dff41 commit 46c5801
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Showing 5 changed files with 97 additions and 34 deletions.
2 changes: 2 additions & 0 deletions include/linux/crc32.h
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,8 @@
extern u32 crc32_le(u32 crc, unsigned char const *p, size_t len);
extern u32 crc32_be(u32 crc, unsigned char const *p, size_t len);

extern u32 __crc32c_le(u32 crc, unsigned char const *p, size_t len);

#define crc32(seed, data, length) crc32_le(seed, (unsigned char const *)(data), length)

/*
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8 changes: 4 additions & 4 deletions lib/Kconfig
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Expand Up @@ -61,14 +61,14 @@ config CRC_ITU_T
functions require M here.

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

config CRC32_SELFTEST
bool "CRC32 perform self test on init"
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79 changes: 56 additions & 23 deletions lib/crc32.c
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Expand Up @@ -46,7 +46,7 @@
#include "crc32table.h"

MODULE_AUTHOR("Matt Domsch <[email protected]>");
MODULE_DESCRIPTION("Ethernet CRC32 calculations");
MODULE_DESCRIPTION("Various CRC32 calculations");
MODULE_LICENSE("GPL");

#if CRC_LE_BITS > 8 || CRC_BE_BITS > 8
Expand Down Expand Up @@ -135,45 +135,66 @@ crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 (*tab)[256])
* @p: pointer to buffer over which CRC is run
* @len: length of buffer @p
*/
u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len)
static inline u32 __pure crc32_le_generic(u32 crc, unsigned char const *p,
size_t len, const u32 (*tab)[256],
u32 polynomial)
{
#if CRC_LE_BITS == 1
int i;
while (len--) {
crc ^= *p++;
for (i = 0; i < 8; i++)
crc = (crc >> 1) ^ ((crc & 1) ? CRCPOLY_LE : 0);
crc = (crc >> 1) ^ ((crc & 1) ? polynomial : 0);
}
# elif CRC_LE_BITS == 2
while (len--) {
crc ^= *p++;
crc = (crc >> 2) ^ crc32table_le[0][crc & 3];
crc = (crc >> 2) ^ crc32table_le[0][crc & 3];
crc = (crc >> 2) ^ crc32table_le[0][crc & 3];
crc = (crc >> 2) ^ crc32table_le[0][crc & 3];
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) ^ crc32table_le[0][crc & 15];
crc = (crc >> 4) ^ crc32table_le[0][crc & 15];
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) ^ crc32table_le[0][crc & 255];
crc = (crc >> 8) ^ tab[0][crc & 255];
}
# else
const u32 (*tab)[] = crc32table_le;

crc = (__force u32) __cpu_to_le32(crc);
crc = crc32_body(crc, p, len, tab);
crc = __le32_to_cpu((__force __le32)crc);
#endif
return crc;
}

#if CRC_LE_BITS == 1
u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len)
{
return crc32_le_generic(crc, p, len, NULL, CRCPOLY_LE);
}
u32 __pure __crc32c_le(u32 crc, unsigned char const *p, size_t len)
{
return crc32_le_generic(crc, p, len, NULL, CRC32C_POLY_LE);
}
#else
u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len)
{
return crc32_le_generic(crc, p, len, crc32table_le, CRCPOLY_LE);
}
u32 __pure __crc32c_le(u32 crc, unsigned char const *p, size_t len)
{
return crc32_le_generic(crc, p, len, crc32ctable_le, CRC32C_POLY_LE);
}
#endif
EXPORT_SYMBOL(crc32_le);
EXPORT_SYMBOL(__crc32c_le);

/**
* crc32_be() - Calculate bitwise big-endian Ethernet AUTODIN II CRC32
Expand All @@ -182,45 +203,57 @@ EXPORT_SYMBOL(crc32_le);
* @p: pointer to buffer over which CRC is run
* @len: length of buffer @p
*/
u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len)
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) ? CRCPOLY_BE :
(crc << 1) ^ ((crc & 0x80000000) ? polynomial :
0);
}
# elif CRC_BE_BITS == 2
while (len--) {
crc ^= *p++ << 24;
crc = (crc << 2) ^ crc32table_be[0][crc >> 30];
crc = (crc << 2) ^ crc32table_be[0][crc >> 30];
crc = (crc << 2) ^ crc32table_be[0][crc >> 30];
crc = (crc << 2) ^ crc32table_be[0][crc >> 30];
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) ^ crc32table_be[0][crc >> 28];
crc = (crc << 4) ^ crc32table_be[0][crc >> 28];
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) ^ crc32table_be[0][crc >> 24];
crc = (crc << 8) ^ tab[0][crc >> 24];
}
# else
const u32 (*tab)[] = crc32table_be;

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_LE_BITS == 1
u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len)
{
return crc32_be_generic(crc, p, len, NULL, CRCPOLY_BE);
}
#else
u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len)
{
return crc32_be_generic(crc, p, len, crc32table_be, CRCPOLY_BE);
}
#endif
EXPORT_SYMBOL(crc32_be);

#ifdef CONFIG_CRC32_SELFTEST
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7 changes: 7 additions & 0 deletions lib/crc32defs.h
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,13 @@
#define CRCPOLY_LE 0xedb88320
#define CRCPOLY_BE 0x04c11db7

/*
* This is the CRC32c polynomial, as outlined by Castagnoli.
* x^32+x^28+x^27+x^26+x^25+x^23+x^22+x^20+x^19+x^18+x^14+x^13+x^11+x^10+x^9+
* x^8+x^6+x^0
*/
#define CRC32C_POLY_LE 0x82F63B78

/*
* 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.
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35 changes: 28 additions & 7 deletions lib/gen_crc32table.c
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,7 @@

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];

/**
* crc32init_le() - allocate and initialize LE table data
Expand All @@ -31,27 +32,38 @@ static uint32_t crc32table_be[BE_TABLE_ROWS][256];
* fact that crctable[i^j] = crctable[i] ^ crctable[j].
*
*/
static void crc32init_le(void)
static void crc32init_le_generic(const uint32_t polynomial,
uint32_t (*tab)[256])
{
unsigned i, j;
uint32_t crc = 1;

crc32table_le[0][0] = 0;
tab[0][0] = 0;

for (i = LE_TABLE_SIZE >> 1; i; i >>= 1) {
crc = (crc >> 1) ^ ((crc & 1) ? CRCPOLY_LE : 0);
crc = (crc >> 1) ^ ((crc & 1) ? polynomial : 0);
for (j = 0; j < LE_TABLE_SIZE; j += 2 * i)
crc32table_le[0][i + j] = crc ^ crc32table_le[0][j];
tab[0][i + j] = crc ^ tab[0][j];
}
for (i = 0; i < LE_TABLE_SIZE; i++) {
crc = crc32table_le[0][i];
crc = tab[0][i];
for (j = 1; j < LE_TABLE_ROWS; j++) {
crc = crc32table_le[0][crc & 0xff] ^ (crc >> 8);
crc32table_le[j][i] = crc;
crc = tab[0][crc & 0xff] ^ (crc >> 8);
tab[j][i] = crc;
}
}
}

static void crc32init_le(void)
{
crc32init_le_generic(CRCPOLY_LE, crc32table_le);
}

static void crc32cinit_le(void)
{
crc32init_le_generic(CRC32C_POLY_LE, crc32ctable_le);
}

/**
* crc32init_be() - allocate and initialize BE table data
*/
Expand Down Expand Up @@ -114,6 +126,15 @@ int main(int argc, char** argv)
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");
}

return 0;
}

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