[PATCH 11/14] crc32: Bolt on crc32c

From: Darrick J. Wong
Date: Sat Jan 07 2012 - 00:52:08 EST

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

Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
---
include/linux/crc32.h | 2 ++
lib/Kconfig | 8 +++---
lib/crc32.c | 62 +++++++++++++++++++++++++++++++------------------
lib/crc32defs.h | 7 ++++++
lib/gen_crc32table.c | 35 ++++++++++++++++++++++------
5 files changed, 80 insertions(+), 34 deletions(-)

diff --git a/include/linux/crc32.h b/include/linux/crc32.h
index 391a259..68267b6 100644
--- a/include/linux/crc32.h
+++ b/include/linux/crc32.h
@@ -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)

/*
diff --git a/lib/Kconfig b/lib/Kconfig
index 2bc5834..cfddafc 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -51,14 +51,14 @@ 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"
diff --git a/lib/crc32.c b/lib/crc32.c
index d56516d..8df9561 100644
--- a/lib/crc32.c
+++ b/lib/crc32.c
@@ -46,7 +46,7 @@
#include "crc32table.h"

MODULE_AUTHOR("Matt Domsch <Matt_Domsch@xxxxxxxx>");
-MODULE_DESCRIPTION("Ethernet CRC32 calculations");
+MODULE_DESCRIPTION("Various CRC32 calculations");
MODULE_LICENSE("GPL");

#if CRC_LE_BITS > 8 || CRC_BE_BITS > 8
@@ -135,46 +135,57 @@ 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;
}
+
+u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len)
+{
+ return crc32_le_generic(crc, p, len, crc32table_le, CRCPOLY_LE);
+}
EXPORT_SYMBOL(crc32_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);
+}
+EXPORT_SYMBOL(__crc32c_le);
+
/**
* crc32_be() - Calculate bitwise big-endian Ethernet AUTODIN II CRC32
* @crc: seed value for computation. ~0 for Ethernet, sometimes 0 for
@@ -182,7 +193,9 @@ 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;
@@ -190,37 +203,40 @@ u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t 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;
}
+
+u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len)
+{
+ return crc32_be_generic(crc, p, len, crc32table_be, CRCPOLY_BE);
+}
EXPORT_SYMBOL(crc32_be);

#ifdef CONFIG_CRC32_SELFTEST
diff --git a/lib/crc32defs.h b/lib/crc32defs.h
index 8181592..6fd1917 100644
--- a/lib/crc32defs.h
+++ b/lib/crc32defs.h
@@ -7,6 +7,13 @@
#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.
* For larger systems choose same as CPU architecture as default.
diff --git a/lib/gen_crc32table.c b/lib/gen_crc32table.c
index 0d9edd1..8f8d543 100644
--- a/lib/gen_crc32table.c
+++ b/lib/gen_crc32table.c
@@ -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
@@ -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
*/
@@ -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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Next message: Darrick J. Wong: "[PATCH 14/14] crc32: Select an algorithm via kconfig"
Previous message: Darrick J. Wong: "[PATCH 10/14] crc32: Add note about this patchset to crc32.c"
In reply to: Darrick J. Wong: "[PATCH 10/14] crc32: Add note about this patchset to crc32.c"
Next in thread: Darrick J. Wong: "[PATCH 14/14] crc32: Select an algorithm via kconfig"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]