riscv: Add checksum library

Provide a 32 and 64 bit version of do_csum. When compiled for 32-bit
will load from the buffer in groups of 32 bits, and when compiled for
64-bit will load in groups of 64 bits.

Additionally provide riscv optimized implementation of csum_ipv6_magic.

Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Xiao Wang <xiao.w.wang@intel.com>
Link: https://lore.kernel.org/r/20240108-optimize_checksum-v15-4-1c50de5f2167@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Charlie Jenkins 2024-01-08 15:57:05 -08:00 committed by Palmer Dabbelt
parent e11e367e9f
commit a04c192eab
No known key found for this signature in database
GPG Key ID: 2E1319F35FBB1889
3 changed files with 338 additions and 0 deletions

View File

@ -12,6 +12,17 @@
#define ip_fast_csum ip_fast_csum
extern unsigned int do_csum(const unsigned char *buff, int len);
#define do_csum do_csum
/* Default version is sufficient for 32 bit */
#ifndef CONFIG_32BIT
#define _HAVE_ARCH_IPV6_CSUM
__sum16 csum_ipv6_magic(const struct in6_addr *saddr,
const struct in6_addr *daddr,
__u32 len, __u8 proto, __wsum sum);
#endif
/* Define riscv versions of functions before importing asm-generic/checksum.h */
#include <asm-generic/checksum.h>

View File

@ -6,6 +6,7 @@ lib-y += memmove.o
lib-y += strcmp.o
lib-y += strlen.o
lib-y += strncmp.o
lib-y += csum.o
lib-$(CONFIG_MMU) += uaccess.o
lib-$(CONFIG_64BIT) += tishift.o
lib-$(CONFIG_RISCV_ISA_ZICBOZ) += clear_page.o

326
arch/riscv/lib/csum.c Normal file
View File

@ -0,0 +1,326 @@
// SPDX-License-Identifier: GPL-2.0
/*
* Checksum library
*
* Influenced by arch/arm64/lib/csum.c
* Copyright (C) 2023 Rivos Inc.
*/
#include <linux/bitops.h>
#include <linux/compiler.h>
#include <linux/jump_label.h>
#include <linux/kasan-checks.h>
#include <linux/kernel.h>
#include <asm/cpufeature.h>
#include <net/checksum.h>
/* Default version is sufficient for 32 bit */
#ifndef CONFIG_32BIT
__sum16 csum_ipv6_magic(const struct in6_addr *saddr,
const struct in6_addr *daddr,
__u32 len, __u8 proto, __wsum csum)
{
unsigned int ulen, uproto;
unsigned long sum = (__force unsigned long)csum;
sum += (__force unsigned long)saddr->s6_addr32[0];
sum += (__force unsigned long)saddr->s6_addr32[1];
sum += (__force unsigned long)saddr->s6_addr32[2];
sum += (__force unsigned long)saddr->s6_addr32[3];
sum += (__force unsigned long)daddr->s6_addr32[0];
sum += (__force unsigned long)daddr->s6_addr32[1];
sum += (__force unsigned long)daddr->s6_addr32[2];
sum += (__force unsigned long)daddr->s6_addr32[3];
ulen = (__force unsigned int)htonl((unsigned int)len);
sum += ulen;
uproto = (__force unsigned int)htonl(proto);
sum += uproto;
/*
* Zbb support saves 4 instructions, so not worth checking without
* alternatives if supported
*/
if (IS_ENABLED(CONFIG_RISCV_ISA_ZBB) &&
IS_ENABLED(CONFIG_RISCV_ALTERNATIVE)) {
unsigned long fold_temp;
/*
* Zbb is likely available when the kernel is compiled with Zbb
* support, so nop when Zbb is available and jump when Zbb is
* not available.
*/
asm_volatile_goto(ALTERNATIVE("j %l[no_zbb]", "nop", 0,
RISCV_ISA_EXT_ZBB, 1)
:
:
:
: no_zbb);
asm(".option push \n\
.option arch,+zbb \n\
rori %[fold_temp], %[sum], 32 \n\
add %[sum], %[fold_temp], %[sum] \n\
srli %[sum], %[sum], 32 \n\
not %[fold_temp], %[sum] \n\
roriw %[sum], %[sum], 16 \n\
subw %[sum], %[fold_temp], %[sum] \n\
.option pop"
: [sum] "+r" (sum), [fold_temp] "=&r" (fold_temp));
return (__force __sum16)(sum >> 16);
}
no_zbb:
sum += ror64(sum, 32);
sum >>= 32;
return csum_fold((__force __wsum)sum);
}
EXPORT_SYMBOL(csum_ipv6_magic);
#endif /* !CONFIG_32BIT */
#ifdef CONFIG_32BIT
#define OFFSET_MASK 3
#elif CONFIG_64BIT
#define OFFSET_MASK 7
#endif
static inline __no_sanitize_address unsigned long
do_csum_common(const unsigned long *ptr, const unsigned long *end,
unsigned long data)
{
unsigned int shift;
unsigned long csum = 0, carry = 0;
/*
* Do 32-bit reads on RV32 and 64-bit reads otherwise. This should be
* faster than doing 32-bit reads on architectures that support larger
* reads.
*/
while (ptr < end) {
csum += data;
carry += csum < data;
data = *(ptr++);
}
/*
* Perform alignment (and over-read) bytes on the tail if any bytes
* leftover.
*/
shift = ((long)ptr - (long)end) * 8;
#ifdef __LITTLE_ENDIAN
data = (data << shift) >> shift;
#else
data = (data >> shift) << shift;
#endif
csum += data;
carry += csum < data;
csum += carry;
csum += csum < carry;
return csum;
}
/*
* Algorithm accounts for buff being misaligned.
* If buff is not aligned, will over-read bytes but not use the bytes that it
* shouldn't. The same thing will occur on the tail-end of the read.
*/
static inline __no_sanitize_address unsigned int
do_csum_with_alignment(const unsigned char *buff, int len)
{
unsigned int offset, shift;
unsigned long csum, data;
const unsigned long *ptr, *end;
/*
* Align address to closest word (double word on rv64) that comes before
* buff. This should always be in the same page and cache line.
* Directly call KASAN with the alignment we will be using.
*/
offset = (unsigned long)buff & OFFSET_MASK;
kasan_check_read(buff, len);
ptr = (const unsigned long *)(buff - offset);
/*
* Clear the most significant bytes that were over-read if buff was not
* aligned.
*/
shift = offset * 8;
data = *(ptr++);
#ifdef __LITTLE_ENDIAN
data = (data >> shift) << shift;
#else
data = (data << shift) >> shift;
#endif
end = (const unsigned long *)(buff + len);
csum = do_csum_common(ptr, end, data);
/*
* Zbb support saves 6 instructions, so not worth checking without
* alternatives if supported
*/
if (IS_ENABLED(CONFIG_RISCV_ISA_ZBB) &&
IS_ENABLED(CONFIG_RISCV_ALTERNATIVE)) {
unsigned long fold_temp;
/*
* Zbb is likely available when the kernel is compiled with Zbb
* support, so nop when Zbb is available and jump when Zbb is
* not available.
*/
asm_volatile_goto(ALTERNATIVE("j %l[no_zbb]", "nop", 0,
RISCV_ISA_EXT_ZBB, 1)
:
:
:
: no_zbb);
#ifdef CONFIG_32BIT
asm_volatile_goto(".option push \n\
.option arch,+zbb \n\
rori %[fold_temp], %[csum], 16 \n\
andi %[offset], %[offset], 1 \n\
add %[csum], %[fold_temp], %[csum] \n\
beq %[offset], zero, %l[end] \n\
rev8 %[csum], %[csum] \n\
.option pop"
: [csum] "+r" (csum), [fold_temp] "=&r" (fold_temp)
: [offset] "r" (offset)
:
: end);
return (unsigned short)csum;
#else /* !CONFIG_32BIT */
asm_volatile_goto(".option push \n\
.option arch,+zbb \n\
rori %[fold_temp], %[csum], 32 \n\
add %[csum], %[fold_temp], %[csum] \n\
srli %[csum], %[csum], 32 \n\
roriw %[fold_temp], %[csum], 16 \n\
addw %[csum], %[fold_temp], %[csum] \n\
andi %[offset], %[offset], 1 \n\
beq %[offset], zero, %l[end] \n\
rev8 %[csum], %[csum] \n\
.option pop"
: [csum] "+r" (csum), [fold_temp] "=&r" (fold_temp)
: [offset] "r" (offset)
:
: end);
return (csum << 16) >> 48;
#endif /* !CONFIG_32BIT */
end:
return csum >> 16;
}
no_zbb:
#ifndef CONFIG_32BIT
csum += ror64(csum, 32);
csum >>= 32;
#endif
csum = (u32)csum + ror32((u32)csum, 16);
if (offset & 1)
return (u16)swab32(csum);
return csum >> 16;
}
/*
* Does not perform alignment, should only be used if machine has fast
* misaligned accesses, or when buff is known to be aligned.
*/
static inline __no_sanitize_address unsigned int
do_csum_no_alignment(const unsigned char *buff, int len)
{
unsigned long csum, data;
const unsigned long *ptr, *end;
ptr = (const unsigned long *)(buff);
data = *(ptr++);
kasan_check_read(buff, len);
end = (const unsigned long *)(buff + len);
csum = do_csum_common(ptr, end, data);
/*
* Zbb support saves 6 instructions, so not worth checking without
* alternatives if supported
*/
if (IS_ENABLED(CONFIG_RISCV_ISA_ZBB) &&
IS_ENABLED(CONFIG_RISCV_ALTERNATIVE)) {
unsigned long fold_temp;
/*
* Zbb is likely available when the kernel is compiled with Zbb
* support, so nop when Zbb is available and jump when Zbb is
* not available.
*/
asm_volatile_goto(ALTERNATIVE("j %l[no_zbb]", "nop", 0,
RISCV_ISA_EXT_ZBB, 1)
:
:
:
: no_zbb);
#ifdef CONFIG_32BIT
asm (".option push \n\
.option arch,+zbb \n\
rori %[fold_temp], %[csum], 16 \n\
add %[csum], %[fold_temp], %[csum] \n\
.option pop"
: [csum] "+r" (csum), [fold_temp] "=&r" (fold_temp)
:
: );
#else /* !CONFIG_32BIT */
asm (".option push \n\
.option arch,+zbb \n\
rori %[fold_temp], %[csum], 32 \n\
add %[csum], %[fold_temp], %[csum] \n\
srli %[csum], %[csum], 32 \n\
roriw %[fold_temp], %[csum], 16 \n\
addw %[csum], %[fold_temp], %[csum] \n\
.option pop"
: [csum] "+r" (csum), [fold_temp] "=&r" (fold_temp)
:
: );
#endif /* !CONFIG_32BIT */
return csum >> 16;
}
no_zbb:
#ifndef CONFIG_32BIT
csum += ror64(csum, 32);
csum >>= 32;
#endif
csum = (u32)csum + ror32((u32)csum, 16);
return csum >> 16;
}
/*
* Perform a checksum on an arbitrary memory address.
* Will do a light-weight address alignment if buff is misaligned, unless
* cpu supports fast misaligned accesses.
*/
unsigned int do_csum(const unsigned char *buff, int len)
{
if (unlikely(len <= 0))
return 0;
/*
* Significant performance gains can be seen by not doing alignment
* on machines with fast misaligned accesses.
*
* There is some duplicate code between the "with_alignment" and
* "no_alignment" implmentations, but the overlap is too awkward to be
* able to fit in one function without introducing multiple static
* branches. The largest chunk of overlap was delegated into the
* do_csum_common function.
*/
if (static_branch_likely(&fast_misaligned_access_speed_key))
return do_csum_no_alignment(buff, len);
if (((unsigned long)buff & OFFSET_MASK) == 0)
return do_csum_no_alignment(buff, len);
return do_csum_with_alignment(buff, len);
}