On ARM v6 and later, we define CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
because the ordinary load/store instructions (ldr, ldrh, ldrb) can
tolerate any misalignment of the memory address. However, load/store
double and load/store multiple instructions (ldrd, ldm) may still only
be used on memory addresses that are 32-bit aligned, and so we have to
use the CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS macro with care, or we
may end up with a severe performance hit due to alignment traps that
require fixups by the kernel.
Fortunately, the get_unaligned() accessors do the right thing: when
building for ARMv6 or later, the compiler will emit unaligned accesses
using the ordinary load/store instructions (but avoid the ones that
require 32-bit alignment). When building for older ARM, those accessors
will emit the appropriate sequence of ldrb/mov/orr instructions. And on
architectures that can truly tolerate any kind of misalignment, the
get_unaligned() accessors resolve to the leXX_to_cpup accessors that
operate on aligned addresses.
Since the compiler will in fact emit ldrd or ldm instructions when
building this code for ARM v6 or later, the solution is to use the
unaligned accessors on the aligned code paths. Given the above, this
either produces the same code, or better in the ARMv6+ case. However,
since that removes the only difference between the aligned and unaligned
variants, we can drop the aligned variant entirely.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
---
include/linux/siphash.h | 106 +++++++++-----------
lib/siphash.c | 103 ++-----------------
2 files changed, 54 insertions(+), 155 deletions(-)
diff --git a/include/linux/siphash.h b/include/linux/siphash.h
index fa7a6b9cedbf..ef3c36b0ae0f 100644
--- a/include/linux/siphash.h
+++ b/include/linux/siphash.h
@@ -15,16 +15,14 @@
#include <linux/types.h>
#include <linux/kernel.h>
+#include <asm/unaligned.h>
#define SIPHASH_ALIGNMENT __alignof__(u64)
typedef struct {
u64 key[2];
} siphash_key_t;
-u64 __siphash_aligned(const void *data, size_t len, const siphash_key_t *key);
-#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
-u64 __siphash_unaligned(const void *data, size_t len, const siphash_key_t *key);
-#endif
+u64 __siphash(const void *data, size_t len, const siphash_key_t *key);
u64 siphash_1u64(const u64 a, const siphash_key_t *key);
u64 siphash_2u64(const u64 a, const u64 b, const siphash_key_t *key);
@@ -48,26 +46,6 @@ static inline u64 siphash_4u32(const u32 a, const u32 b, const u32 c,
}
-static inline u64 ___siphash_aligned(const __le64 *data, size_t len,
- const siphash_key_t *key)
-{
- if (__builtin_constant_p(len) && len == 4)
- return siphash_1u32(le32_to_cpup((const __le32 *)data), key);
- if (__builtin_constant_p(len) && len == 8)
- return siphash_1u64(le64_to_cpu(data[0]), key);
- if (__builtin_constant_p(len) && len == 16)
- return siphash_2u64(le64_to_cpu(data[0]), le64_to_cpu(data[1]),
- key);
- if (__builtin_constant_p(len) && len == 24)
- return siphash_3u64(le64_to_cpu(data[0]), le64_to_cpu(data[1]),
- le64_to_cpu(data[2]), key);
- if (__builtin_constant_p(len) && len == 32)
- return siphash_4u64(le64_to_cpu(data[0]), le64_to_cpu(data[1]),
- le64_to_cpu(data[2]), le64_to_cpu(data[3]),
- key);
- return __siphash_aligned(data, len, key);
-}
-
/**
* siphash - compute 64-bit siphash PRF value
* @data: buffer to hash
@@ -77,11 +55,30 @@ static inline u64 ___siphash_aligned(const __le64 *data, size_t len,
static inline u64 siphash(const void *data, size_t len,
const siphash_key_t *key)
{
-#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
- if (!IS_ALIGNED((unsigned long)data, SIPHASH_ALIGNMENT))
- return __siphash_unaligned(data, len, key);
-#endif
- return ___siphash_aligned(data, len, key);
+ if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) {
+ if (__builtin_constant_p(len) && len == 4)
+ return siphash_1u32(get_unaligned_le32(data),
+ key);
+ if (__builtin_constant_p(len) && len == 8)
+ return siphash_1u64(get_unaligned_le64(data),
+ key);
+ if (__builtin_constant_p(len) && len == 16)
+ return siphash_2u64(get_unaligned_le64(data),
+ get_unaligned_le64(data + 8),
+ key);
+ if (__builtin_constant_p(len) && len == 24)
+ return siphash_3u64(get_unaligned_le64(data),
+ get_unaligned_le64(data + 8),
+ get_unaligned_le64(data + 16),
+ key);
+ if (__builtin_constant_p(len) && len == 32)
+ return siphash_4u64(get_unaligned_le64(data),
+ get_unaligned_le64(data + 8),
+ get_unaligned_le64(data + 16),
+ get_unaligned_le64(data + 24),
+ key);
+ }
+ return __siphash(data, len, key);
}
#define HSIPHASH_ALIGNMENT __alignof__(unsigned long)
@@ -89,12 +86,7 @@ typedef struct {
unsigned long key[2];
} hsiphash_key_t;
-u32 __hsiphash_aligned(const void *data, size_t len,
- const hsiphash_key_t *key);
-#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
-u32 __hsiphash_unaligned(const void *data, size_t len,
- const hsiphash_key_t *key);
-#endif
+u32 __hsiphash(const void *data, size_t len, const hsiphash_key_t *key);
u32 hsiphash_1u32(const u32 a, const hsiphash_key_t *key);
u32 hsiphash_2u32(const u32 a, const u32 b, const hsiphash_key_t *key);
@@ -103,24 +95,6 @@ u32 hsiphash_3u32(const u32 a, const u32 b, const u32 c,
u32 hsiphash_4u32(const u32 a, const u32 b, const u32 c, const u32 d,
const hsiphash_key_t *key);
-static inline u32 ___hsiphash_aligned(const __le32 *data, size_t len,
- const hsiphash_key_t *key)
-{
- if (__builtin_constant_p(len) && len == 4)
- return hsiphash_1u32(le32_to_cpu(data[0]), key);
- if (__builtin_constant_p(len) && len == 8)
- return hsiphash_2u32(le32_to_cpu(data[0]), le32_to_cpu(data[1]),
- key);
- if (__builtin_constant_p(len) && len == 12)
- return hsiphash_3u32(le32_to_cpu(data[0]), le32_to_cpu(data[1]),
- le32_to_cpu(data[2]), key);
- if (__builtin_constant_p(len) && len == 16)
- return hsiphash_4u32(le32_to_cpu(data[0]), le32_to_cpu(data[1]),
- le32_to_cpu(data[2]), le32_to_cpu(data[3]),
- key);
- return __hsiphash_aligned(data, len, key);
-}
-
/**
* hsiphash - compute 32-bit hsiphash PRF value
* @data: buffer to hash
@@ -130,11 +104,27 @@ static inline u32 ___hsiphash_aligned(const __le32 *data, size_t len,
static inline u32 hsiphash(const void *data, size_t len,
const hsiphash_key_t *key)
{
-#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
- if (!IS_ALIGNED((unsigned long)data, HSIPHASH_ALIGNMENT))
- return __hsiphash_unaligned(data, len, key);
-#endif
- return ___hsiphash_aligned(data, len, key);
+ if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) {
+ if (__builtin_constant_p(len) && len == 4)
+ return hsiphash_1u32(get_unaligned_le32(data),
+ key);
+ if (__builtin_constant_p(len) && len == 8)
+ return hsiphash_2u32(get_unaligned_le32(data),
+ get_unaligned_le32(data + 4),
+ key);
+ if (__builtin_constant_p(len) && len == 12)
+ return hsiphash_3u32(get_unaligned_le32(data),
+ get_unaligned_le32(data + 4),
+ get_unaligned_le32(data + 8),
+ key);
+ if (__builtin_constant_p(len) && len == 16)
+ return hsiphash_4u32(get_unaligned_le32(data),
+ get_unaligned_le32(data + 4),
+ get_unaligned_le32(data + 8),
+ get_unaligned_le32(data + 12),
+ key);
+ }
+ return __hsiphash(data, len, key);
}
#endif /* _LINUX_SIPHASH_H */
diff --git a/lib/siphash.c b/lib/siphash.c
index 3ae58b4edad6..3b2ba1a10ad9 100644
--- a/lib/siphash.c
+++ b/lib/siphash.c
@@ -49,40 +49,7 @@
SIPROUND; \
return (v0 ^ v1) ^ (v2 ^ v3);
-u64 __siphash_aligned(const void *data, size_t len, const siphash_key_t *key)
-{
- const u8 *end = data + len - (len % sizeof(u64));
- const u8 left = len & (sizeof(u64) - 1);
- u64 m;
- PREAMBLE(len)
- for (; data != end; data += sizeof(u64)) {
- m = le64_to_cpup(data);
- v3 ^= m;
- SIPROUND;
- SIPROUND;
- v0 ^= m;
- }
-#if defined(CONFIG_DCACHE_WORD_ACCESS) && BITS_PER_LONG == 64
- if (left)
- b |= le64_to_cpu((__force __le64)(load_unaligned_zeropad(data) &
- bytemask_from_count(left)));
-#else
- switch (left) {
- case 7: b |= ((u64)end[6]) << 48;
- case 6: b |= ((u64)end[5]) << 40;
- case 5: b |= ((u64)end[4]) << 32;
- case 4: b |= le32_to_cpup(data); break;
- case 3: b |= ((u64)end[2]) << 16;
- case 2: b |= le16_to_cpup(data); break;
- case 1: b |= end[0];
- }
-#endif
- POSTAMBLE
-}
-EXPORT_SYMBOL(__siphash_aligned);
-
-#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
-u64 __siphash_unaligned(const void *data, size_t len, const siphash_key_t *key)
+u64 __siphash(const void *data, size_t len, const siphash_key_t *key)
{
const u8 *end = data + len - (len % sizeof(u64));
const u8 left = len & (sizeof(u64) - 1);
@@ -112,8 +79,7 @@ u64 __siphash_unaligned(const void *data, size_t len, const siphash_key_t *key)
#endif
POSTAMBLE
}
-EXPORT_SYMBOL(__siphash_unaligned);
-#endif
+EXPORT_SYMBOL(__siphash);
/**
* siphash_1u64 - compute 64-bit siphash PRF value of a u64
@@ -250,39 +216,7 @@ EXPORT_SYMBOL(siphash_3u32);
HSIPROUND; \
return (v0 ^ v1) ^ (v2 ^ v3);
-u32 __hsiphash_aligned(const void *data, size_t len, const hsiphash_key_t *key)
-{
- const u8 *end = data + len - (len % sizeof(u64));
- const u8 left = len & (sizeof(u64) - 1);
- u64 m;
- HPREAMBLE(len)
- for (; data != end; data += sizeof(u64)) {
- m = le64_to_cpup(data);
- v3 ^= m;
- HSIPROUND;
- v0 ^= m;
- }
-#if defined(CONFIG_DCACHE_WORD_ACCESS) && BITS_PER_LONG == 64
- if (left)
- b |= le64_to_cpu((__force __le64)(load_unaligned_zeropad(data) &
- bytemask_from_count(left)));
-#else
- switch (left) {
- case 7: b |= ((u64)end[6]) << 48;
- case 6: b |= ((u64)end[5]) << 40;
- case 5: b |= ((u64)end[4]) << 32;
- case 4: b |= le32_to_cpup(data); break;
- case 3: b |= ((u64)end[2]) << 16;
- case 2: b |= le16_to_cpup(data); break;
- case 1: b |= end[0];
- }
-#endif
- HPOSTAMBLE
-}
-EXPORT_SYMBOL(__hsiphash_aligned);
-
-#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
-u32 __hsiphash_unaligned(const void *data, size_t len,
+u32 __hsiphash(const void *data, size_t len,
const hsiphash_key_t *key)
{
const u8 *end = data + len - (len % sizeof(u64));
@@ -312,8 +246,7 @@ u32 __hsiphash_unaligned(const void *data, size_t len,
#endif
HPOSTAMBLE
}
-EXPORT_SYMBOL(__hsiphash_unaligned);
-#endif
+EXPORT_SYMBOL(__hsiphash);
/**
* hsiphash_1u32 - compute 64-bit hsiphash PRF value of a u32
@@ -418,30 +351,7 @@ EXPORT_SYMBOL(hsiphash_4u32);
HSIPROUND; \
return v1 ^ v3;
-u32 __hsiphash_aligned(const void *data, size_t len, const hsiphash_key_t *key)
-{
- const u8 *end = data + len - (len % sizeof(u32));
- const u8 left = len & (sizeof(u32) - 1);
- u32 m;
- HPREAMBLE(len)
- for (; data != end; data += sizeof(u32)) {
- m = le32_to_cpup(data);
- v3 ^= m;
- HSIPROUND;
- v0 ^= m;
- }
- switch (left) {
- case 3: b |= ((u32)end[2]) << 16;
- case 2: b |= le16_to_cpup(data); break;
- case 1: b |= end[0];
- }
- HPOSTAMBLE
-}
-EXPORT_SYMBOL(__hsiphash_aligned);
-
-#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
-u32 __hsiphash_unaligned(const void *data, size_t len,
- const hsiphash_key_t *key)
+u32 __hsiphash(const void *data, size_t len, const hsiphash_key_t *key)
{
const u8 *end = data + len - (len % sizeof(u32));
const u8 left = len & (sizeof(u32) - 1);
@@ -460,8 +370,7 @@ u32 __hsiphash_unaligned(const void *data, size_t len,
}
HPOSTAMBLE
}
-EXPORT_SYMBOL(__hsiphash_unaligned);
-#endif
+EXPORT_SYMBOL(__hsiphash);
/**
* hsiphash_1u32 - compute 32-bit hsiphash PRF value of a u32
--
2.11.0
