[RFC PATCH-mm] kernel: add new endian and unaligned access helpers

From: Harvey Harrison
Date: Thu Nov 20 2008 - 20:12:23 EST

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Add the following API for the 6 endian types in the kernel
__le16,__le32, __le64, __be16, __be32, __be64:

u16 load_le16(const __le16 *p)
void store_le16(__le16 *p, u16 val)

u16 load_le16_noalign(const __le16 *p)
void store_le16_noalign(__le16 *p, u16 val)

Some general comments:

get/put_unaligned are being replaced because get/put in the kernel
usually implies some kind of reference is being taken/released, which
is not the case here. They work with void * pointers which defeats
sparse checking. Also, put_unaligned takes its arguments in the
opposite order from what is expected. The new names are chosen
to allow the APIs to live in parallel without breaking compilation.
The get/put_unaligned API can be removed once all users are converted.

load_le16 is a synonym for the existing le16_to_cpup and is added to
be symmetric with the load_le16_noalign API. On arches where unaligned
access is OK, the unaligned calls are replaced with aligned calls.

store_le16 is a new API and is added to be symmetric with the unaligned
functions. It is implemented as a macro to allow compile-time byteswapping
when the value is a constant. This will also allow use in many places
currently that are of the form:

*(__le16 *)ptr = cpu_to_le16(foo);

In addition, some drivers/filesystems/arches already provide this API
privately, which will allow them to be consolidated into this common
code.

Signed-off-by: Harvey Harrison <harvey.harrison@xxxxxxxxx>
---
Andrew, depends on the unaligned patches and the byteorder patches in -mm,
so needs to come after both sets.

include/asm-generic/unaligned.h | 117 +++++++++++++++++++++++----------------
include/linux/byteorder.h | 26 +++++++--
2 files changed, 89 insertions(+), 54 deletions(-)

diff --git a/include/asm-generic/unaligned.h b/include/asm-generic/unaligned.h
index 55d1126..54d4a48 100644
--- a/include/asm-generic/unaligned.h
+++ b/include/asm-generic/unaligned.h
@@ -6,6 +6,20 @@

#ifdef _UNALIGNED_ACCESS_OK

+# define load_le16_noalign load_le16
+# define load_le32_noalign load_le32
+# define load_le64_noalign load_le64
+# define load_be16_noalign load_be16
+# define load_be32_noalign load_be32
+# define load_be64_noalign load_be64
+
+# define store_le16_noalign store_le16
+# define store_le32_noalign store_le32
+# define store_le64_noalign store_le64
+# define store_be16_noalign store_be16
+# define store_be32_noalign store_be32
+# define store_be64_noalign store_be64
+
static inline u16 get_unaligned_le16(const void *p)
{
return le16_to_cpup(p);
@@ -102,60 +116,67 @@ static inline u64 __get_be64_noalign(const u8 *p)
return ((u64)__get_be32_noalign(p) << 32) | __get_be32_noalign(p + 4);
}

-static inline u16 get_unaligned_le16(const void *p)
+static inline u16 load_le16_noalign(const __le16 *p)
{
#ifdef __LITTLE_ENDIAN
- return ((const struct __una_u16 *)p)->x;
+ return ((__force const struct __una_u16 *)p)->x;
#else
- return __get_le16_noalign(p);
+ return __get_le16_noalign((__force const u8 *)p);
#endif
}

-static inline u32 get_unaligned_le32(const void *p)
+static inline u32 load_le32_noalign(const __le32 *p)
{
#ifdef __LITTLE_ENDIAN
- return ((const struct __una_u32 *)p)->x;
+ return ((__force const struct __una_u32 *)p)->x;
#else
- return __get_le32_noalign(p);
+ return __get_le32_noalign((__force const u8 *)p);
#endif
}

-static inline u64 get_unaligned_le64(const void *p)
+static inline u64 load_le64_noalign(const __le64 *p)
{
#ifdef __LITTLE_ENDIAN
- return ((const struct __una_u64 *)p)->x;
+ return ((__force const struct __una_u64 *)p)->x;
#else
- return __get_le64_noalign(p);
+ return __get_le64_noalign((__force const u8 *)p);
#endif
}

-static inline u16 get_unaligned_be16(const void *p)
+static inline u16 load_be16_noalign(const __be16 *p)
{
#ifdef __BIG_ENDIAN
- return ((const struct __una_u16 *)p)->x;
+ return ((__force const struct __una_u16 *)p)->x;
#else
- return __get_be16_noalign(p);
+ return __get_be16_noalign((__force const u8 *)p);
#endif
}

-static inline u32 get_unaligned_be32(const void *p)
+static inline u32 load_be32_noalign(const __be32 *p)
{
#ifdef __BIG_ENDIAN
- return ((const struct __una_u32 *)p)->x;
+ return ((__force const struct __una_u32 *)p)->x;
#else
- return __get_be32_noalign(p);
+ return __get_be32_noalign((__force const u8 *)p);
#endif
}

-static inline u64 get_unaligned_be64(const void *p)
+static inline u64 load_be64_noalign(const __be64 *p)
{
#ifdef __BIG_ENDIAN
- return ((const struct __una_u64 *)p)->x;
+ return ((__force const struct __una_u64 *)p)->x;
#else
- return __get_be64_noalign(p);
+ return __get_be64_noalign((__force const u8 *)p);
#endif
}

+# define get_unaligned_le16(p) load_le16_noalign((const void *)(p))
+# define get_unaligned_le32(p) load_le32_noalign((const void *)(p))
+# define get_unaligned_le64(p) load_le64_noalign((const void *)(p))
+# define get_unaligned_be16(p) load_be16_noalign((const void *)(p))
+# define get_unaligned_be32(p) load_be32_noalign((const void *)(p))
+# define get_unaligned_be64(p) load_be64_noalign((const void *)(p))
+
static inline void __put_le16_noalign(u8 *p, u16 val)
{
*p++ = val;
@@ -192,57 +213,57 @@ static inline void __put_be64_noalign(u8 *p, u64 val)
__put_be32_noalign(p + 4, val);
}

-static inline void put_unaligned_le16(u16 val, void *p)
+static inline void store_le16_noalign(__le16 *p, u16 val)
{
#ifdef __LITTLE_ENDIAN
- ((struct __una_u16 *)p)->x = val;
+ ((__force struct __una_u16 *)p)->x = val;
#else
- __put_le16_noalign(p, val);
+ __put_le16_noalign((__force u8 *)p, val);
#endif
}

-static inline void put_unaligned_le32(u32 val, void *p)
+static inline void store_le32_noalign(__le32 *p, u32 val)
{
#ifdef __LITTLE_ENDIAN
- ((struct __una_u32 *)p)->x = val;
+ ((__force struct __una_u32 *)p)->x = val;
#else
- __put_le32_noalign(p, val);
+ __put_le32_noalign((__force u8 *)p, val);
#endif
}

-static inline void put_unaligned_le64(u64 val, void *p)
+static inline void store_le64_noalign(__le64 *p, u64 val)
{
#ifdef __LITTLE_ENDIAN
- ((struct __una_u64 *)p)->x = val;
+ ((__force struct __una_u64 *)p)->x = val;
#else
- __put_le64_noalign(p, val);
+ __put_le64_noalign((__force u8 *)p, val);
#endif
}

-static inline void put_unaligned_be16(u16 val, void *p)
+static inline void store_be16_noalign(__be16 *p, u16 val)
{
#ifdef __BIG_ENDIAN
- ((struct __una_u16 *)p)->x = val;
+ ((__force struct __una_u16 *)p)->x = val;
#else
- __put_be16_noalign(p, val);
+ __put_be16_noalign((__force u8 *)p, val);
#endif
}

-static inline void put_unaligned_be32(u32 val, void *p)
+static inline void store_be32_noalign(__be32 *p, u32 val)
{
#ifdef __BIG_ENDIAN
- ((struct __una_u32 *)p)->x = val;
+ ((__force struct __una_u32 *)p)->x = val;
#else
- __put_be32_noalign(p, val);
+ __put_be32_noalign((__force u8 *)p, val);
#endif
}

-static inline void put_unaligned_be64(u64 val, void *p)
+static inline void store_be64_noalign(__be64 *p, u64 val)
{
#ifdef __BIG_ENDIAN
- ((struct __una_u64 *)p)->x = val;
+ ((__force struct __una_u64 *)p)->x = val;
#else
- __put_be64_noalign(p, val);
+ __put_be64_noalign((__force u8 *)p, val);
#endif
}

@@ -256,17 +277,17 @@ extern void __bad_unaligned_access_size(void);

#define __get_unaligned_le(ptr) ((__force typeof(*(ptr)))({ \
__builtin_choose_expr(sizeof(*(ptr)) == 1, *(ptr), \
- __builtin_choose_expr(sizeof(*(ptr)) == 2, get_unaligned_le16((ptr)), \
- __builtin_choose_expr(sizeof(*(ptr)) == 4, get_unaligned_le32((ptr)), \
- __builtin_choose_expr(sizeof(*(ptr)) == 8, get_unaligned_le64((ptr)), \
+ __builtin_choose_expr(sizeof(*(ptr)) == 2, load_le16_noalign(ptr), \
+ __builtin_choose_expr(sizeof(*(ptr)) == 4, load_le32_noalign(ptr), \
+ __builtin_choose_expr(sizeof(*(ptr)) == 8, load_le64_noalign(ptr), \
__bad_unaligned_access_size())))); \
}))

#define __get_unaligned_be(ptr) ((__force typeof(*(ptr)))({ \
__builtin_choose_expr(sizeof(*(ptr)) == 1, *(ptr), \
- __builtin_choose_expr(sizeof(*(ptr)) == 2, get_unaligned_be16((ptr)), \
- __builtin_choose_expr(sizeof(*(ptr)) == 4, get_unaligned_be32((ptr)), \
- __builtin_choose_expr(sizeof(*(ptr)) == 8, get_unaligned_be64((ptr)), \
+ __builtin_choose_expr(sizeof(*(ptr)) == 2, load_be16_noalign(ptr), \
+ __builtin_choose_expr(sizeof(*(ptr)) == 4, load_be32_noalign(ptr), \
+ __builtin_choose_expr(sizeof(*(ptr)) == 8, load_be64_noalign(ptr), \
__bad_unaligned_access_size())))); \
}))

@@ -277,13 +298,13 @@ extern void __bad_unaligned_access_size(void);
*(u8 *)__gu_p = (__force u8)(val); \
break; \
case 2: \
- put_unaligned_le16((__force u16)(val), __gu_p); \
+ store_le16_noalign(__gu_p, (__force u16)(val)); \
break; \
case 4: \
- put_unaligned_le32((__force u32)(val), __gu_p); \
+ store_le32_noalign(__gu_p, (__force u32)(val)); \
break; \
case 8: \
- put_unaligned_le64((__force u64)(val), __gu_p); \
+ store_le64_noalign(__gu_p, (__force u64)(val)); \
break; \
default: \
__bad_unaligned_access_size(); \
@@ -298,13 +319,13 @@ extern void __bad_unaligned_access_size(void);
*(u8 *)__gu_p = (__force u8)(val); \
break; \
case 2: \
- put_unaligned_be16((__force u16)(val), __gu_p); \
+ store_be16_noalign(__gu_p, (__force u16)(val)); \
break; \
case 4: \
- put_unaligned_be32((__force u32)(val), __gu_p); \
+ store_be32_noalign(__gu_p, (__force u32)(val)); \
break; \
case 8: \
- put_unaligned_be64((__force u64)(val), __gu_p); \
+ store_be64_noalign(__gu_p, (__force u64)(val)); \
break; \
default: \
__bad_unaligned_access_size(); \
diff --git a/include/linux/byteorder.h b/include/linux/byteorder.h
index 29f002d..ba87b00 100644
--- a/include/linux/byteorder.h
+++ b/include/linux/byteorder.h
@@ -292,6 +292,20 @@ static inline __be64 __cpu_to_be64p(const __u64 *p)
# define cpu_to_be32 __cpu_to_be32
# define cpu_to_be64 __cpu_to_be64

+# define load_le16 __le16_to_cpup
+# define load_le32 __le32_to_cpup
+# define load_le64 __le64_to_cpup
+# define load_be16 __be16_to_cpup
+# define load_be32 __be32_to_cpup
+# define load_be64 __be64_to_cpup
+
+# define store_le16(p, val) (*(__le16 *)(p) = __cpu_to_le16(val))
+# define store_le32(p, val) (*(__le32 *)(p) = __cpu_to_le32(val))
+# define store_le64(p, val) (*(__le64 *)(p) = __cpu_to_le64(val))
+# define store_be16(p, val) (*(__be16 *)(p) = __cpu_to_be16(val))
+# define store_be32(p, val) (*(__be32 *)(p) = __cpu_to_be32(val))
+# define store_be64(p, val) (*(__be64 *)(p) = __cpu_to_be64(val))
+
# define le16_to_cpup __le16_to_cpup
# define le32_to_cpup __le32_to_cpup
# define le64_to_cpup __le64_to_cpup
@@ -340,32 +354,32 @@ static inline __be64 __cpu_to_be64p(const __u64 *p)

static inline void le16_add_cpu(__le16 *var, u16 val)
{
- *var = cpu_to_le16(le16_to_cpup(var) + val);
+ store_le16(var, load_le16(var) + val);
}

static inline void le32_add_cpu(__le32 *var, u32 val)
{
- *var = cpu_to_le32(le32_to_cpup(var) + val);
+ store_le32(var, load_le32(var) + val);
}

static inline void le64_add_cpu(__le64 *var, u64 val)
{
- *var = cpu_to_le64(le64_to_cpup(var) + val);
+ store_le64(var, load_le64(var) + val);
}

static inline void be16_add_cpu(__be16 *var, u16 val)
{
- *var = cpu_to_be16(be16_to_cpup(var) + val);
+ store_be16(var, load_be16(var) + val);
}

static inline void be32_add_cpu(__be32 *var, u32 val)
{
- *var = cpu_to_be32(be32_to_cpup(var) + val);
+ store_be32(var, load_be32(var) + val);
}

static inline void be64_add_cpu(__be64 *var, u64 val)
{
- *var = cpu_to_be64(be64_to_cpup(var) + val);
+ store_be64(var, load_be64(var) + val);
}

#endif /* __KERNEL__ */
--
1.6.0.4.1013.gc6a01

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