On 04/25/2016 03:48 PM, Sam Ravnborg wrote:
> Hi Dave.
>
>> Sparc64 requires type-aligned memory access. Since data buffers may not
>> be properly aligned, implement a safe copy from memory per data type.
>>
>> Signed-off-by: Dave Kleikamp <[email protected]>
>> ---
>> defs.h | 41 +++++++++++++++++++++++++++++++++++++++++
>> 1 files changed, 41 insertions(+), 0 deletions(-)
>>
>> diff --git a/defs.h b/defs.h
>> index e3afc58..d9d4559 100644
>> --- a/defs.h
>> +++ b/defs.h
>> @@ -2187,6 +2187,45 @@ struct builtin_debug_table {
>> * Facilitators for pulling correctly-sized data out of a buffer at a
>> * known address.
>> */
>> +
>> +#ifdef NEED_ALIGNED_MEM_ACCESS
>> +
>> +#define DEF_LOADER(TYPE) \
>> +static inline TYPE \
>> +load_##TYPE (char *addr) \
>> +{ \
>> + TYPE ret; \
>> + size_t i = sizeof(TYPE); \
>> + while (i--) \
>> + ((char *)&ret)[i] = addr[i]; \
>> + return ret; \
>> +}
>> +
>> +DEF_LOADER(int);
>> +DEF_LOADER(uint);
>> +DEF_LOADER(long);
>> +DEF_LOADER(ulong);
>> +DEF_LOADER(ulonglong);
>> +DEF_LOADER(ushort);
>> +DEF_LOADER(short);
>> +typedef void *pointer_t;
>> +DEF_LOADER(pointer_t);
>> +
>> +#define LOADER(TYPE) load_##TYPE
> A simpler model would be
> #define LOADER(TYPE, addr) \
> ({ \
> TYPE ret; \
> memcpy(&ret, (void *)addr, sizeof(TYPE)); \
> ret; \
> })
This does simplify things a bit.
>
> I would expect the compiler to optimize this away for archs
> that do not require aligned access.
I hesitate to to replace the macros for every architecture with this.
I'll let Dave A. make that call, but I think it can improve the
NEED_ALIGNED_MEM_ACCESS case.
>
> Quick test:
>
> #include <string.h>
> #include <stdio.h>
>
> #define LOADER(TYPE, addr) \
> ({ \
> TYPE ret; \
> memcpy(&ret, (void*)addr, sizeof(TYPE)); \
> ret; \
> })
>
> #define INT(ADDR) LOADER(int, ADDR)
>
> void main(void)
> {
> int i = 37;
> int j = -17;
>
> printf("i=%d j=%d\n", INT(&i), INT(&j));
> }
>
>
> Sam
>
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