Re: [Crash-utility] [PATCH V3 2/3] Implement byte-by-byte memory access facilitators

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 <dave.kleikamp(a)oracle.com&gt; >> --- >> 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 > -- Crash-utility mailing list Crash-utility(a)redhat.com https://www.redhat.com/mailman/listinfo/crash-utility