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

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; \ })

I would expect the compiler to optimize this away for archs that do not require aligned access.

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