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>
---
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