[IA64] preserve personality flag bits across exec

In its <asm/elf.h> ia64 defines SET_PERSONALITY in a way that unconditionally
sets the personality of the current process to PER_LINUX, losing any flag bits
from the upper 3 bytes of current->personality.  This is wrong. Those bits are
intended to be inherited across exec (other code takes care of ensuring that
security sensitive bits like ADDR_NO_RANDOMIZE are not passed to unsuspecting
setuid/setgid applications).

Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/include/asm/elf.h

@@ -201,7 +201,9 @@ extern void ia64_elf_core_copy_regs (struct pt_regs *src, elf_gregset_t dst);
    relevant until we have real hardware to play with... */
 #define ELF_PLATFORM	NULL
 
-#define SET_PERSONALITY(ex)	set_personality(PER_LINUX)
+#define SET_PERSONALITY(ex)	\
+	set_personality((current->personality & ~PER_MASK) | PER_LINUX)
+
 #define elf_read_implies_exec(ex, executable_stack)					\
 	((executable_stack!=EXSTACK_DISABLE_X) && ((ex).e_flags & EF_IA_64_LINUX_EXECUTABLE_STACK) != 0)