On Tuesday 14 August 2012, Catalin Marinas wrote:

+
+void elf_set_personality(int personality)
+{
+       switch (personality & PER_MASK) {
+       case PER_LINUX:
+               clear_thread_flag(TIF_32BIT);
+               break;
+       case PER_LINUX32:
+               set_thread_flag(TIF_32BIT);
+               break;
+       default:
+               pr_warning("Process %s tried to assume unknown personality %d\n",
+                          current->comm, personality);
+               return;
+       }
+
+       current->personality = personality;
+}
+EXPORT_SYMBOL(elf_set_personality);

This looks wrong: PER_LINUX/PER_LINUX32 decides over the output of the
uname system call, while TIF_32BIT decides over the instruction set
when returning to user space. You definitely should not set the personality
to the value you pass from the elf loader. Instead, just do

#define SET_PERSONALITY(ex) clear_thread_flag(TIF_32BIT);
#defined COMPAT_SET_PERSONALITY(ex) set_thread_flag(TIF_32BIT);

I also don't see a reason to export this. You'd have trouble loading
the elf interpreter module from user space without the elf interpreter.

	Arnd