ARM: 6878/1: fix personality flag propagation across an exec

Our SET_PERSONALITY() implementation was overwriting all existing
personality flags, including ADDR_NO_RANDOMIZE, making them unavailable
to processes being exec'd after a call to personality() in user space.
This prevents the gdb test suite from running successfully.
Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/kernel/elf.c

@@ -40,15 +40,22 @@ EXPORT_SYMBOL(elf_check_arch);
 void elf_set_personality(const struct elf32_hdr *x)
 {
 	unsigned int eflags = x->e_flags;
-	unsigned int personality = PER_LINUX_32BIT;
+	unsigned int personality = current->personality & ~PER_MASK;
+
+	/*
+	 * We only support Linux ELF executables, so always set the
+	 * personality to LINUX.
+	 */
+	personality |= PER_LINUX;
 
 	/*
 	 * APCS-26 is only valid for OABI executables
 	 */
-	if ((eflags & EF_ARM_EABI_MASK) == EF_ARM_EABI_UNKNOWN) {
-		if (eflags & EF_ARM_APCS_26)
-			personality = PER_LINUX;
-	}
+	if ((eflags & EF_ARM_EABI_MASK) == EF_ARM_EABI_UNKNOWN &&
+	    (eflags & EF_ARM_APCS_26))
+		personality &= ~ADDR_LIMIT_32BIT;
+	else
+		personality |= ADDR_LIMIT_32BIT;
 
 	set_personality(personality);