[PATCH] sanitize TLS API

This removes the TLS clear operation.  I've left the flags mask and the
writable flag just so that we have the option to introduce extensions
without breaking the ABI.

arch/i386/kernel/process.c

@@ -851,17 +851,6 @@ asmlinkage int sys_set_thread_area(unsigned long base, unsigned long flags)
 	if (flags & ~TLS_FLAGS_MASK)
 		return -EINVAL;
 
-	/*
-	 * Clear the TLS?
-	 */
-	if (flags & TLS_FLAG_CLEAR) {
-		cpu = get_cpu();
-        	t->tls_desc.a = t->tls_desc.b = 0;
-		load_TLS_desc(t, cpu);
-		put_cpu();
-		return 0;
-	}
-
 	if (flags & TLS_FLAG_WRITABLE)
 		writable = 1;
 

include/asm-i386/desc.h

@@ -86,10 +86,9 @@ static inline void set_ldt_desc(unsigned int cpu, void *addr, unsigned int size)
 	_set_tssldt_desc(&cpu_gdt_table[cpu][LDT_ENTRY], (int)addr, ((size << 3)-1), 0x82);
 }
 
-#define TLS_FLAGS_MASK			0x00000003
+#define TLS_FLAGS_MASK			0x00000001
 
 #define TLS_FLAG_WRITABLE		0x00000001
-#define TLS_FLAG_CLEAR			0x00000002
 
 static inline void load_TLS_desc(struct thread_struct *t, unsigned int cpu)
 {

include/asm-i386/unistd.h

@@ -247,6 +247,7 @@
 #define __NR_futex		240
 #define __NR_sched_setaffinity	241
 #define __NR_sched_getaffinity	242
+#define __NR_set_thread_area	243
 
 /* user-visible error numbers are in the range -1 - -124: see <asm-i386/errno.h> */