syscalls: Add sys_set/get_thread_area helpers

They are actually banned in kernel for now, but
we might end up needing them, so better to have
them in-place.
Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>

include/syscall-codes.h

@@ -22,6 +22,9 @@
 #define __NR_exit		60
 #define __NR_unlink		87
 
+#define __NR_set_thread_area	205
+#define __NR_get_thread_area	211
+
 #else /* CONFIG_X86_64 */
 # error x86-32 bit mode not yet implemented
 #endif /* CONFIG_X86_64 */

include/syscall.h

@@ -3,6 +3,7 @@
 
 #include <sys/types.h>
 
+#include "types.h"
 #include "compiler.h"
 #include "syscall-codes.h"
 
@@ -210,6 +211,17 @@ static always_inline long sys_rt_sigreturn(void)
 	return syscall0(__NR_rt_sigreturn);
 }
 
+static always_inline long sys_set_thread_area(user_desc_t *info)
+{
+	return syscall1(__NR_set_thread_area, (long)info);
+}
+
+static always_inline long sys_get_thread_area(user_desc_t *info)
+{
+	return syscall1(__NR_get_thread_area, (long)info);
+}
+
+
 #else /* CONFIG_X86_64 */
 # error x86-32 bit mode not yet implemented
 #endif /* CONFIG_X86_64 */

include/types.h

@@ -56,6 +56,19 @@ typedef signed char		s8;
 
 #ifdef CONFIG_X86_64
 
+typedef struct {
+	unsigned int	entry_number;
+	unsigned int	base_addr;
+	unsigned int	limit;
+	unsigned int	seg_32bit:1;
+	unsigned int	contents:2;
+	unsigned int	read_exec_only:1;
+	unsigned int	limit_in_pages:1;
+	unsigned int	seg_not_present:1;
+	unsigned int	useable:1;
+	unsigned int	lm:1;
+} user_desc_t;
+
 typedef struct {
 	unsigned long	r15;
 	unsigned long	r14;