Intrinsics that Allow Reading from and Writing to the FS Base and GS Base Registers

There are eight intrinsics that allow reading and writing the value of the FS base and GS base registers at all privilege levels and in 64-bit mode only.

These intrinsics are mapped to corresponding Post 32nm processor extension instructions.

• _readfsbase_u32(), _readfsbase_u64()
  Read the value of the FS base register.
• _readgsbase_u32(), _readgsbase_u64()
  Read the value of the GS base register.
• _writefsbase_u32(), _writefsbase_u64()
  Write the value to the FS base register.
• _writegsbase_u32(), _writegsbase_u64()
  Write the value to the GS base register.