64-bit %fs segment

04d2a8a3 · Nickolai Zeldovich · 7e161483 · 04d2a8a3 · 04d2a8a3
--- a/include/amd64.h
+++ b/include/amd64.h
@@ -133,6 +133,20 @@ ltr(u16 sel)
 }

 static inline void
+writefs(u16 v)
+{
+  __asm volatile("movw %0, %%fs" : : "r" (v));
+}
+
+static inline u16
+readfs(void)
+{
+  u16 v;
+  __asm volatile("movw %%fs, %0" : "=r" (v));
+  return v;
+}
+
+static inline void
 writegs(u16 v)
 {
  __asm volatile("movw %0, %%gs" : : "r" (v));

--- a/kernel/hwvm.cc
+++ b/kernel/hwvm.cc
@@ -127,6 +127,8 @@ switchvm(struct proc *p)
    lcr3(v2p(p->vmap->pml4));  // switch to new address space
  else
    switchkvm();
+
+  writefs(UDSEG);
  writemsr(MSR_FS_BASE, p->user_fs_);

  popcli();