x86/fsgsbase: Revert FSGSBASE support

[linux-2.6-microblaze.git] / arch / x86 / kernel / process_64.c

diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 8f23909..250e4c4 100644 (file)
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -161,40 +161,6 @@ enum which_selector {
        GS
 };
 
-/*
- * Out of line to be protected from kprobes. It is not used on Xen
- * paravirt. When paravirt support is needed, it needs to be renamed
- * with native_ prefix.
- */
-static noinline unsigned long __rdgsbase_inactive(void)
-{
-       unsigned long gsbase;
-
-       lockdep_assert_irqs_disabled();
-
-       native_swapgs();
-       gsbase = rdgsbase();
-       native_swapgs();
-
-       return gsbase;
-}
-NOKPROBE_SYMBOL(__rdgsbase_inactive);
-
-/*
- * Out of line to be protected from kprobes. It is not used on Xen
- * paravirt. When paravirt support is needed, it needs to be renamed
- * with native_ prefix.
- */
-static noinline void __wrgsbase_inactive(unsigned long gsbase)
-{
-       lockdep_assert_irqs_disabled();
-
-       native_swapgs();
-       wrgsbase(gsbase);
-       native_swapgs();
-}
-NOKPROBE_SYMBOL(__wrgsbase_inactive);
-
 /*
  * Saves the FS or GS base for an outgoing thread if FSGSBASE extensions are
  * not available.  The goal is to be reasonably fast on non-FSGSBASE systems.
@@ -244,22 +210,8 @@ static __always_inline void save_fsgs(struct task_struct *task)
 {
        savesegment(fs, task->thread.fsindex);
        savesegment(gs, task->thread.gsindex);
-       if (static_cpu_has(X86_FEATURE_FSGSBASE)) {
-               unsigned long flags;
-
-               /*
-                * If FSGSBASE is enabled, we can't make any useful guesses
-                * about the base, and user code expects us to save the current
-                * value.  Fortunately, reading the base directly is efficient.
-                */
-               task->thread.fsbase = rdfsbase();
-               local_irq_save(flags);
-               task->thread.gsbase = __rdgsbase_inactive();
-               local_irq_restore(flags);
-       } else {
-               save_base_legacy(task, task->thread.fsindex, FS);
-               save_base_legacy(task, task->thread.gsindex, GS);
-       }
+       save_base_legacy(task, task->thread.fsindex, FS);
+       save_base_legacy(task, task->thread.gsindex, GS);
 }
 
 #if IS_ENABLED(CONFIG_KVM)
@@ -338,22 +290,10 @@ static __always_inline void load_seg_legacy(unsigned short prev_index,
 static __always_inline void x86_fsgsbase_load(struct thread_struct *prev,
                                              struct thread_struct *next)
 {
-       if (static_cpu_has(X86_FEATURE_FSGSBASE)) {
-               /* Update the FS and GS selectors if they could have changed. */
-               if (unlikely(prev->fsindex || next->fsindex))
-                       loadseg(FS, next->fsindex);
-               if (unlikely(prev->gsindex || next->gsindex))
-                       loadseg(GS, next->gsindex);
-
-               /* Update the bases. */
-               wrfsbase(next->fsbase);
-               __wrgsbase_inactive(next->gsbase);
-       } else {
-               load_seg_legacy(prev->fsindex, prev->fsbase,
-                               next->fsindex, next->fsbase, FS);
-               load_seg_legacy(prev->gsindex, prev->gsbase,
-                               next->gsindex, next->gsbase, GS);
-       }
+       load_seg_legacy(prev->fsindex, prev->fsbase,
+                       next->fsindex, next->fsbase, FS);
+       load_seg_legacy(prev->gsindex, prev->gsbase,
+                       next->gsindex, next->gsbase, GS);
 }
 
 static unsigned long x86_fsgsbase_read_task(struct task_struct *task,
@@ -399,46 +339,13 @@ static unsigned long x86_fsgsbase_read_task(struct task_struct *task,
        return base;
 }
 
-unsigned long x86_gsbase_read_cpu_inactive(void)
-{
-       unsigned long gsbase;
-
-       if (static_cpu_has(X86_FEATURE_FSGSBASE)) {
-               unsigned long flags;
-
-               /* Interrupts are disabled here. */
-               local_irq_save(flags);
-               gsbase = __rdgsbase_inactive();
-               local_irq_restore(flags);
-       } else {
-               rdmsrl(MSR_KERNEL_GS_BASE, gsbase);
-       }
-
-       return gsbase;
-}
-
-void x86_gsbase_write_cpu_inactive(unsigned long gsbase)
-{
-       if (static_cpu_has(X86_FEATURE_FSGSBASE)) {
-               unsigned long flags;
-
-               /* Interrupts are disabled here. */
-               local_irq_save(flags);
-               __wrgsbase_inactive(gsbase);
-               local_irq_restore(flags);
-       } else {
-               wrmsrl(MSR_KERNEL_GS_BASE, gsbase);
-       }
-}
-
 unsigned long x86_fsbase_read_task(struct task_struct *task)
 {
        unsigned long fsbase;
 
        if (task == current)
                fsbase = x86_fsbase_read_cpu();
-       else if (static_cpu_has(X86_FEATURE_FSGSBASE) ||
-                (task->thread.fsindex == 0))
+       else if (task->thread.fsindex == 0)
                fsbase = task->thread.fsbase;
        else
                fsbase = x86_fsgsbase_read_task(task, task->thread.fsindex);
@@ -452,8 +359,7 @@ unsigned long x86_gsbase_read_task(struct task_struct *task)
 
        if (task == current)
                gsbase = x86_gsbase_read_cpu_inactive();
-       else if (static_cpu_has(X86_FEATURE_FSGSBASE) ||
-                (task->thread.gsindex == 0))
+       else if (task->thread.gsindex == 0)
                gsbase = task->thread.gsbase;
        else
                gsbase = x86_fsgsbase_read_task(task, task->thread.gsindex);
@@ -493,11 +399,10 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
        p->thread.sp = (unsigned long) fork_frame;
        p->thread.io_bitmap_ptr = NULL;
 
-       save_fsgs(me);
-       p->thread.fsindex = me->thread.fsindex;
-       p->thread.fsbase = me->thread.fsbase;
-       p->thread.gsindex = me->thread.gsindex;
-       p->thread.gsbase = me->thread.gsbase;
+       savesegment(gs, p->thread.gsindex);
+       p->thread.gsbase = p->thread.gsindex ? 0 : me->thread.gsbase;
+       savesegment(fs, p->thread.fsindex);
+       p->thread.fsbase = p->thread.fsindex ? 0 : me->thread.fsbase;
        savesegment(es, p->thread.es);
        savesegment(ds, p->thread.ds);
        memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));