Merge branch 'x86-fpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 FPU updates from Ingo Molnar:
 "x86 FPU handling fixes, cleanups and enhancements from Oleg.

  The signal handling race fix and the __restore_xstate_sig() preemption
  fix for eager-mode is marked for -stable as well"

* 'x86-fpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86: copy_thread: Don't nullify ->ptrace_bps twice
  x86, fpu: Shift "fpu_counter = 0" from copy_thread() to arch_dup_task_struct()
  x86, fpu: copy_process: Sanitize fpu->last_cpu initialization
  x86, fpu: copy_process: Avoid fpu_alloc/copy if !used_math()
  x86, fpu: Change __thread_fpu_begin() to use use_eager_fpu()
  x86, fpu: __restore_xstate_sig()->math_state_restore() needs preempt_disable()
  x86, fpu: shift drop_init_fpu() from save_xstate_sig() to handle_signal()

6 files changed, 20 insertions, 19 deletions

diff --git a/arch/x86/include/asm/fpu-internal.h b/arch/x86/include/asm/fpu-internal.h
index 412ececa00b9..e97622f57722 100644
--- a/arch/x86/include/asm/fpu-internal.h
+++ b/arch/x86/include/asm/fpu-internal.h
@@ -344,7 +344,7 @@ static inline void __thread_fpu_end(struct task_struct *tsk)
 
 static inline void __thread_fpu_begin(struct task_struct *tsk)
 {
-        if (!static_cpu_has_safe(X86_FEATURE_EAGER_FPU))
+        if (!use_eager_fpu())
                 clts();
         __thread_set_has_fpu(tsk);
 }
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index f804dc935d2a..e127ddaa2d5a 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -64,14 +64,16 @@ EXPORT_SYMBOL_GPL(task_xstate_cachep);
  */
 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
 {
-        int ret;
-
         *dst = *src;
-        if (fpu_allocated(&src->thread.fpu)) {
-                memset(&dst->thread.fpu, 0, sizeof(dst->thread.fpu));
-                ret = fpu_alloc(&dst->thread.fpu);
-                if (ret)
-                        return ret;
+
+        dst->thread.fpu_counter = 0;
+        dst->thread.fpu.has_fpu = 0;
+        dst->thread.fpu.last_cpu = ~0;
+        dst->thread.fpu.state = NULL;
+        if (tsk_used_math(src)) {
+                int err = fpu_alloc(&dst->thread.fpu);
+                if (err)
+                        return err;
                 fpu_copy(dst, src);
         }
         return 0;
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 7bc86bbe7485..8f3ebfe710d0 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -138,6 +138,7 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
 
         p->thread.sp = (unsigned long) childregs;
         p->thread.sp0 = (unsigned long) (childregs+1);
+        memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
 
         if (unlikely(p->flags & PF_KTHREAD)) {
                 /* kernel thread */
@@ -152,9 +153,7 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
                 childregs->orig_ax = -1;
                 childregs->cs = __KERNEL_CS | get_kernel_rpl();
                 childregs->flags = X86_EFLAGS_IF | X86_EFLAGS_FIXED;
-                p->thread.fpu_counter = 0;
                 p->thread.io_bitmap_ptr = NULL;
-                memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
                 return 0;
         }
         *childregs = *current_pt_regs();
@@ -165,13 +164,10 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
         p->thread.ip = (unsigned long) ret_from_fork;
         task_user_gs(p) = get_user_gs(current_pt_regs());
 
-        p->thread.fpu_counter = 0;
         p->thread.io_bitmap_ptr = NULL;
         tsk = current;
         err = -ENOMEM;
 
-        memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
-
         if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
                 p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr,
                                                 IO_BITMAP_BYTES, GFP_KERNEL);
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index ca5b02d405c3..3ed4a68d4013 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -163,7 +163,6 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
         p->thread.sp = (unsigned long) childregs;
         p->thread.usersp = me->thread.usersp;
         set_tsk_thread_flag(p, TIF_FORK);
-        p->thread.fpu_counter = 0;
         p->thread.io_bitmap_ptr = NULL;
 
         savesegment(gs, p->thread.gsindex);
@@ -193,8 +192,6 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
                 childregs->sp = sp;
 
         err = -ENOMEM;
-        memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
-
         if (unlikely(test_tsk_thread_flag(me, TIF_IO_BITMAP))) {
                 p->thread.io_bitmap_ptr = kmemdup(me->thread.io_bitmap_ptr,
                                                   IO_BITMAP_BYTES, GFP_KERNEL);
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 2851d63c1202..ed37a768d0fc 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -675,6 +675,11 @@ handle_signal(struct ksignal *ksig, struct pt_regs *regs)
                  * handler too.
                  */
                 regs->flags &= ~(X86_EFLAGS_DF|X86_EFLAGS_RF|X86_EFLAGS_TF);
+                /*
+                 * Ensure the signal handler starts with the new fpu state.
+                 */
+                if (used_math())
+                        drop_init_fpu(current);
         }
         signal_setup_done(failed, ksig, test_thread_flag(TIF_SINGLESTEP));
 }
diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index 940b142cc11f..4c540c4719d8 100644
--- a/arch/x86/kernel/xsave.c
+++ b/arch/x86/kernel/xsave.c
@@ -271,8 +271,6 @@ int save_xstate_sig(void __user *buf, void __user *buf_fx, int size)
         if (use_fxsr() && save_xstate_epilog(buf_fx, ia32_fxstate))
                 return -1;
 
-        drop_init_fpu(tsk);     /* trigger finit */
-
         return 0;
 }
 
@@ -402,8 +400,11 @@ int __restore_xstate_sig(void __user *buf, void __user *buf_fx, int size)
                         set_used_math();
                 }
 
-                if (use_eager_fpu())
+                if (use_eager_fpu()) {
+                        preempt_disable();
                         math_state_restore();
+                        preempt_enable();
+                }
 
                 return err;
         } else {