1 files changed, 51 insertions, 34 deletions

diff --git a/arch/i386/kernel/process.c b/arch/i386/kernel/process.c
index 06dfa65ad18..84664710b78 100644
--- a/arch/i386/kernel/process.c
+++ b/arch/i386/kernel/process.c
@@ -300,6 +300,7 @@ early_param("idle", idle_setup);
 void show_regs(struct pt_regs * regs)
 {
 	unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;
+	unsigned long d0, d1, d2, d3, d6, d7;
 
 	printk("\n");
 	printk("Pid: %d, comm: %20s\n", current->pid, current->comm);
@@ -324,6 +325,17 @@ void show_regs(struct pt_regs * regs)
 	cr3 = read_cr3();
 	cr4 = read_cr4_safe();
 	printk("CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n", cr0, cr2, cr3, cr4);
+
+	get_debugreg(d0, 0);
+	get_debugreg(d1, 1);
+	get_debugreg(d2, 2);
+	get_debugreg(d3, 3);
+	printk("DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n",
+			d0, d1, d2, d3);
+	get_debugreg(d6, 6);
+	get_debugreg(d7, 7);
+	printk("DR6: %08lx DR7: %08lx\n", d6, d7);
+
 	show_trace(NULL, regs, &regs->esp);
 }
 
@@ -538,8 +550,31 @@ int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
 	return 1;
 }
 
-static noinline void __switch_to_xtra(struct task_struct *next_p,
-				    struct tss_struct *tss)
+#ifdef CONFIG_SECCOMP
+void hard_disable_TSC(void)
+{
+	write_cr4(read_cr4() | X86_CR4_TSD);
+}
+void disable_TSC(void)
+{
+	preempt_disable();
+	if (!test_and_set_thread_flag(TIF_NOTSC))
+		/*
+		 * Must flip the CPU state synchronously with
+		 * TIF_NOTSC in the current running context.
+		 */
+		hard_disable_TSC();
+	preempt_enable();
+}
+void hard_enable_TSC(void)
+{
+	write_cr4(read_cr4() & ~X86_CR4_TSD);
+}
+#endif /* CONFIG_SECCOMP */
+
+static noinline void
+__switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
+		 struct tss_struct *tss)
 {
 	struct thread_struct *next;
 
@@ -555,6 +590,17 @@ static noinline void __switch_to_xtra(struct task_struct *next_p,
 		set_debugreg(next->debugreg[7], 7);
 	}
 
+#ifdef CONFIG_SECCOMP
+	if (test_tsk_thread_flag(prev_p, TIF_NOTSC) ^
+	    test_tsk_thread_flag(next_p, TIF_NOTSC)) {
+		/* prev and next are different */
+		if (test_tsk_thread_flag(next_p, TIF_NOTSC))
+			hard_disable_TSC();
+		else
+			hard_enable_TSC();
+	}
+#endif
+
 	if (!test_tsk_thread_flag(next_p, TIF_IO_BITMAP)) {
 		/*
 		 * Disable the bitmap via an invalid offset. We still cache
@@ -586,33 +632,6 @@ static noinline void __switch_to_xtra(struct task_struct *next_p,
 }
 
 /*
- * This function selects if the context switch from prev to next
- * has to tweak the TSC disable bit in the cr4.
- */
-static inline void disable_tsc(struct task_struct *prev_p,
-			       struct task_struct *next_p)
-{
-	struct thread_info *prev, *next;
-
-	/*
-	 * gcc should eliminate the ->thread_info dereference if
-	 * has_secure_computing returns 0 at compile time (SECCOMP=n).
-	 */
-	prev = task_thread_info(prev_p);
-	next = task_thread_info(next_p);
-
-	if (has_secure_computing(prev) || has_secure_computing(next)) {
-		/* slow path here */
-		if (has_secure_computing(prev) &&
-		    !has_secure_computing(next)) {
-			write_cr4(read_cr4() & ~X86_CR4_TSD);
-		} else if (!has_secure_computing(prev) &&
-			   has_secure_computing(next))
-			write_cr4(read_cr4() | X86_CR4_TSD);
-	}
-}
-
-/*
  *	switch_to(x,yn) should switch tasks from x to y.
  *
  * We fsave/fwait so that an exception goes off at the right time
@@ -689,11 +708,9 @@ struct task_struct fastcall * __switch_to(struct task_struct *prev_p, struct tas
 	/*
 	 * Now maybe handle debug registers and/or IO bitmaps
 	 */
-	if (unlikely((task_thread_info(next_p)->flags & _TIF_WORK_CTXSW)
-	    || test_tsk_thread_flag(prev_p, TIF_IO_BITMAP)))
-		__switch_to_xtra(next_p, tss);
-
-	disable_tsc(prev_p, next_p);
+	if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV ||
+		     task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT))
+		__switch_to_xtra(prev_p, next_p, tss);
 
 	/*
 	 * Leave lazy mode, flushing any hypercalls made here.