Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input

[karo-tx-linux.git] / arch / x86 / kernel / traps.c

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index b3a9d24dba25cc1c8b276ce3cffb2c8cd83e9fe5..9d2073e2ecc92f5c97d51178236d8b2bc63ac029 100644 (file)
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -110,15 +110,11 @@ static inline void preempt_conditional_cli(struct pt_regs *regs)
 
 enum ctx_state ist_enter(struct pt_regs *regs)
 {
-       /*
-        * We are atomic because we're on the IST stack (or we're on x86_32,
-        * in which case we still shouldn't schedule.
-        */
-       preempt_count_add(HARDIRQ_OFFSET);
+       enum ctx_state prev_state;
 
        if (user_mode_vm(regs)) {
                /* Other than that, we're just an exception. */
-               return exception_enter();
+               prev_state = exception_enter();
        } else {
                /*
                 * We might have interrupted pretty much anything.  In
@@ -127,12 +123,27 @@ enum ctx_state ist_enter(struct pt_regs *regs)
                 * but we need to notify RCU.
                 */
                rcu_nmi_enter();
-               return IN_KERNEL;  /* the value is irrelevant. */
+               prev_state = IN_KERNEL;  /* the value is irrelevant. */
        }
+
+       /*
+        * We are atomic because we're on the IST stack (or we're on x86_32,
+        * in which case we still shouldn't schedule).
+        *
+        * This must be after exception_enter(), because exception_enter()
+        * won't do anything if in_interrupt() returns true.
+        */
+       preempt_count_add(HARDIRQ_OFFSET);
+
+       /* This code is a bit fragile.  Test it. */
+       rcu_lockdep_assert(rcu_is_watching(), "ist_enter didn't work");
+
+       return prev_state;
 }
 
 void ist_exit(struct pt_regs *regs, enum ctx_state prev_state)
 {
+       /* Must be before exception_exit. */
        preempt_count_sub(HARDIRQ_OFFSET);
 
        if (user_mode_vm(regs))
@@ -141,6 +152,44 @@ void ist_exit(struct pt_regs *regs, enum ctx_state prev_state)
                rcu_nmi_exit();
 }
 
+/**
+ * ist_begin_non_atomic() - begin a non-atomic section in an IST exception
+ * @regs:      regs passed to the IST exception handler
+ *
+ * IST exception handlers normally cannot schedule.  As a special
+ * exception, if the exception interrupted userspace code (i.e.
+ * user_mode_vm(regs) would return true) and the exception was not
+ * a double fault, it can be safe to schedule.  ist_begin_non_atomic()
+ * begins a non-atomic section within an ist_enter()/ist_exit() region.
+ * Callers are responsible for enabling interrupts themselves inside
+ * the non-atomic section, and callers must call is_end_non_atomic()
+ * before ist_exit().
+ */
+void ist_begin_non_atomic(struct pt_regs *regs)
+{
+       BUG_ON(!user_mode_vm(regs));
+
+       /*
+        * Sanity check: we need to be on the normal thread stack.  This
+        * will catch asm bugs and any attempt to use ist_preempt_enable
+        * from double_fault.
+        */
+       BUG_ON(((current_stack_pointer() ^ this_cpu_read_stable(kernel_stack))
+               & ~(THREAD_SIZE - 1)) != 0);
+
+       preempt_count_sub(HARDIRQ_OFFSET);
+}
+
+/**
+ * ist_end_non_atomic() - begin a non-atomic section in an IST exception
+ *
+ * Ends a non-atomic section started with ist_begin_non_atomic().
+ */
+void ist_end_non_atomic(void)
+{
+       preempt_count_add(HARDIRQ_OFFSET);
+}
+
 static nokprobe_inline int
 do_trap_no_signal(struct task_struct *tsk, int trapnr, char *str,
                  struct pt_regs *regs, long error_code)
@@ -810,18 +859,16 @@ void math_state_restore(void)
                local_irq_disable();
        }
 
+       /* Avoid __kernel_fpu_begin() right after __thread_fpu_begin() */
+       kernel_fpu_disable();
        __thread_fpu_begin(tsk);
-
-       /*
-        * Paranoid restore. send a SIGSEGV if we fail to restore the state.
-        */
        if (unlikely(restore_fpu_checking(tsk))) {
                drop_init_fpu(tsk);
                force_sig_info(SIGSEGV, SEND_SIG_PRIV, tsk);
-               return;
+       } else {
+               tsk->thread.fpu_counter++;
        }
-
-       tsk->thread.fpu_counter++;
+       kernel_fpu_enable();
 }
 EXPORT_SYMBOL_GPL(math_state_restore);