prctl: Add force disable speculation

[mirror_ubuntu-artful-kernel.git] / arch / x86 / kernel / cpu / bugs.c

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 1b9ddf98b0e5558ad206e4aad556d08205be4279..5903a6a6759e539d8282e335f47234861f3e641b 100644 (file)
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -492,21 +492,37 @@ static void ssb_select_mitigation()
 
 static int ssb_prctl_set(struct task_struct *task, unsigned long ctrl)
 {
-       bool rds = !!test_tsk_thread_flag(task, TIF_RDS);
+       bool update;
 
        if (ssb_mode != SPEC_STORE_BYPASS_PRCTL)
                return -ENXIO;
 
-       if (ctrl == PR_SPEC_ENABLE)
-               clear_tsk_thread_flag(task, TIF_RDS);
-       else
-               set_tsk_thread_flag(task, TIF_RDS);
+       switch (ctrl) {
+       case PR_SPEC_ENABLE:
+               /* If speculation is force disabled, enable is not allowed */
+               if (task_spec_ssb_force_disable(task))
+                       return -EPERM;
+               task_clear_spec_ssb_disable(task);
+               update = test_and_clear_tsk_thread_flag(task, TIF_RDS);
+               break;
+       case PR_SPEC_DISABLE:
+               task_set_spec_ssb_disable(task);
+               update = !test_and_set_tsk_thread_flag(task, TIF_RDS);
+               break;
+       case PR_SPEC_FORCE_DISABLE:
+               task_set_spec_ssb_disable(task);
+               task_set_spec_ssb_force_disable(task);
+               update = !test_and_set_tsk_thread_flag(task, TIF_RDS);
+               break;
+       default:
+               return -ERANGE;
+       }
 
        /*
         * If being set on non-current task, delay setting the CPU
         * mitigation until it is next scheduled.
         */
-       if (task == current && rds != !!test_tsk_thread_flag(task, TIF_RDS))
+       if (task == current && update)
                speculative_store_bypass_update();
 
        return 0;
@@ -518,7 +534,9 @@ static int ssb_prctl_get(struct task_struct *task)
        case SPEC_STORE_BYPASS_DISABLE:
                return PR_SPEC_DISABLE;
        case SPEC_STORE_BYPASS_PRCTL:
-               if (test_tsk_thread_flag(task, TIF_RDS))
+               if (task_spec_ssb_force_disable(task))
+                       return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE;
+               if (task_spec_ssb_disable(task))
                        return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
                return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
        default:
@@ -531,9 +549,6 @@ static int ssb_prctl_get(struct task_struct *task)
 int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which,
                             unsigned long ctrl)
 {
-       if (ctrl != PR_SPEC_ENABLE && ctrl != PR_SPEC_DISABLE)
-               return -ERANGE;
-
        switch (which) {
        case PR_SPEC_STORE_BYPASS:
                return ssb_prctl_set(task, ctrl);