errno overhaul, getting rid of some ambiguity. In the hopes of tracking

down a rare but annoying problem related to remote coverage exposed by
syzkaller.

diff --git a/sys/dev/kcov.c b/sys/dev/kcov.c
index d0f75ed..ec24374 100644 (file)
--- a/sys/dev/kcov.c
+++ b/sys/dev/kcov.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: kcov.c,v 1.40 2021/12/19 07:45:59 anton Exp $ */
+/*     $OpenBSD: kcov.c,v 1.41 2021/12/21 06:08:57 anton Exp $ */
 
 /*
  * Copyright (c) 2018 Anton Lindqvist <anton@openbsd.org>
@@ -358,10 +358,14 @@ kcovioctl(dev_t dev, u_long cmd, caddr_t data, int flag, struct proc *p)
                break;
        case KIOENABLE:
                /* Only one kcov descriptor can be enabled per thread. */
-               if (p->p_kd != NULL || kd->kd_state != KCOV_STATE_READY) {
+               if (p->p_kd != NULL) {
                        error = EBUSY;
                        break;
                }
+               if (kd->kd_state != KCOV_STATE_READY) {
+                       error = ENXIO;
+                       break;
+               }
                mode = *((int *)data);
                if (mode != KCOV_MODE_TRACE_PC && mode != KCOV_MODE_TRACE_CMP) {
                        error = EINVAL;
@@ -375,9 +379,12 @@ kcovioctl(dev_t dev, u_long cmd, caddr_t data, int flag, struct proc *p)
                break;
        case KIODISABLE:
                /* Only the enabled thread may disable itself. */
-               if ((p->p_kd != kd && kd->kd_kr == NULL) ||
-                   kd->kd_state != KCOV_STATE_TRACE) {
-                       error = EBUSY;
+               if ((p->p_kd != kd && kd->kd_kr == NULL)) {
+                       error = EPERM;
+                       break;
+               }
+               if (kd->kd_state != KCOV_STATE_TRACE) {
+                       error = ENXIO;
                        break;
                }
                kd->kd_state = KCOV_STATE_READY;
@@ -772,13 +779,16 @@ kcov_remote_attach(struct kcov_dev *kd, struct kio_remote_attach *arg)
        MUTEX_ASSERT_LOCKED(&kcov_mtx);
 
        if (kd->kd_state != KCOV_STATE_READY)
-               return (EBUSY);
+               return (ENXIO);
 
-       if (arg->subsystem == KCOV_REMOTE_COMMON)
+       if (arg->subsystem == KCOV_REMOTE_COMMON) {
                kr = kcov_remote_register_locked(KCOV_REMOTE_COMMON,
                    curproc->p_p);
-       if (kr == NULL)
+               if (kr == NULL)
+                       return (EBUSY);
+       } else {
                return (EINVAL);
+       }
 
        kr->kr_state = KCOV_STATE_READY;
        kr->kr_kd = kd;