Add temporary verbose logging when remote coverage fails to attach.

In the hopes of tracking down a rare bug seen on syzkaller.

diff --git a/sys/dev/kcov.c b/sys/dev/kcov.c
index e1e7fbb..05a4b3a 100644 (file)
--- a/sys/dev/kcov.c
+++ b/sys/dev/kcov.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: kcov.c,v 1.45 2022/01/11 06:00:41 anton Exp $ */
+/*     $OpenBSD: kcov.c,v 1.46 2022/01/11 06:23:05 anton Exp $ */
 
 /*
  * Copyright (c) 2018 Anton Lindqvist <anton@openbsd.org>
@@ -64,6 +64,8 @@ struct kcov_dev {
        size_t           kd_nmemb;      /* [I] */
        size_t           kd_size;       /* [I] */
 
+       int              kd_pid;        /* XXX */
+
        struct kcov_remote *kd_kr;      /* [M] */
 
        TAILQ_ENTRY(kcov_dev)   kd_entry;       /* [M] */
@@ -83,6 +85,8 @@ struct kcov_remote {
        int kr_nsections;       /* [M] # threads in remote section */
        int kr_state;           /* [M] */
 
+       int kr_pid;             /* XXX */
+
        TAILQ_ENTRY(kcov_remote) kr_entry;      /* [M] */
 };
 
@@ -297,6 +301,7 @@ kcovopen(dev_t dev, int flag, int mode, struct proc *p)
 
        kd = malloc(sizeof(*kd), M_SUBPROC, M_WAITOK | M_ZERO);
        kd->kd_unit = minor(dev);
+       kd->kd_pid = curproc->p_p->ps_pid;
        mtx_enter(&kcov_mtx);
        KASSERT(kd_lookup(kd->kd_unit) == NULL);
        TAILQ_INSERT_TAIL(&kd_list, kd, kd_entry);
@@ -394,6 +399,40 @@ kcovioctl(dev_t dev, u_long cmd, caddr_t data, int flag, struct proc *p)
        case KIOREMOTEATTACH:
                error = kcov_remote_attach(kd,
                    (struct kio_remote_attach *)data);
+               /* XXX */
+               if (error == EBUSY) {
+                       struct kio_remote_attach *arg = (struct kio_remote_attach *)data;
+                       struct kcov_remote *kr;
+
+                       mtx_leave(&kcov_mtx);
+                       printf("%s[%d,%p]: subsystem %d, id %d\n",
+                           curproc->p_p->ps_comm, curproc->p_p->ps_pid, curproc->p_p,
+                           arg->subsystem, arg->id);
+                       TAILQ_FOREACH(kr, &kr_list, kr_entry) {
+                               struct kcov_dev *kd = kr->kr_kd;
+                               struct process *pr;
+
+                               printf("kr: subsystem %d, id %p, nsections %d, state %d, kd %p, pid %d",
+                                   kr->kr_subsystem, kr->kr_id, kr->kr_nsections, kr->kr_state, kd, kr->kr_pid);
+                               pr = prfind(kr->kr_pid);
+                               if (pr != NULL)
+                                       printf(", comm %s\n", pr->ps_comm);
+                               else
+                                       printf("\n");
+
+                               if (kd != NULL) {
+                                       printf("  kd: state %d, mode %d, pid %d",
+                                           kd->kd_state, kd->kd_mode, kd->kd_pid);
+
+                                       pr = prfind(kr->kr_pid);
+                                       if (pr != NULL)
+                                               printf(", comm %s\n", pr->ps_comm);
+                                       else
+                                               printf("\n");
+                               }
+                       }
+                       return (error);
+               }
                break;
        default:
                error = ENOTTY;
@@ -798,6 +837,7 @@ kcov_remote_attach(struct kcov_dev *kd, struct kio_remote_attach *arg)
 
        kr->kr_state = KCOV_STATE_READY;
        kr->kr_kd = kd;
+       kr->kr_pid = curproc->p_p->ps_pid;
        kd->kd_kr = kr;
        return (0);
 }