all: clarify the error in case of ExecFailure

Whenever the status is set, also include the reason. It should help
easier debug execution and machine check time problems.

2 files changed, 14 insertions, 3 deletions

diff --git a/pkg/fuzzer/queue/queue.go b/pkg/fuzzer/queue/queue.go
index 58c9f1561..6e17225e2 100644
--- a/pkg/fuzzer/queue/queue.go
+++ b/pkg/fuzzer/queue/queue.go
@@ -7,6 +7,7 @@ import (
 	"bytes"
 	"context"
 	"encoding/gob"
+	"errors"
 	"fmt"
 	"math/rand"
 	"strings"
@@ -99,12 +100,14 @@ func (r *Request) Done(res *Result) {
 	close(r.done)
 }
 
+var errContextAborted = errors.New("context closed while waiting the result")
+
 // Wait() blocks until we have the result.
 func (r *Request) Wait(ctx context.Context) *Result {
 	r.initChannel()
 	select {
 	case <-ctx.Done():
-		return &Result{Status: ExecFailure}
+		return &Result{Status: ExecFailure, Err: errContextAborted}
 	case <-r.done:
 		return r.result
 	}
@@ -537,6 +540,8 @@ func (rq *RandomQueue) Next() *Request {
 	return item
 }
 
+var errEvictedFromQueue = errors.New("evicted from the random queue")
+
 func (rq *RandomQueue) Submit(req *Request) {
 	rq.mu.Lock()
 	defer rq.mu.Unlock()
@@ -545,7 +550,10 @@ func (rq *RandomQueue) Submit(req *Request) {
 	} else {
 		pos := rq.rnd.Intn(rq.maxSize + 1)
 		if pos < len(rq.queue) {
-			rq.queue[pos].Done(&Result{Status: ExecFailure})
+			rq.queue[pos].Done(&Result{
+				Status: ExecFailure,
+				Err:    errEvictedFromQueue,
+			})
 			rq.queue[pos] = req
 		}
 	}
diff --git a/pkg/rpcserver/runner.go b/pkg/rpcserver/runner.go
index de38d29f7..e6ea5acdf 100644
--- a/pkg/rpcserver/runner.go
+++ b/pkg/rpcserver/runner.go
@@ -300,7 +300,10 @@ func (runner *Runner) sendRequest(req *queue.Request) error {
 			// but so far we don't have a better handling than counting this.
 			// This error is observed a lot on the seeded syz_mount_image calls.
 			runner.stats.statExecBufferTooSmall.Add(1)
-			req.Done(&queue.Result{Status: queue.ExecFailure})
+			req.Done(&queue.Result{
+				Status: queue.ExecFailure,
+				Err:    fmt.Errorf("program serialization failed: %w", err),
+			})
 			return nil
 		}
 		data = progData