pkg/manager: show number of times coverage for each call has overflowed

If the overflows happen often, it's bad.
Add visibility into this.

2 files changed, 39 insertions, 3 deletions

diff --git a/pkg/fuzzer/fuzzer.go b/pkg/fuzzer/fuzzer.go
index 3dac022ad..3e5f94fc3 100644
--- a/pkg/fuzzer/fuzzer.go
+++ b/pkg/fuzzer/fuzzer.go
@@ -50,7 +50,7 @@ func NewFuzzer(ctx context.Context, cfg *Config, rnd *rand.Rand,
 		}
 	}
 	f := &Fuzzer{
-		Stats:  newStats(),
+		Stats:  newStats(target),
 		Config: cfg,
 		Cover:  newCover(),
 
@@ -170,6 +170,10 @@ func (fuzzer *Fuzzer) processResult(req *queue.Request, res *queue.Result, flags
 
 	if res.Info != nil {
 		fuzzer.statExecTime.Add(int(res.Info.Elapsed / 1e6))
+		for call, info := range res.Info.Calls {
+			fuzzer.handleCallInfo(req, info, call)
+		}
+		fuzzer.handleCallInfo(req, res.Info.Extra, -1)
 	}
 
 	// Corpus candidates may have flaky coverage, so we give them a second chance.
@@ -231,6 +235,22 @@ func (fuzzer *Fuzzer) triageProgCall(p *prog.Prog, info *flatrpc.CallInfo, call
 	}
 }
 
+func (fuzzer *Fuzzer) handleCallInfo(req *queue.Request, info *flatrpc.CallInfo, call int) {
+	if info == nil || info.Flags&flatrpc.CallFlagCoverageOverflow == 0 {
+		return
+	}
+	syscallIdx := len(fuzzer.Syscalls) - 1
+	if call != -1 {
+		syscallIdx = req.Prog.Calls[call].Meta.ID
+	}
+	stat := &fuzzer.Syscalls[syscallIdx]
+	if req.ExecOpts.ExecFlags&flatrpc.ExecFlagCollectComps != 0 {
+		stat.CompsOverflows.Add(1)
+	} else {
+		stat.CoverOverflows.Add(1)
+	}
+}
+
 func signalPrio(p *prog.Prog, info *flatrpc.CallInfo, call int) (prio uint8) {
 	if call == -1 {
 		return 0
diff --git a/pkg/fuzzer/stats.go b/pkg/fuzzer/stats.go
index 7990f8b13..40c71d309 100644
--- a/pkg/fuzzer/stats.go
+++ b/pkg/fuzzer/stats.go
@@ -3,9 +3,17 @@
 
 package fuzzer
 
-import "github.com/google/syzkaller/pkg/stat"
+import (
+	"sync/atomic"
+
+	"github.com/google/syzkaller/pkg/stat"
+	"github.com/google/syzkaller/prog"
+)
 
 type Stats struct {
+	// Indexed by prog.Syscall.ID + the last element for extra/remote.
+	Syscalls []SyscallStats
+
 	statCandidates          *stat.Val
 	statNewInputs           *stat.Val
 	statJobs                *stat.Val
@@ -27,8 +35,16 @@ type Stats struct {
 	statExecCollide         *stat.Val
 }
 
-func newStats() Stats {
+type SyscallStats struct {
+	// Number of times coverage buffer for this syscall has overflowed.
+	CoverOverflows atomic.Uint64
+	// Number of times comparisons buffer for this syscall has overflowed.
+	CompsOverflows atomic.Uint64
+}
+
+func newStats(target *prog.Target) Stats {
 	return Stats{
+		Syscalls: make([]SyscallStats, len(target.Syscalls)+1),
 		statCandidates: stat.New("candidates", "Number of candidate programs in triage queue",
 			stat.Console, stat.Graph("corpus")),
 		statNewInputs: stat.New("new inputs", "Potential untriaged corpus candidates",