all: replace collide mode by `async` call property

Replace the currently existing straightforward approach to race triggering
(that was almost entirely implemented inside syz-executor) with a more
flexible one.

The `async` call property instructs syz-executor not to block until the
call has completed execution and proceed immediately to the next call.
The decision on what calls to mark with `async` is made by syz-fuzzer.

Ultimately this should let us implement more intelligent race provoking
strategies as well as make more fine-grained reproducers.

1 files changed, 16 insertions, 0 deletions

diff --git a/tools/syz-execprog/execprog.go b/tools/syz-execprog/execprog.go
index 6c69e0ff6..d22b5a0bf 100644
--- a/tools/syz-execprog/execprog.go
+++ b/tools/syz-execprog/execprog.go
@@ -38,6 +38,19 @@ var (
 	flagHints     = flag.Bool("hints", false, "do a hints-generation run")
 	flagEnable    = flag.String("enable", "none", "enable only listed additional features")
 	flagDisable   = flag.String("disable", "none", "enable all additional features except listed")
+	// The following flag is only kept to let syzkaller remain compatible with older execprog versions.
+	// In order to test incoming patches or perform bug bisection, syz-ci must use the exact syzkaller
+	// version that detected the bug (as descriptions and syntax could've already been changed), and
+	// therefore it must be able to invoke older versions of syz-execprog.
+	// Unfortunately there's no clean way to drop that flag from newer versions of syz-execprog. If it
+	// were false by default, it would be easy - we could modify `instance.ExecprogCmd` only to pass it
+	// when it's true - which would never be the case in the newer versions (this is how we got rid of
+	// fault injection args). But the collide flag was true by default, so it must be passed by value
+	// (-collide=%v). The least kludgy solution is to silently accept this flag also in the newer versions
+	// of syzkaller, but do not process it, as there's no such functionality anymore.
+	// Note, however, that we do not have to do the same for `syz-prog2c`, as `collide` was there false
+	// by default.
+	flagCollide = flag.Bool("collide", false, "(DEPRECATED) collide syscalls to provoke data races")
 )
 
 func main() {
@@ -73,6 +86,9 @@ func main() {
 			log.Logf(0, "%-24v: %v", feat.Name, feat.Reason)
 		}
 	}
+	if *flagCollide {
+		log.Fatalf("setting -collide to true is deprecated now")
+	}
 	config, execOpts := createConfig(target, features, featuresFlags)
 	if err = host.Setup(target, features, featuresFlags, config.Executor); err != nil {
 		log.Fatal(err)