proc/priv/init: early init check

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/proc/priv/init/early.go

@@ -0,0 +1,18 @@
+package init0
+
+import (
+	"os"
+	"path"
+
+	"git.gensokyo.uk/security/fortify/internal/fmsg"
+)
+
+// used by the parent process
+
+// TryArgv0 calls [Main] if argv0 indicates the process is started from a file named "init".
+func TryArgv0() {
+	if len(os.Args) > 0 && path.Base(os.Args[0]) == "init" {
+		Main()
+		fmsg.Exit(0)
+	}
+}

internal/proc/priv/init/main.go

@@ -5,7 +5,6 @@ import (
 	"os"
 	"os/exec"
 	"os/signal"
-	"path"
 	"syscall"
 	"time"
 
@@ -38,14 +37,6 @@ func Main() {
 		panic("unreachable")
 	}
 
-	// re-exec
-	if len(os.Args) > 0 && (os.Args[0] != "fortify" || os.Args[1] != "init" || len(os.Args) != 2) && path.IsAbs(os.Args[0]) {
-		if err := syscall.Exec(os.Args[0], []string{"fortify", "init"}, os.Environ()); err != nil {
-			fmsg.Println("cannot re-exec self:", err)
-			// continue anyway
-		}
-	}
-
 	// receive setup payload
 	var (
 		payload    Payload