From 5210f20b16a224f58117ffb71b2a0691c02a50ed Mon Sep 17 00:00:00 2001 From: Paul Buetow Date: Sat, 30 May 2026 16:31:26 +0300 Subject: test(signalfd4): lock in args[3] flags index for eventfd handler Audit of signalfd4(2) confirmed the tracing is correct: classified as KindEventfd in FamilyIPC like its fd-creating siblings (eventfd2, timerfd_create, inotify_init1, signalfd), flags captured from args[3] per signalfd4(ufd, mask, sizemask, flags), and the return value left Unclassified (it is an fd, not a byte count). Add testdata fixtures FormatSignalfd4/FormatExitSignalfd4 (real Linux 7.0 tracepoint data) and a codegen lock-in test asserting the generated handler reads flags from args[3], with negative guards against args[0] (ufd), args[1] (mask pointer) and args[2] (sizemask). Co-Authored-By: Claude Opus 4.8 --- internal/generate/codegen_test.go | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) (limited to 'internal/generate/codegen_test.go') diff --git a/internal/generate/codegen_test.go b/internal/generate/codegen_test.go index 3753b17..68a372e 100644 --- a/internal/generate/codegen_test.go +++ b/internal/generate/codegen_test.go @@ -1330,6 +1330,39 @@ func TestGeneratePidfdOpenHandlerUsesArg1Flags(t *testing.T) { requireContains(t, output, "ev->ret = ctx->ret;") } +// TestGenerateSignalfd4HandlerUsesArg3Flags locks in that signalfd4(2) is +// emitted as a KindEventfd handler whose flags are read from args[3]. The raw +// syscall is signalfd4(int ufd, const sigset_t *mask, size_t sizemask, int +// flags): args[0] (ufd) is an existing signalfd or -1, args[1]/args[2] are the +// mask pointer and its size — none of those are the flags. A wrong index would +// silently report bogus SFD_NONBLOCK/SFD_CLOEXEC bits, so guard args[3] +// explicitly. The exit returns the new (or modified) fd, captured as a plain +// ret with no read/write byte classification. +func TestGenerateSignalfd4HandlerUsesArg3Flags(t *testing.T) { + output := generateFromPair(t, FormatSignalfd4, FormatExitSignalfd4) + + requireContains(t, output, "struct eventfd_event *ev") + requireContains(t, output, "ev->event_type = ENTER_EVENTFD_EVENT;") + requireContains(t, output, "ev->trace_id = SYS_ENTER_SIGNALFD4;") + // signalfd4(ufd, mask, sizemask, flags): flags is at args[3]. + requireContains(t, output, "__s32 flags = (__s32)ctx->args[3];") + // Must not mistake ufd (args[0]), the mask pointer (args[1]) or sizemask + // (args[2]) for the flags argument. + for _, wrong := range []string{ + "flags = (__s32)ctx->args[0]", + "flags = (__s32)ctx->args[1]", + "flags = (__s32)ctx->args[2]", + } { + if strings.Contains(output, wrong) { + t.Errorf("signalfd4 handler must read flags from args[3], not via %q", wrong) + } + } + requireContains(t, output, "ev->ret = -1;") + requireContains(t, output, "SEC(\"tracepoint/syscalls/sys_exit_signalfd4\")") + requireContains(t, output, "ev->event_type = EXIT_EVENTFD_EVENT;") + requireContains(t, output, "ev->ret = ctx->ret;") +} + func TestGenerateEpollCtlHandler(t *testing.T) { output := generateFromPair(t, FormatEpollCtl, FormatExitEpollCtl) -- cgit v1.2.3