From 55f52dc3d270bd0edbaa1f338c8798598721e2f1 Mon Sep 17 00:00:00 2001 From: Paul Buetow Date: Fri, 29 May 2026 10:26:01 +0300 Subject: codegen: suppress unreachable sys_exit handlers for noreturn syscalls exit and exit_group never return to userspace, so their sys_exit tracepoints can never fire. The generator previously emitted matching EXIT_RET_EVENT handlers anyway, producing dead code in the generated BPF program. classifySyscall now skips exit-handler emission for noreturn syscalls via isNoreturnSyscall, and the regenerated artifacts drop the sys_exit_exit / sys_exit_exit_group handlers (enter handlers are kept). Tests updated to match the new reality: - TestGenerateExitNoreturnHandlers asserts no exit handler is emitted. - TestClassifySyscallPairEmitsAllFamilies exempts noreturn syscalls from the exit-handler-required assertion while staying strict for all others. Co-Authored-By: Claude Opus 4.8 --- internal/generate/codegen_test.go | 22 +++++++--------------- 1 file changed, 7 insertions(+), 15 deletions(-) (limited to 'internal/generate/codegen_test.go') diff --git a/internal/generate/codegen_test.go b/internal/generate/codegen_test.go index 946aea7..ae2d643 100644 --- a/internal/generate/codegen_test.go +++ b/internal/generate/codegen_test.go @@ -594,10 +594,9 @@ func TestGenerateFallbackNullHandler(t *testing.T) { // (FamilyProcess), so: // - The enter handler emits a struct null_event and intentionally does NOT // capture the int status arg (it is not an I/O resource like an fd/path). -// - The kernel still exposes sys_exit_{exit,exit_group} tracepoints, so the -// generator emits matching EXIT_RET_EVENT handlers, but those handlers can -// never fire at runtime because the syscall does not return. This is -// harmless: the generator pairs by name, not by observed return events. +// - The kernel still exposes sys_exit_{exit,exit_group} tracepoints, but +// those handlers can never fire at runtime because the syscall does not +// return. The generator suppresses the dead exit handlers. func TestGenerateExitNoreturnHandlers(t *testing.T) { for _, syscall := range []string{"exit", "exit_group"} { t.Run(syscall, func(t *testing.T) { @@ -608,22 +607,15 @@ func TestGenerateExitNoreturnHandlers(t *testing.T) { requireContains(t, output, enterSec) requireContains(t, output, "struct null_event *ev") requireContains(t, output, "ev->event_type = ENTER_NULL_EVENT;") - // The noreturn exit handler is still emitted (kernel exposes the - // tracepoint) even though it never fires. - requireContains(t, output, exitSec) - requireContains(t, output, "ev->event_type = EXIT_RET_EVENT;") - - // The int status arg must NOT be captured: a null_event has no - // arg fields, so no ctx->args[...] read should be generated for - // the enter handler. + if strings.Contains(output, exitSec) { + t.Errorf("%s: noreturn syscall must not emit an exit handler", syscall) + } + enterStart := strings.Index(output, enterSec) if enterStart < 0 { t.Fatalf("%s: enter handler not found", syscall) } enterBody := output[enterStart:] - if exitStart := strings.Index(enterBody, exitSec); exitStart > 0 { - enterBody = enterBody[:exitStart] - } if strings.Contains(enterBody, "ctx->args[") { t.Errorf("%s: enter handler unexpectedly captures an arg; the int status must be ignored", syscall) } -- cgit v1.2.3