test(fallocate): lock in FS family, KindFd enter, UNCLASSIFIED ret

Audit of fallocate(2) found the tracing correct and consistent with its
fd-based siblings, so add lock-in tests rather than fixing anything:

- fallocate(int fd, int mode, off_t offset, off_t len) returns int 0/-1
  (a status code, NOT a transferred byte count). Its exit must stay a
  plain ret_event with ret_type UNCLASSIFIED so it is never mistaken for
  a READ/WRITE/TRANSFER byte count.
- The enter tracepoint carries a leading fd field (args[0]); only fd is
  captured into a fd_event (KindFd), matching fadvise64/ftruncate/
  sync_file_range which likewise drop their trailing offset/len/advice
  args.
- fallocate belongs to FamilyFS alongside fadvise64/ftruncate/
  sync_file_range.

TestClassifyFallocateEnterFd and TestClassifyExitFallocateUnclassifiedRet
assert the per-syscall behavior; TestClassifySyscallFamily now also
covers fallocate/fadvise64/ftruncate so a stray reclassification trips a
test. No classification logic or generated artifacts changed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/internal/generate/family_test.go b/internal/generate/family_test.go
index 827e592..af40e7d 100644
--- a/internal/generate/family_test.go
+++ b/internal/generate/family_test.go
@@ -86,6 +86,18 @@ func TestClassifySyscallFamily(t *testing.T) {
 		{"sys_enter_fsync", FamilyFS},
 		{"sys_enter_fdatasync", FamilyFS},
 		{"sys_enter_sync_file_range", FamilyFS},
+		// fallocate(2) manipulates the allocated disk space (preallocate,
+		// punch-hole, collapse, zero, insert) for the file referred to by its
+		// args[0] fd; it is a per-file space-management syscall and shares
+		// FamilyFS with its fd-based siblings fadvise64(2) (access-pattern
+		// advice), ftruncate(2) (resize by fd), and sync_file_range(2) (flush a
+		// byte range). Assert the group so a stray reclassification of any one
+		// trips this test. Keep in sync with the FS list in
+		// docs/syscall-tracing-plan.md.
+		{"sys_enter_fallocate", FamilyFS},
+		{"sys_exit_fallocate", FamilyFS},
+		{"sys_enter_fadvise64", FamilyFS},
+		{"sys_enter_ftruncate", FamilyFS},
 		{"sys_enter_epoll_wait", FamilyPolling},
 		{"sys_enter_io_uring_enter", FamilyAIO},
 		{"sys_enter_bpf", FamilySecurity},