all modules: wrap Linux-only code in #ifdef __linux__ — full macOS build works

Every kernel-LPE module that uses Linux-only headers (splice, posix_fadvise,
linux/netlink.h, sys/ptrace.h, etc.) now follows the same #ifdef __linux__
pattern the new modules already used: Linux body in the ifdef, stub
detect/exploit/cleanup returning SKELETONKEY_PRECOND_FAIL on non-Linux,
platform-neutral rule strings + module struct + register fn left outside.

14 modules wrapped:
  dirty_pipe (already done above), af_packet, af_packet2,
  cgroup_release_agent, cls_route4, dirty_cow, fuse_legacy,
  netfilter_xtcompat, nf_tables, nft_fwd_dup, nft_payload,
  overlayfs, overlayfs_setuid, ptrace_traceme.

Several modules previously had ad-hoc partial stubs (af_packet2 faked
SIOCSIFFLAGS/MAP_LOCKED, netfilter_xtcompat faked sysv-msg syscalls,
the nft_* modules had 3 partial __linux__ islands each, fuse_legacy /
nf_tables had inner-only ifdef blocks) — all replaced with the uniform
outer-wrap shape from dirty_pipe / dirtydecrypt / fragnesia / pack2theroot.

Where a module includes core/kernel_range.h, core/finisher.h, or
core/offsets.h, those are now inside the ifdef block as well — silences
clangd's "unused-includes" LSP warning on macOS while keeping them
present for the real Linux build.

No exploit logic, constant, struct, shellcode byte, or rule string was
modified — only include placement and ifdef markers.

Build verification:
  macOS (local): make clean && make → Mach-O x86_64, 31 modules
                 registered, --scan reports each Linux-only module as
                 "Linux-only module — not applicable here".
  Linux (docker gcc:latest + libglib2.0-dev): make clean && make →
                 ELF 64-bit, 31 modules. Exploit code paths unchanged.

modules/fuse_legacy_cve_2022_0185/skeletonkey_modules.c

@@ -59,15 +59,20 @@
 
 #include "skeletonkey_modules.h"
 #include "../../core/registry.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+#include <unistd.h>
+
+#ifdef __linux__
+
 #include "../../core/kernel_range.h"
 #include "../../core/offsets.h"
 #include "../../core/finisher.h"
 
-#include <stdio.h>
-#include <stdlib.h>
 #include <stdint.h>
-#include <string.h>
-#include <unistd.h>
 #include <sched.h>
 #include <fcntl.h>
 #include <errno.h>
@@ -378,7 +383,6 @@ struct fuse_arb_ctx {
     bool    trigger_armed;
 };
 
-#ifdef __linux__
 static int fuse_arb_write(uintptr_t kaddr, const void *buf, size_t len,
                           void *ctx_void)
 {
@@ -504,15 +508,6 @@ static int fuse_arb_write(uintptr_t kaddr, const void *buf, size_t len,
             (unsigned long)kaddr);
     return 0;
 }
-#else
-static int fuse_arb_write(uintptr_t kaddr, const void *buf, size_t len,
-                          void *ctx_void)
-{
-    (void)kaddr; (void)buf; (void)len; (void)ctx_void;
-    fprintf(stderr, "[-] fuse_arb_write: linux-only primitive\n");
-    return -1;
-}
-#endif /* __linux__ */
 
 /* ------------------------------------------------------------------ */
 /* exploit                                                             */
@@ -732,7 +727,6 @@ static skeletonkey_result_t fuse_legacy_exploit(const struct skeletonkey_ctx *ct
      * runs because the arb_write primitive re-fires the trigger and
      * needs the live spray.
      * --------------------------------------------------------------- */
-#ifdef __linux__
     if (ctx->full_chain) {
         if (!ctx->json) {
             fprintf(stderr, "[*] fuse_legacy: --full-chain requested — resolving "
@@ -792,7 +786,6 @@ static skeletonkey_result_t fuse_legacy_exploit(const struct skeletonkey_ctx *ct
         }
         return SKELETONKEY_EXPLOIT_FAIL;
     }
-#endif /* __linux__ */
 
     /* Clean up our IPC queues and mapping. The kernel slab state
      * after the overflow may be unstable; we exit cleanly on success
@@ -826,6 +819,28 @@ static skeletonkey_result_t fuse_legacy_exploit(const struct skeletonkey_ctx *ct
     return SKELETONKEY_EXPLOIT_FAIL;
 }
 
+#else  /* !__linux__ */
+
+/* Non-Linux dev builds: fsopen/fsconfig + userns+mountns clone are
+ * Linux-only kernel surface. Stub out cleanly so the module still
+ * registers and `--list` / `--detect-rules` work on macOS/BSD dev
+ * boxes — and so the top-level `make` actually completes there. */
+static skeletonkey_result_t fuse_legacy_detect(const struct skeletonkey_ctx *ctx)
+{
+    if (!ctx->json)
+        fprintf(stderr, "[i] fuse_legacy: Linux-only module "
+                "(fsopen + fsconfig + userns mount) — not applicable here\n");
+    return SKELETONKEY_PRECOND_FAIL;
+}
+static skeletonkey_result_t fuse_legacy_exploit(const struct skeletonkey_ctx *ctx)
+{
+    (void)ctx;
+    fprintf(stderr, "[-] fuse_legacy: Linux-only module — cannot run here\n");
+    return SKELETONKEY_PRECOND_FAIL;
+}
+
+#endif /* __linux__ */
+
 /* ------------------------------------------------------------------ */
 /* embedded detection rules                                            */
 /* ------------------------------------------------------------------ */