kit

ifunc_init.c (1614B)

---

 /* IFUNC startup init for kit-ld static ELF binaries.
  *
  * The linker (src/link/link_layout.c::layout_iplt) materializes one
  * iplt stub + one .igot.plt slot per defined STT_GNU_IFUNC symbol and
  * also emits a parallel .iplt.pairs data section: alternating
  * (resolver_ptr, slot_ptr) u64 pairs in the same order as the slots.
  * For the ELF emit path, the linker additionally synthesizes a
  * .init_array entry pointing at __kit_ifunc_init below; the
  * freestanding _start (or any standard CRT) walks .init_array before
  * user code, so by the time test_main / main runs, every slot holds
  * the chosen implementation pointer and the iplt stub's load+branch
  * tail-calls correctly.
  *
  * The JIT path doesn't hit this function: link_jit.c pre-resolves
  * slots in-process at load time and intentionally skips the
  * .init_array synthesis (so __kit_ifunc_init never becomes an undef
  * ref the JIT user has to satisfy).
  *
  * The .iplt.pairs span symbols are weak so this object can also be
  * linked into images that don't carry IFUNCs (or that were linked by
  * a non-kit linker that doesn't synthesize __start_iplt_pairs /
  * __stop_iplt_pairs) — the function is then a no-op. */
 
 extern void* __start_iplt_pairs[] __attribute__((weak));
 extern void* __stop_iplt_pairs[] __attribute__((weak));
 
 typedef void* (*kit_ifunc_resolver_t)(void);
 
 void __kit_ifunc_init(void) {
   void** p = __start_iplt_pairs;
   void** end = __stop_iplt_pairs;
   if (!p || !end) return;
   for (; p < end; p += 2) {
     kit_ifunc_resolver_t r = (kit_ifunc_resolver_t)p[0];
     void** slot = (void**)p[1];
     *slot = r();
   }
 }