adding THP_PAGES option to disable transparent huge pages.

In some scenarios, THP could lead to more memory fragmentations for
example thus an new distinct option while the user can still wish huge
pages.
simpler than using prctl api and also making it contained within
isoalloc without touching system configurations.

Makefile

@@ -83,6 +83,7 @@ MALLOC_HOOK = -DMALLOC_HOOK=1
 ## Use Huge pages for any allocation that is a multiple
 ## of 2 megabytes. See PERFORMANCE.md for additional info
 HUGE_PAGES = -DHUGE_PAGES=1
+THP_PAGES = -DTHP_PAGES=1
 
 ## Enable the built-in heap profiler. When this is enabled
 ## IsoAlloc will write a file to disk upon exit of the
@@ -316,7 +317,7 @@ endif
 CFLAGS += $(COMMON_CFLAGS) $(DISABLE_CANARY) $(BUILD_ERROR_FLAGS) $(HOOKS) $(HEAP_PROFILER) -fvisibility=hidden \
 	-std=$(STDC) $(SANITIZER_SUPPORT) $(ALLOC_SANITY) $(MEMCPY_SANITY) $(UNINIT_READ_SANITY) $(CPU_PIN) $(SCHED_GETCPU) \
 	$(EXPERIMENTAL) $(UAF_PTR_PAGE) $(VERIFY_FREE_BIT_SLOTS) $(NAMED_MAPPINGS) $(ABORT_ON_NULL) $(NO_ZERO_ALLOCATIONS) \
-	$(ABORT_NO_ENTROPY) $(ISO_DTOR_CLEANUP) $(RANDOMIZE_FREELIST) $(USE_SPINLOCK) $(HUGE_PAGES) $(USE_MLOCK) \
+	$(ABORT_NO_ENTROPY) $(ISO_DTOR_CLEANUP) $(RANDOMIZE_FREELIST) $(USE_SPINLOCK) $(HUGE_PAGES) ${THP_PAGES} $(USE_MLOCK) \
 	$(MEMORY_TAGGING) $(STRONG_SIZE_ISOLATION) $(MEMSET_SANITY) $(AUTO_CTOR_DTOR) $(SIGNAL_HANDLER) \
 	$(BIG_ZONE_META_DATA_GUARD) $(BIG_ZONE_GUARD) $(PROTECT_UNUSED_BIG_ZONE) $(MASK_PTRS) $(SANITIZE_CHUNKS) $(FUZZ_MODE) \
 	$(PERM_FREE_REALLOC) $(ARM_MTE) $(DONT_USE_NEON)

src/iso_alloc_util.c

@@ -157,7 +157,7 @@ void *mmap_pages(size_t size, bool populate, const char *name, int32_t prot) {
         LOG_AND_ABORT("Failed to mmap rw pages");
     }
 
-#if __linux__ && MAP_HUGETLB && HUGE_PAGES && MADV_HUGEPAGE
+#if __linux__ && MAP_HUGETLB && HUGE_PAGES && THP_PAGES && MADV_HUGEPAGE
     if(sz == ZONE_USER_SIZE || sz == (ZONE_USER_SIZE >> 1)) {
         madvise(p, sz, MADV_HUGEPAGE);
     }