Add heap poisoning mechanism to fill absorbed block header with the right pattern.

Note: block_absorb() is called in tlsf_free(), which is eventually called in multi_heap_free()
after the memory fill is done. As the block_absorb merges 2 blocks together, the previous block
header of the merged block is now in the middle of the memory block but not filled with 0xfe.

- Remove dependencies with the heap component of the IDF.
- The tlsf_poison_fill_region_hook() function is defined as weak in IDF and checked for NULL
in block_absorb() function in order to minimize the dependencies between IDF and the TLSF.
- The the implementation of tlsf_poison_fill_region_hook() must be provided at the discretion
of the user.

tlsf.c

@@ -456,6 +456,12 @@ static inline __attribute__((always_inline)) block_header_t* block_absorb(block_
 	/* Note: Leaves flags untouched. */
 	prev->size += block_size(block) + block_header_overhead;
 	block_link_next(prev);
+
+	if (block_absorb_post_hook != NULL)
+	{
+		block_absorb_post_hook(block, sizeof(block_header_t), POISONING_AFTER_FREE);
+	}
+
 	return prev;
 }
 

tlsf.h

@@ -8,6 +8,7 @@
 #define INCLUDED_tlsf
 
 #include <stddef.h>
+#include <stdbool.h>
 
 #if defined(__cplusplus)
 extern "C" {
@@ -52,6 +53,16 @@ void tlsf_walk_pool(pool_t pool, tlsf_walker walker, void* user);
 int tlsf_check(tlsf_t tlsf);
 int tlsf_check_pool(pool_t pool);
 
+/*!
+ * @brief Weak function filling the given memory with a given fill pattern.
+ * 
+ * @param start: pointer to the start of the memory region to fill
+ * @param size: size of the memory region to fill
+ * @param is_free: Indicate if the pattern to use the fill the region should be 
+ * an after free or after allocation pattern.
+ */
+__attribute__((weak)) void block_absorb_post_hook(void *start, size_t size, bool is_free);
+
 #if defined(__cplusplus)
 };
 #endif

tlsf_common.h

@@ -6,15 +6,19 @@
 
 #pragma once
 #include <stddef.h>
-
-#if defined __has_include && __has_include("tlsf_platform.h")
-#include "tlsf_platform.h"
-#endif
+#include <assert.h>
 
 #if defined(__cplusplus)
 extern "C" {
 #endif
 
+/*
+** Constants definition for poisoning.
+** These defines are used as 3rd argument of tlsf_poison_fill_region() for readability purposes.
+*/
+#define POISONING_AFTER_FREE true
+#define POISONING_AFTER_MALLOC !POISONING_AFTER_FREE
+
 /*
 ** Cast and min/max macros.
 */