From e67fbecfc88b7a54d0f1fc7d0c06c9e2eeee8f96 Mon Sep 17 00:00:00 2001
From: John Hodge <tpg@mutabah.net>
Date: Mon, 18 Aug 2014 18:26:20 +0800
Subject: [PATCH] Usermode/libc - Move free logic to another method, allowing
 libraries to catch and pass failures

---
 Usermode/Libraries/libc.so_src/heap.c | 27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/Usermode/Libraries/libc.so_src/heap.c b/Usermode/Libraries/libc.so_src/heap.c
index 53460326..d65fc33f 100644
--- a/Usermode/Libraries/libc.so_src/heap.c
+++ b/Usermode/Libraries/libc.so_src/heap.c
@@ -9,6 +9,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <assert.h>
+#include <stdbool.h>
 #include "lib.h"
 
 #if 0
@@ -72,6 +73,7 @@ static const heap_head	_heap_zero_allocation;
 EXPORT void	*malloc(size_t bytes);
 void	*_malloc(size_t bytes, void *owner);
 EXPORT void	*calloc(size_t bytes, size_t count);
+bool	_libc_free(void *mem);
 EXPORT void	free(void *mem);
 EXPORT void	*realloc(void *mem, size_t bytes);
 EXPORT void	*sbrk(int increment);
@@ -222,26 +224,30 @@ EXPORT void *calloc(size_t __nmemb, size_t __size)
  \param mem	Pointer - Memory to free
 */
 EXPORT void free(void *mem)
+{
+	if( !_libc_free(mem) ) {
+		Heap_Validate(1);
+		exit(0);
+	}
+}
+
+bool _libc_free(void *mem)
 {
 	heap_head	*head = (heap_head*)mem - 1;
 
 	// Free of NULL or the zero allocation does nothing
 	if(!mem || mem == _heap_zero_allocation.data)
-		return ;
+		return true;
 	
 	// Sanity check the head address
 	if(head->magic != MAGIC) {
 		if( head->magic != MAGIC_FREE ) {
-			_SysDebug("Double free of %p", mem);
-			Heap_Validate(1);
-			exit(0);
+			_SysDebug("Double free of %p by %p", mem, __builtin_return_address(0));
 		}
 		else {
-			_SysDebug("Free of invalid pointer %p", mem);
-			Heap_Validate(1);
-			exit(0);
+			_SysDebug("Free of invalid pointer %p by ", mem, __builtin_return_address(0));
 		}
-		return;
+		return false;
 	}
 	
 	head->magic = MAGIC_FREE;
@@ -266,8 +272,9 @@ EXPORT void free(void *mem)
 		heap_foot *prevFoot = PREV_FOOT(head);
 		if( prevFoot->magic != MAGIC )
 		{
+			_SysDebug("Heap corruption, previous foot magic invalid");
 			Heap_Validate(1);
-			exit(1);
+			return false;
 		}
 		
 		heap_head *prevHead = prevFoot->header;
@@ -282,6 +289,8 @@ EXPORT void free(void *mem)
 			prevFoot->header = NULL;
 		}
 	}
+	
+	return true;
 }
 
 /**
-- 
2.20.1