Ildasm.exe 的使用方法
示例：
在应用Ildasm.exe具体反编译代码之前，先附上MSDN对于用Ildasm.exe反编译的经典帮助。
然后我们用Ildasm.exe具体反编译经典的"Hello World"控制台程序的可执行文件，展现出来的视图为：
分析具体IL代码
1.MANIFEST清单：
MANIFEST是一个附加信息列表，主要包含程序集的一些属性，如程序集名称、版本号、哈希算法等；
2.ConsoleApplication1.Program类：
这才是我们介绍的主角。
首先是Program类： 代码为
.classprivateauto ansi beforefieldinit ConsoleApplication1.Program
extends [mscorlib]System.Object
{
}//end of class ConsoleApplication1.Program
1）.class，表示Program是一个类。并且它继承自程序集—mscorlib的System.Object类；
2）private，表示访问权限；
3）auto，表示程序的内存加载全部由CLR来控制；
4）ansi，是为了在没有托管代码与托管代码之间实现无缝转换。这里主要指C、C++代码等；
5）beforefieldinit，是用来标记运行库（CLR）可以在静态字段方法生成后的任意时刻，来加载构造器（构造函数）;
其次是 .ctor方法，代码为：
.methodpublichidebysig specialname rtspecialname
instancevoid.ctor() cil managed
{
//Code size 7 (0x7)
.maxstack8
IL_0000: ldarg.0
IL_0001: call instancevoid[mscorlib]System.Object::.ctor()
IL_0006: ret
}//end of method Program::.ctor
1）cil managed:表示其中为IL代码，指示编译器编译为托管代码；
2）.maxstack:表示调用构造函数.otor期间的评估堆栈(Evaluation Stack) ;
3)IL_0000:标记代码行开头；
4）ldarg.0:表示转载第一个成员参数，在实例方法中指的是当前实例的引用；
5）call：call一般用于调用静态方法，因为静态方法是在编译期就确定的。而这里的构造函数.otor()也是在编译期就制定的。而另一指令callvirt则表示调用实例方法， 它是在运行时确定的，因为如前述，当调用方法的继承关系时，就要比较基类与派生类的同名函数的实现方法（virtual和new），以确定调用的函数所属的Method Table；
6）ret：表示执行完毕，返回；
最后是Main（）方法，代码为：
.methodprivatehidebysigstaticvoidMain() cil managed
{
.entrypoint
//Code size 13 (0xd)
.maxstack8
IL_0000: nop
IL_0001: ldstr"Hello world"
IL_0006: callvoid[mscorlib]System.Console::WriteLine(string)
IL_000b: nop
IL_000c: ret
}//end of method Program::Main
1） .entrypoint指令表示CLR加载程序时，是首先从.entrypoint开始的，即从Main方法作为程序的入口函数；
2）ldstr：表示将字符串压栈，在这里就是将"Hello World."压栈；
3）hidebysig:表示当把此类作为基类，存在派生类时，此方法不被继承，同上构造函数；
至此，我们对IL代码的一些指令有了了解。
IL指令说明
MSIL Instruction Set
Base Instructions
| **Instruction** | **Description** | **Stack Transition** | |
| 1 | add | add two values, returning a new value | …, value1, value2à…, result |
| 2 |
add.ovf. |
add integer value with overflow check | …, value1, value2à…, result |
| 3 | and | bitwise AND | …, value1, value2à…, result |
| 4 | arglist | get argument list | …à…, argListHandle |
| 5 |
beq. |
branch on equal | …, value1, value2à… |
| 6 |
bge. |
branch on greater than or equal to | …, value1, value2à… |
| 7 |
bge.un. |
branch on greater/equal, unsigned or unordered | …, value1, value2à… |
| 8 |
bgt. |
branch on greater than | …, value1, value2à… |
| 9 |
bgt.un |
branch on greater than, unsigned or unordered | …, value1, value2à… |
| 10 |
ble. |
branch on less than or equal to | …, value1, value2à… |
| 11 |
ble..un |
branch on less/equal, unsigned or unordered | …, value1, value2à… |
| 12 |
blt. |
branch on less than | …, value1, value2à… |
| 13 |
blt.un. |
branch on less than, unsigned or unordered | …, value1, value2à… |
| 14 |
bne.un |
branch on not equal or unorded | …, value1, value2à… |
| 15 |
br. |
unconditional branch | …,à… |
| 16 | break | breakpoint instruction | …,à… |
| 17 |
brfalse. |
branch on false, null, or zero | …, valueà… |
| 18 |
brtrue. |
branch on non-false or non-null | …, valueà… |
| 19 | call | call a method | …, arg1, arg2 … argnà…, retVal (not always returned) |
| 20 | calli | indirect method call | …, arg1, arg2 … argn, ftnà…, retVal (not always returned) |
| 21 | ceq | compare equal | …, value1, value2à…, result |
| 22 | cgt | compare greater than | …, value1, value2à…, result |
| 23 | cgt.un | compare greater than, unsigned or unordered | …, value1, value2à…, result |
| 24 | ckfinite | check for a finite real number | …, valueà…, value |
| 25 | clt | compare less than | …, value1, value2à…, result |
| 26 | clt.un | compare less than, unsigned or unordered | …, value1, value2à…, result |
| 27 |
conv. |
data conversion | …, valueà…, result |
| 28 |
conv.ovf |
data conversion with overflow detection | …, valueà…, result |
| 29 |
conv.ovf. |
unsigned data conversion with overflow detection | …, valueà…, result |
| 30 | cpblk | copy data from memory to memory | …, destaddr, srcaddr, sizeà… |
| 31 | div | divide values | …, value1, value2à…, result |
| 32 | div.un | divide integer values, unsigned | …, value1, value2à…, result |
| 33 | dup | duplicate the top value of the stack | …, valueà…, value, value |
| 34 | endfilter | end filter clause of SEH | …, valueà… |
| 35 | endfinally | end the finally or fault clause of exception block | …à… |
| 36 | initblk | initialize a block of memory to a value | …, addr, value, sizeà… |
| 37 | jmp | jump to method | …à… |
| 38 |
ldarg. |
load argument onto the stack | …à…, value |
| 39 |
ldarga. |
load an argument address | …,à…, address of argument number *argNum* |
| 40 |
ldc. |
load numeric constant | …à…, num |
| 41 | ldftn | load method pointer | …à…, ftn |
| 42 |
ldind. |
load value indirect onto the stack | …, addrà…, value |
| 43 | ldloc | load local variable onto the stack | …à…, value |
| 44 |
ldloca. |
load local variable address | …à…, address |
| 45 | ldnull | load a null pointer | …à…, null value |
| 46 |
leave. |
exit a protected region of code | …,à |
| 47 | localloc | allocate space in the local dynamic memory pool | sizeàaddress |
| 48 | mul | multiply values | …, value1, value2à…, result |
| 49 |
mul.ovf |
multiply integer values with overflow check | …, value1, value2à…, result |
| 50 | neg | negate | …, valueà…, result |
| 51 | nop | no operation | …,à…, |
| 52 | not | bitwise complement | …, valueà…, result |
| 53 | or | bitwise OR | …, value1, value2à…, result |
| 54 | pop | remove the top element of the stack | …, valueà… |
| 55 | rem | compute the remainder | …, value1, value2à…, result |
| 56 | rem.un | compute integer remainder, unsigned | …, value1, value2à…, result |
| 57 | ret | return from method |
retValon callee evaluation stack (not always present)à
…, retValon caller evaluation stack (not always present) |
| 58 | shl | shift integer left | …, value, shiftAmountà…, result |
| 59 | shr | shift integer right | …, value, shiftAmountà…, result |
| 60 | shr.un | shift integer right, unsigned | …, value, shiftAmountà…, result |
| 61 | starg. | store a value in an argument slot | …, valueà…, |
| 62 | stind. | store value indirect from stack | …, addr, valà… |
| 63 | stloc | pop value from stack to local variable | …, valueà… |
| 64 | sub | substract numeric values | …, value1, value2à…, result |
| 65 | sub.ovf. | substract integer values, checking for overflow | …, value1, value2à…, result |
| 66 | switch | table switch on value | …, valueà…, |
| 67 | xor | bitwise XOR | ..., value1, value2à..., result |
Object Model Instructions
| **Instruction** | **Description** | **Stack Transition** | |
| 1 | box | convert value type to object reference | …, valueTypeà…, obj |
| 2 | callvirt | call a method associated, a runtime, with an object | …, obj, arg1, … argNà…, returnVal (not always returned) |
| 3 | cast class | cast an object to a class | …, objà…, obj2 |
| 4 | cpobj | copy a value type | …, *destValObj, srcValObj*à…, |
| 5 | initobj | Initialize a value type | …,addrOfValObjà…, |
| 6 | isinst | test if an object is is an instance of a class or interface | …, objà…, result |
| 7 |
ldelem. |
load an element fo an array | …,array, indexà…, value |
| 8 | ldelema | load address of an element of an array | …, array, indexà…, address |
| 9 | ldfld | load field of an object | …,objà…, value |
| 10 | ldflda | load field address | …,objà…, address |
| 11 | ldlen | load the length of an array | …, arrayà…, length |
| 12 | ldobj | copy value type to the stack | …, addrOfValObjà…, valObj |
| 13 | ldsfld | load static field of a class | …,à…, value |
| 14 | ldsflda | load static field address | …,à…, address |
| 15 | ldstr | load a literal string | …,à…, string |
| 16 | ldtoken | load the runtime representation of metadata token | …à…, RuntimeHandle |
| 17 | ldvirtfn | load a virtual method pointer | … objectà…, ftn |
| 18 | mkrefany | push a typed reference on the stack | …, ptrà…, typedRef |
| 19 | newarr | Create a zero-base, on-dimensional array | …, *numElems*à…, *array* |
| 20 | newobj | create a new object | …, *arg1*, … *argN*à…, *obj* |
| 21 | refanytype | load the type out of a typed reference | …,TypedRefà…, type |
| 22 | refanyval | load the address out of a typed reference | …,TypedRefà…, address |
| 23 | rethrow | rethrow the current exception | …,à…, |
| 24 | sizeof | load the size in bytes of a value type | …,à…, size (4 bytes, unsigned) |
| 25 |
stelem. |
store an element of an array | …, *array*, *index*, *value*à…, |
| 26 | stfld | store into a field of an object | …, *obj*, *value*à…, |
| 27 | stobj | store a value type from the stack into memory | …, addr, valObjà…, |
| 28 | stsfld | store a static field of class | …, *val*à…, |
| 29 | throw | throw an exception | …, *object*à…, |
| 30 | unbox | convert boxed value type to its raw form |
转自：http://www.cnblogs.com/yangmingming/archive/2010/02/03/1662307.html
原文链接: https://www.cnblogs.com/scottckt/archive/2010/10/13/1850255.html
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