Xposed源码剖析——hook具体实现

之前我们看到了xposed各种初始化的工作，其实都是完成了针对系统中各种method的hook和替换工作。
那么具体如何替换，其实都是调用了其中的。XposedBridge_hookMethodNative函数。这里，我们详细的看看XposedBridge_hookMethodNative函数中，做了一些什么操作。

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-javadoc" style="color:#8800;box-sizing: border-box;">/**
*
* 将输入的Class中的Method方法的nativeFunc替换为xposedCallHandler
*
*<span class="hljs-javadoctag" style="color:#66066;box-sizing: border-box;"> @param</span> env JniEnv
*<span class="hljs-javadoctag" style="color:#66066;box-sizing: border-box;"> @param</span> reflectedMethodIndirect 待反射的函数
*<span class="hljs-javadoctag" style="color:#66066;box-sizing: border-box;"> @param</span> declaredClassIndirect 定义的class
*<span class="hljs-javadoctag" style="color:#66066;box-sizing: border-box;"> @param</span> slot 函数偏移量
*<span class="hljs-javadoctag" style="color:#66066;box-sizing: border-box;"> @param</span> additionalInfoIndirect 添加的函数
*
*/</span>
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">void</span> XposedBridge_hookMethodNative(JNIEnv* env, jclass clazz, jobject reflectedMethodIndirect,
jobject declaredClassIndirect, jint slot, jobject additionalInfoIndirect) {
<span class="hljs-comment" style="color:#8800;box-sizing: border-box;">// 容错</span>
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">if</span> (declaredClassIndirect == NULL || reflectedMethodIndirect == NULL) {
dvmThrowIllegalArgumentException(<span class="hljs-string" style="color:#0880;box-sizing: border-box;">"method and declaredClass must not be null"</span>);
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">return</span>;
}

<span class="hljs-comment" style="color:#8800;box-sizing: border-box;">// 根据函数的偏移量，从classloader中找到准备替换的函数。</span>
ClassObject* declaredClass = (ClassObject*) dvmDecodeIndirectRef(dvmThreadSelf(), declaredClassIndirect);
Method* method = dvmSlotToMethod(declaredClass, slot);
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">if</span> (method == NULL) {
dvmThrowNoSuchMethodError(<span class="hljs-string" style="color:#0880;box-sizing: border-box;">"Could not get internal representation for method"</span>);
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">return</span>;
}

<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">if</span> (isMethodHooked(method)) {
<span class="hljs-comment" style="color:#8800;box-sizing: border-box;">// already hooked</span>
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">return</span>;
}

<span class="hljs-comment" style="color:#8800;box-sizing: border-box;">// 保存替换前的数据信息</span>
XposedHookInfo* hookInfo = (XposedHookInfo*) calloc(<span class="hljs-number" style="color:#06666;box-sizing: border-box;">1</span>, sizeof(XposedHookInfo));
memcpy(hookInfo, method, sizeof(hookInfo->originalMethodStruct));
hookInfo->reflectedMethod = dvmDecodeIndirectRef(dvmThreadSelf(), env->NewGlobalRef(reflectedMethodIndirect));
hookInfo->additionalInfo = dvmDecodeIndirectRef(dvmThreadSelf(), env->NewGlobalRef(additionalInfoIndirect));

<span class="hljs-comment" style="color:#8800;box-sizing: border-box;">// 替换函数方法 , 让nativeFunction指向本地的hookedMethodCallback</span>
SET_METHOD_FLAG(method, ACC_NATIVE);
method->nativeFunc = &hookedMethodCallback;
method->insns = (<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">const</span> u2*) hookInfo;
method->registersSize = method->insSize;
method->outsSize = <span class="hljs-number" style="color:#06666;box-sizing: border-box;">0</span>;

<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">if</span> (PTR_gDvmJit != NULL) {
<span class="hljs-comment" style="color:#8800;box-sizing: border-box;">// reset JIT cache</span>
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">char</span> currentValue = *((<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">char</span>*)PTR_gDvmJit + MEMBER_OFFSET_VAR(DvmJitGlobals,codeCacheFull));
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">if</span> (currentValue == <span class="hljs-number" style="color:#06666;box-sizing: border-box;">0</span> || currentValue == <span class="hljs-number" style="color:#06666;box-sizing: border-box;">1</span>) {
MEMBER_VAL(PTR_gDvmJit, DvmJitGlobals, codeCacheFull) = <span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">true</span>;
} <span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">else</span> {
ALOGE(<span class="hljs-string" style="color:#0880;box-sizing: border-box;">"Unexpected current value for codeCacheFull: %d"</span>, currentValue);
}
}
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li><li style="box-sizing: border-box; padding: 0px 5px;">53</li><li style="box-sizing: border-box; padding: 0px 5px;">54</li><li style="box-sizing: border-box; padding: 0px 5px;">55</li></ul>

对vm不熟悉的，解释一下几个不怎么常用的函数。

名称	说明
dvmDecodeIndirectRef	将间接引用jobject转换为对象引用Object*
dvmSlotToMethod	根据偏移量，从ClassLoader中获取函数指针

<code class="hljs objectivec has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-comment" style="color:#8800;box-sizing: border-box;">/**
* hook方法调用时的回调
*/</span>
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">void</span> hookedMethodCallback(<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">const</span> u4* args, JValue* pResult, <span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">const</span> Method* method, ::Thread* <span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">self</span>) {
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">if</span> (!isMethodHooked(method)) {
dvmThrowNoSuchMethodError(<span class="hljs-string" style="color:#0880;box-sizing: border-box;">"Could not find Xposed original method - how did you even get here?"</span>);
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">return</span>;
}

XposedHookInfo* hookInfo = (XposedHookInfo*) method->insns;
Method* original = (Method*) hookInfo;
Object* originalReflected = hookInfo->reflectedMethod;
Object* additionalInfo = hookInfo->additionalInfo;

<span class="hljs-comment" style="color:#8800;box-sizing: border-box;">// convert/box arguments</span>
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">const</span> <span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">char</span>* desc = &method->shorty[<span class="hljs-number" style="color:#06666;box-sizing: border-box;">1</span>]; <span class="hljs-comment" style="color:#8800;box-sizing: border-box;">// [0] is the return type.</span>
Object* thisObject = <span class="hljs-literal" style="color:#06666;box-sizing: border-box;">NULL</span>;
size_t srcIndex = <span class="hljs-number" style="color:#06666;box-sizing: border-box;">0</span>;
size_t dstIndex = <span class="hljs-number" style="color:#06666;box-sizing: border-box;">0</span>;

<span class="hljs-comment" style="color:#8800;box-sizing: border-box;">// for non-static methods determine the "this" pointer</span>
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">if</span> (!dvmIsStaticMethod(original)) {
thisObject = (Object*) args[<span class="hljs-number" style="color:#06666;box-sizing: border-box;">0</span>];
srcIndex++;
}

ArrayObject* argsArray = dvmAllocArrayByClass(objectArrayClass, strlen(method->shorty) - <span class="hljs-number" style="color:#06666;box-sizing: border-box;">1</span>, ALLOC_DEFAULT);
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">if</span> (argsArray == <span class="hljs-literal" style="color:#06666;box-sizing: border-box;">NULL</span>) {
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">return</span>;
}

<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">while</span> (*desc != <span class="hljs-string" style="color:#0880;box-sizing: border-box;">'\0'</span>) {
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">char</span> descChar = *(desc++);
JValue value;
Object* obj;

<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">switch</span> (descChar) {
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">case</span> <span class="hljs-string" style="color:#0880;box-sizing: border-box;">'Z'</span>:
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">case</span> <span class="hljs-string" style="color:#0880;box-sizing: border-box;">'C'</span>:
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">case</span> <span class="hljs-string" style="color:#0880;box-sizing: border-box;">'F'</span>:
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">case</span> <span class="hljs-string" style="color:#0880;box-sizing: border-box;">'B'</span>:
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">case</span> <span class="hljs-string" style="color:#0880;box-sizing: border-box;">'S'</span>:
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">case</span> <span class="hljs-string" style="color:#0880;box-sizing: border-box;">'I'</span>:
value<span class="hljs-variable" style="color:#66066;box-sizing: border-box;">.i</span> = args[srcIndex++];
obj = (Object*) dvmBoxPrimitive(value, dvmFindPrimitiveClass(descChar));
dvmReleaseTrackedAlloc(obj, <span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">self</span>);
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">break</span>;
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">case</span> <span class="hljs-string" style="color:#0880;box-sizing: border-box;">'D'</span>:
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">case</span> <span class="hljs-string" style="color:#0880;box-sizing: border-box;">'J'</span>:
value<span class="hljs-variable" style="color:#66066;box-sizing: border-box;">.j</span> = dvmGetArgLong(args, srcIndex);
srcIndex += <span class="hljs-number" style="color:#06666;box-sizing: border-box;">2</span>;
obj = (Object*) dvmBoxPrimitive(value, dvmFindPrimitiveClass(descChar));
dvmReleaseTrackedAlloc(obj, <span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">self</span>);
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">break</span>;
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">case</span> <span class="hljs-string" style="color:#0880;box-sizing: border-box;">'['</span>:
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">case</span> <span class="hljs-string" style="color:#0880;box-sizing: border-box;">'L'</span>:
obj  = (Object*) args[srcIndex++];
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">break</span>;
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">default</span>:
ALOGE(<span class="hljs-string" style="color:#0880;box-sizing: border-box;">"Unknown method signature description character: %c"</span>, descChar);
obj = <span class="hljs-literal" style="color:#06666;box-sizing: border-box;">NULL</span>;
srcIndex++;
}
setObjectArrayElement(argsArray, dstIndex++, obj);
}

<span class="hljs-comment" style="color:#8800;box-sizing: border-box;">// 调用Java中的对应方法，即之前我们用到，的handleHookedMethod</span>
JValue result;
dvmCallMethod(<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">self</span>, xposedHandleHookedMethod, <span class="hljs-literal" style="color:#06666;box-sizing: border-box;">NULL</span>, &result,
originalReflected, (<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">int</span>) original, additionalInfo, thisObject, argsArray);

dvmReleaseTrackedAlloc(argsArray, <span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">self</span>);

<span class="hljs-comment" style="color:#8800;box-sizing: border-box;">// exceptions are thrown to the caller</span>
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">if</span> (dvmCheckException(<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">self</span>)) {
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">return</span>;
}

<span class="hljs-comment" style="color:#8800;box-sizing: border-box;">// return result with proper type</span>
ClassObject* returnType = dvmGetBoxedReturnType(method);
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">if</span> (returnType->primitiveType == PRIM_VOID) {
<span class="hljs-comment" style="color:#8800;box-sizing: border-box;">// ignored</span>
} <span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">else</span> <span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">if</span> (result<span class="hljs-variable" style="color:#66066;box-sizing: border-box;">.l</span> == <span class="hljs-literal" style="color:#06666;box-sizing: border-box;">NULL</span>) {
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">if</span> (dvmIsPrimitiveClass(returnType)) {
dvmThrowNullPointerException(<span class="hljs-string" style="color:#0880;box-sizing: border-box;">"null result when primitive expected"</span>);
}
pResult->l = <span class="hljs-literal" style="color:#06666;box-sizing: border-box;">NULL</span>;
} <span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">else</span> {
<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">if</span> (!dvmUnboxPrimitive(result<span class="hljs-variable" style="color:#66066;box-sizing: border-box;">.l</span>, returnType, pResult)) {
dvmThrowClassCastException(result<span class="hljs-variable" style="color:#66066;box-sizing: border-box;">.l</span>->clazz, returnType);
}
}
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li><li style="box-sizing: border-box; padding: 0px 5px;">53</li><li style="box-sizing: border-box; padding: 0px 5px;">54</li><li style="box-sizing: border-box; padding: 0px 5px;">55</li><li style="box-sizing: border-box; padding: 0px 5px;">56</li><li style="box-sizing: border-box; padding: 0px 5px;">57</li><li style="box-sizing: border-box; padding: 0px 5px;">58</li><li style="box-sizing: border-box; padding: 0px 5px;">59</li><li style="box-sizing: border-box; padding: 0px 5px;">60</li><li style="box-sizing: border-box; padding: 0px 5px;">61</li><li style="box-sizing: border-box; padding: 0px 5px;">62</li><li style="box-sizing: border-box; padding: 0px 5px;">63</li><li style="box-sizing: border-box; padding: 0px 5px;">64</li><li style="box-sizing: border-box; padding: 0px 5px;">65</li><li style="box-sizing: border-box; padding: 0px 5px;">66</li><li style="box-sizing: border-box; padding: 0px 5px;">67</li><li style="box-sizing: border-box; padding: 0px 5px;">68</li><li style="box-sizing: border-box; padding: 0px 5px;">69</li><li style="box-sizing: border-box; padding: 0px 5px;">70</li><li style="box-sizing: border-box; padding: 0px 5px;">71</li><li style="box-sizing: border-box; padding: 0px 5px;">72</li><li style="box-sizing: border-box; padding: 0px 5px;">73</li><li style="box-sizing: border-box; padding: 0px 5px;">74</li><li style="box-sizing: border-box; padding: 0px 5px;">75</li><li style="box-sizing: border-box; padding: 0px 5px;">76</li><li style="box-sizing: border-box; padding: 0px 5px;">77</li><li style="box-sizing: border-box; padding: 0px 5px;">78</li><li style="box-sizing: border-box; padding: 0px 5px;">79</li><li style="box-sizing: border-box; padding: 0px 5px;">80</li><li style="box-sizing: border-box; padding: 0px 5px;">81</li><li style="box-sizing: border-box; padding: 0px 5px;">82</li><li style="box-sizing: border-box; padding: 0px 5px;">83</li><li style="box-sizing: border-box; padding: 0px 5px;">84</li><li style="box-sizing: border-box; padding: 0px 5px;">85</li><li style="box-sizing: border-box; padding: 0px 5px;">86</li><li style="box-sizing: border-box; padding: 0px 5px;">87</li><li style="box-sizing: border-box; padding: 0px 5px;">88</li><li style="box-sizing: border-box; padding: 0px 5px;">89</li><li style="box-sizing: border-box; padding: 0px 5px;">90</li><li style="box-sizing: border-box; padding: 0px 5px;">91</li><li style="box-sizing: border-box; padding: 0px 5px;">92</li><li style="box-sizing: border-box; padding: 0px 5px;">93</li></ul>

原文地址： http://blog.csdn.net/yzzst/article/details/47913867