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    <title>Stop Talking, Start Doing - 停止空想，开始行动</title>
    <description>My personal blog, with some boring research staff and some tricks I was fancy to. I'll try my best to make this blog fun and useful. Not just a place I complain about all happens in my Lab.
</description>
    <link>https://codersherlock.github.com//</link>
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    <pubDate>Wed, 29 Aug 2018 16:34:12 -0400</pubDate>
    <lastBuildDate>Wed, 29 Aug 2018 16:34:12 -0400</lastBuildDate>
    <generator>Jekyll v3.8.3</generator>
    
      <item>
        <title>Xv6 introduction</title>
        <description>&lt;p&gt;I hate xv6, a stupid, useless education-oriented system. In this article, I will generally talk about how to implement system call to this operating system.&lt;/p&gt;

&lt;hr /&gt;

&lt;h2 id=&quot;xv6-systemcall&quot;&gt;Xv6 Systemcall&lt;/h2&gt;
&lt;p&gt;To invoke a system call, we have to first define a user mode function to be the interface of the kernel instruction  in file &lt;em&gt;user.h&lt;/em&gt;.&lt;/p&gt;

&lt;div class=&quot;language-c highlighter-rouge&quot;&gt;&lt;div class=&quot;highlight&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;function&lt;/span&gt; &lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;&lt;/div&gt;

&lt;p&gt;This interface-like function will then pass the function name, in this case function, to &lt;em&gt;usys.S&lt;/em&gt;. When using user mode function in programs, &lt;em&gt;usys.S&lt;/em&gt; will generate a reference to SYS_function and push system call number of this function into %eax. After that, system can know from &lt;em&gt;syscall.c&lt;/em&gt; and determining whether this system call is available. We must define same name system function and add it into &lt;em&gt;syscall.h&lt;/em&gt; and &lt;em&gt;syscall.c&lt;/em&gt;.&lt;/p&gt;

&lt;div class=&quot;language-c highlighter-rouge&quot;&gt;&lt;div class=&quot;highlight&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;&lt;span class=&quot;cp&quot;&gt;#define SYS_function ##		// ## is the system call number
&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;[&lt;/span&gt;&lt;span class=&quot;n&quot;&gt;SYS_function&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;]&lt;/span&gt;  &lt;span class=&quot;n&quot;&gt;sys_function&lt;/span&gt;	&lt;span class=&quot;c1&quot;&gt;// real system function name&lt;/span&gt;
&lt;span class=&quot;k&quot;&gt;extern&lt;/span&gt; &lt;span class=&quot;kt&quot;&gt;int&lt;/span&gt; &lt;span class=&quot;n&quot;&gt;sys_function&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;(&lt;/span&gt;&lt;span class=&quot;kt&quot;&gt;void&lt;/span&gt;&lt;span class=&quot;p&quot;&gt;);&lt;/span&gt;	&lt;span class=&quot;c1&quot;&gt;// real system function declaration&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;&lt;/div&gt;

&lt;p&gt;After adding these sentences to syscall files, we can implement real function in specific place where you want to make the function works well.&lt;/p&gt;

&lt;p&gt;Sometimes, we need to pass variables among system calls. In this case, variables’ values are not necessary and even can’t be pass directly into system_function. When invoke a system call function, all variables of this system call will be pushed into current process’ stack. In file &lt;em&gt;syscall.c&lt;/em&gt;, multiple functions are provided to get these variables from the process. I won’t waste time on explaining how to use these functions especially when elegant and detailed comments were written in source codes. However, I will explain concepts and how process organized and works in xv6 in future articles.&lt;/p&gt;
</description>
        <pubDate>Fri, 28 Jul 2017 14:56:55 -0400</pubDate>
        <link>https://codersherlock.github.com//archivers/intro-xv6</link>
        <guid isPermaLink="true">https://codersherlock.github.com//archivers/intro-xv6</guid>
        
        
        <category>xv6</category>
        
      </item>
    
      <item>
        <title>Some of my previews experiment works: 2016</title>
        <description>&lt;p&gt;This blog contains only some basic record of my works. For some details, I will write a unique blog just for some specific topics.&lt;/p&gt;

&lt;h1 id=&quot;2016-10&quot;&gt;2016-10&lt;/h1&gt;

&lt;h2 id=&quot;time-experiment-of-rsync&quot;&gt;Time Experiment of rsync&lt;/h2&gt;

&lt;p&gt;Patch is based on rsync with version 3.1.2. [&lt;a href=&quot;https://download.samba.org/pub/rsync/rsync-3.1.2.tar.gz&quot;&gt;Rsync&lt;/a&gt;|&lt;a href=&quot;/static/2016-10/rsync/rsync-3.1.2-time.patch&quot;&gt;Patch&lt;/a&gt;]&lt;/p&gt;

&lt;h3 id=&quot;how-to-collect-data&quot;&gt;How to collect data&lt;/h3&gt;

&lt;p&gt;Basically, everything of transmission time and computation time will be output with overall time will be printed on the console.
But we also need some bash script to collect data through different size of random size and with different modification through them.&lt;/p&gt;

&lt;ul&gt;
  &lt;li&gt;Start from 8K to 64M, modify at beginning, [&lt;a href=&quot;/static/2016-10/rsync/small2Big_change_at_begin.sh&quot;&gt;Bash script&lt;/a&gt;]&lt;/li&gt;
  &lt;li&gt;Start from 8K to 64M, modify at last, [&lt;a href=&quot;/static/2016-10/rsync/small2Big_change_at_last.sh&quot;&gt;Bash script&lt;/a&gt;]&lt;/li&gt;
  &lt;li&gt;Start from 8K to 64M, modify at random place with a (slow) python script, [&lt;a href=&quot;/static/2016-10/rsync/small2Big_change_at_anyplace.sh&quot;&gt;Bash script&lt;/a&gt;|&lt;a href=&quot;/static/2016-10/rsync/addbyte.py&quot;&gt;Python program&lt;/a&gt;]&lt;/li&gt;
&lt;/ul&gt;

&lt;h2 id=&quot;time-experiment-of-seafile&quot;&gt;Time Experiment of seafile&lt;/h2&gt;

&lt;p&gt;Patch is based on seafile 5.1.4. You can find the release from &lt;a href=&quot;https://github.com/haiwen/seafile/releases&quot;&gt;seafile official repo&lt;/a&gt;. You may follow official compile instructions from &lt;a href=&quot;https://manual.seafile.com/build_seafile/linux.html&quot;&gt;here&lt;/a&gt;. [&lt;a href=&quot;&quot;&gt;Patch &lt;strong&gt;no longer avaiable, new version at following sections&lt;/strong&gt;&lt;/a&gt;]&lt;/p&gt;

&lt;h3 id=&quot;how-to-collect-data-1&quot;&gt;How to collect data&lt;/h3&gt;

&lt;p&gt;We also need everything be done using scripting. But this time I only design added some distance between two increasing files’ sizes.&lt;/p&gt;

&lt;ul&gt;
  &lt;li&gt;Start from 8K to 16M, 4 times increasing, modify at beginning/ at 1024 different places with python script. [&lt;a href=&quot;/static/2016-11/seafile/trans.sh&quot;&gt;Bash Script&lt;/a&gt;|&lt;a href=&quot;/static/2016-11/seafile/addbyte.py&quot;&gt;Python program&lt;/a&gt;]&lt;/li&gt;
  &lt;li&gt;After using this auto testing script, everything of output will be marked in log files of seafile, which located in &lt;strong&gt;~/.ccnet/log/seafile.log&lt;/strong&gt;&lt;/li&gt;
  &lt;li&gt;We need to use this simple awk code and vim operation to extract data.&lt;/li&gt;
&lt;/ul&gt;

&lt;div class=&quot;language-bash highlighter-rouge&quot;&gt;&lt;div class=&quot;highlight&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;&lt;span class=&quot;c&quot;&gt;# CDC: content defined chucks&lt;/span&gt;
&lt;span class=&quot;c&quot;&gt;# HUT: Http upload traffic&lt;/span&gt;
&lt;span class=&quot;c&quot;&gt;# ALL: overall time of one commit &amp;amp; upload&lt;/span&gt;
&lt;span class=&quot;nb&quot;&gt;awk&lt;/span&gt; &lt;span class=&quot;s1&quot;&gt;'/CDC|HUT|ALL/ {print $4,$5}'&lt;/span&gt; ~/.ccnet/log/seafile.log &lt;span class=&quot;o&quot;&gt;&amp;gt;&lt;/span&gt; results.stat
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;&lt;/div&gt;

&lt;h3 id=&quot;install-seafile-on-odroid-xu&quot;&gt;Install Seafile on odroid xu&lt;/h3&gt;

&lt;p&gt;Due to failure of my cross-compile to seafile on android. I used develop board as a replacement experiment platform for ARM-seafile testing. I used a &lt;a href=&quot;http://www.hardkernel.com/main/products/prdt_info.php?g_code=G137510300620&quot;&gt;odroid xu&lt;/a&gt; as hardware standard. Because all I need is an ARM platform, only an ARM-Ubuntu is enough for me. But develop prototype on a board is much fun than coding, I won’t address much this time. But I’ll start a blog telling some really cool stuff I made for a strange aim.&lt;/p&gt;

&lt;p&gt;To install a ubuntu with GUI is my all preparation work. I found to way to do this.&lt;/p&gt;

&lt;ul&gt;
  &lt;li&gt;
    &lt;p&gt;&lt;a href=&quot;http://www.armhf.com/boards/odroid-xu/&quot;&gt;armhf&lt;/a&gt; is a website for arm-based ubuntu. It has a detailed instruction to follow at &lt;a href=&quot;http://www.armhf.com/boards/odroid-xu/odroid-sd-install/&quot;&gt;here&lt;/a&gt;. They also provide ubuntu 12.04/ 14.04 and debian 7.5 to choose. But unfortunately odroid xu’s hdmi output doesn’t supported by ubuntu native firmware. So install ubuntu-desktop might can’t be boot up for video output.&lt;/p&gt;
  &lt;/li&gt;
  &lt;li&gt;
    &lt;p&gt;Burn images is much easy to install a pre-complied ubuntu system. I found this on odroid xu’s forum, which contains xubuntu image [&lt;a href=&quot;http://odroid.in/ubuntu_14.04lts/ubuntu-14.04lts-xubuntu-odroid-xu-20140714.img.xz&quot;&gt;download&lt;/a&gt;] for odroid xu. With this image, you just need to use dd command to write whole system mirror into sdcard.&lt;/p&gt;
  &lt;/li&gt;
&lt;/ul&gt;

&lt;div class=&quot;language-bash highlighter-rouge&quot;&gt;&lt;div class=&quot;highlight&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;&lt;span class=&quot;c&quot;&gt;# If .img end with xz, use this command to uncompress first&lt;/span&gt;
unxz ubuntu-14.04lts-xubuntu-odroid-xu-20140714.img.xz    
&lt;span class=&quot;c&quot;&gt;# Burn image into SD-card&lt;/span&gt;
&lt;span class=&quot;nb&quot;&gt;sudo dd &lt;/span&gt;&lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;=&lt;/span&gt;ubuntu-14.04lts-xubuntu-odroid-xu-20140714.img &lt;span class=&quot;nv&quot;&gt;of&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;=&lt;/span&gt;/dev/sdb &lt;span class=&quot;nv&quot;&gt;bs&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;=&lt;/span&gt;1M &lt;span class=&quot;nv&quot;&gt;conv&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;=&lt;/span&gt;fsync
&lt;span class=&quot;nb&quot;&gt;sync&lt;/span&gt;
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;&lt;/div&gt;

&lt;h1 id=&quot;2016-11&quot;&gt;2016-11&lt;/h1&gt;

&lt;h2 id=&quot;android-kernel&quot;&gt;Android Kernel&lt;/h2&gt;

&lt;h3 id=&quot;how-to-build-an-android-kernel&quot;&gt;How to build an Android Kernel?&lt;/h3&gt;

&lt;p&gt;Generally, I won’t tell anything in this parts, just mark some related links, and point out some mistakes or error solutions.&lt;/p&gt;

&lt;ul&gt;
  &lt;li&gt;
    &lt;p&gt;&lt;a href=&quot;http://source.android.com/source/building-kernels.html#figuring-out-which-kernel-to-build&quot;&gt;Google Official Guide&lt;/a&gt;
– If you don’t have AOSP sources, you have to download prebuilt toolchains which recommended in this guide might not be correct. Use following links to choose your fitting tools.
— &lt;a href=&quot;https://android.googlesource.com/?format=HTML&quot;&gt;ASOP git root&lt;/a&gt;, under sub class “/platform/prebuilts/gcc”&lt;/p&gt;
  &lt;/li&gt;
  &lt;li&gt;
    &lt;p&gt;&lt;a href=&quot;https://softwarebakery.com/building-the-android-kernel-on-linux&quot;&gt;Packing and Flashing a Boot.img&lt;/a&gt; &lt;strong&gt;[highly recommend]&lt;/strong&gt;&lt;/p&gt;
  &lt;/li&gt;
&lt;/ul&gt;

&lt;h1 id=&quot;2016-12&quot;&gt;2016-12&lt;/h1&gt;

&lt;h2 id=&quot;android-kernel-1&quot;&gt;Android Kernel&lt;/h2&gt;

&lt;h3 id=&quot;how-to-compile-with-ftrace&quot;&gt;How to compile with ftrace?&lt;/h3&gt;

&lt;p&gt;If we want to debug under android, ftrace is a great tool for working. But, ftrace is not available in android if we used default configure file. Android kernel configuration is in &lt;strong&gt;arch/arm64/kernel/configs&lt;/strong&gt;. We need to add few lines under that.&lt;/p&gt;

&lt;div class=&quot;language-bash highlighter-rouge&quot;&gt;&lt;div class=&quot;highlight&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;&lt;span class=&quot;nv&quot;&gt;CONFIG_STRICT_MEMORY_RWX&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;=&lt;/span&gt;y
&lt;span class=&quot;nv&quot;&gt;CONFIG_FUNCTION_TRACER&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;=&lt;/span&gt;y
&lt;span class=&quot;nv&quot;&gt;CONFIG_FUNCTION_GRAPH_TRACER&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;=&lt;/span&gt;y
&lt;span class=&quot;nv&quot;&gt;CONFIG_DYNAMIC_FTRACE&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;=&lt;/span&gt;y
&lt;span class=&quot;nv&quot;&gt;CONFIG_PERSISTENT_TRACER&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;=&lt;/span&gt;y
&lt;span class=&quot;nv&quot;&gt;CONFIG_IRQSOFF_TRACER&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;=&lt;/span&gt;y
&lt;span class=&quot;nv&quot;&gt;CONFIG_PREEMPT_TRACER&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;=&lt;/span&gt;y
&lt;span class=&quot;nv&quot;&gt;CONFIG_SCHED_TRACER&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;=&lt;/span&gt;y
&lt;span class=&quot;nv&quot;&gt;CONFIG_STACK_TRACER&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;=&lt;/span&gt;y
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;&lt;/div&gt;

&lt;h3 id=&quot;how-to-extract-android-images-dump-an-image&quot;&gt;How to extract android images: Dump an image&lt;/h3&gt;

&lt;p&gt;If we want to hold a rooted status after flashing boot, we need to extract an image from android devices. We can first use following command to find which blocks belongs to. According to some references, &lt;a href=&quot;http://forum.xda-developers.com/showthread.php?t=2450045&quot;&gt;this article&lt;/a&gt; provide three ways to dump an image, I picked one for easy using.&lt;/p&gt;

&lt;div class=&quot;language-bash highlighter-rouge&quot;&gt;&lt;div class=&quot;highlight&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;adb shell
&lt;span class=&quot;nb&quot;&gt;ls&lt;/span&gt; &lt;span class=&quot;nt&quot;&gt;-al&lt;/span&gt; /dev/block/platform/&lt;span class=&quot;nv&quot;&gt;$SOME&lt;/span&gt;&lt;span class=&quot;se&quot;&gt;\_&lt;/span&gt;DEVICE../../by-name &lt;span class=&quot;c&quot;&gt;# {Partitions} -&amp;gt; {Device Block}&lt;/span&gt;

&lt;span class=&quot;c&quot;&gt;# dump file&lt;/span&gt;
su
&lt;span class=&quot;nb&quot;&gt;dd &lt;/span&gt;&lt;span class=&quot;k&quot;&gt;if&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;=&lt;/span&gt;/dev/block/mmcblk0p37 &lt;span class=&quot;nv&quot;&gt;of&lt;/span&gt;&lt;span class=&quot;o&quot;&gt;=&lt;/span&gt;/sdcard/boot.img
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;&lt;/div&gt;
</description>
        <pubDate>Fri, 28 Oct 2016 12:27:33 -0400</pubDate>
        <link>https://codersherlock.github.com//archivers/some-of-my-previews-exper-work</link>
        <guid isPermaLink="true">https://codersherlock.github.com//archivers/some-of-my-previews-exper-work</guid>
        
        
        <category>Research</category>
        
      </item>
    
      <item>
        <title>Using charles proxy to monitor mobile SSL traffics</title>
        <description>&lt;p&gt;In this blog, I will generally talk about how to use proper tools to monitor SSL traffics of a mobile devices. Currently, I only can dealing with those SSL traffics which use an obviously certification. Some applications may not using system root cert or they doesn’t provide us a method to modify their own certs. For these situation, I still didn’t find a good solutions for it. But I’ll keep updating this if I get one.&lt;br /&gt;
My current solution is using AP to forward all SSL traffic to a proxy, &lt;a href=&quot;https://www.charlesproxy.com/&quot;&gt;charles proxy&lt;/a&gt; is my first choice (Prof asked). It’s a non-free software which still update new versions now. So mainly, I’ll talk about how to charles SSL proxy.&lt;/p&gt;

&lt;h3 id=&quot;preparations&quot;&gt;Preparations&lt;/h3&gt;
&lt;ul&gt;
  &lt;li&gt;Monitor device situation: Linux Machine with wireless adapter&lt;/li&gt;
  &lt;li&gt;Download the newest version(4.0.1) of charles&lt;/li&gt;
  &lt;li&gt;Target android devices with root privilege&lt;/li&gt;
&lt;/ul&gt;

&lt;h3 id=&quot;install-charles-and-configuration&quot;&gt;Install Charles and Configuration&lt;/h3&gt;

&lt;ul&gt;
  &lt;li&gt;You have to install charles first. After downloading the charles proxy, you have to unzip it and configure some basic settings.&lt;/li&gt;
&lt;/ul&gt;

&lt;div class=&quot;language-bash highlighter-rouge&quot;&gt;&lt;div class=&quot;highlight&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;&lt;span class=&quot;c&quot;&gt;# open charles first&lt;/span&gt;
./bin/charles  
&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;&lt;/div&gt;
&lt;ul&gt;
  &lt;li&gt;Save charles’ private key and public key&lt;/li&gt;
&lt;/ul&gt;

&lt;p&gt;In Help -&amp;gt; SSL Proxying -&amp;gt; Export Charles Root Certificate and Private Key, enter a password and save the public and private key in *.p12 format.&lt;br /&gt;
You also need to save charles Root Certificate, it also contains in the same menu. For convience, save it as *.pem format.&lt;/p&gt;

&lt;ul&gt;
  &lt;li&gt;Set Proxy and SSL Proxy&lt;/li&gt;
&lt;/ul&gt;
</description>
        <pubDate>Thu, 27 Oct 2016 22:50:33 -0400</pubDate>
        <link>https://codersherlock.github.com//archivers/charles-is-not-a-good-tool</link>
        <guid isPermaLink="true">https://codersherlock.github.com//archivers/charles-is-not-a-good-tool</guid>
        
        
        <category>Network</category>
        
      </item>
    
      <item>
        <title>Stop Talking is the worst title of one blog</title>
        <description>
</description>
        <pubDate>Wed, 26 Oct 2016 22:50:33 -0400</pubDate>
        <link>https://codersherlock.github.com//archivers/hello</link>
        <guid isPermaLink="true">https://codersherlock.github.com//archivers/hello</guid>
        
        
        <category>Nonsense</category>
        
      </item>
    
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