WangLu's Notes

Flash encryption and secure boot are useful security features for ESP32S3 chip. While not perfect, they definitely make it harder to extract the secrets in the chip. However, it is tricky to enable both features at the same time. The topic is actually discussed in the official documentation: ESP32S3 Security Features Security Features Enablement Workflows Especially, the second one mentioned it is recommended to enable flash encryption before secure boot. But I still find the documentation confusing. In the end I was able to successfully enable both, here's my findings. My Understanding After my adventure, here's what I think could have worked. WARNING, this is untested. Follow  Security Features Enablement Workflows : Burn all the keys, as long as their purpose eFuses and read/write protections Burn other security eFuses, but DO NOT burn ENABLE_SECURITY_DOWNLOAD in the middle, which is mentined at the end of the instruction for both flash encryption and secure boot. Burn...

最近的新玩具: https://github.com/coolwanglu/quine-chameleon 受mame的100个语言的quine-relay的启发，我想可否做一个完全图，即多个语言互相转换。 这样的程序英文叫multiquines，Wikipedia上有介绍，程序运行时需要指定一个参数，比如输出语言，然后程序会输出自身代码的对应那种语言的版本。如果指定参数就是这个程序源代码所使用的语言，那就是quine了。 网上有一个5种语言的multiquines，我看了看，不是太优美。我一开始就是朝着multiquines的方向写。然而后来注意到，不指定任何参数的时候对multiquines来说是没定义的（或者什么都不应该输出），这个有点浪费，于是我做了ouroboros（就像quine-relay那样）和随机转换两种模式。 再后来我注意到反而是不指定参数这部分更有趣，而且为了同时支持带参数和不带参数，需要各种判断，造成代码臃肿。于是我就把这两部分拆开，目前在源码中分别叫chameleon.*和multiquines.*。分别进行优化。 写这个东西最大的乐趣当然是不断加入新的语言。我开始不久就把自己熟悉的语言放进去了，然后慢慢添加新语言，不会的就现学现卖。基本上需要的语言特性和函数有如下几个 - 支持双引号定义的字符串，支持反斜杠转义 - 将字符串按分隔符切成数组 - 生成随机数 - 支持命令行参数 - 数组查找 - 字符串转义，或者json输出，或者字符串／正则式替换 - 输出（不带换行） 按目前的设计，第一条决定了一个语言是否能很容易的加入。这里比quine-relay难的地方在于，任何两个语言都要互相输出，所以最好能有一个公共的转义和还原的标准。而quine-relay中每个语言只需要考虑下一个语言的转义就好了，更方便预处理，支持新语言（比如whitespace，brainfuck）以及其他特性（比如字符串压缩） 我在写这个玩具的过程中也很自然的学习了一些新语言。之前为了写dunnet.js而研究了emacs lisp，这里还加入了其他lisp系列比如clojure，racket，发现写写脚本也还挺顺手的。只可惜scheme由于标准库太小以及srfi实现不统一没能加入。另外就是接触了之前完全不想接触的perl和aw...

Emscripten is a C/C++ -> LLVM -> JavaScript compiler. It's useful and interesting, but one of its biggest limitations is about the sync/async model: JavaScript is single-threaded event-driven languages, therefore you cannot do a sleep() in the hope of receiving and processing extra events. Demo First of all, please enjoy this demo , on which I really spent some time. tl;dr Motivation: to make `sleep` and other similar functions actually work in our Runtime, without lots of labor work porting the C/C++ code I actually made it worked  `sync->async` is doable and I think it's not too hard - there are already implementations for JS I think this is a feature that cannot be supported by merely an external library Does it fit emscripten? Or is it possible to write a plugin for emscripten? Demo explained(?) The demo is basically a stop-time animation: //draw something //wait for some while //draw something else //wait... You can verify this ...

偶然从某论坛看到的 valgrind --tool=memcheck --leak-check=yes --show-reachable=yes ./a.out 目前只会这么一种用法，但是一下子就找到了病根，太棒了！ 以后再研究研究。