mmap equivalent in Windows or How To Map Physical Memory to Userspace.

Windows unfortunately has no equivalent of mmap that can access physical memory e.g by mapping /dev/mem to some userspace address, however this can be achieved by a simple(not really) kernel-mode driver that I've personally used in Windows 7 x64, though there should be no reason why it wouldn't work in Windows 8/8.1/10

I found it in this article on CodeProject.

Now, even if you compile the driver, on x64 Windows systems the driver needs to be signed, this for development purposes can be disabled, follow the article on MSDN on how to do that.

But beware, fiddling with physical memory can lead to some very dangerous results if you aren't careful, e.g permanent hardware failure or data loss.

The scary Virtual Machine

Sorry for the cheesy thread title, but I had no idea what to put there.

But anyway, I recently came across more virtual machines, and honestly, when you get to the jist of it, they aren't all that difficult to understand nor implement.

For instance, this guy here wrote his own C compiler for the C89 standard, and made it work for his own custom virtual CPU, for which he wrote several "emulators"(emulator;virtual machine it's all the same in this context) in C, Java and finally, Javascript. This actually gave me an idea to implement some VMs in Javascript as well, I mean you can run the thing in your browser.

Now, Virtual Machines like VirtualBox, VMWare and QEMU are different, they try to emulate a whole computer with the peripherals and also takes advantage of a CPU's special virtualization options for HW virtualization, they are indeed harder to write and understand and I myself couldn't even begin to comprehend VirtualBox's code.

But we aren't interested in those(or at least I am not) right now, we just want to emulate a CPU, or even create our own, the sky is the limit.

Back to the Roots.

Initially this blog was about compiling stuff for Windows, then I turned it into a RE blog, but today I plan to go back to the roots and post some stuff about compilation.

The goal was to cross-compile MySQL from Linux x86_64 to Android, ARM-v7a. But there are a few problems here.
1.) Google's NDK offers a very slimmed-down version of GCC and they provide their own standard C library called Bionic which is missing a ton of stuff, widechar support being one of them among many missing headers.
2.) The Crystax NDK does not add these missing headers, so the only option left was to compile my own GCC with GLIBC. I did that nearly 2 years ago with crosstool-ng and have successfully compiled php like that(but not with all features).
3.) Some targets built by the CMake system have to be run, this isn't possible when cross-compiling, so you need to first build MySQL for the host, and then gather the tools you need further increasing the complexity of the task of compiling MySQL for Android.
4.) Static linking of GLIBC, this is the most important part, as it needs to be set  in the CMAKE_C_FLAGS before you build(and it takes a while)

Needless to say I managed to compile it, with default features, but I forgot to statically link GLIBC, and mysql did not run.