The C ! operator

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In C, the ! (“logical NOT”) operator used on a value x evaluates to 0 when x is not 0, and 1 when x is 0. In other words, it’s equivalent to the following C: read more

The real reason for driver signing in Vista x64

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In Windows Vista x64, drivers are required to be signed by someone holding a VeriSign code certificate or they won’t load. There is no way to (permanently) disable this signing even if you are Administrator. The F8 startup menu has an option to disable it, but you must select it every time you boot up. Microsoft’s claimed reason for this is that it prevents Trojans from installing kernel-mode rootkits. That is a load of crap.

Asking the kernel how to make a syscall

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Imagine you’re an i386 user mode application on a modern operating system, and you want to make a syscall, for example to request some memory or create a new thread. But syscalls can be made in various ways on the i386 family of CPUs (int, call gates, sysenter, syscall), and CPUs tend to support only a subset of them. But hardcoding “int” into the kernel is a waste of resources on modern CPUs, because sysenter is a lot faster. read more

First assembly puzzle!

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This is our first assembly language puzzle for the new site! These puzzles are tests to see whether you are good enough of an assembly nerd, and to learn some tricks if you’re not =^_^= read more