New answers tagged x86
You can use output of the /proc/ioports: $ cat /proc/ioports 0000-0cf7 : PCI Bus 0000:00 0000-001f : dma1 0020-0021 : pic1 0040-0043 : timer0 0050-0053 : timer1 0060-0060 : keyboard 0064-0064 : keyboard 0070-0077 : rtc0 0080-008f : dma page reg 00a0-00a1 : pic2 00c0-00df : dma2 00f0-00ff : fpu ... And cat ...
It seems %gs is reserved for GCC'c stack protection feature on x86 Linux kernel with CONFIG_CC_STACKPROTECTOR enabled in order to set up stack canaries. You can see some explanation at arch/x86/include/asm/stackportector.h.
Don't rely on the high scoring answers to this question because these methods are not always correct. I've a computer with a Intel Atom N230 CPU which according to all of the tests mentioned is capable to support 64 bit OS'es. According to http://en.wikipedia.org/wiki/Intel_Atom#32-bit_and_64-bit_hardware_support the CPU is not capable of running 64 bit ...
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