Directly access your physical memory (dev/mem)

Not super related but a pleasantly surprising linux /dev trick I discovered yesterday was piping “hello” to /dev/udp/<ip>/<port> in order to check connectivity between two machines (the other was listening using nc)

This is pretty tangential but seeing this reminds me of the days when the puredyne distro used to pipe /dev/mem to /dev/dsp as a noisy startup chime.

The 'devmem' command is pretty neat when doing embedded systems, allowing you to write entire device drivers in bash!

Make a game of it: How many random bytes can you write (to random locations) before (your program | the entire system) goes badly awry or unresponsive?

Take that, memory-safe programming languages!

Drawing to the vga frame buffer back in dos used to be as simple as setting a pointer to 0xA0000 in your c(++) program and writing to it. Fond memories!

This is also handy for directly accessing memory that's been mapped in from peripherals and special-purpose processors. Though it might not always work because of clock gating.

I'm surprised access through /dev/mem happens below the caching layer. I wouldn't have even thought of that possibility. Any idea why that is?

Isn't this a security risk?