4 ms·
That was a very long time ago. Microcode can be loaded by the BIOS.
by TomV1971 9y ago
That was a very long time ago.
Microcode can be loaded by the BIOS.
- Operyl 9y agoCan also be loaded at boot time by the kernel, etc.
- cjbprime 9y agoOr even after boot time, I think -- you shut down one CPU at a time to load it.
- xxs 9y agoMost of the microcode nowadays is loaded by the OS (not BIOS)
- chopin 9y agoToday I learned something. Doesn't that open a huge attack surface? This code would run super-privileged isn't it?
- 0x0 9y agoCPUs will only accept uploads of microcode if they can verify the digital signature, of which the private keys are only known to the CPU manufacturer (i.e. Intel or AMD). Probably it will also only allow upgrades, not downgrades, on a running system. So the only "attack" you can perform if you've gained root is to patch CPU security vulnerabilities by upgrading to a newer valid microcode, and then also only until the next reboot.