How to know in which mode the kernel is booted?

[Narasimha1997]

As I've seen, the bootloader can boot in legacy BIOS ams UEFI modes. However, there is no way for the kernel to directly know in which mode it has been booted. This can be useful in different parts of the kernel (For example, during the initialisation of 8259 PIC as trying to enable PIC in UEFI mode double faults immediately).

One way I've seen is to iterate over the memory map and check if the regions are of type UnknownBios or UnknownUefi and take decisions. But this isn't an idiomatic way.

The best way would be to pass a flag in BootInfo struct called is_uefi which is true or false based on the mode the kernel is booted.