You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
24 lines
883 B
24 lines
883 B
*Concepts you may want to Google beforehand: interrupts, pipelining*
|
|
|
|
**Goal: Enter 32-bit protected mode and test our code from previous lessons**
|
|
|
|
To jump into 32-bit mode:
|
|
|
|
1. Disable interrupts
|
|
2. Load our GDT
|
|
3. Set a bit on the CPU control register `cr0`
|
|
4. Flush the CPU pipeline by issuing a carefully crafted far jump
|
|
5. Update all the segment registers
|
|
6. Update the stack
|
|
7. Call to a well-known label which contains the first useful code in 32 bits
|
|
|
|
We will encapsulate this process on the file `32bit-switch.asm`. Open it
|
|
and take a look at the code.
|
|
|
|
After entering 32-bit mode, we will call `BEGIN_PM` which is the entry point
|
|
for our actual useful code (e.g. kernel code, etc). You can read the code
|
|
at `32bit-main.asm`. Compile and run this last file and you will see the two
|
|
messages on the screen.
|
|
|
|
Congratulations! Our next step will be to write a simple kernel
|