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| author | Joursoir <chat@joursoir.net> | 2021-10-01 12:19:08 +0000 |
|---|---|---|
| committer | Joursoir <chat@joursoir.net> | 2021-10-01 12:19:08 +0000 |
| commit | e46551eebeeed2e79f1784f1c2b5f48c65d95b1d (patch) | |
| tree | e7a7f9b2e14c04a0d334be0af12e6b8394d3fba0 | |
| parent | 1d47855c80b63176cd55980cf68d5c187c44a766 (diff) | |
| download | mfsos-e46551eebeeed2e79f1784f1c2b5f48c65d95b1d.tar.gz mfsos-e46551eebeeed2e79f1784f1c2b5f48c65d95b1d.tar.bz2 mfsos-e46551eebeeed2e79f1784f1c2b5f48c65d95b1d.zip | |
x86/boot/head: check a20 line
| -rw-r--r-- | arch/x86/boot/head.s | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/x86/boot/head.s b/arch/x86/boot/head.s index a1bc6d1..d24e36c 100644 --- a/arch/x86/boot/head.s +++ b/arch/x86/boot/head.s @@ -23,5 +23,13 @@ _start: mov $0x90000, %ebp # Update stack position so it is right mov %ebp, %esp # at the top of the free space. +check_a20: + mov $0x112345, %edi # Odd megabyte address + mov $0x012345, %esi # Even megabyte address + mov %esi, (%esi) # If A20 line is disabled two pointers + mov %edi, (%edi) # would point to the address 0x012345 + cmpsd # Compare values at addresses + je . # If equivalent, loop forever + call kernel_main jmp . # infinite loop |