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Set Target Operating Mode #18

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Merged
phil-opp merged 1 commit into from Jul 10, 2018
Merged

Set Target Operating Mode #18

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12 changes: 12 additions & 0 deletions src/second_stage.s
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,18 @@ second_stage:
lea si, second_stage_start_str
call println

set_target_operating_mode:
# Some BIOSs assume the processor will only operate in Legacy Mode. We change the Target
# Operating Mode to "Long Mode Target Only", so the firmware expects each CPU to enter Long Mode
# once and then stay in it. This allows the firmware to enable mode-specifc optimizations.
# We save the flags, because CF is set if the callback is not supported (in which case, this is
# a NOP)
pushf
mov ax, 0xec00
mov bl, 0x2
int 0x15
popf

load_kernel_from_disk:
# start of memory buffer
lea eax, _kernel_buffer
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