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clear the carry flag before calling BIOS functions

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This commit is contained in:
Elaina Claus
2025-09-05 10:33:42 -04:00
parent c3871d2b7d
commit a53534acd2
4 changed files with 6 additions and 0 deletions
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1
include/BIOS/func/E820_memory_map.nasm
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@@ -53,6 +53,7 @@ GetMemoryMap:
.loop_L1: .loop_L1:
mov eax, 0x0000E820 ; select 0xE820 function mov eax, 0x0000E820 ; select 0xE820 function
mov edx, 0x534D4150 ; 'SMAP' magic mov edx, 0x534D4150 ; 'SMAP' magic
clc ; clear carry
int 0x15 int 0x15
jc GetMemoryMap.error jc GetMemoryMap.error
cmp eax, 0x534D4150 cmp eax, 0x534D4150

2
include/BIOS/func/a20enable.nasm
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@@ -105,6 +105,7 @@ EnableA20:
je EnableA20.endp ; A20 is already enabled je EnableA20.endp ; A20 is already enabled
mov ax, 0x2403 mov ax, 0x2403
clc ; clear carry
int 0x15 int 0x15
jc EnableA20.do_fallback_a20 ; carry = error...not supported? jc EnableA20.do_fallback_a20 ; carry = error...not supported?
cmp ah, 0 cmp ah, 0
@@ -121,6 +122,7 @@ EnableA20:
ERROR STAGE2_A20_FAILED ERROR STAGE2_A20_FAILED
.do_bios_a20: .do_bios_a20:
mov ax, 0x2401 mov ax, 0x2401
clc ; clear carry
int 0x15 int 0x15
jmp EnableA20.a20_check jmp EnableA20.a20_check
.do_fast_a20: .do_fast_a20:

1
include/BIOS/func/ext_read.nasm
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@@ -111,6 +111,7 @@ read_disk_raw:
mov ah, 0x42 ; call # mov ah, 0x42 ; call #
mov dl, byte [bp + 14] ; drive # mov dl, byte [bp + 14] ; drive #
clc ; clear carry
int 0x13 int 0x13
jnc .endf jnc .endf

2
src/mbr/mbr.nasm
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@@ -96,6 +96,8 @@ main:
mov ah, 0x41 mov ah, 0x41
mov bx, 0x55AA mov bx, 0x55AA
mov dl, 0x80 mov dl, 0x80
clc
int 0x13 int 0x13
jnc main.find_active jnc main.find_active
ERROR MBR_ERROR_NO_INT32E ; no extended function support ERROR MBR_ERROR_NO_INT32E ; no extended function support