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Alloc'ing from heap we set up.

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This commit is contained in:
Thomas Oltmann 2025-07-05 19:34:54 +02:00
parent 50d9e63041
commit 517fcba43b
1 changed files with 12 additions and 18 deletions
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30
lboot.S
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@ -40,8 +40,6 @@ _start: cli
mov $msg_fin, %si
call print
// hang: sleep indefinitely
hang: hlt
jmp hang
.set COM1, 0x3F8
@ -179,22 +177,14 @@ _mhnext: add $24, %si
_mhdone: ret
// alloc: take ECX bytes from usable space in memmap
// alloc: take ECX bytes from heap, return ptr in EAX
// The allocation does not get marked in the memmap.
// No realignment is performed, so only alloc aligned sizes.
alloc: mov $memmap-24, %si
_anext: add $24, %si
cmp memmap_end, %si // ran over end of memmap?
jae _aerr
cmpl $1, 16(%si)
jne _anext
// TODO check that entry has enough space
cmpl $0, 4(%si) // memory is above 4Gb?
jne _aerr
mov 0(%si), %eax
addl %ecx, 0(%si)
adcl $0, 4(%si)
subl %ecx, 8(%si)
sbbl $0, 12(%si)
alloc: cmp heap_size, %ecx
ja _aerr
mov heap_start, %eax
add %ecx, heap_start
sub %ecx, heap_size
ret
_aerr: mov $msg_aerr, %si
call print
@ -247,6 +237,10 @@ gdt: // entry 0: null descriptor
gdt_ptr: .word gdt_size-1
.long gdt
// hang: sleep indefinitely
hang: hlt
jmp hang
// Messages to print
msg_start: .asciz "Netboot via fernlader v1 ...\r\n"
msg_a20: .asciz " * Enabling A20\r\n"
@ -255,7 +249,7 @@ msg_getmap: .asciz " * Memory Map\r\n"
msg_mkheap: .asciz " * Making Space\r\n"
msg_paging: .asciz " * Paging\r\n"
msg_fin: .asciz "Finished.\r\n"
msg_aerr: .asciz "panic: Unable to allocate memory.\r\n"
msg_aerr: .asciz "panic: Out of heap space.\r\n"
heap_start: .long 0
heap_size: .long 0