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Prekernel: Split early boot printing into two subroutines

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Tim Schumacher 2021-10-02 01:56:42 +02:00 committed by Linus Groh
parent 0a54a86a8b
commit e8808b259a
1 changed files with 46 additions and 17 deletions
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63
Kernel/Prekernel/Arch/x86/boot.S
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@ -98,6 +98,46 @@ code64_sel:
start:
jmp real_start
/*
param 1: pointer to C string
returns: Length of string (including null byte)
*/
print_no_halt:
pushl %ebp
movl %esp, %ebp
pushl %esi
pushl %ecx
movl 8(%ebp), %esi
mov $0xb8000, %ecx /* VRAM address. */
mov $0x07, %ah /* grey-on-black text. */
.Lprint_str_loop:
lodsb /* Loads a byte from address at %esi into %al and increments %esi. */
test %al, %al
jz .Lprint_str_end
movw %ax, (%ecx)
add $2, %ecx
jmp .Lprint_str_loop
.Lprint_str_end:
mov %esi, %eax
sub 8(%ebp), %eax
popl %ecx
popl %esi
movl %ebp, %esp
popl %ebp
ret
/*
this function assumes that paging is disabled (or everything is mapped 1:1)
param 1: pointer to string ended with null terminator (C string)
@ -122,24 +162,13 @@ print_and_halt:
movl %esp, %ebp
movl 4(%ebp), %esi
mov $0xb8000, %ecx /* VRAM address. */
mov $0x07, %ah /* grey-on-black text. */
/* Print string using non-destructive methods */
pushl %esi
call print_no_halt
addl $4, %esp
.print_str_loop:
lodsb /* Loads a byte from address at %esi into %al and increments %esi. */
test %al, %al
jz .print_str_end
movw %ax, (%ecx)
add $2, %ecx
jmp .print_str_loop
.print_str_end:
/* Calculate string length into %ecx */
mov %esi, %ecx
sub 4(%ebp), %ecx
/* print_no_halt returns the string length (including null byte) in eax. */
mov %eax, %ecx
movw %cx, (COPIED_STRING_LOCATION) /* Store string length for later use. */
/* Copy string into lower memory */