我正在尝试使用我的打印功能在屏幕上打印一些东西。
我偶然发现了一个小问题 - 当我像这样传递字符数组时：
char s[] = "abc";
print(s);
它工作正常，但是当我这样称呼它时，没有任何效果。
print("abc");
这是我的函数声明
//print function
void print(char* message);
我错过了什么吗？printf 的工作方式相同，您可以通过第二种方式传递字符串。
编辑：
定义
void print_at(char* message, int col, int row){
if(col >= 0 && row >= 0){
set_cursor(get_screen_offset(col,row));
}
int i = 0;
while(message[i] != 0){
print_char(message[i++],-1,-1,WHITE_ON_BLACK);
}
}
void print(char* message){
print_at(message, -1,-1);
}
EDIT2：kernel.o 的 objdump
void start(){
clear_screen();
char s[] = "abc";
print("abc");
print(s);
while(1);
}
部分.text的反汇编：
00000000 <_start>:
0: 55 push ebp
1: 89 e5 mov ebp,esp
3: 83 ec 28 sub esp,0x28
6: e8 00 00 00 00 call b <_start+0xb> //clear_screen()
b: c7 45 f4 61 62 63 00 mov DWORD PTR [ebp-0xc],0x636261 //"bca"
12: c7 04 24 00 00 00 00 mov DWORD PTR [esp],0x0
19: e8 00 00 00 00 call 1e <_start+0x1e> //print()
1e: 8d 45 f4 lea eax,[ebp-0xc]
21: 89 04 24 mov DWORD PTR [esp],eax
24: e8 00 00 00 00 call 29 <_start+0x29> //print()
29: eb fe jmp 29 <_start+0x29>
2b: 90 nop
编辑3：
由于这可能与我初始化环境的方式有关，因此这里有两个负责的文件：
pmode.asm - 初始化段，并跳转到内核的开始
[bits 16]
switch_to_pm:
cli ; switch interuppts off
lgdt [gdt_descriptor] ; load global descriptor table
mov eax, cr0 ; set control registers first bit to protected mode
or eax, 0x1
mov cr0, eax
jmp CODE_SEG:init_pm ;flush cache by far jump
[bits 32]
init_pm:
mov ax, DATA_SEG
mov ds, ax
mov ss, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ebp, 0x90000
mov esp, ebp
call BEGIN_PM
这是我构建gdt的方式：
; GDT
gdt_start:
gdt_null: ; the mandatory null descriptor
dd 0x0 ; ' dd ' means define double word ( i.e. 4 bytes )
dd 0x0
gdt_code: ; the code segment descriptor
; base =0 x0 , limit =0 xfffff ,
; 1 st flags : ( present )1 ( privilege )00 ( descriptor type )1 -> 1001 b
; type flags : ( code )1 ( conforming )0 ( readable )1 ( accessed )0 -> 1010 b
; 2 nd flags : ( granularity )1 (32- bit default )1 (64- bit seg )0 ( AVL )0 -> 1100 b
dw 0xffff ; Limit ( bits 0-15)
dw 0x0 ; Base ( bits 0-15)
db 0x0 ; Base ( bits 16-23)
db 10011010b ; 1 st flags , type flags
db 11001111b ; 2 nd flags , Limit ( bits 16-19)
db 0x0 ; Base ( bits 24-31)
gdt_data: ; the data segment descriptor
; Same as code segment except for the type flags :
; type flags : ( code )0 ( expand down )0 ( writable )1 ( accessed )0 -> 0010 b
dw 0xffff ; Limit ( bits 0-15)
dw 0x0 ; Base ( bits 0-15)
db 0x0 ; Base ( bits 16-23)
db 10010010b ; 1 st flags , type flags
db 11001111b ; 2 nd flags , Limit ( bits 16-19)
db 0x0 ; Base ( bits 24-31)
gdt_end: ; The reason for putting a label at the end of the
; GDT is so we can have the assembler calculate
; the size of the GDT for the GDT decriptor ( below )
; GDT descriptior
gdt_descriptor:
dw gdt_end - gdt_start - 1 ; Size of our GDT , always less one
; of the true size
dd gdt_start ; Start address of our GDT
; Define some handy constants for the GDT segment descriptor offsets , which
; are what segment registers must contain when in protected mode. For example ,
; when we set DS = 0 x10 in PM , the CPU knows that we mean it to use the ; segment described at offset 0 x10 ( i.e. 16 bytes ) in our GDT , which in our
; case is the DATA segment (0 x0 -> NULL ; 0 x08 -> CODE ; 0 x10 -> DATA )
CODE_SEG equ gdt_code - gdt_start
DATA_SEG equ gdt_data - gdt_start