I studied the training to develop core leadership, especially bran kernel that I'm testing with qemu, either through -kernel, or -cdromI crash. As far as I understand, this is what happens:
as soon as I turned on interrupts ( sti), the interrupt pits are caught by my irq handler. I reused the code from the Bran example:
.intel_syntax noprefix
.global irq00
.extern_default_handler
irq00:
cli
push 0
push 32
jmp irq_common_stub
irq_common_stub:
pushad
push ds
push es
push fs
push gs
mov ax, 0x10
mov ds, ax
mov es, ax
mov fs, ax
mov gs, ax
push eax
mov eax, irq_default_handler
call eax
etc...
add esp, 8
sti
iret
now when i turn on the qemu trace ( -d cpu,exec,in_asm) options , i see the following:
IN:
0x0010121b: mov %eax, %fs
0x0010121d: mov %eax, %gs
0x0010121f: mov %esp, %eax
0x00101222: mov 0x100e81, %eax
0x00101227: call *%eax
Trace 0xb3aa3360 [0010121b]
EAX=83535657 EBX=00009500 ECX=0000000f EDX=00000000
ESI=00000000 EDI=0010a000 EBP=00000000 ESP=00107fc8
EIP=83535657 EFL=00000046 [---Z-P-] CPL=0 II=0 A20=1 SMM=0 HLT=0
ES =0010 00000000 ffffffff 00cf9300 DPL=0 DS [-WA]
CS =0008 00000000 ffffffff 00cf9300 DPL=0 CS32 [-R-]
SS =0008 00000000 ffffffff 00cf9300 DPL=0 DS [-WA]
DS =0008 00000000 ffffffff 00cf9300 DPL=0 DS [-WA]
FS =0008 00000000 ffffffff 00cf9300 DPL=0 DS [-WA]
GS =0008 00000000 ffffffff 00cf9300 DPL=0 DS [-WA]
LDT=0000 00000000 0000ffff 00008200 DPL=0 LDT
TR =0000 00000000 0000ffff 00008b00 DPL=0 TSS32-busy
GDT= 00108060 0000001f
IDT= 001080a0 0000071f
CR0=00000011 CR2=00000000 CR3=00000000 CR4=00000000
DR0=00000000 DR1=00000000 DR2=00000000 DR3=00000000
DR6=ffff0ff0 DR7=00000400
CCS=00000000 CCD=00000000 CCO=SUBL
EFER=0000000000000000
qemu fatal: trying to execute code outside RAM or ROM at 0x83535657
finaly a objdump -d kernel.binlet me check if my
void irq_default_handler(isr_stack_frame_t sf);
Function C is at the address I expect:
00100e81 <irq_default_handler>
eax eip , mov C.
, :
typedef struct {
uint32_t gs, ds, es, ds;
uint32_t edi, esi, ebp, ebx, edx, ecx, eax;
uint32_t int_number, err_code;
uint32_t eip, cs, eflags, useresp, ss;
} isr_stack_frame_t;
, . , eip . C. .