| 0,0 → 1,62 |
|---|
| iglobal |
| prev_user_of_fpu dd 0x1 ; set to OS |
| endg |
| |
| label fpu_tss at 0xB080 |
| label fpu_stack dword at 0xB060 |
| |
| |
| align 4 |
| fpu_handler: |
| |
| ; clear TS flag in CR0 -> for task switching |
| clts |
| |
| ; save FPU context of the previous task |
| mov eax,[prev_user_of_fpu] |
| shl eax,8 |
| add eax,0x80000+0x10 |
| fsave [eax] |
| |
| ; next task switch save our FPU context |
| ; now restore context of current task (if exists) |
| mov eax,[0x3000] |
| mov [prev_user_of_fpu],eax |
| shl eax,8 |
| add eax,0x80000 |
| cmp [eax+0x7f],byte 0 |
| je bs7_first_fpu |
| frstor [eax+0x10] |
| bs7_first_fpu: |
| mov [eax+0x7f],byte 1 |
| |
| ; prepare structure in stack for proper IRET |
| movzx eax,word [fpu_tss+l.ss-tss_sceleton] ; push ss |
| push eax |
| mov eax,[fpu_tss+l.esp-tss_sceleton] ; push esp |
| push eax |
| mov eax,[fpu_tss+l.eflags-tss_sceleton] ; push eflags |
| push eax |
| |
| movzx eax,word [fpu_tss+l.cs-tss_sceleton] ; push cs |
| push eax |
| mov eax,[fpu_tss+l.eip-tss_sceleton] ; push eip |
| push eax |
| |
| ; save eax |
| push dword [fpu_tss+l.eax-tss_sceleton] |
| |
| ; restore all segment registers |
| mov ax,[fpu_tss+l.es-tss_sceleton] |
| mov es,ax |
| mov ax,[fpu_tss+l.fs-tss_sceleton] |
| mov fs,ax |
| mov ax,[fpu_tss+l.gs-tss_sceleton] |
| mov gs,ax |
| mov ax,[fpu_tss+l.ds-tss_sceleton] |
| mov ds,ax |
| |
| ; restore eax |
| pop eax |
| |
| iret |