; ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ ; kernel.asm ; ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ ; Forrest Yu, 2005 ; ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %include "sconst.inc" ; 导入函数 extern cstart extern kernel_main extern exception_handler extern spurious_irq extern clock_handler extern disp_str extern delay extern irq_table extern page_fault_handler extern divide_error_handler ;added by xw, 18/12/22 extern disp_int extern schedule extern switch_pde ; 导入全局变量 extern gdt_ptr extern idt_ptr extern p_proc_current extern tss extern disp_pos extern k_reenter extern sys_call_table extern cr3_ready ;add by visual 2016.4.5 extern p_proc_current extern p_proc_next ;added by xw, 18/4/26 extern kernel_initial ;added by xw, 18/6/10 bits 32 [SECTION .bss] StackSpace resb 2 * 1024 StackTop: ; used only as irq-stack in minios. added by xw ; added by xw, 18/6/15 KernelStackSpace resb 2 * 1024 KernelStackTop: ; used as stack of kernel itself ; ~xw [section .text] ; 代码在此 global _start ; 导出 _start ;global restart global restart_initial ;Added by xw, 18/4/21 global restart_restore ;Added by xw, 18/4/21 global sched ;Added by xw, 18/4/21 global sys_call global read_cr2 ;//add by visual 2016.5.9 global refresh_page_cache ; // add by visual 2016.5.12 global halt ;added by xw, 18/6/11 global get_arg ;added by xw, 18/6/18 global divide_error global single_step_exception global nmi global breakpoint_exception global overflow global bounds_check global inval_opcode global copr_not_available global double_fault global copr_seg_overrun global inval_tss global segment_not_present global stack_exception global general_protection global page_fault global copr_error global hwint00 global hwint01 global hwint02 global hwint03 global hwint04 global hwint05 global hwint06 global hwint07 global hwint08 global hwint09 global hwint10 global hwint11 global hwint12 global hwint13 global hwint14 global hwint15 _start: ; 此时内存看上去是这样的（更详细的内存情况在 LOADER.ASM 中有说明）： ; ┃ ┃ ; ┃ ... ┃ ; ┣━━━━━━━━━━━━━━━━━━┫ ; ┃■■■■■■Page Tables■■■■■■┃ ; ┃■■■■■(大小由LOADER决定)■■■■┃ PageTblBase ; 00101000h ┣━━━━━━━━━━━━━━━━━━┫ ; ┃■■■■Page Directory Table■■■■┃ PageDirBase = 1M ; 00100000h ┣━━━━━━━━━━━━━━━━━━┫ ; ┃□□□□ Hardware Reserved □□□□┃ B8000h ← gs ; 9FC00h ┣━━━━━━━━━━━━━━━━━━┫ ; ┃■■■■■■■LOADER.BIN■■■■■■┃ somewhere in LOADER ← esp ; 90000h ┣━━━━━━━━━━━━━━━━━━┫ ; ┃■■■■■■■KERNEL.BIN■■■■■■┃ ; 80000h ┣━━━━━━━━━━━━━━━━━━┫ ; ┃■■■■■■■■KERNEL■■■■■■■┃ 30400h ← KERNEL 入口 (KernelEntryPointPhyAddr) ; 30000h ┣━━━━━━━━━━━━━━━━━━┫ ; ┋ ... ┋ ; ┋ ┋ ; 0h ┗━━━━━━━━━━━━━━━━━━┛ ← cs, ds, es, fs, ss ; ; ; GDT 以及相应的描述符是这样的： ; ; Descriptors Selectors ; ┏━━━━━━━━━━━━━━━━━━┓ ; ┃ Dummy Descriptor ┃ ; ┣━━━━━━━━━━━━━━━━━━┫ ; ┃ DESC_FLAT_C (0～4G) ┃ 8h = cs ; ┣━━━━━━━━━━━━━━━━━━┫ ; ┃ DESC_FLAT_RW (0～4G) ┃ 10h = ds, es, fs, ss ; ┣━━━━━━━━━━━━━━━━━━┫ ; ┃ DESC_VIDEO ┃ 1Bh = gs ; ┗━━━━━━━━━━━━━━━━━━┛ ; ; 注意! 在使用 C 代码的时候一定要保证 ds, es, ss 这几个段寄存器的值是一样的 ; 因为编译器有可能编译出使用它们的代码, 而编译器默认它们是一样的. 比如串拷贝操作会用到 ds 和 es. ; ; ; 把 esp 从 LOADER 挪到 KERNEL ; modified by xw, 18/6/15 ;mov esp, StackTop ; 堆栈在 bss 段中 mov esp, KernelStackTop ; 堆栈在 bss 段中 mov dword [disp_pos], 0 sgdt [gdt_ptr] ; cstart() 中将会用到 gdt_ptr call cstart ; 在此函数中改变了gdt_ptr，让它指向新的GDT lgdt [gdt_ptr] ; 使用新的GDT lidt [idt_ptr] jmp SELECTOR_KERNEL_CS:csinit csinit: ; “这个跳转指令强制使用刚刚初始化的结构”——<> P90. xor eax, eax mov ax, SELECTOR_TSS ltr ax jmp kernel_main ; 中断和异常 -- 硬件中断 ; --------------------------------- %macro hwint_master 1 ;call save call save_int ;save registers and some other things. modified by xw, 17/12/11 inc dword [k_reenter] ;If k_reenter isn't equal to 0, there is no switching to the irq-stack, ;which is performed in save_int. Added by xw, 18/4/21 in al, INT_M_CTLMASK ; `. or al, (1 << %1) ; | 屏蔽当前中断 out INT_M_CTLMASK, al ; / mov al, EOI ; `. 置EOI位 out INT_M_CTL, al ; / sti ; CPU在响应中断的过程中会自动关中断，这句之后就允许响应新的中断 push %1 ; `. call [irq_table + 4 * %1] ; | 中断处理程序 pop ecx ; / ; ┛ cli dec dword [k_reenter] in al, INT_M_CTLMASK ; `. and al, ~(1 << %1) ; | 恢复接受当前中断 out INT_M_CTLMASK, al ; / ret %endmacro ALIGN 16 hwint00: ; Interrupt routine for irq 0 (the clock). hwint_master 0 ALIGN 16 hwint01: ; Interrupt routine for irq 1 (keyboard) hwint_master 1 ALIGN 16 hwint02: ; Interrupt routine for irq 2 (cascade!) hwint_master 2 ALIGN 16 hwint03: ; Interrupt routine for irq 3 (second serial) hwint_master 3 ALIGN 16 hwint04: ; Interrupt routine for irq 4 (first serial) hwint_master 4 ALIGN 16 hwint05: ; Interrupt routine for irq 5 (XT winchester) hwint_master 5 ALIGN 16 hwint06: ; Interrupt routine for irq 6 (floppy) hwint_master 6 ALIGN 16 hwint07: ; Interrupt routine for irq 7 (printer) hwint_master 7 ; --------------------------------- %macro hwint_slave 1 ;added by xw, 18/5/29 call save_int ;save registers and some other things. inc dword [k_reenter] ;If k_reenter isn't equal to 0, there is no switching to the irq-stack, ;which is performed in save_int. Added by xw, 18/4/21 in al, INT_S_CTLMASK ; `. or al, (1 << (%1 - 8)) ; | 屏蔽当前中断 out INT_S_CTLMASK, al ; / mov al, EOI ; `. out INT_M_CTL, al ; / 置EOI位(master) nop ; `.一定注意：slave和master都要置EOI out INT_S_CTL, al ; / 置EOI位(slave) sti ; CPU在响应中断的过程中会自动关中断，这句之后就允许响应新的中断 push %1 ; `. call [irq_table + 4 * %1] ; | 中断处理程序 pop ecx ; / cli dec dword [k_reenter] in al, INT_S_CTLMASK ; `. and al, ~(1 << (%1 - 8)) ; | 恢复接受当前中断 out INT_S_CTLMASK, al ; / ret ;~xw %endmacro ; --------------------------------- ALIGN 16 hwint08: ; Interrupt routine for irq 8 (realtime clock). hwint_slave 8 ALIGN 16 hwint09: ; Interrupt routine for irq 9 (irq 2 redirected) hwint_slave 9 ALIGN 16 hwint10: ; Interrupt routine for irq 10 hwint_slave 10 ALIGN 16 hwint11: ; Interrupt routine for irq 11 hwint_slave 11 ALIGN 16 hwint12: ; Interrupt routine for irq 12 hwint_slave 12 ALIGN 16 hwint13: ; Interrupt routine for irq 13 (FPU exception) hwint_slave 13 ALIGN 16 hwint14: ; Interrupt routine for irq 14 (AT winchester) hwint_slave 14 ALIGN 16 hwint15: ; Interrupt routine for irq 15 hwint_slave 15 ; ==================================================================================== ; exception ; ==================================================================================== ;restructured exception-handling procedure ;added by xw, 18/12/18 %macro exception_no_errcode 2 push 0xFFFFFFFF ;no err code call save_exception ;save registers and some other things. mov esi, esp ;esp points to pushed address of restart_exception at present add esi, 4 * 17 ;we use esi to help to fetch arguments of exception handler from the stack. ;17 is calculated by: 4+8+retaddr+errcode+eip+cs+eflag=17 mov eax, [esi] ;saved eflags push eax mov eax, [esi - 4] ;saved cs push eax mov eax, [esi - 4 * 2] ;saved eip push eax mov eax, [esi - 4 * 3] ;saved err code push eax push %1 ;vector_no sti call %2 cli add esp, 4 * 5 ;clear arguments of exception handler in stack ret ;returned to 'restart_exception' procedure %endmacro %macro exception_errcode 2 call save_exception ;save registers and some other things. mov esi, esp ;esp points to pushed address of restart_exception at present add esi, 4 * 17 ;we use esi to help to fetch arguments of exception handler from the stack. ;17 is calculated by: 4+8+retaddr+errcode+eip+cs+eflag=17 mov eax, [esi] ;saved eflags push eax mov eax, [esi - 4] ;saved cs push eax mov eax, [esi - 4 * 2] ;saved eip push eax mov eax, [esi - 4 * 3] ;saved err code push eax push %1 ;vector_no sti call %2 cli add esp, 4 * 5 ;clear arguments of exception handler in stack ret ;returned to 'restart_exception' procedure %endmacro divide_error: ; vector_no = 0 ; exception_no_errcode 0, exception_handler exception_no_errcode 0, divide_error_handler ;added by xw, 18/12/22 single_step_exception: ; vector_no = 1 exception_no_errcode 1, exception_handler nmi: ; vector_no = 2 exception_no_errcode 2, exception_handler breakpoint_exception: ; vector_no = 3 exception_no_errcode 3, exception_handler overflow: ; vector_no = 4 exception_no_errcode 4, exception_handler bounds_check: ; vector_no = 5 exception_no_errcode 5, exception_handler inval_opcode: ; vector_no = 6 exception_no_errcode 6, exception_handler copr_not_available: ; vector_no = 7 exception_no_errcode 7, exception_handler double_fault: ; vector_no = 8 exception_errcode 8, exception_handler copr_seg_overrun: ; vector_no = 9 exception_no_errcode 9, exception_handler inval_tss: ; vector_no = 10 exception_errcode 10, exception_handler segment_not_present: ; vector_no = 11 exception_errcode 11, exception_handler stack_exception: ; vector_no = 12 exception_errcode 12, exception_handler general_protection: ; vector_no = 13 exception_errcode 13, exception_handler page_fault: ; vector_no = 14 exception_errcode 14, page_fault_handler copr_error: ; vector_no = 16 exception_no_errcode 16, exception_handler ;environment saving when an exception occurs ;added by xw, 18/12/18 save_exception: pushad ; `. push ds ; | push es ; | 保存原寄存器值 push fs ; | push gs ; / mov dx, ss mov ds, dx mov es, dx mov fs, dx ;value of fs and gs in user process is different to that in kernel mov dx, SELECTOR_VIDEO - 2 ;added by xw, 18/6/20 mov gs, dx mov esi, esp push restart_exception jmp [esi + RETADR - P_STACKBASE] ;the err code is in higher address than retaddr in stack, so there is ;no need to modify the position jumped to, that is, ;"jmp [esi + RETADR - 4 - P_STACKBASE]" is actually wrong. ;added by xw, 18/12/18 restart_exception: call sched pop gs pop fs pop es pop ds popad add esp, 4 * 2 ;clear retaddr and error code in stack iretd ; ==================================================================================== ; save ; ==================================================================================== save_int: pushad ; `. push ds ; | push es ; | 保存原寄存器值 push fs ; | push gs ; / cmp dword [k_reenter], 0 ;Added by xw, 18/4/19 jnz instack mov ebx, [p_proc_current] ;xw mov dword [ebx + ESP_SAVE_INT], esp ;xw save esp position in the kernel-stack of the process ; or dword [ebx + SAVE_TYPE], 1 ;set 1st-bit of save_type, added by xw, 17/12/04 mov dx, ss mov ds, dx mov es, dx mov fs, dx ;value of fs and gs in user process is different to that in kernel mov dx, SELECTOR_VIDEO - 2 ;added by xw, 18/6/20 mov gs, dx mov esi, esp mov esp, StackTop ;switches to the irq-stack from current process's kernel stack push restart_int ;added by xw, 18/4/19 jmp [esi + RETADR - P_STACKBASE] instack: ;already in the irq-stack push restart_restore ;modified by xw, 18/4/19 ; jmp [esp + RETADR - P_STACKBASE] jmp [esp + 4 + RETADR - P_STACKBASE] ;modified by xw, 18/6/4 save_syscall: ;can't modify EAX, for it contains syscall number ;can't modify EBX, for it contains the syscall argument pushad ; `. push ds ; | push es ; | 保存原寄存器值 push fs ; | push gs ; / mov edx, [p_proc_current] ;xw mov dword [edx + ESP_SAVE_SYSCALL], esp ;xw save esp position in the kernel-stack of the process mov dx, ss mov ds, dx mov es, dx mov fs, dx ;value of fs and gs in user process is different to that in kernel mov dx, SELECTOR_VIDEO - 2 ;added by xw, 18/6/20 mov gs, dx mov esi, esp push restart_syscall ;modified by xw, 17/12/04 jmp [esi + RETADR - P_STACKBASE] ;modified end ; ==================================================================================== ; sched(process switch) ; ==================================================================================== sched: ;could be called by C function, you must save ebp, ebx, edi, esi, ;for C function assumes that they stay unchanged. added by xw, 18/4/19 ;save_context pushfd pushad ;modified by xw, 18/6/4 cli mov ebx, [p_proc_current] mov dword [ebx + ESP_SAVE_CONTEXT], esp ;save esp position in the kernel-stack of the process ;schedule call schedule ;schedule is a C function, save eax, ecx, edx if you want them to stay unchanged. ;prepare to run new process mov ebx, [p_proc_next] ;added by xw, 18/4/26 mov dword [p_proc_current], ebx call renew_env ;renew process executing environment mov ebx, [p_proc_current] mov esp, [ebx + ESP_SAVE_CONTEXT] ;switch to a new kernel stack popad popfd ret ; ==================================================================================== ; renew_env ; ==================================================================================== ;renew process executing environment. Added by xw, 18/4/19 renew_env: call switch_pde ;to change the global variable cr3_ready mov eax,[cr3_ready] ;to switch the page directory table mov cr3,eax mov eax, [p_proc_current] lldt [eax + P_LDT_SEL] ;load LDT lea ebx, [eax + INIT_STACK_SIZE] mov dword [tss + TSS3_S_SP0], ebx ;renew esp0 ret ; ==================================================================================== ; sys_call ; ==================================================================================== sys_call: ;get syscall number from eax ;syscall that's called gets its argument from pushed ebx ;so we can't modify eax and ebx in save_syscall call save_syscall ;save registers and some other things. modified by xw, 17/12/11 sti push ebx ;push the argument the syscall need call [sys_call_table + eax * 4] ;将参数压入堆栈后再调用函数 add by visual 2016.4.6 add esp, 4 ;clear the argument in the stack, modified by xw, 17/12/11 cli mov edx, [p_proc_current] mov esi, [edx + ESP_SAVE_SYSCALL] mov [esi + EAXREG - P_STACKBASE], eax ;the return value of C function is in EAX ret ; ==================================================================================== ; restart ; ==================================================================================== restart_int: mov eax, [p_proc_current] mov esp, [eax + ESP_SAVE_INT] ;switch back to the kernel stack from the irq-stack cmp dword [kernel_initial], 0 ;added by xw, 18/6/10 jnz restart_restore call sched ;save current process's context, invoke schedule(), and then ;switch to the chosen process's kernel stack and restore it's context ;added by xw, 18/4/19 ; call renew_env jmp restart_restore restart_syscall: mov eax, [p_proc_current] mov esp, [eax + ESP_SAVE_SYSCALL] ;xw restore esp position call sched ;added by xw, 18/4/26 jmp restart_restore ;xw restart_reenter: restart_restore: ; dec dword [k_reenter] pop gs pop fs pop es pop ds popad add esp, 4 iretd ;to launch the first process in the os. added by xw, 18/4/19 restart_initial: ; mov eax, [p_proc_current] ; lldt [eax + P_LDT_SEL] ; lea ebx, [eax + INIT_STACK_SIZE] ; mov dword [tss + TSS3_S_SP0], ebx call renew_env ;renew process executing environment mov eax, [p_proc_current] mov esp, [eax + ESP_SAVE_INT] ;restore esp position jmp restart_restore ; ==================================================================================== ; read_cr2 //add by visual 2016.5.9 ; ==================================================================================== read_cr2: mov eax,cr2 ret ; ==================================================================================== ; refresh_page_cache //add by visual 2016.5.12 ; ==================================================================================== refresh_page_cache: mov eax,cr3 mov cr3,eax ret ; ==================================================================================== ; halt //added by xw, 18/6/11 ; ==================================================================================== halt: hlt ; ==================================================================================== ; u32 get_arg(void *uesp, int order) //added by xw, 18/6/18 ; ==================================================================================== ; used to get the specified argument of the syscall from user space stack ; @uesp: user space stack pointer ; @order: which argument you want to get ; @uesp+0: the number of args, @uesp+8: the first arg, @uesp+12: the second arg... get_arg: push ebp mov ebp, esp push esi push edi mov esi, dword [ebp + 8] ;void *uesp mov edi, dword [ebp + 12] ;int order mov eax, dword [esi + edi * 4 + 4] pop edi pop esi pop ebp ret