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一个朋友写的操作系统源码

00318      o16  mov ax, KERNEL_VDATA_SELECTOR                                       ;\
00319           mov ds, ax              /* we don't touch ss, becasue it was      */;\
00320           mov es, ax              /* already setup by kernel TSS if the     */;\
00321           mov fs, ax              /* previous mode is user. If the previous */;\
00322           mov gs, ax              /* mode is kernel, reload is trivial.     */;\
00323           mov eax,esp             /* use eax as a base pointer.             */;\
00324           push esp                /* esp points to common stack frame       */;\
00325           push 60(eax)            /* get cs pushed.                         */;\
00326           inb INT_CTLMASK                                                     ;\
00327           orb al, [1<<irq]                                                    ;\
00328           outb INT_CTLMASK        /* disable the irq                        */;\
00329           movb al, ENABLE                                                     ;\
00330           outb INT_CTL            /* reenable master 8259                   */;\
00331           sti                     /* enable interrupts                      */;\
00332           test (esp), RING0                                                   ;\
00333           je 1f                   /* if ring0                               */;\
00334           call [handler]          /* call interrupt handler                 */;\
00335           add esp, 4*2            /* pop used C arguments                   */;\
00336        2: cli                     /* disable interrupts                     */;\
00337           cmpb (_runrun), 0                                                   ;\
00338           je 2f                                                               ;\
00339           sti                     /* unlock                                 */;\
00340           call _swtch                                                         ;\
00341           jmp 2b                                                              ;\
00342        2: pop gs                  /* return to user mode                    */;\
00343           pop fs                                                              ;\
00344           pop es                                                              ;\
00345           pop ds                                                              ;\
00346           popad                                                               ;\
00347           add esp, 4*2            /* pop padding space                      */;\
00348           inb INT_CTLMASK                                                     ;\
00349           andb al, ~[1<<irq]                                                  ;\
00350           outb INT_CTLMASK        /* enable irq                             */;\
00351           iretd                                                               ;\
00352        1: call [handler]          /* call interrupt handler                 */;\
00353           add esp, 4*2            /* pop used C arguemts                    */;\
00354           cli                     /* disable interrupts                     */;\
00355           pop gs                  /* return to kernel mode                  */;\
00356           pop fs                                                              ;\
00357           pop es                                                              ;\
00358           pop ds                                                              ;\
00359           popad                                                               ;\
00360           add esp, 4*2            /* pop padding space                      */;\
00361           inb INT_CTLMASK                                                     ;\
00362           andb al, ~[1<<irq]                                                  ;\
00363           outb INT_CTLMASK        /* enable irq                             */;\
00364           iretd                                                               ;\
00365   
00366   ! Each of tese entry points is an expansion of the hwint_master macro
00367           .align 16
00368   _hwint00:            ! Interrupt routine for clock interrupt.
00369           hwint_master(0, _clock_handler)
00370   
00371           .align 16
00372   _hwint01:            ! Interrupt routine for keyboard interrup.
00373           hwint_master(1, _kbd_hw_int)
00374           
00375           .align 16
00376   _hwint02:
00377           hwint_master(2, _nohandler)
00378   
00379           .align 16
00380   _hwint03:
00381           hwint_master(3, _nohandler)
00382   
00383           .align 16
00384   _hwint04:
00385           hwint_master(4, _nohandler)
00386   
00387           .align 16
00388   _hwint05:
00389           hwint_master(5, _nohandler)
00390   
00391           .align 16
00392   _hwint06:
00393           hwint_master(6, _nohandler)
00394   
00395           .align 16
00396   _hwint07:
00397           hwint_master(7, _nohandler)
00398   
00399   !*===========================================================================*
00400   !*                          hwint08 - 15                                     *
00401   !*===========================================================================*
00402   ! Note this is a macro, it looks like a subroutine.
00403   #define hwint_slave(irq, handler)        \
00404           cld                     /* set direction flag to a know value     */;\
00405           push 0                  /* padding for error code                 */;\
00406           push irq                /* interrupt irq                          */;\
00407           pushad                  /* save general registers                 */;\
00408           push ds                 /* save ds                                */;\
00409           push es                 /* save es                                */;\
00410           push fs                 /* save fs                                */;\
00411           push gs                 /* save gs                                */;\
00412      o16  mov ax, KERNEL_VDATA_SELECTOR                                       ;\
00413           mov ds, ax              /* we don't touch ss, becasue it was      */;\
00414           mov es, ax              /* already setup by kernel TSS if the     */;\
00415           mov fs, ax              /* previous mode is user. If the previous */;\
00416           mov gs, ax              /* mode is kernel, reload is trivial.     */;\
00417           mov eax,esp             /* use eax as a base pointer.             */;\
00418           push esp                /* esp points to common stack frame       */;\
00419           push 60(eax)            /* get cs pushed.                         */;\
00420           inb INT2_CTLMASK                                                    ;\
00421           orb al, [1<<[irq-8]]                                                ;\
00422           outb INT2_CTLMASK       /* disable the irq                        */;\
00423           movb al, ENABLE                                                     ;\
00424           outb INT_CTL            /* reenable master 8259                   */;\
00425           jmp .+2                 /* delay                                  */;\
00426           outb INT2_CTL           /* reenable slave 8259                    */;\
00427           sti                     /* enable interrupts                      */;\
00428           test (esp), RING0                                                   ;\
00429           je 1f                   /* if ring0                               */;\
00430           call [handler]          /* call interrupt handler                 */;\
00431           add esp, 4*2            /* pop used C arguments                   */;\
00432        2: cli                     /* disable interrupts                     */;\
00433           cmpb (_runrun), 0                                                   ;\
00434           je 2f                                                               ;\
00435           sti                     /* unlock                                 */;\
00436           call _swtch                                                         ;\
00437           jmp 2b                                                              ;\
00438        2: pop gs                  /* return to user mode                    */;\
00439           pop fs                                                              ;\
00440           pop es                                                              ;\
00441           pop ds                                                              ;\
00442           popad                                                               ;\
00443           add esp, 4*2            /* pop padding space                      */;\
00444           inb INT2_CTLMASK                                                    ;\
00445           andb al, ~[1<<[irq-8]]                                              ;\
00446           outb INT2_CTLMASK       /* enable irq                             */;\
00447           iretd                                                               ;\
00448        1: call [handler]          /* call interrupt handler                 */;\
00449           add esp, 4*2            /* pop used C arguemts                    */;\
00450           cli                     /* disable interrupts                     */;\
00451           pop gs                  /* return to kernel mode                  */;\
00452           pop fs                                                              ;\
00453           pop es                                                              ;\
00454           pop ds                                                              ;\
00455           popad                                                               ;\
00456           add esp, 4*2            /* pop padding space                      */;\
00457           inb INT2_CTLMASK                                                    ;\
00458           andb al, ~[1<<[irq-8]]                                                  ;\
00459           outb INT2_CTLMASK       /* enable irq                             */;\
00460           iretd                                                               ;\
00461   
00462   ! Each of tese entry points is an expansion of the hwint_master macro
00463           .align 16
00464   _hwint08:
00465           hwint_slave(8, _nohandler)
00466   
00467           .align 16
00468   _hwint09:
00469           hwint_slave(9, _nohandler)
00470   
00471           .align 16
00472   _hwint10:
00473           hwint_slave(10, _nohandler)
00474   
00475           .align 16
00476   _hwint11:
00477           hwint_slave(11, _nohandler)
00478   
00479           .align 16
00480   _hwint12:
00481           hwint_slave(12, _nohandler)
00482   
00483           .align 16
00484   _hwint13:
00485           hwint_slave(13, _nohandler)
00486   
00487           .align 16
00488   _hwint14:
00489           hwint_slave(14, _nohandler)
00490   
00491           .align 16
00492   _hwint15:
00493           hwint_slave(15, _nohandler)
00494   
00495   !*===========================================================================*
00496   !*                       exception handlers                                  *
00497   !*===========================================================================*
00498   ! If an exception vector doesn't have an error code to be pushed by processor, 
00499   ! we would like to fill this space with a padding value, so that we can use one
00500   ! routine to handle them all. See src/type.h for the layout of the stackframe
00501   
00502   _divide_error:
00503           push 0                        ! padding for error code 
00504           push DIVIDE_VECTOR
00505           jmp trap
00506   
00507   _single_step_exception:
00508           push 0                        ! padding for error code 
00509           push DEBUG_VECTOR
00510           jmp trap
00511   
00512   _nmi:
00513           push 0                        ! padding for error code 
00514           push NMI_VECTOR
00515           jmp trap
00516   
00517   _breakpoint_exception:
00518           push 0                        ! padding for error code 
00519           push BREAKPOINT_VECTOR
00520           jmp trap
00521   
00522   _overflow:
00523           push 0                        ! padding for error code 
00524           push OVERFLOW_VECTOR
00525           jmp trap
00526   
00527   _bounds_check:
00528           push 0                        ! padding for error code 
00529           push BOUNDS_VECTOR
00530           jmp trap
00531   
00532   _inval_opcode:
00533           push 0                        ! padding for error code 
00534           push INVAL_OP_VECTOR
00535           jmp trap
00536