PDP计算机 Unix v1 源代码-贝尔实验室

/ u1 -- unix unkni: / used for all system calls sysent: incb sysflg / indicate a system routine is beq 1f / in progress jmp panic / called if trap inside system 1: mov $s.syst+2,clockp mov r0,-(sp) / save user registers mov sp,u.r0 / pointer to bottom of users stack in u.r0 mov r1,-(sp) mov r2,-(sp) mov r3,-(sp) mov r4,-(sp) mov r5,-(sp) mov ac,-(sp) / "accumulator" register for extended / arithmetic unit mov mq,-(sp) / "multiplier quotient" register for the / extended arithmetic unit mov sc,-(sp) / "step count" register for the extended / arithmetic unit mov sp,u.sp / u.sp points to top of users stack mov 18.(sp),r0 / store pc in r0 mov -(r0),r0 / sys inst in r0 10400xxx sub $sys,r0 / get xxx code asl r0 / multiply by 2 to jump indirect in bytes cmp r0,$2f-1f / limit of table (35) exceeded bhis badsys / yes, bad system call bic $341,20.(sp) / set users processor priority to 0 and clear / carry bit jmp *1f(r0) / jump indirect thru table of addresses / to proper system routine. 1: sysrele / 0 sysexit / 1 sysfork / 2 sysread / 3 syswrite / 4 sysopen / 5 sysclose / 6 syswait / 7 syscreat / 8 syslink / 9 sysunlink / 10 sysexec / 11 syschdir / 12 systime / 13 sysmkdir / 14 syschmod / 15 syschown / 16 sysbreak / 17 sysstat / 18 sysseek / 19 systell / 20 sysmount / 21 sysumount / 22 syssetuid / 23 sysgetuid / 24 sysstime / 25 sysquit / 26 sysintr / 27 sysfstat / 28 sysemt / 29 sysmdate / 30 sysstty / 31 sysgtty / 32 sysilgins / 33 2: error: mov u.sp,r1 bis $1,20.(r1) / set c bit in processor status word below / users stack sysret: tstb u.bsys / is a process about to be terminated because bne sysexit / of an error? yes, go to sysexit mov u.sp,sp / no point stack to users stack clr r1 / zero r1 to check last mentioned i-node jsr r0,iget / if last mentioned i-node has been modified / it is written out tstb smod / has the super block been modified beq 1f / no, 1f clrb smod / yes, clear smod bis $1000,sb0 / set write bit in I/O queue for super block / output jsr r0,ppoke / write out modified super block to disk 1: tstb mmod / has the super block for the dismountable file / system beq 1f / been modified? no, 1f clrb mmod / yes, clear mmod movb mntd,sb1 / set the I/O queue bis $1000,sb1 / set write bit in I/O queue for detached sb jsr r0,ppoke / write it out to its device 1: tstb uquant / is the time quantum 0? bne 1f / no, don't swap it out sysrele: jsr r0,tswap / yes, swap it out 1: mov (sp)+,sc / restore user registers mov (sp)+,mq mov (sp)+,ac mov (sp)+,r5 mov (sp)+,r4 mov (sp)+,r3 mov (sp)+,r2 mov (sp)+,r1 mov (sp)+,r0 mov $s.chrgt+2,clockp decb sysflg / turn system flag off jsr r0,isintr / is there an interrupt from the user br intract / yes, output gets flushed, take interrupt / action rti / no return from interrupt badsys: incb u.bsys / turn on the user's bad-system flag mov $3f,u.namep / point u.namep to "core\0\0" jsr r0,namei / get the i-number for the core image file br 1f / error neg r1 / negate the i-number to open the core image file / for writing jsr r0,iopen / open the core image file jsr r0,itrunc / free all associated blocks br 2f 1: mov $17,r1 / put i-node mode (17) in r1 jsr r0,maknod / make an i-node mov u.dirbuf,r1 / put i-nodes number in r1 2: mov $core,u.base / move address core to u.base mov $ecore-core,u.count / put the byte count in u.count mov $u.off,u.fofp / more user offset to u.fofp clr u.off / clear user offset jsr r0,writei / write out the core image to the user mov $user,u.base / pt. u.base to user mov $64.,u.count / u.count = 64 jsr r0,writei / write out all the user parameters neg r1 / make i-number positive jsr r0,iclose / close the core image file br sysexit / 3: <core\0\0> sysexit: / terminate process clr u.intr / clear interrupt control word clr r1 / clear r1 1: / r1 has file descriptor (index to u.fp list) Search the whole list jsr r0,fclose / close all files the process opened br .+2 / ignore error return inc r1 / increment file descriptor cmp r1,$10. / end of u.fp list? blt 1b / no, go back movb u.uno,r1 / yes, move dying process's number to r1 clrb p.stat-1(r1) / free the process asl r1 / use r1 for index into the below tables mov p.pid-2(r1),r3 / move dying process's name to r3 mov p.ppid-2(r1),r4 / move its parents name to r4 clr r2 clr r5 / initialize reg 1: / find children of this dying process, if they are zombies, free them add $2,r2 / search parent process table for dying process's name cmp p.ppid-2(r2),r3 / found it? bne 3f / no asr r2 / yes, it is a parent cmpb p.stat-1(r2),$3 / is the child of this dying process a / zombie bne 2f / no clrb p.stat-1(r2) / yes, free the child process 2: asl r2 3: / search the process name table for the dying process's parent cmp p.pid-2(r2),r4 / found it? bne 3f / no mov r2,r5 / yes, put index to p.pid table (parents / process # x2) in r5 3: cmp r2,$nproc+nproc / has whole table been searched? blt 1b / no, go back mov r5,r1 / yes, r1 now has parents process # x2 beq 2f / no parent has been found. The process just dies asr r1 / set up index to p.stat movb p.stat-1(r1),r2 / move status of parent to r2 beq 2f / if its been freed, 2f cmp r2,$3 / is parent a zombie? beq 2f / yes, 2f movb u.uno,r3 / move dying process's number to r3 movb $3,p.stat-1(r3) / make the process a zombie cmp r2,$2 / is the parent waiting for this child to die bne 2f / yes, notify parent not to wait any more decb p.stat-1(r1) / awaken it by putting it (parent) mov $runq+4,r2 / on the runq jsr r0, putlu 2: / the process dies clrb u.uno / put zero as the process number, so "swap" will jsr r0,swap / overwrite process with another process 0 / and thereby kill it; halt? intract: / interrupt action cmp *(sp),$rti / are you in a clock interrupt? bne 1f / no, 1f cmp (sp)+,(sp)+ / pop clock pointer 1: / now in user area mov r1,-(sp) / save r1 mov u.ttyp,r1 / pointer to tty buffer in control-to r1 cmpb 6(r1),$177 / is the interrupt char equal to "del" beq 1f / yes, 1f clrb 6(r1) / no, clear the byte (must be a quit character) mov (sp)+,r1 / restore r1 clr u.quit / clear quit flag bis $20,2(sp) / set trace for quit (sets t bit of ps-trace trap) rti / return from interrupt 1: / interrupt char = del clrb 6(r1) / clear the interrupt byte in the buffer mov (sp)+,r1 / restore r1 cmp u.intr,$core / should control be transferred to loc core? blo 1f jmp *u.intr / user to do rti yes, transfer to loc core 1: sys 1 / exit syswait: / wait for a process to die movb u.uno,r1 / put parents process number in r1 asl r1 / x2 to get index into p.pid table mov p.pid-2(r1),r1 / get the name of this process clr r2 clr r3 / initialize reg 3 1: add $2,r2 / use r2 for index into p.ppid table / search table / of parent processes for this process name cmp p.ppid-2(r2),r1 / r2 will contain the childs process number bne 3f / branch if no match of parent process name inc r3 / yes, a match, r3 indicates number of children asr r2 / r2/2 to get index to p.stat table cmpb p.stat-1(r2),$3 / is the child process a zombie? bne 2f / no, skip it clrb p.stat-1(r2) / yes, free it asl r2 / r2x2 to get index into p.pid table mov p.pid-2(r2),*u.r0 / put childs process name in (u.r0) br sysret1 / return cause child is dead 2: asl r2 / r2x2 to get index into p.ppid table 3: cmp r2,$nproc+nproc / have all processes been checked? blt 1b / no, continue search tst r3 / one gets here if there are no children or children / that are still active be