process.c

<B>Digital的Unix操作系统VAX 4.2源码</B>

extern Intfunc *onsyserr();

private badaddr;
private read_err(), write_err();

/*
 * Read from the process' instruction area.
 */

public iread(buff, addr, nbytes)
char *buff;
Address addr;
int nbytes;
{
    Intfunc *f;

    f = onsyserr(EIO, read_err);
    badaddr = addr;
    if (coredump) {
	coredump_readtext(buff, addr, nbytes);
    } else {
	pio(process, PREAD, TEXTSEG, buff, addr, nbytes);
    }
    onsyserr(EIO, f);
}

/* 
 * Write to the process' instruction area, usually in order to set
 * or unset a breakpoint.
 */

public iwrite(buff, addr, nbytes)
char *buff;
Address addr;
int nbytes;
{
    Intfunc *f;

    if (coredump) {
	error("no process to write to");
    }
    f = onsyserr(EIO, write_err);
    badaddr = addr;
    pio(process, PWRITE, TEXTSEG, buff, addr, nbytes);
    onsyserr(EIO, f);
}

/*
 * Read for the process' data area.
 */

public dread(buff, addr, nbytes)
char *buff;
Address addr;
int nbytes;
{
    Intfunc *f;

    f = onsyserr(EIO, read_err);
    badaddr = addr;
    if (coredump) {
	coredump_readdata(buff, addr, nbytes);
    } else {
	pio(process, PREAD, DATASEG, buff, addr, nbytes);
    }
    onsyserr(EIO, f);
}

/*
 * Write to the process' data area.
 */

public dwrite(buff, addr, nbytes)
char *buff;
Address addr;
int nbytes;
{
    Intfunc *f;

    if (coredump) {
	error("no process to write to");
    }
    f = onsyserr(EIO, write_err);
    badaddr = addr;
    pio(process, PWRITE, DATASEG, buff, addr, nbytes);
    onsyserr(EIO, f);
}

/*
 * Trap for errors in reading or writing to a process.
 * The current approach is to "ignore" read errors and complain
 * bitterly about write errors.
 */

private read_err()
{
    /*
     * Ignore.
     */
}

private write_err()
{
    error("can't write to process (address 0x%x)", badaddr);
}

/*
 * Ptrace interface.
 */

/*
 * This magic macro enables us to look at the process' registers
 * in its user structure.
 */

#define regloc(reg)     (ctob(UPAGES) + ( sizeof(int) * (reg) ))

#define WMASK           (~(sizeof(Word) - 1))
#define cachehash(addr) ((unsigned) ((addr >> 2) % CSIZE))

#define FIRSTSIG        SIGINT
#define LASTSIG         SIGQUIT
#define ischild(pid)    ((pid) == 0)
#define traceme()       ptrace(0, 0, 0, 0)
#define setrep(n)       (1 << ((n)-1))
#define istraced(p)     (p->sigset&setrep(p->signo))

/*
 * Ptrace options (specified in first argument).
 */

#define UREAD   3       /* read from process's user structure */
#define UWRITE  6       /* write to process's user structure */
#define IREAD   1       /* read from process's instruction space */
#define IWRITE  4       /* write to process's instruction space */
#define DREAD   2       /* read from process's data space */
#define DWRITE  5       /* write to process's data space */
#define CONT    7       /* continue stopped process */
#define SSTEP   9       /* continue for approximately one instruction */
#define PKILL   8       /* terminate the process */

/*
 * Start up a new process by forking and exec-ing the
 * given argument list, returning when the process is loaded
 * and ready to execute.  The PROCESS information (pointed to
 * by the first argument) is appropriately filled.
 *
 * If the given PROCESS structure is associated with an already running
 * process, we terminate it.
 */

/* VARARGS2 */
private pstart(p, argv, infile, outfile)
Process p;
String argv[];
String infile;
String outfile;
{
    int status;

    if (p->pid != 0) {
	pterm(p);
    }
    psigtrace(p, SIGTRAP, true);
    p->pid = vfork();
    if (p->pid == -1) {
	panic("can't fork");
    }
    if (ischild(p->pid)) {
	traceme();
	if (infile != nil) {
	    infrom(infile);
	}
	if (outfile != nil) {
	    outto(outfile);
	}
	execv(argv[0], argv);
	write(2, "can't exec ", 11);
	write(2, argv[0], strlen(argv[0]));
	write(2, "\n", 1);
	_exit(1);
    }
    pwait(p->pid, &status);
    getinfo(p, status);
    if (p->status != STOPPED) {
	error("program could not begin execution");
    }
    ptraced(p->pid);
}

/*
 * Terminate a ptrace'd process.
 */

public pterm (p)
Process p;
{
    integer status;

    if (p != nil and p->pid != 0) {
	ptrace(PKILL, p->pid, 0, 0);
	pwait(p->pid, &status);
	unptraced(p->pid);
    }
}

/*
 * Continue a stopped process.  The first argument points to a Process
 * structure.  Before the process is restarted it's user area is modified
 * according to the values in the structure.  When this routine finishes,
 * the structure has the new values from the process's user area.
 *
 * Pcont terminates when the process stops with a signal pending that
 * is being traced (via psigtrace), or when the process terminates.
 */

private pcont(p, signo)
Process p;
int signo;
{
    int s, status;

    if (p->pid == 0) {
	error("program not active");
    }
    s = signo;
    do {
	setinfo(p, s);
	if (traceexec) {
	    printf("!! pcont from 0x%x with signal %d (%d)\n",
		p->reg[PROGCTR], s, p->signo);
	    fflush(stdout);
	}
	sigs_off();
	if (ptrace(CONT, p->pid, p->reg[PROGCTR], p->signo) < 0) {
	    panic("error %d trying to continue process", errno);
	}
	pwait(p->pid, &status);
	sigs_on();
	getinfo(p, status);
	if (traceexec and not istraced(p)) {
	    printf("!! ignored signal %d at 0x%x\n", p->signo, p->reg[PROGCTR]);
	    fflush(stdout);
	}
	s = p->signo;
    } while (p->status == STOPPED and not istraced(p));
    if (traceexec) {
	printf("!! pcont to 0x%x on signal %d\n", p->reg[PROGCTR], p->signo);
	fflush(stdout);
    }
}

/*
 * Single step as best ptrace can.
 */

public pstep(p, signo)
Process p;
integer signo;
{
    int status;

    setinfo(p, signo);
    if (traceexec) {
	printf("!! pstep from pc 0x%x with signal %d (%d)\n",
	    p->reg[PROGCTR], signo, p->signo);
	fflush(stdout);
    }
    sigs_off();
    if (ptrace(SSTEP, p->pid, p->reg[PROGCTR], p->signo) < 0) {
	panic("error %d trying to step process", errno);
    }
    pwait(p->pid, &status);
    sigs_on();
    getinfo(p, status);
    if (traceexec) {
	printf("!! pstep to pc 0x%x on signal %d\n", p->reg[PROGCTR], p->signo);
	fflush(stdout);
    }
    if (p->status != STOPPED) {
	error("program unexpectedly exited with %d\n", p->exitval);
    }
}

/*
 * Return from execution when the given signal is pending.
 */

public psigtrace(p, sig, sw)
Process p;
int sig;
Boolean sw;
{
    if (sw) {
	p->sigset |= setrep(sig);
    } else {
	p->sigset &= ~setrep(sig);
    }
}

/*
 * Don't catch any signals.
 * Particularly useful when letting a process finish uninhibited.
 */

public unsetsigtraces(p)
Process p;
{
    p->sigset = 0;
}

/*
 * Turn off attention to signals not being caught.
 */

private Intfunc *sigfunc[NSIG];

private sigs_off()
{
    register int i;

    for (i = FIRSTSIG; i < LASTSIG; i++) {
	if (i != SIGKILL) {
	    sigfunc[i] = signal(i, SIG_IGN);
	}
    }
}

/*
 * Turn back on attention to signals.
 */

private sigs_on()
{
    register int i;

    for (i = FIRSTSIG; i < LASTSIG; i++) {
	if (i != SIGKILL) {
	    signal(i, sigfunc[i]);
	}
    }
}

/*
 * Get process information from user area.
 */

private int rloc[] ={
    R0, R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, AP, FP, SP, PC
};

private getinfo(p, status)
register Process p;
register int status;
{
    register int i;
    Address addr;

    p->signo = (status&0177);
    p->exitval = ((status >> 8)&0377);
    if (p->signo != STOPPED) {
	p->status = FINISHED;
	p->pid = 0;
	p->reg[PROGCTR] = 0;
    } else {
	p->status = p->signo;
	p->signo = p->exitval;
	p->exitval = 0;
	p->mask = ptrace(UREAD, p->pid, regloc(PS), 0);
	for (i = 0; i < NREG; i++) {
	    p->reg[i] = ptrace(UREAD, p->pid, regloc(rloc[i]), 0);
	    p->oreg[i] = p->reg[i];
	}
	savetty(stdout, &(p->ttyinfo));
	addr = (Address) &(((struct user *) 0)->u_signal[p->signo]);
	p->sigstatus = (Address) ptrace(UREAD, p->pid, addr, 0);
    }
}

/*
 * Set process's user area information from given process structure.
 */

private setinfo(p, signo)
register Process p;
int signo;
{
    register int i;
    register int r;

    if (signo == DEFSIG) {
	if (istraced(p) and (p->sigstatus == 0 or p->sigstatus == 1)) {
	    p->signo = 0;
	}
    } else {
	p->signo = signo;
    }
    for (i = 0; i < NREG; i++) {
	if ((r = p->reg[i]) != p->oreg[i]) {
	    ptrace(UWRITE, p->pid, regloc(rloc[i]), r);
	}
    }
    restoretty(stdout, &(p->ttyinfo));
}

/*
 * Return the address associated with the current signal.
 * (Plus two since the address points to the beginning of a procedure).
 */

public Address usignal (p)
Process p;
{
    Address r;

    r = p->sigstatus;
    if (r != 0 and r != 1) {
	r += 2;
    }
    return r;
}

/*
 * Structure for reading and writing by words, but dealing with bytes.
 */

typedef union {
    Word pword;
    Byte pbyte[sizeof(Word)];
} Pword;

/*
 * Read (write) from (to) the process' address space.
 * We must deal with ptrace's inability to look anywhere other
 * than at a word boundary.
 */

private Word fetch();
private store();

private pio(p, op, seg, buff, addr, nbytes)
Process p;
PioOp op;
PioSeg seg;
char *buff;
Address addr;
int nbytes;
{
    register int i;
    register Address newaddr;
    register char *cp;
    char *bufend;
    Pword w;
    Address wordaddr;
    int byteoff;

    if (p->status != STOPPED) {
	error("program is not active");
    }
    cp = buff;
    newaddr = addr;
    wordaddr = (newaddr&WMASK);
    if (wordaddr != newaddr) {
	w.pword = fetch(p, seg, wordaddr);
	for (i = newaddr - wordaddr; i < sizeof(Word) and nbytes > 0; i++) {
	    if (op == PREAD) {
		*cp++ = w.pbyte[i];
	    } else {
		w.pbyte[i] = *cp++;
	    }
	    nbytes--;
	}
	if (op == PWRITE) {
	    store(p, seg, wordaddr, w.pword);
	}
	newaddr = wordaddr + sizeof(Word);
    }
    byteoff = (nbytes&(~WMASK));
    nbytes -= byteoff;
    bufend = cp + nbytes;
    while (cp < bufend) {
	if (op == PREAD) {
	    *((Word *) cp) = fetch(p, seg, newaddr);
	} else {
	    store(p, seg, newaddr, *((Word *) cp));
	}
	cp += sizeof(Word);
	newaddr += sizeof(Word);
    }
    if (byteoff > 0) {
	w.pword = fetch(p, seg, newaddr);
	for (i = 0; i < byteoff; i++) {
	    if (op == PREAD) {
		*cp++ = w.pbyte[i];
	    } else {
		w.pbyte[i] = *cp++;
	    }
	}
	if (op == PWRITE) {
	    store(p, seg, newaddr, w.pword);
	}
    }
}

/*
 * Get a word from a process at the given address.
 * The address is assumed to be on a word boundary.
 *
 * A simple cache scheme is used to avoid redundant ptrace calls
 * to the instruction space since it is assumed to be pure.
 *
 * It is necessary to use a write-through scheme so that
 * breakpoints right next to each other don't interfere.
 */

private Integer nfetchs, nreads, nwrites;

private Word fetch(p, seg, addr)
Process p;
PioSeg seg;
register int addr;
{
    register CacheWord *wp;
    register Word w;

    switch (seg) {
	case TEXTSEG:
	    ++nfetchs;
	    wp = &p->word[cachehash(addr)];
	    if (addr == 0 or wp->addr != addr) {
		++nreads;
		w = ptrace(IREAD, p->pid, addr, 0);
		wp->addr = addr;
		wp->val = w;
	    } else {
		w = wp->val;
	    }
	    break;

	case DATASEG:
	    w = ptrace(DREAD, p->pid, addr, 0);
	    break;

	default:
	    panic("fetch: bad seg %d", seg);
	    /* NOTREACHED */
    }
    return w;
}

/*
 * Put a word into the process' address space at the given address.
 * The address is assumed to be on a word boundary.
 */

private store(p, seg, addr, data)
Process p;
PioSeg seg;
int addr;
Word data;
{
    register CacheWord *wp;

    switch (seg) {
	case TEXTSEG:
	    ++nwrites;
	    wp = &p->word[cachehash(addr)];
	    wp->addr = addr;
	    wp->val = data;
	    ptrace(IWRITE, p->pid, addr, data);
	    break;

	case DATASEG:
	    ptrace(DWRITE, p->pid, addr, data);
	    break;

	default:
	    panic("store: bad seg %d", seg);
	    /* NOTREACHED */
    }
}

public printptraceinfo()
{
    printf("%d fetchs, %d reads, %d writes\n", nfetchs, nreads, nwrites);
}

/*
 * Redirect input.
 * Assuming this is called from a child, we should be careful to avoid
 * (possibly) shared standard I/O buffers.
 */

private infrom (filename)
String filename;
{
    Fileid in;

    in = open(filename, 0);
    if (in == -1) {
	write(2, "can't read ", 11);
	write(2, filename, strlen(filename));
	write(2, "\n", 1);
	_exit(1);
    }
    fswap(0, in);
}

/*
 * Redirect standard output.
 * Same assumptions as for "infrom" above.
 */

private outto (filename)
String filename;
{
    Fileid out;

    out = creat(filename, 0666);
    if (out == -1) {
	write(2, "can't write ", 12);
	write(2, filename, strlen(filename));
	write(2, "\n", 1);
	_exit(1);
    }
    fswap(1, out);
}

/*
 * Swap file numbers, useful for redirecting standard input or output.
 */

private fswap(oldfd, newfd)
Fileid oldfd;
Fileid newfd;
{
    if (oldfd != newfd) {
	close(oldfd);
	dup(newfd);
	close(newfd);
    }
}