msh: instead of fixing "ls | cd", "cd | ls" etc just disallow

  builtins in pipes. They make no sense there anyway.
msh: shrink umask builtin.

function                                             old     new   delta
execute                                             2508    2509      +1
doset                                                326     317      -9
forkexec                                            1370    1345     -25
doumask                                              165     101     -64
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/3 up/down: 1/-98)             Total: -97 bytes

1 files changed, 85 insertions, 95 deletions

diff --git a/shell/msh.c b/shell/msh.c
index 99b03947e..ee54ef2d4 100644
--- a/shell/msh.c
+++ b/shell/msh.c
@@ -86,7 +86,7 @@ static char *itoa(int n)
 # include "busybox.h" /* for applet_names */
 #endif
 
-/*#define MSHDEBUG 1*/
+//#define MSHDEBUG 4
 
 #ifdef MSHDEBUG
 int mshdbg = MSHDEBUG;
@@ -244,11 +244,6 @@ static const char *const T_CMD_NAMES[] = {
 };
 #endif
 
-/*
- * actions determining the environment of a process
- */
-#define FEXEC    1      /* execute without forking */
-
 #define AREASIZE (90000)
 
 /*
@@ -402,8 +397,6 @@ struct var {
 
 static int yyparse(void);
 
-static int execute(struct op *t, int *pin, int *pout, int act);
-
 
 /* -------- io.h -------- */
 /* io buffer */
@@ -495,7 +488,8 @@ static char **getwords(struct wdblock *wb);
 
 /* -------- misc stuff -------- */
 
-static int forkexec(struct op *t, int *pin, int *pout, int act, char **wp);
+static int forkexec(struct op *t, int *pin, int *pout, int no_fork, char **wp);
+static int execute(struct op *t, int *pin, int *pout, int no_fork);
 static int iosetup(struct ioword *iop, int pipein, int pipeout);
 static void brkset(struct brkcon *bc);
 static int dolabel(struct op *t);
@@ -564,10 +558,13 @@ static const char *const signame[] = {
 };
 
 
+typedef int (*builtin_func_ptr)(struct op *);
+
 struct builtincmd {
         const char *name;
-        int (*builtinfunc)(struct op *t);
+        builtin_func_ptr builtinfunc;
 };
+
 static const struct builtincmd builtincmds[] = {
         { "."       , dodot      },
         { ":"       , dolabel    },
@@ -1373,7 +1370,7 @@ static void onecommand(void)
         if (!FLAG['n']) {
                 DBGPRINTF(("ONECOMMAND: calling execute, t=outtree=%p\n",
                                    outtree));
-                execute(outtree, NOPIPE, NOPIPE, 0);
+                execute(outtree, NOPIPE, NOPIPE, /* no_fork: */ 0);
         }
 
         if (!interactive && intr) {
@@ -2450,7 +2447,7 @@ static struct op *findcase(struct op *t, const char *w)
  * execute tree
  */
 
-static int execute(struct op *t, int *pin, int *pout, int act)
+static int execute(struct op *t, int *pin, int *pout, int no_fork)
 {
         struct op *t1;
         volatile int i, rv, a;
@@ -2495,17 +2492,17 @@ static int execute(struct op *t, int *pin, int *pout, int act)
                 outtree = outtree_save;
 
                 if (t->left)
-                        rv = execute(t->left, pin, pout, 0);
+                        rv = execute(t->left, pin, pout, /* no_fork: */ 0);
                 if (t->right)
-                        rv = execute(t->right, pin, pout, 0);
+                        rv = execute(t->right, pin, pout, /* no_fork: */ 0);
                 break;
 
         case TPAREN:
-                rv = execute(t->left, pin, pout, 0);
+                rv = execute(t->left, pin, pout, /* no_fork: */ 0);
                 break;
 
         case TCOM:
-                rv = forkexec(t, pin, pout, act, wp);
+                rv = forkexec(t, pin, pout, no_fork, wp);
                 break;
 
         case TPIPE:
@@ -2517,14 +2514,14 @@ static int execute(struct op *t, int *pin, int *pout, int act)
                                 break;
                         pv[0] = remap(pv[0]);
                         pv[1] = remap(pv[1]);
-                        (void) execute(t->left, pin, pv, 0);
-                        rv = execute(t->right, pv, pout, 0);
+                        (void) execute(t->left, pin, pv, /* no_fork: */ 0);
+                        rv = execute(t->right, pv, pout, /* no_fork: */ 0);
                 }
                 break;
 
         case TLIST:
-                (void) execute(t->left, pin, pout, 0);
-                rv = execute(t->right, pin, pout, 0);
+                (void) execute(t->left, pin, pout, /* no_fork: */ 0);
+                rv = execute(t->right, pin, pout, /* no_fork: */ 0);
                 break;
 
         case TASYNC:
@@ -2544,7 +2541,7 @@ static int execute(struct op *t, int *pin, int *pout, int act)
                                         close(0);
                                         xopen(bb_dev_null, O_RDONLY);
                                 }
-                                _exit(execute(t->left, pin, pout, FEXEC));
+                                _exit(execute(t->left, pin, pout, /* no_fork: */ 1));
                         }
                         interactive = hinteractive;
                         if (i != -1) {
@@ -2562,10 +2559,10 @@ static int execute(struct op *t, int *pin, int *pout, int act)
 
         case TOR:
         case TAND:
-                rv = execute(t->left, pin, pout, 0);
+                rv = execute(t->left, pin, pout, /* no_fork: */ 0);
                 t1 = t->right;
                 if (t1 != NULL && (rv == 0) == (t->type == TAND))
-                        rv = execute(t1, pin, pout, 0);
+                        rv = execute(t1, pin, pout, /* no_fork: */ 0);
                 break;
 
         case TFOR:
@@ -2585,7 +2582,7 @@ static int execute(struct op *t, int *pin, int *pout, int act)
                 brkset(&bc);
                 for (t1 = t->left; i-- && *wp != NULL;) {
                         setval(vp, *wp++);
-                        rv = execute(t1, pin, pout, 0);
+                        rv = execute(t1, pin, pout, /* no_fork: */ 0);
                 }
                 brklist = brklist->nextlev;
                 break;
@@ -2597,17 +2594,17 @@ static int execute(struct op *t, int *pin, int *pout, int act)
                                 goto broken;
                 brkset(&bc);
                 t1 = t->left;
-                while ((execute(t1, pin, pout, 0) == 0) == (t->type == TWHILE))
-                        rv = execute(t->right, pin, pout, 0);
+                while ((execute(t1, pin, pout, /* no_fork: */ 0) == 0) == (t->type == TWHILE))
+                        rv = execute(t->right, pin, pout, /* no_fork: */ 0);
                 brklist = brklist->nextlev;
                 break;
 
         case TIF:
         case TELIF:
                 if (t->right != NULL) {
-                        rv = !execute(t->left, pin, pout, 0) ?
-                                execute(t->right->left, pin, pout, 0) :
-                                execute(t->right->right, pin, pout, 0);
+                        rv = !execute(t->left, pin, pout, /* no_fork: */ 0) ?
+                                execute(t->right->left, pin, pout, /* no_fork: */ 0) :
+                                execute(t->right->right, pin, pout, /* no_fork: */ 0);
                 }
                 break;
 
@@ -2623,7 +2620,7 @@ static int execute(struct op *t, int *pin, int *pout, int act)
                 t1 = findcase(t->left, cp);
                 if (t1 != NULL) {
                         DBGPRINTF7(("EXECUTE: TCASE, calling execute(t=%p, t1=%p)...\n", t, t1));
-                        rv = execute(t1, pin, pout, 0);
+                        rv = execute(t1, pin, pout, /* no_fork: */ 0);
                         DBGPRINTF7(("EXECUTE: TCASE, back from execute(t=%p, t1=%p)...\n", t, t1));
                 }
                 break;
@@ -2641,7 +2638,7 @@ static int execute(struct op *t, int *pin, int *pout, int act)
                 if (rv >= 0) {
                         t1 = t->left;
                         if (t1) {
-                                rv = execute(t1, pin, pout, 0);
+                                rv = execute(t1, pin, pout, /* no_fork: */ 0);
                         }
                 }
                 break;
@@ -2669,8 +2666,6 @@ static int execute(struct op *t, int *pin, int *pout, int act)
         return rv;
 }
 
-typedef int (*builtin_func_ptr)(struct op *);
-
 static builtin_func_ptr inbuilt(const char *s)
 {
         const struct builtincmd *bp;
@@ -2681,17 +2676,17 @@ static builtin_func_ptr inbuilt(const char *s)
         return NULL;
 }
 
-static int forkexec(struct op *t, int *pin, int *pout, int act, char **wp)
+static int forkexec(struct op *t, int *pin, int *pout, int no_fork, char **wp)
 {
         pid_t newpid;
         int i;
         builtin_func_ptr bltin = NULL;
-        int f;
-        const char *cp = NULL;
+        const char *bltin_name = NULL;
+        const char *cp;
         struct ioword **iopp;
         int resetsig;
         char **owp;
-        int forked = 0;
+        int forked;
 
         int *hpin = pin;
         int *hpout = pout;
@@ -2712,11 +2707,10 @@ static int forkexec(struct op *t, int *pin, int *pout, int act, char **wp)
         (void) &owp;
 #endif
 
-        DBGPRINTF(("FORKEXEC: t=%p, pin %p, pout %p, act %d\n", t, pin,
-                           pout, act));
+        DBGPRINTF(("FORKEXEC: t=%p, pin %p, pout %p, no_fork %d\n", t, pin,
+                        pout, no_fork));
         DBGPRINTF7(("FORKEXEC: t->words is %s\n",
-                                ((t->words == NULL) ? "NULL" : t->words[0])));
-
+                        ((t->words == NULL) ? "NULL" : t->words[0])));
         owp = wp;
         resetsig = 0;
         if (t->type == TCOM) {
@@ -2725,32 +2719,36 @@ static int forkexec(struct op *t, int *pin, int *pout, int act, char **wp)
                 cp = *wp;
 
                 /* strip all initial assignments */
-                /* not correct wrt PATH=yyy command  etc */
+                /* FIXME: not correct wrt PATH=yyy command etc */
                 if (FLAG['x']) {
                         DBGPRINTF9(("FORKEXEC: echo'ing, cp=%p, wp=%p, owp=%p\n",
                                                 cp, wp, owp));
                         echo(cp ? wp : owp);
                 }
 
-                if (cp == NULL && t->ioact == NULL) {
-                        while ((cp = *owp++) != NULL && assign(cp, COPYV))
-                                continue;
-                        DBGPRINTF(("FORKEXEC: returning setstatus()\n"));
-                        return setstatus(0);
-                }
-                if (cp != NULL) {
+                if (cp == NULL) {
+                        if (t->ioact == NULL) {
+                                while ((cp = *owp++) != NULL && assign(cp, COPYV))
+                                        continue;
+                                DBGPRINTF(("FORKEXEC: returning setstatus(0)\n"));
+                                return setstatus(0);
+                        }
+                } else { /* cp != NULL */
+                        bltin_name = cp;
                         bltin = inbuilt(cp);
                 }
         }
 
+        forked = 0;
         t->words = wp;
-        f = act;
-
-        DBGPRINTF(("FORKEXEC: bltin %p, f&FEXEC 0x%x, owp %p\n", bltin,
-                           f & FEXEC, owp));
-
-        if (!bltin && (f & FEXEC) == 0) {
-                /* Save values in case the child process alters them */
+        DBGPRINTF(("FORKEXEC: bltin %p, no_fork %d, owp %p\n", bltin,
+                        no_fork, owp));
+        /* Don't fork if it is a lone builtin (not in pipe)
+         * OR we are told to _not_ fork */
+        if ((!bltin || pin || pout)   /* not lone bltin AND */
+         && !no_fork                  /* not told to avoid fork */
+        ) {
+                /* Save values in case child alters them after vfork */
                 hpin = pin;
                 hpout = pout;
                 hwp = *wp;
@@ -2760,9 +2758,7 @@ static int forkexec(struct op *t, int *pin, int *pout, int act, char **wp)
                 hexecflg = execflg;
 
                 DBGPRINTF3(("FORKEXEC: calling vfork()...\n"));
-
                 newpid = vfork();
-
                 if (newpid == -1) {
                         DBGPRINTF(("FORKEXEC: ERROR, cannot vfork()!\n"));
                         return -1;
@@ -2783,8 +2779,7 @@ static int forkexec(struct op *t, int *pin, int *pout, int act, char **wp)
                 }
 
                 /* Child */
-                DBGPRINTF(("FORKEXEC: child process, bltin=%p\n", bltin));
-
+                DBGPRINTF(("FORKEXEC: child process, bltin=%p (%s)\n", bltin, bltin_name));
                 if (interactive) {
                         signal(SIGINT, SIG_IGN);
                         signal(SIGQUIT, SIG_IGN);
@@ -2802,20 +2797,6 @@ static int forkexec(struct op *t, int *pin, int *pout, int act, char **wp)
                         if (!bltin)
                                 export(lookup(cp));
 
-#if 1
-        /* How to fix it:
-         * explicitly pass pin[0] and pout[1] to builtins
-         * instead of making them rely on fd 0/1,
-         * and do not xmove_fd(pin[0]/pout[1]) below if bltin != NULL.
-         */
-        if ((pin || pout) && bltin && bltin != doexec) {
-                err("piping to/from shell builtins not yet done");
-                if (forked)
-                        _exit(-1);
-                return -1;
-        }
-#endif
-
         if (pin) {
                 xmove_fd(pin[0], 0);
                 if (pin[1] != 0)
@@ -2830,33 +2811,36 @@ static int forkexec(struct op *t, int *pin, int *pout, int act, char **wp)
         iopp = t->ioact;
         if (iopp) {
                 if (bltin && bltin != doexec) {
-                        prs(cp);
+                        prs(bltin_name);
                         err(": cannot redirect shell command");
                         if (forked)
                                 _exit(-1);
                         return -1;
                 }
-                while (*iopp)
+                while (*iopp) {
                         if (iosetup(*iopp++, pin != NULL, pout != NULL)) {
                                 /* system-detected error */
                                 if (forked)
                                         _exit(-1);
                                 return -1;
                         }
+                }
         }
 
         if (bltin) {
+                if (forked || pin || pout) {
+                        /* Builtin in pipe: disallowed */
+                        /* TODO: allow "exec"? */
+                        prs(bltin_name);
+                        err(": cannot run builtin as part of pipe");
+                        if (forked)
+                                _exit(-1);
+                        return -1;
+                }
                 i = setstatus(bltin(t));
                 if (forked)
                         _exit(i);
                 DBGPRINTF(("FORKEXEC: returning i=%d\n", i));
-/* Builtins in pipes ("ls /dev/null | cd"):
- * here "cd" (which is not a child) will return to main msh,
- * and we will read from ls's output as if it is our next command!
- * Result: "/dev/null: cannot execute"
- * and then we reach EOF on stdin and exit.
- * See above for possible way to fix this.
- */
                 return i;
         }
 
@@ -2869,7 +2853,7 @@ static int forkexec(struct op *t, int *pin, int *pout, int act, char **wp)
         }
 
         if (t->type == TPAREN)
-                _exit(execute(t->left, NOPIPE, NOPIPE, FEXEC));
+                _exit(execute(t->left, NOPIPE, NOPIPE, /* no_fork: */ 1));
         if (wp[0] == NULL)
                 _exit(0);
 
@@ -2880,7 +2864,7 @@ static int forkexec(struct op *t, int *pin, int *pout, int act, char **wp)
         if (!execflg)
                 trap[0] = NULL;
 
-        DBGPRINTF(("FORKEXEC: calling leave(), pid=%d\n", newpid));
+        DBGPRINTF(("FORKEXEC: calling leave(), pid=%d\n", getpid()));
 
         leave();
         /* NOTREACHED */
@@ -2927,6 +2911,7 @@ static int iosetup(struct ioword *iop, int pipein, int pipeout)
                         iop->io_flag = IOCLOSE;
                 iop->io_flag &= ~(IOREAD | IOWRITE);
         }
+
         switch (iop->io_flag) {
         case IOREAD:
                 u = open(cp, O_RDONLY);
@@ -2944,6 +2929,8 @@ static int iosetup(struct ioword *iop, int pipein, int pipeout)
                         lseek(u, (long) 0, SEEK_END);
                         break;
                 }
+                /* fall through to creation if >>file doesn't exist */
+
         case IOWRITE:
                 u = creat(cp, 0666);
                 break;
@@ -2956,6 +2943,7 @@ static int iosetup(struct ioword *iop, int pipein, int pipeout)
                 close(iop->io_unit);
                 return 0;
         }
+
         if (u < 0) {
                 prs(cp);
                 prs(": cannot ");
@@ -3148,7 +3136,7 @@ static int run(struct ioarg *argp, int (*f) (struct ioarg *))
                 yynerrs = 0;
                 failpt = rt;
                 if (setjmp(failpt) == 0 && yyparse() == 0)
-                        rv = execute(outtree, NOPIPE, NOPIPE, 0);
+                        rv = execute(outtree, NOPIPE, NOPIPE, /* no_fork: */ 0);
                 quitenv();
         } else {
                 DBGPRINTF(("RUN: error from newenv()!\n"));
@@ -3267,20 +3255,21 @@ static int dologin(struct op *t)
 
 static int doumask(struct op *t)
 {
-        int i, n;
+        int i;
         char *cp;
 
         cp = t->words[1];
         if (cp == NULL) {
                 i = umask(0);
                 umask(i);
-                for (n = 3 * 4; (n -= 3) >= 0;)
-                        fputc('0' + ((i >> n) & 07), stderr);
-                fputc('\n', stderr);
+                printf("%04o\n", i);
         } else {
-                for (n = 0; *cp >= '0' && *cp <= '7'; cp++)
-                        n = n * 8 + (*cp - '0');
-                umask(n);
+                i = bb_strtou(cp, NULL, 8);
+                if (errno) {
+                        err("umask: bad octal number");
+                        return 1;
+                }
+                umask(i);
         }
         return 0;
 }
@@ -3292,14 +3281,15 @@ static int doexec(struct op *t)
         xint *ofail;
 
         t->ioact = NULL;
-        for (i = 0; (t->words[i] = t->words[i + 1]) != NULL; i++);
+        for (i = 0; (t->words[i] = t->words[i + 1]) != NULL; i++)
+                continue;
         if (i == 0)
                 return 1;
         execflg = 1;
         ofail = failpt;
         failpt = ex;
         if (setjmp(failpt) == 0)
-                execute(t, NOPIPE, NOPIPE, FEXEC);
+                execute(t, NOPIPE, NOPIPE, /* no_fork: */ 1);
         failpt = ofail;
         execflg = 0;
         return 1;