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Add checking for buffer overruns.

--- a/6/isel.c

+++ b/6/isel.c

@@ -422,7 +422,7 @@

 }

-static int isfunc(Isel *s, Node *n)

+static int isconstfunc(Isel *s, Node *n)

 {

     Node *d;

@@ -441,7 +441,7 @@

     AsmOp op;

     Loc *f;

-    if (isfunc(s, n)) {

+    if (isconstfunc(s, n)) {

         op = Icall;

         f = locmeml(htget(s->globls, n), NULL, NULL, mode(n));

     } else {

@@ -696,7 +696,7 @@

             r = loc(s, n);

             break;

         case Ovar:

-            if (isfunc(s, n)) {

+            if (isconstfunc(s, n)) {

                 r = locreg(ModeQ);

                 a = loc(s, n);

                 g(s, Ilea, a, r, NULL);

--- a/6/main.c

+++ b/6/main.c

@@ -6,6 +6,7 @@

 #include <assert.h>

 #include <sys/types.h>

 #include <sys/stat.h>

+#include <sys/time.h>

 #include <fcntl.h>

 #include <unistd.h>

 #include <err.h>

@@ -56,6 +57,7 @@

 {

     char *tmpdir;

     char *base;

+    struct timeval tv;

     tmpdir = getenv("TMPDIR");

     if (!tmpdir)

@@ -65,7 +67,9 @@

         base++;

     else

         base = path;

-    snprintf(buf, bufsz, "%s/tmp%lx-%s%s", tmpdir, random(), base, suffix);

+    gettimeofday(&tv, NULL);

+    srandom(tv.tv_usec);

+    snprintf(buf, bufsz, "%s/tmp%lx%lx-%s%s", tmpdir, random(), (long)tv.tv_usec, base, suffix);

     return buf;

 }

@@ -88,7 +92,6 @@

     int i;

     Stab *globls;

     char buf[1024];

-

     while ((opt = getopt(argc, argv, "d:hSo:I:")) != -1) {

         switch (opt) {

             case 'o':

--- a/6/simp.c

+++ b/6/simp.c

@@ -68,6 +68,7 @@

 static Type *tyintptr;

 static Type *tyword;

 static Type *tyvoid;

+static Node *abortfunc;

 size_t alignto(size_t sz, Type *t)

 {

@@ -859,9 +860,29 @@

     return r;

 }

+static void checkidx(Simp *s, Node *len, Node *idx)

+{

+    Node *cmp, *die;

+    Node *ok, *fail;

+

+    /* create expressions */

+    cmp = mkexpr(idx->line, Olt, ptrsized(s, idx), ptrsized(s, len), NULL);

+    cmp->expr.type = mktype(-1, Tybool);

+    ok = genlbl();

+    fail = genlbl();

+    die = mkexpr(idx->line, Ocall, abortfunc, NULL);

+    die->expr.type = mktype(-1, Tyvoid);

+

+    /* insert them */

+    cjmp(s, cmp, ok, fail);

+    append(s, fail);

+    append(s, die);

+    append(s, ok);

+}

+

 static Node *idxaddr(Simp *s, Node *seq, Node *idx)

 {

-    Node *a, *t, *u, *v; /* temps */

+    Node *a, *t, *u, *v, *w; /* temps */

     Node *r; /* result */

     Type *ty;

     size_t sz;

@@ -868,15 +889,19 @@

     a = rval(s, seq, NULL);

     ty = exprtype(seq)->sub[0];

-    if (exprtype(seq)->type == Tyarray)

+    if (exprtype(seq)->type == Tyarray) {

         t = addr(s, a, ty);

-    else if (seq->expr.type->type == Tyslice)

+        w = exprtype(a)->asize;

+    } else if (seq->expr.type->type == Tyslice) {

         t = load(addr(s, a, mktyptr(seq->line, ty)));

-    else

+        w = slicelen(s, a);

+    } else {

         die("Can't index type %s\n", tystr(seq->expr.type));

+    }

     assert(t->expr.type->type == Typtr);

     u = rval(s, idx, NULL);

     u = ptrsized(s, u);

+    checkidx(s, w, u);

     sz = tysize(ty);

     v = mul(u, disp(seq->line, sz));

     r = add(t, v);

@@ -1813,6 +1838,29 @@

     free(name);

 }

+static void initconsts(Htab *globls)

+{

+    Type *ty;

+    Node *name;

+    Node *dcl;

+

+    tyintptr = mktype(-1, Tyuint64);

+    tyword = mktype(-1, Tyuint);

+    tyvoid = mktype(-1, Tyvoid);

+

+    ty = mktyfunc(-1, NULL, 0, mktype(-1, Tyvoid));

+    name = mknsname(-1, "_rt", "abort_oob");

+    dcl = mkdecl(-1, name, ty);

+    dcl->decl.isconst = 1;

+    dcl->decl.isextern = 1;

+    htput(globls, dcl, asmname(dcl->decl.name));

+

+    abortfunc = mkexpr(-1, Ovar, name, NULL);

+    abortfunc->expr.type = ty;

+    abortfunc->expr.did = dcl->decl.did;

+    abortfunc->expr.isconst = 1;

+}

+

 void gen(Node *file, char *out)

 {

     Htab *globls, *strtab;

@@ -1822,16 +1870,12 @@

     size_t i;

     FILE *fd;

-    /* declare useful constants */

-    tyintptr = mktype(-1, Tyuint64);

-    tyword = mktype(-1, Tyuint);

-    tyvoid = mktype(-1, Tyvoid);

-

     fn = NULL;

     nfn = 0;

     blob = NULL;

     nblob = 0;

     globls = mkht(varhash, vareq);

+    initconsts(globls);

     /* We need to define all global variables before use */

     fillglobls(file->file.globls, globls);

--- a/rt/Makefile

+++ b/rt/Makefile

@@ -1,5 +1,5 @@

 OBJ = _myrrt.o

-ASMSRC = start.s common.s

+ASMSRC = start.s common.s abort.s

 all: _myrrt.o