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path: root/src/cmd/6g/gsubr.c
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Diffstat (limited to 'src/cmd/6g/gsubr.c')
-rw-r--r--src/cmd/6g/gsubr.c109
1 files changed, 65 insertions, 44 deletions
diff --git a/src/cmd/6g/gsubr.c b/src/cmd/6g/gsubr.c
index 2fd9d9400..20b79c0be 100644
--- a/src/cmd/6g/gsubr.c
+++ b/src/cmd/6g/gsubr.c
@@ -30,6 +30,10 @@
#include "gg.h"
+// TODO(rsc): Can make this bigger if we move
+// the text segment up higher in 6l for all GOOS.
+vlong unmappedzero = 4096;
+
void
clearp(Prog *p)
{
@@ -832,6 +836,7 @@ gins(int as, Node *f, Node *t)
// Node nod;
// int32 v;
Prog *p;
+ Addr af, at;
// if(f != N && f->op == OINDEX) {
// regalloc(&nod, &regnode, Z);
@@ -861,22 +866,46 @@ gins(int as, Node *f, Node *t)
return nil;
}
+ memset(&af, 0, sizeof af);
+ memset(&at, 0, sizeof at);
+ if(f != N)
+ naddr(f, &af, 1);
+ if(t != N)
+ naddr(t, &at, 1);
p = prog(as);
if(f != N)
- naddr(f, &p->from);
+ p->from = af;
if(t != N)
- naddr(t, &p->to);
+ p->to = at;
if(debug['g'])
print("%P\n", p);
return p;
}
+static void
+checkoffset(Addr *a, int canemitcode)
+{
+ Prog *p;
+
+ if(a->offset < unmappedzero)
+ return;
+ if(!canemitcode)
+ fatal("checkoffset %#llx, cannot emit code", a->offset);
+
+ // cannot rely on unmapped nil page at 0 to catch
+ // reference with large offset. instead, emit explicit
+ // test of 0(reg).
+ p = gins(ATESTB, nodintconst(0), N);
+ p->to = *a;
+ p->to.offset = 0;
+}
+
/*
* generate code to compute n;
* make a refer to result.
*/
void
-naddr(Node *n, Addr *a)
+naddr(Node *n, Addr *a, int canemitcode)
{
a->scale = 0;
a->index = D_NONE;
@@ -920,6 +949,7 @@ naddr(Node *n, Addr *a)
a->type = n->val.u.reg+D_INDIR;
a->sym = n->sym;
a->offset = n->xoffset;
+ checkoffset(a, canemitcode);
break;
case OPARAM:
@@ -1002,7 +1032,7 @@ naddr(Node *n, Addr *a)
break;
case OADDR:
- naddr(n->left, a);
+ naddr(n->left, a, canemitcode);
if(a->type >= D_INDIR) {
a->type -= D_INDIR;
break;
@@ -1018,24 +1048,28 @@ naddr(Node *n, Addr *a)
case OLEN:
// len of string or slice
- naddr(n->left, a);
+ naddr(n->left, a, canemitcode);
a->offset += Array_nel;
+ if(a->offset >= unmappedzero && a->offset-Array_nel < unmappedzero)
+ checkoffset(a, canemitcode);
break;
case OCAP:
// cap of string or slice
- naddr(n->left, a);
+ naddr(n->left, a, canemitcode);
a->offset += Array_cap;
+ if(a->offset >= unmappedzero && a->offset-Array_cap < unmappedzero)
+ checkoffset(a, canemitcode);
break;
// case OADD:
// if(n->right->op == OLITERAL) {
// v = n->right->vconst;
-// naddr(n->left, a);
+// naddr(n->left, a, canemitcode);
// } else
// if(n->left->op == OLITERAL) {
// v = n->left->vconst;
-// naddr(n->right, a);
+// naddr(n->right, a, canemitcode);
// } else
// goto bad;
// a->offset += v;
@@ -1618,7 +1652,6 @@ optoas(int op, Type *t)
enum
{
ODynam = 1<<0,
- OPtrto = 1<<1,
};
static Node clean[20];
@@ -1707,7 +1740,7 @@ lit:
reg1 = &clean[cleani-2];
reg->op = OEMPTY;
reg1->op = OEMPTY;
- naddr(n, a);
+ naddr(n, a, 1);
goto yes;
odot:
@@ -1720,7 +1753,7 @@ odot:
n1 = *nn;
n1.type = n->type;
n1.xoffset += oary[0];
- naddr(&n1, a);
+ naddr(&n1, a, 1);
goto yes;
}
@@ -1744,7 +1777,7 @@ odot:
a->type = D_NONE;
a->index = D_NONE;
- naddr(&n1, a);
+ naddr(&n1, a, 1);
goto yes;
oindex:
@@ -1755,18 +1788,12 @@ oindex:
// set o to type of array
o = 0;
- if(isptr[l->type->etype]) {
- o += OPtrto;
- if(l->type->type->etype != TARRAY)
- fatal("not ptr ary");
- if(l->type->type->bound < 0)
- o += ODynam;
- } else {
- if(l->type->etype != TARRAY)
- fatal("not ary");
- if(l->type->bound < 0)
- o += ODynam;
- }
+ if(isptr[l->type->etype])
+ fatal("ptr ary");
+ if(l->type->etype != TARRAY)
+ fatal("not ary");
+ if(l->type->bound < 0)
+ o += ODynam;
w = n->type->width;
if(isconst(r, CTINT))
@@ -1785,10 +1812,7 @@ oindex:
// load the array (reg)
if(l->ullman > r->ullman) {
regalloc(reg, types[tptr], N);
- if(o & OPtrto)
- cgen(l, reg);
- else
- agen(l, reg);
+ agen(l, reg);
}
// load the index (reg1)
@@ -1804,10 +1828,7 @@ oindex:
// load the array (reg)
if(l->ullman <= r->ullman) {
regalloc(reg, types[tptr], N);
- if(o & OPtrto)
- cgen(l, reg);
- else
- agen(l, reg);
+ agen(l, reg);
}
// check bounds
@@ -1818,9 +1839,16 @@ oindex:
n2.type = types[tptr];
n2.xoffset = Array_nel;
} else {
+ if(l->type->width >= unmappedzero && l->op == OIND) {
+ // cannot rely on page protections to
+ // catch array ptr == 0, so dereference.
+ n2 = *reg;
+ n2.op = OINDREG;
+ n2.type = types[TUINT8];
+ n2.xoffset = 0;
+ gins(ATESTB, nodintconst(0), &n2);
+ }
nodconst(&n2, types[TUINT64], l->type->bound);
- if(o & OPtrto)
- nodconst(&n2, types[TUINT64], l->type->type->bound);
}
gins(optoas(OCMP, types[TUINT32]), reg1, &n2);
p1 = gbranch(optoas(OLT, types[TUINT32]), T);
@@ -1836,7 +1864,7 @@ oindex:
gmove(&n2, reg);
}
- naddr(reg1, a);
+ naddr(reg1, a, 1);
a->offset = 0;
a->scale = w;
a->index = a->type;
@@ -1850,10 +1878,7 @@ oindex_const:
// can multiply by width statically
regalloc(reg, types[tptr], N);
- if(o & OPtrto)
- cgen(l, reg);
- else
- agen(l, reg);
+ agen(l, reg);
v = mpgetfix(r->val.u.xval);
if(o & ODynam) {
@@ -1881,10 +1906,6 @@ oindex_const:
if(v < 0) {
yyerror("out of bounds on array");
} else
- if(o & OPtrto) {
- if(v >= l->type->type->bound)
- yyerror("out of bounds on array");
- } else
if(v >= l->type->bound) {
yyerror("out of bounds on array");
}
@@ -1895,7 +1916,7 @@ oindex_const:
n2.xoffset = v*w;
a->type = D_NONE;
a->index = D_NONE;
- naddr(&n2, a);
+ naddr(&n2, a, 1);
goto yes;
yes:
generated by cgit v1.2.3 (git 2.39.1) at 2025-05-10 22:45:55 +0000