Fix data size for value copy in dt_cg_store_var()

The size of the data to be copied in dt_cg_store_var() was determined
wrongly.  For strings constants we were copying the size of the string
constant even if that might be larger than the maximum string size.

The offsets for lvars and gvars was also not taking into account the
length prefix to be stored for each string value.

Signed-off-by: Kris Van Hees <kris.van.hees@oracle.com>
Reviewed-by: Eugene Loh <eugene.loh@oracle.com>

libdtrace/dt_cg.c

@@ -2231,7 +2231,8 @@ dt_cg_store_var(dt_node_t *src, dt_irlist_t *dlp, dt_regset_t *drp,
 
 	/* global and local variables (that is, not thread-local) */
 	if (!(idp->di_flags & DT_IDFLG_TLS)) {
-		int reg;
+		int	reg;
+		size_t	size;
 
 		if ((reg = dt_regset_alloc(drp)) == -1)
 			longjmp(yypcb->pcb_jmpbuf, EDT_NOREG);
@@ -2245,29 +2246,23 @@ dt_cg_store_var(dt_node_t *src, dt_irlist_t *dlp, dt_regset_t *drp,
 
 		/* store by value or by reference */
 		if (src->dn_flags & DT_NF_REF) {
-			size_t	size;
+			size_t		srcsz;
 
 			emit(dlp, BPF_ALU64_IMM(BPF_ADD, reg, idp->di_offset));
 
 			/*
 			 * Determine the amount of data to be copied.  It is
-			 * usually the size of the identifier, except for
-			 * string constants where it is the size of the string
-			 * constant (adjusted for the variable-width length
-			 * prefix).  An assignment of a string constant is a
-			 * store of type 'string' with a RHS of type
-			 * DT_TOK_STRING.
+			 * the lesser of the size of the identifier and the
+			 * size of the data being copied in.
 			 */
-			if (dt_node_is_string(src) &&
-			    src->dn_right->dn_op == DT_TOK_STRING)
-				size = dt_node_type_size(src->dn_right) +
-				       DT_STRLEN_BYTES;
-			else
-				size = idp->di_size;
+			srcsz = dt_node_type_size(src->dn_right);
+			if (dt_node_is_string(src))
+				srcsz += DT_STRLEN_BYTES;
+			size = MIN(srcsz, idp->di_size);
 
 			dt_cg_memcpy(dlp, drp, reg, src->dn_reg, size);
 		} else {
-			size_t	size = idp->di_size;
+			size = idp->di_size;
 
 			assert(size > 0 && size <= 8 &&
 			       (size & (size - 1)) == 0);

libdtrace/dt_ident.c

@@ -1009,8 +1009,13 @@ dt_ident_set_data(dt_ident_t *idp, void *data)
 void
 dt_ident_set_storage(dt_ident_t *idp, uint_t alignment, uint_t size)
 {
+	dtrace_hdl_t	*dtp = yypcb->pcb_hdl;
 	dt_idhash_t	*dhp = idp->di_hash;
 
+	if (idp->di_ctfp == DT_STR_CTFP(dtp) &&
+	    idp->di_type == DT_STR_TYPE(dtp))
+		size += DT_STRLEN_BYTES;
+
 	idp->di_offset = (dhp->dh_nextoff + (alignment - 1)) & ~(alignment - 1);
 	idp->di_size = size;
 

test/unittest/codegen/tst.str_store_var.d

@@ -0,0 +1,26 @@
+/*
+ * Oracle Linux DTrace.
+ * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
+ * Licensed under the Universal Permissive License v 1.0 as shown at
+ * http://oss.oracle.com/licenses/upl.
+ */
+
+#pragma D option rawbytes
+#pragma D option strsize=6
+#pragma D option quiet
+
+string	x;
+
+BEGIN
+{
+	x = "abcdefgh";
+	trace(x);
+	x = "12";
+	trace(x);
+	exit(0);
+}
+
+ERROR
+{
+	exit(1);
+}

test/unittest/codegen/tst.str_store_var.r

@@ -0,0 +1,7 @@
+
+             0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f  0123456789abcdef
+         0: 00 06 61 62 63 64 65 66 00                       ..abcdef.
+
+             0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f  0123456789abcdef
+         0: 00 02 31 32 00 00 00 00 00                       ..12.....
+

test/unittest/variables/gvar/tst.str-size.d

@@ -0,0 +1,34 @@
+/*
+ * Oracle Linux DTrace.
+ * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
+ * Licensed under the Universal Permissive License v 1.0 as shown at
+ * http://oss.oracle.com/licenses/upl.
+ */
+
+/*
+ * ASSERTION: Enough space is allocated for each string variable.
+ *
+ * SECTION: Variables/Scalar Variables
+ */
+
+#pragma D option quiet
+#pragma D option strsize=5
+
+BEGIN
+{
+	x = "abcd";
+	y = "abcd";
+	z = "abcd";
+	exit(0);
+}
+
+END {
+	trace(x);
+	trace(y);
+	trace(z);
+}
+
+ERROR
+{
+	exit(1);
+}

test/unittest/variables/gvar/tst.str-size.r

@@ -0,0 +1 @@
+abcdabcdabcd

test/unittest/variables/lvar/tst.str-size.d

@@ -0,0 +1,31 @@
+/*
+ * Oracle Linux DTrace.
+ * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
+ * Licensed under the Universal Permissive License v 1.0 as shown at
+ * http://oss.oracle.com/licenses/upl.
+ */
+
+/*
+ * ASSERTION: Enough space is allocated for each string variable.
+ *
+ * SECTION: Variables/Scalar Variables
+ */
+
+#pragma D option quiet
+#pragma D option strsize=5
+
+BEGIN
+{
+	this->x = "abcd";
+	this->y = "abcd";
+	this->z = "abcd";
+	trace(this->x);
+	trace(this->y);
+	trace(this->z);
+	exit(0);
+}
+
+ERROR
+{
+	exit(1);
+}

test/unittest/variables/lvar/tst.str-size.r

@@ -0,0 +1 @@
+abcdabcdabcd