10854 empty struct array confuses CTF

Reviewed by: Andy Fiddaman <omnios@citrus-it.co.uk>
Reviewed by: Robert Mustacchi <rm@fingolfin.org>
Approved by: Dan McDonald <danmcd@joyent.com>

3 files changed, 104 insertions, 27 deletions

diff --git a/usr/src/lib/libctf/common/ctf_dwarf.c b/usr/src/lib/libctf/common/ctf_dwarf.c
index 2f501a2334..3079831715 100644
--- a/usr/src/lib/libctf/common/ctf_dwarf.c
+++ b/usr/src/lib/libctf/common/ctf_dwarf.c
@@ -1456,13 +1456,102 @@ ctf_dwarf_create_sou(ctf_cu_t *cup, Dwarf_Die die, ctf_id_t *idp,
 }
 
 static int
+ctf_dwarf_array_upper_bound(ctf_cu_t *cup, Dwarf_Die range, ctf_arinfo_t *ar)
+{
+	Dwarf_Attribute attr;
+	Dwarf_Unsigned uval;
+	Dwarf_Signed sval;
+	Dwarf_Half form;
+	Dwarf_Error derr;
+	const char *formstr = NULL;
+	int ret = 0;
+
+	ctf_dprintf("setting array upper bound\n");
+
+	ar->ctr_nelems = 0;
+
+	ret = ctf_dwarf_attribute(cup, range, DW_AT_upper_bound, &attr);
+	/*
+	 * Treat the lack of an upper bound attribute as a zero element array
+	 * and return success, otherwise return the error.
+	 */
+	if (ret != 0) {
+		if (ret == ENOENT)
+			return (0);
+		return (ret);
+	}
+
+	if (dwarf_whatform(attr, &form, &derr) != DW_DLV_OK) {
+		(void) snprintf(cup->cu_errbuf, cup->cu_errlen,
+		    "failed to get DW_AT_upper_bound attribute form: %s\n",
+		    dwarf_errmsg(derr));
+		ret = ECTF_CONVBKERR;
+		goto done;
+	}
+
+	/*
+	 * Compilers can indicate array bounds using signed or unsigned values.
+	 * Additionally, some compilers may also store the array bounds
+	 * using as DW_FORM_data{1,2,4,8} (which DWARF treats as raw data and
+	 * expects the caller to understand how to interpret the value).
+	 *
+	 * GCC 4.4.4 appears to always use unsigned values to encode the
+	 * array size (using '(unsigned)-1' to represent a zero-length or
+	 * unknown length array). Later versions of GCC use a signed value of
+	 * -1 for zero/unknown length arrays, and unsigned values to encode
+	 * known array sizes.
+	 *
+	 * Both dwarf_formsdata() and dwarf_formudata() will retrieve values
+	 * as their respective signed/unsigned forms, but both will also
+	 * retreive DW_FORM_data{1,2,4,8} values and treat them as signed or
+	 * unsigned integers (i.e. dwarf_formsdata() treats DW_FORM_dataXX
+	 * as signed integers and dwarf_formudata() treats DW_FORM_dataXX as
+	 * unsigned integers). Both will return an error if the form is not
+	 * their respective signed/unsigned form, or DW_FORM_dataXX.
+	 *
+	 * To obtain the upper bound, we use the appropriate
+	 * dwarf_form[su]data() function based on the form of DW_AT_upper_bound.
+	 * Additionally, we let dwarf_formudata() handle the DW_FORM_dataXX
+	 * forms (via the default option in the switch). If the value is in an
+	 * unexpected form (i.e. not DW_FORM_udata or DW_FORM_dataXX),
+	 * dwarf_formudata() will return failure (i.e. not DW_DLV_OK) and set
+	 * derr with the specific error value.
+	 */
+	switch (form) {
+	case DW_FORM_sdata:
+		if (dwarf_formsdata(attr, &sval, &derr) == DW_DLV_OK) {
+			ar->ctr_nelems = sval + 1;
+			goto done;
+		}
+		break;
+	case DW_FORM_udata:
+	default:
+		if (dwarf_formudata(attr, &uval, &derr) == DW_DLV_OK) {
+			ar->ctr_nelems = uval + 1;
+			goto done;
+		}
+		break;
+	}
+
+	if (dwarf_get_FORM_name(form, &formstr) != DW_DLV_OK)
+		formstr = "unknown DWARF form";
+
+	(void) snprintf(cup->cu_errbuf, cup->cu_errlen,
+	    "failed to get %s (%hu) value for DW_AT_upper_bound: %s\n",
+	    formstr, form, dwarf_errmsg(derr));
+	ret = ECTF_CONVBKERR;
+
+done:
+	dwarf_dealloc(cup->cu_dwarf, attr, DW_DLA_ATTR);
+	return (ret);
+}
+
+static int
 ctf_dwarf_create_array_range(ctf_cu_t *cup, Dwarf_Die range, ctf_id_t *idp,
     ctf_id_t base, int isroot)
 {
 	int ret;
 	Dwarf_Die sib;
-	Dwarf_Unsigned val;
-	Dwarf_Signed sval;
 	ctf_arinfo_t ar;
 
 	ctf_dprintf("creating array range\n");
@@ -1482,30 +1571,8 @@ ctf_dwarf_create_array_range(ctf_cu_t *cup, Dwarf_Die range, ctf_id_t *idp,
 	if ((ar.ctr_index = ctf_dwarf_long(cup)) == CTF_ERR)
 		return (ctf_errno(cup->cu_ctfp));
 
-	/*
-	 * Array bounds can be signed or unsigned, but there are several kinds
-	 * of signless forms (data1, data2, etc) that take their sign from the
-	 * routine that is trying to interpret them.  That is, data1 can be
-	 * either signed or unsigned, depending on whether you use the signed or
-	 * unsigned accessor function.  GCC will use the signless forms to store
-	 * unsigned values which have their high bit set, so we need to try to
-	 * read them first as unsigned to get positive values.  We could also
-	 * try signed first, falling back to unsigned if we got a negative
-	 * value.
-	 */
-	if ((ret = ctf_dwarf_unsigned(cup, range, DW_AT_upper_bound,
-	    &val)) == 0) {
-		ar.ctr_nelems = val + 1;
-	} else if (ret != ENOENT) {
-		return (ret);
-	} else if ((ret = ctf_dwarf_signed(cup, range, DW_AT_upper_bound,
-	    &sval)) == 0) {
-		ar.ctr_nelems = sval + 1;
-	} else if (ret != ENOENT) {
+	if ((ret = ctf_dwarf_array_upper_bound(cup, range, &ar)) != 0)
 		return (ret);
-	} else {
-		ar.ctr_nelems = 0;
-	}
 
 	if ((*idp = ctf_add_array(cup->cu_ctfp, isroot, &ar)) == CTF_ERR)
 		return (ctf_errno(cup->cu_ctfp));
diff --git a/usr/src/test/util-tests/tests/ctf/check-array.c b/usr/src/test/util-tests/tests/ctf/check-array.c
index be7a192480..46be6332cb 100644
--- a/usr/src/test/util-tests/tests/ctf/check-array.c
+++ b/usr/src/test/util-tests/tests/ctf/check-array.c
@@ -10,7 +10,7 @@
  */
 
 /*
- * Copyright 2019, Joyent, Inc.
+ * Copyright 2020 Joyent, Inc.
  */
 
 /*
@@ -36,6 +36,7 @@ static check_symbol_t check_syms[] = {
 	{ "g", "int [4][5][6][7][8]" },
 	{ "h", "int [4][5][6][7][8][9]" },
 	{ "i", "int [4][5][6][7][8][9][10]" },
+	{ "empty", "int [0]" },
 	{ NULL }
 };
 
@@ -72,11 +73,18 @@ static check_descent_t check_array_i[] = {
 	{ NULL },
 };
 
+static check_descent_t check_array_empty[] = {
+	{ "int [0]", CTF_K_ARRAY, "int", 0 },
+	{ "int", CTF_K_INTEGER },
+	{ NULL }
+};
+
 static check_descent_test_t descents[] = {
 	{ "a", check_array_a },
 	{ "b", check_array_b },
 	{ "c", check_array_c },
 	{ "i", check_array_i },
+	{ "empty", check_array_empty },
 	{ NULL }
 };
 
diff --git a/usr/src/test/util-tests/tests/ctf/test-array.c b/usr/src/test/util-tests/tests/ctf/test-array.c
index 9c15771caf..14fc21d5dd 100644
--- a/usr/src/test/util-tests/tests/ctf/test-array.c
+++ b/usr/src/test/util-tests/tests/ctf/test-array.c
@@ -10,7 +10,7 @@
  */
 
 /*
- * Copyright (c) 2019, Joyent, Inc.
+ * Copyright 2020 Joyent, Inc.
  */
 
 /*
@@ -27,3 +27,5 @@ int f[4][5][6][7];
 int g[4][5][6][7][8];
 int h[4][5][6][7][8][9];
 int i[4][5][6][7][8][9][10];
+
+int empty[] = { };