[DTrace-devel] [PATCH v2] Fix length stored by substr() and optimize the implementation
Kris Van Hees
kris.van.hees at oracle.com
Wed Nov 10 01:43:33 UTC 2021
In certain cases, substr() would store an incorrect length for the
result string. This problem is resolved with this patch.
Better comments have been added as well to make the code easier to
follow.
The code handling the case where (idx < 0) failed to recognize that
when the adjusted idx value was more negative than the value of cnt,
the result would always be the empty string. This has been corrected
which improved code performance as well.
Another important change can be found in label .Lcheck_idx (formerly
.Ladjust_cnt). The original four conditionals were overkill, and the
case for (cnt > 0) was jumping to .Lcnt_pos incorrectly (causing the
incorrect string length value). It now correctly jumps to .Lcopy.
In fact, the .Lcnt_pos code was unnecessary.
Copying the substring now makes use of the probe_read_str() helper
rather than the probe_read() helper.
10 new tests are added to test various special conditions.
Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
---
bpf/substr.S | 132 ++++++++++++------
.../tst.substr-multi-const-idx-neg-no-cnt.d | 30 ++++
.../tst.substr-multi-const-idx-neg-no-cnt.r | 11 ++
...ubstr-multi-const-idx-neg-too-far-no-cnt.d | 30 ++++
...ubstr-multi-const-idx-neg-too-far-no-cnt.r | 11 ++
.../tst.substr-multi-const-idx-neg-too-far.d | 30 ++++
.../tst.substr-multi-const-idx-neg-too-far.r | 11 ++
.../tst.substr-multi-const-idx-pos-no-cnt.d | 31 ++++
.../tst.substr-multi-const-idx-pos-no-cnt.r | 12 ++
.../tst.substr-multi-var-idx-neg-no-cnt.d | 40 ++++++
.../tst.substr-multi-var-idx-neg-no-cnt.r | 11 ++
....substr-multi-var-idx-neg-too-far-no-cnt.d | 40 ++++++
....substr-multi-var-idx-neg-too-far-no-cnt.r | 11 ++
.../tst.substr-multi-var-idx-neg-too-far.d | 40 ++++++
.../tst.substr-multi-var-idx-neg-too-far.r | 11 ++
.../tst.substr-multi-var-idx-pos-no-cnt.d | 42 ++++++
.../tst.substr-multi-var-idx-pos-no-cnt.r | 12 ++
.../funcs/substr/tst.substr-stored-len.d | 29 ++++
.../funcs/substr/tst.substr-stored-len.r | 10 ++
.../funcs/substr/tst.substr-strsize.d | 34 +++++
.../funcs/substr/tst.substr-strsize.r | 16 +++
21 files changed, 550 insertions(+), 44 deletions(-)
create mode 100644 test/unittest/funcs/substr/tst.substr-multi-const-idx-neg-no-cnt.d
create mode 100644 test/unittest/funcs/substr/tst.substr-multi-const-idx-neg-no-cnt.r
create mode 100644 test/unittest/funcs/substr/tst.substr-multi-const-idx-neg-too-far-no-cnt.d
create mode 100644 test/unittest/funcs/substr/tst.substr-multi-const-idx-neg-too-far-no-cnt.r
create mode 100644 test/unittest/funcs/substr/tst.substr-multi-const-idx-neg-too-far.d
create mode 100644 test/unittest/funcs/substr/tst.substr-multi-const-idx-neg-too-far.r
create mode 100644 test/unittest/funcs/substr/tst.substr-multi-const-idx-pos-no-cnt.d
create mode 100644 test/unittest/funcs/substr/tst.substr-multi-const-idx-pos-no-cnt.r
create mode 100644 test/unittest/funcs/substr/tst.substr-multi-var-idx-neg-no-cnt.d
create mode 100644 test/unittest/funcs/substr/tst.substr-multi-var-idx-neg-no-cnt.r
create mode 100644 test/unittest/funcs/substr/tst.substr-multi-var-idx-neg-too-far-no-cnt.d
create mode 100644 test/unittest/funcs/substr/tst.substr-multi-var-idx-neg-too-far-no-cnt.r
create mode 100644 test/unittest/funcs/substr/tst.substr-multi-var-idx-neg-too-far.d
create mode 100644 test/unittest/funcs/substr/tst.substr-multi-var-idx-neg-too-far.r
create mode 100644 test/unittest/funcs/substr/tst.substr-multi-var-idx-pos-no-cnt.d
create mode 100644 test/unittest/funcs/substr/tst.substr-multi-var-idx-pos-no-cnt.r
create mode 100644 test/unittest/funcs/substr/tst.substr-stored-len.d
create mode 100644 test/unittest/funcs/substr/tst.substr-stored-len.r
create mode 100644 test/unittest/funcs/substr/tst.substr-strsize.d
create mode 100644 test/unittest/funcs/substr/tst.substr-strsize.r
diff --git a/bpf/substr.S b/bpf/substr.S
index e263274b..514dedba 100644
--- a/bpf/substr.S
+++ b/bpf/substr.S
@@ -5,88 +5,132 @@
#define DT_STRLEN_BYTES 2
-#define BPF_FUNC_probe_read 4
+#define BPF_FUNC_probe_read_str 45
/*
* void dt_substr(char *dst, const char *src, int32_t idx, int32_t cnt,
* uint64_t argc)
+ *
+ * %r1 = dst, %r2 = src, %r3 = idx, %r4 = cnt, %r5 = argc
*/
.text
.align 4
.global dt_substr
.type dt_substr, @function
dt_substr :
+ /* Store the arguments (sign-extend idx). */
mov %r9, %r1 /* %r9 = dst */
stxdw [%fp+-8], %r2 /* Spill src */
lsh %r3, 32 /* Sign-extend idx */
arsh %r3, 32
mov %r6, %r3 /* %r6 = idx */
- lddw %r8, STRSZ /* %r8 = STRSZ (temporary) */
- jgt %r5, 2, .Lhave_cnt
- mov %r4, %r8 /* cnt = STRSZ */
+ /* Initialize the string length with its maximum value. */
+ lddw %r8, STRSZ /* %r8 = len = STRSZ */
+
+ /*
+ * If we do not have a cnt, use the maximum value.
+ * Otherwise, sign-extend cnt.
+ */
+ jgt %r5, 2, .Lhave_cnt /* if (argc > 2) goto Lhave_cnt; */
+ mov %r7, %r8 /* cnt = STRSZ */
+ ja .Lcnt_set
.Lhave_cnt:
lsh %r4, 32 /* Sign-extend cnt */
arsh %r4, 32
mov %r7, %r4 /* %r7 = cnt */
+.Lcnt_set:
/*
- * Get the source string length and validate it. If the length is 0,
- * the result is the empty string. If the length is greater than the
- * maximum string length (STRSZ), cap it at that value.
+ * Get the source string length and validate it.
+ * If the length is 0, the result is the empty string.
+ * If the length is less than the maximum string length (STRSZ), use
+ * the length we got. (The length is initialized in %r8 as the default
+ * string length.)
*/
ldxdw %r1, [%fp+-8]
call dt_strlen /* len = dt_strlen(src) */
- jeq %r0, 0, .Lempty
- mov %r1, %r8 /* %r1 = STRSZ */
- jle %r0, %r8, .Llen_ok
- mov %r0, %r8 /* len = STRSZ */
-.Llen_ok:
+ jeq %r0, 0, .Lempty /* if (len == 0) goto Lempty; */
+ jge %r0, %r8, .Llen_set /* if (len >= STRSZ) goto Llen_set; */
mov %r8, %r0 /* %r8 = len */
+.Llen_set:
- jsge %r6, 0, .Ladjust_cnt
+ jsge %r6, 0, .Lcheck_idx /* if (idx s>= 0) goto Lcheck_idx; */
+ /*
+ * If idx is negative it is a count from the end of the string. Turn
+ * it into the equivalent character offset (len + idx).
+ * If the offset is positive, we can use it as the index.
+ * If not, we need to determine whether idx + cnt falls within the
+ * [0, len[ interval. If it does not, the result is the empty string.
+ * If it does, we will slice from idx = 0 for cnt + idx characters.
+ */
add %r6, %r8 /* idx += len */
- jsge %r6, 0, .Ladjust_cnt
+ jsge %r6, 0, .Lcheck_idx /* if (idx s>= 0) goto Lcheck_idx; */
mov %r0, 0
- sub32 %r0, %r6 /* neg messes up the verifier */
- jsle %r7, %r0, .Ladjust_cnt
- add32 %r7, %r6 /* cnt += idx */
+ sub %r0, %r6 /* neg messes up the verifier */
+ jsle %r7, %r0, .Lempty /* if (cnt s<= -idx) goto Lempty; */
+ add %r7, %r6 /* cnt += idx */
mov %r6, 0 /* idx = 0 */
-.Ladjust_cnt:
- jsge %r6, %r1, .Lempty
- jsge %r6, %r8, .Lempty
- jslt %r6, 0, .Lempty
- jsge %r7, 0, .Lcnt_pos
- mov %r0, %r8
- sub32 %r0, %r6
- add32 %r7, %r0 /* cnt += len - idx */
- lsh %r7, 32
- arsh %r7, 32
- jsle %r7, 0, .Lempty
-.Lcnt_pos:
- sub %r1, %r6
- jsge %r1, %r7, .Lcopy
- mov %r7, %r1 /* cnt = STRSZ - idx */
+.Lcheck_idx:
+ /*
+ * Validate the idx value. If idx is greater than the string length,
+ * we get the empty string.
+ */
+ jsge %r6, %r8, .Lempty /* if (idx s>= len) goto Lempty; */
-.Lcopy:
- ldxdw %r8, [%fp+-8]
- add %r8, DT_STRLEN_BYTES
- add %r8, %r6 /* %r8 = src + DT_STRLEN_BYTES + idx */
+ /* If cnt is positive (or 0), we are ready to copy the slice. */
+ jsge %r7, 0, .Lcopy /* if (cnt s>= 0) goto Lcopy; */
- mov %r1, %r7
- mov %r2, %r9
- call dt_strlen_store /* dt_strlen_store(cnt, dst) */
- add %r9, DT_STRLEN_BYTES /* %r9 = dst + DT_STRLEN_BYTES */
+ /*
+ * If cnt is negative it is a count from the last character in string.
+ * Use the equivalent character offset to calculate the true (positive)
+ * cnt:
+ * start = idx
+ * end = (len - 1) - (-cnt)
+ * new_cnt = end - start + 1
+ * = (len - 1) - (-cnt) - idx + 1
+ * = len - 1 + cnt - idx + 1
+ * = len + cnt - idx
+ * which is equivalent with:
+ * cnt += len - idx
+ */
+ mov %r0, %r8
+ sub %r0, %r6
+ add %r7, %r0 /* cnt += len - idx */
+ jsle %r7, 0, .Lempty /* if (cnt s<= 0) goto Lempty; */
+.Lcopy:
+ /*
+ * Use the probe_read_str() BPF helper to copy (cnt + 1) bytes from
+ * &src[DT_STRLEN_BYTES + idx] to &dst[DT_STRLEN_BYTES]. We ensure
+ * that cnt is capped at STRSZ.
+ */
mov %r1, %r9
+ add %r1, DT_STRLEN_BYTES
mov %r2, %r7
- mov %r3, %r8
- call BPF_FUNC_probe_read
+ lddw %r0, STRSZ
+ jle %r2, %r0, .Lcnt_ok /* if (cnt <= STRSZ) goto Lcnt_ok; */
+ mov %r2, %r0 /* cnt = STRSZ */
+.Lcnt_ok:
+ add %r2, 1
+ ldxdw %r3, [%fp+-8]
+ add %r3, DT_STRLEN_BYTES
+ add %r3, %r6
+ call BPF_FUNC_probe_read_str /*
+ * rc = probe_read_str(
+ * &dst[DT_STRLEN_BYTES],
+ * cnt + 1,
+ * &src[DT_STRLEN_BYTES + idx]);
+ */
+
+ /* Store the result string length (rc - 1) at dst. */
+ mov %r1, %r0
+ sub %r1, 1
+ mov %r2, %r9
+ call dt_strlen_store /* dt_strlen_store(rc - 1, dst) */
- add %r9, %r7
- stb [%r9+0], 0
exit
.Lempty:
diff --git a/test/unittest/funcs/substr/tst.substr-multi-const-idx-neg-no-cnt.d b/test/unittest/funcs/substr/tst.substr-multi-const-idx-neg-no-cnt.d
new file mode 100644
index 00000000..39ebf280
--- /dev/null
+++ b/test/unittest/funcs/substr/tst.substr-multi-const-idx-neg-no-cnt.d
@@ -0,0 +1,30 @@
+/*
+ * 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: The substr() subroutine supports negative index values passed as
+ * constants.
+ *
+ * SECTION: Actions and Subroutines/substr()
+ */
+
+#pragma D option quiet
+
+BEGIN
+{
+ printf("\n% 3d %s", -10, substr("abcdefghijklmnop", -10));
+ printf("\n% 3d %s", -9, substr("abcdefghijklmnop", -9));
+ printf("\n% 3d %s", -8, substr("abcdefghijklmnop", -8));
+ printf("\n% 3d %s", -7, substr("abcdefghijklmnop", -7));
+ printf("\n% 3d %s", -6, substr("abcdefghijklmnop", -6));
+ printf("\n% 3d %s", -5, substr("abcdefghijklmnop", -5));
+ printf("\n% 3d %s", -4, substr("abcdefghijklmnop", -4));
+ printf("\n% 3d %s", -3, substr("abcdefghijklmnop", -3));
+ printf("\n% 3d %s", -2, substr("abcdefghijklmnop", -2));
+ printf("\n% 3d %s", -1, substr("abcdefghijklmnop", -1));
+ exit(0);
+}
diff --git a/test/unittest/funcs/substr/tst.substr-multi-const-idx-neg-no-cnt.r b/test/unittest/funcs/substr/tst.substr-multi-const-idx-neg-no-cnt.r
new file mode 100644
index 00000000..468f586b
--- /dev/null
+++ b/test/unittest/funcs/substr/tst.substr-multi-const-idx-neg-no-cnt.r
@@ -0,0 +1,11 @@
+
+-10 ghijklmnop
+ -9 hijklmnop
+ -8 ijklmnop
+ -7 jklmnop
+ -6 klmnop
+ -5 lmnop
+ -4 mnop
+ -3 nop
+ -2 op
+ -1 p
diff --git a/test/unittest/funcs/substr/tst.substr-multi-const-idx-neg-too-far-no-cnt.d b/test/unittest/funcs/substr/tst.substr-multi-const-idx-neg-too-far-no-cnt.d
new file mode 100644
index 00000000..95af3f37
--- /dev/null
+++ b/test/unittest/funcs/substr/tst.substr-multi-const-idx-neg-too-far-no-cnt.d
@@ -0,0 +1,30 @@
+/*
+ * 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: The substr() subroutine supports negative index values passed as
+ * constants, with some values out of range.
+ *
+ * SECTION: Actions and Subroutines/substr()
+ */
+
+#pragma D option quiet
+
+BEGIN
+{
+ printf("\n% 3d %s", -10, substr("abcde", -10));
+ printf("\n% 3d %s", -9, substr("abcde", -9));
+ printf("\n% 3d %s", -8, substr("abcde", -8));
+ printf("\n% 3d %s", -7, substr("abcde", -7));
+ printf("\n% 3d %s", -6, substr("abcde", -6));
+ printf("\n% 3d %s", -5, substr("abcde", -5));
+ printf("\n% 3d %s", -4, substr("abcde", -4));
+ printf("\n% 3d %s", -3, substr("abcde", -3));
+ printf("\n% 3d %s", -2, substr("abcde", -2));
+ printf("\n% 3d %s", -1, substr("abcde", -1));
+ exit(0);
+}
diff --git a/test/unittest/funcs/substr/tst.substr-multi-const-idx-neg-too-far-no-cnt.r b/test/unittest/funcs/substr/tst.substr-multi-const-idx-neg-too-far-no-cnt.r
new file mode 100644
index 00000000..4c911183
--- /dev/null
+++ b/test/unittest/funcs/substr/tst.substr-multi-const-idx-neg-too-far-no-cnt.r
@@ -0,0 +1,11 @@
+
+-10 abcde
+ -9 abcde
+ -8 abcde
+ -7 abcde
+ -6 abcde
+ -5 abcde
+ -4 bcde
+ -3 cde
+ -2 de
+ -1 e
diff --git a/test/unittest/funcs/substr/tst.substr-multi-const-idx-neg-too-far.d b/test/unittest/funcs/substr/tst.substr-multi-const-idx-neg-too-far.d
new file mode 100644
index 00000000..05ea8f01
--- /dev/null
+++ b/test/unittest/funcs/substr/tst.substr-multi-const-idx-neg-too-far.d
@@ -0,0 +1,30 @@
+/*
+ * 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: The substr() subroutine supports negative index values passed as
+ * constants, with some values out of range.
+ *
+ * SECTION: Actions and Subroutines/substr()
+ */
+
+#pragma D option quiet
+
+BEGIN
+{
+ printf("\n% 3d % 3d %s", -10, 3, substr("abcde", -10, 3));
+ printf("\n% 3d % 3d %s", -9, 3, substr("abcde", -9, 3));
+ printf("\n% 3d % 3d %s", -8, 3, substr("abcde", -8, 3));
+ printf("\n% 3d % 3d %s", -7, 3, substr("abcde", -7, 3));
+ printf("\n% 3d % 3d %s", -6, 3, substr("abcde", -6, 3));
+ printf("\n% 3d % 3d %s", -5, 3, substr("abcde", -5, 3));
+ printf("\n% 3d % 3d %s", -4, 3, substr("abcde", -4, 3));
+ printf("\n% 3d % 3d %s", -3, 3, substr("abcde", -3, 3));
+ printf("\n% 3d % 3d %s", -2, 3, substr("abcde", -2, 3));
+ printf("\n% 3d % 3d %s", -1, 3, substr("abcde", -1, 3));
+ exit(0);
+}
diff --git a/test/unittest/funcs/substr/tst.substr-multi-const-idx-neg-too-far.r b/test/unittest/funcs/substr/tst.substr-multi-const-idx-neg-too-far.r
new file mode 100644
index 00000000..e989b7c3
--- /dev/null
+++ b/test/unittest/funcs/substr/tst.substr-multi-const-idx-neg-too-far.r
@@ -0,0 +1,11 @@
+
+-10 3
+ -9 3
+ -8 3
+ -7 3 a
+ -6 3 ab
+ -5 3 abc
+ -4 3 bcd
+ -3 3 cde
+ -2 3 de
+ -1 3 e
diff --git a/test/unittest/funcs/substr/tst.substr-multi-const-idx-pos-no-cnt.d b/test/unittest/funcs/substr/tst.substr-multi-const-idx-pos-no-cnt.d
new file mode 100644
index 00000000..1ef6aaf3
--- /dev/null
+++ b/test/unittest/funcs/substr/tst.substr-multi-const-idx-pos-no-cnt.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: The substr() subroutine supports positive index values passed as
+ * constants.
+ *
+ * SECTION: Actions and Subroutines/substr()
+ */
+
+#pragma D option quiet
+
+BEGIN
+{
+ printf("\n% 3d %s", 0, substr("abcdefghijklmnop", 0));
+ printf("\n% 3d %s", 1, substr("abcdefghijklmnop", 1));
+ printf("\n% 3d %s", 2, substr("abcdefghijklmnop", 2));
+ printf("\n% 3d %s", 3, substr("abcdefghijklmnop", 3));
+ printf("\n% 3d %s", 4, substr("abcdefghijklmnop", 4));
+ printf("\n% 3d %s", 5, substr("abcdefghijklmnop", 5));
+ printf("\n% 3d %s", 6, substr("abcdefghijklmnop", 6));
+ printf("\n% 3d %s", 7, substr("abcdefghijklmnop", 7));
+ printf("\n% 3d %s", 8, substr("abcdefghijklmnop", 8));
+ printf("\n% 3d %s", 9, substr("abcdefghijklmnop", 9));
+ printf("\n% 3d %s", 10, substr("abcdefghijklmnop", 10));
+ exit(0);
+}
diff --git a/test/unittest/funcs/substr/tst.substr-multi-const-idx-pos-no-cnt.r b/test/unittest/funcs/substr/tst.substr-multi-const-idx-pos-no-cnt.r
new file mode 100644
index 00000000..78f8b580
--- /dev/null
+++ b/test/unittest/funcs/substr/tst.substr-multi-const-idx-pos-no-cnt.r
@@ -0,0 +1,12 @@
+
+ 0 abcdefghijklmnop
+ 1 bcdefghijklmnop
+ 2 cdefghijklmnop
+ 3 defghijklmnop
+ 4 efghijklmnop
+ 5 fghijklmnop
+ 6 ghijklmnop
+ 7 hijklmnop
+ 8 ijklmnop
+ 9 jklmnop
+ 10 klmnop
diff --git a/test/unittest/funcs/substr/tst.substr-multi-var-idx-neg-no-cnt.d b/test/unittest/funcs/substr/tst.substr-multi-var-idx-neg-no-cnt.d
new file mode 100644
index 00000000..4b496e92
--- /dev/null
+++ b/test/unittest/funcs/substr/tst.substr-multi-var-idx-neg-no-cnt.d
@@ -0,0 +1,40 @@
+/*
+ * 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: The substr() subroutine supports negative index values passed by
+ * variable.
+ *
+ * SECTION: Actions and Subroutines/substr()
+ */
+
+#pragma D option quiet
+
+BEGIN
+{
+ idx = -10;
+ printf("\n% 3d %s", idx, substr("abcdefghijklmnop", idx));
+ idx = -9;
+ printf("\n% 3d %s", idx, substr("abcdefghijklmnop", idx));
+ idx = -8;
+ printf("\n% 3d %s", idx, substr("abcdefghijklmnop", idx));
+ idx = -7;
+ printf("\n% 3d %s", idx, substr("abcdefghijklmnop", idx));
+ idx = -6;
+ printf("\n% 3d %s", idx, substr("abcdefghijklmnop", idx));
+ idx = -5;
+ printf("\n% 3d %s", idx, substr("abcdefghijklmnop", idx));
+ idx = -4;
+ printf("\n% 3d %s", idx, substr("abcdefghijklmnop", idx));
+ idx = -3;
+ printf("\n% 3d %s", idx, substr("abcdefghijklmnop", idx));
+ idx = -2;
+ printf("\n% 3d %s", idx, substr("abcdefghijklmnop", idx));
+ idx = -1;
+ printf("\n% 3d %s", idx, substr("abcdefghijklmnop", idx));
+ exit(0);
+}
diff --git a/test/unittest/funcs/substr/tst.substr-multi-var-idx-neg-no-cnt.r b/test/unittest/funcs/substr/tst.substr-multi-var-idx-neg-no-cnt.r
new file mode 100644
index 00000000..468f586b
--- /dev/null
+++ b/test/unittest/funcs/substr/tst.substr-multi-var-idx-neg-no-cnt.r
@@ -0,0 +1,11 @@
+
+-10 ghijklmnop
+ -9 hijklmnop
+ -8 ijklmnop
+ -7 jklmnop
+ -6 klmnop
+ -5 lmnop
+ -4 mnop
+ -3 nop
+ -2 op
+ -1 p
diff --git a/test/unittest/funcs/substr/tst.substr-multi-var-idx-neg-too-far-no-cnt.d b/test/unittest/funcs/substr/tst.substr-multi-var-idx-neg-too-far-no-cnt.d
new file mode 100644
index 00000000..aa9bc5c7
--- /dev/null
+++ b/test/unittest/funcs/substr/tst.substr-multi-var-idx-neg-too-far-no-cnt.d
@@ -0,0 +1,40 @@
+/*
+ * 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: The substr() subroutine supports negative index values passed by
+ * variable, with some values out of range.
+ *
+ * SECTION: Actions and Subroutines/substr()
+ */
+
+#pragma D option quiet
+
+BEGIN
+{
+ idx = -10;
+ printf("\n% 3d %s", idx, substr("abcde", idx));
+ idx = -9;
+ printf("\n% 3d %s", idx, substr("abcde", idx));
+ idx = -8;
+ printf("\n% 3d %s", idx, substr("abcde", idx));
+ idx = -7;
+ printf("\n% 3d %s", idx, substr("abcde", idx));
+ idx = -6;
+ printf("\n% 3d %s", idx, substr("abcde", idx));
+ idx = -5;
+ printf("\n% 3d %s", idx, substr("abcde", idx));
+ idx = -4;
+ printf("\n% 3d %s", idx, substr("abcde", idx));
+ idx = -3;
+ printf("\n% 3d %s", idx, substr("abcde", idx));
+ idx = -2;
+ printf("\n% 3d %s", idx, substr("abcde", idx));
+ idx = -1;
+ printf("\n% 3d %s", idx, substr("abcde", idx));
+ exit(0);
+}
diff --git a/test/unittest/funcs/substr/tst.substr-multi-var-idx-neg-too-far-no-cnt.r b/test/unittest/funcs/substr/tst.substr-multi-var-idx-neg-too-far-no-cnt.r
new file mode 100644
index 00000000..4c911183
--- /dev/null
+++ b/test/unittest/funcs/substr/tst.substr-multi-var-idx-neg-too-far-no-cnt.r
@@ -0,0 +1,11 @@
+
+-10 abcde
+ -9 abcde
+ -8 abcde
+ -7 abcde
+ -6 abcde
+ -5 abcde
+ -4 bcde
+ -3 cde
+ -2 de
+ -1 e
diff --git a/test/unittest/funcs/substr/tst.substr-multi-var-idx-neg-too-far.d b/test/unittest/funcs/substr/tst.substr-multi-var-idx-neg-too-far.d
new file mode 100644
index 00000000..8f2a10f1
--- /dev/null
+++ b/test/unittest/funcs/substr/tst.substr-multi-var-idx-neg-too-far.d
@@ -0,0 +1,40 @@
+/*
+ * 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: The substr() subroutine supports negative index values passed by
+ * variable, with some values out of range.
+ *
+ * SECTION: Actions and Subroutines/substr()
+ */
+
+#pragma D option quiet
+
+BEGIN
+{
+ idx = -10;
+ printf("\n% 3d % 3d %s", idx, 3, substr("abcde", idx, 3));
+ idx = -9;
+ printf("\n% 3d % 3d %s", idx, 3, substr("abcde", idx, 3));
+ idx = -8;
+ printf("\n% 3d % 3d %s", idx, 3, substr("abcde", idx, 3));
+ idx = -7;
+ printf("\n% 3d % 3d %s", idx, 3, substr("abcde", idx, 3));
+ idx = -6;
+ printf("\n% 3d % 3d %s", idx, 3, substr("abcde", idx, 3));
+ idx = -5;
+ printf("\n% 3d % 3d %s", idx, 3, substr("abcde", idx, 3));
+ idx = -4;
+ printf("\n% 3d % 3d %s", idx, 3, substr("abcde", idx, 3));
+ idx = -3;
+ printf("\n% 3d % 3d %s", idx, 3, substr("abcde", idx, 3));
+ idx = -2;
+ printf("\n% 3d % 3d %s", idx, 3, substr("abcde", idx, 3));
+ idx = -1;
+ printf("\n% 3d % 3d %s", idx, 3, substr("abcde", idx, 3));
+ exit(0);
+}
diff --git a/test/unittest/funcs/substr/tst.substr-multi-var-idx-neg-too-far.r b/test/unittest/funcs/substr/tst.substr-multi-var-idx-neg-too-far.r
new file mode 100644
index 00000000..e989b7c3
--- /dev/null
+++ b/test/unittest/funcs/substr/tst.substr-multi-var-idx-neg-too-far.r
@@ -0,0 +1,11 @@
+
+-10 3
+ -9 3
+ -8 3
+ -7 3 a
+ -6 3 ab
+ -5 3 abc
+ -4 3 bcd
+ -3 3 cde
+ -2 3 de
+ -1 3 e
diff --git a/test/unittest/funcs/substr/tst.substr-multi-var-idx-pos-no-cnt.d b/test/unittest/funcs/substr/tst.substr-multi-var-idx-pos-no-cnt.d
new file mode 100644
index 00000000..0de17717
--- /dev/null
+++ b/test/unittest/funcs/substr/tst.substr-multi-var-idx-pos-no-cnt.d
@@ -0,0 +1,42 @@
+/*
+ * 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: The substr() subroutine supports positive index values passed by
+ * variable.
+ *
+ * SECTION: Actions and Subroutines/substr()
+ */
+
+#pragma D option quiet
+
+BEGIN
+{
+ idx = 0;
+ printf("\n% 3d %s", idx, substr("abcdefghijklmnop", idx));
+ idx = 1;
+ printf("\n% 3d %s", idx, substr("abcdefghijklmnop", idx));
+ idx = 2;
+ printf("\n% 3d %s", idx, substr("abcdefghijklmnop", idx));
+ idx = 3;
+ printf("\n% 3d %s", idx, substr("abcdefghijklmnop", idx));
+ idx = 4;
+ printf("\n% 3d %s", idx, substr("abcdefghijklmnop", idx));
+ idx = 5;
+ printf("\n% 3d %s", idx, substr("abcdefghijklmnop", idx));
+ idx = 6;
+ printf("\n% 3d %s", idx, substr("abcdefghijklmnop", idx));
+ idx = 7;
+ printf("\n% 3d %s", idx, substr("abcdefghijklmnop", idx));
+ idx = 8;
+ printf("\n% 3d %s", idx, substr("abcdefghijklmnop", idx));
+ idx = 9;
+ printf("\n% 3d %s", idx, substr("abcdefghijklmnop", idx));
+ idx = 10;
+ printf("\n% 3d %s", idx, substr("abcdefghijklmnop", idx));
+ exit(0);
+}
diff --git a/test/unittest/funcs/substr/tst.substr-multi-var-idx-pos-no-cnt.r b/test/unittest/funcs/substr/tst.substr-multi-var-idx-pos-no-cnt.r
new file mode 100644
index 00000000..78f8b580
--- /dev/null
+++ b/test/unittest/funcs/substr/tst.substr-multi-var-idx-pos-no-cnt.r
@@ -0,0 +1,12 @@
+
+ 0 abcdefghijklmnop
+ 1 bcdefghijklmnop
+ 2 cdefghijklmnop
+ 3 defghijklmnop
+ 4 efghijklmnop
+ 5 fghijklmnop
+ 6 ghijklmnop
+ 7 hijklmnop
+ 8 ijklmnop
+ 9 jklmnop
+ 10 klmnop
diff --git a/test/unittest/funcs/substr/tst.substr-stored-len.d b/test/unittest/funcs/substr/tst.substr-stored-len.d
new file mode 100644
index 00000000..97d2b0f6
--- /dev/null
+++ b/test/unittest/funcs/substr/tst.substr-stored-len.d
@@ -0,0 +1,29 @@
+/*
+ * 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: The substr() subroutine stores the correct string length prefix.
+ *
+ * SECTION: Actions and Subroutines/substr()
+ */
+
+#pragma D option quiet
+#pragma D option rawbytes
+#pragma D option strsize=13
+
+BEGIN
+{
+ trace(strjoin((x = substr("abcdef", 2)), (y = substr("ABCDEF", 3))));
+ trace(x);
+ trace(y);
+ exit(0);
+}
+
+ERROR
+{
+ exit(1);
+}
diff --git a/test/unittest/funcs/substr/tst.substr-stored-len.r b/test/unittest/funcs/substr/tst.substr-stored-len.r
new file mode 100644
index 00000000..c29f54ba
--- /dev/null
+++ b/test/unittest/funcs/substr/tst.substr-stored-len.r
@@ -0,0 +1,10 @@
+
+ 0 1 2 3 4 5 6 7 8 9 a b c d e f 0123456789abcdef
+ 0: 00 07 63 64 65 66 44 45 46 00 00 00 00 00 00 00 ..cdefDEF.......
+
+ 0 1 2 3 4 5 6 7 8 9 a b c d e f 0123456789abcdef
+ 0: 00 04 63 64 65 66 00 00 00 00 00 00 00 00 00 00 ..cdef..........
+
+ 0 1 2 3 4 5 6 7 8 9 a b c d e f 0123456789abcdef
+ 0: 00 03 44 45 46 00 00 00 00 00 00 00 00 00 00 00 ..DEF...........
+
diff --git a/test/unittest/funcs/substr/tst.substr-strsize.d b/test/unittest/funcs/substr/tst.substr-strsize.d
new file mode 100644
index 00000000..b4d0cc63
--- /dev/null
+++ b/test/unittest/funcs/substr/tst.substr-strsize.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: The substr() subroutine stores the correct substring when the
+ * count is not specified, or greater or equal to the maximum string
+ * size.
+ *
+ * SECTION: Actions and Subroutines/substr()
+ */
+
+#pragma D option quiet
+#pragma D option rawbytes
+#pragma D option strsize=13
+
+BEGIN
+{
+ x = "1234567890123";
+ trace(x);
+ trace(substr(x, 0));
+ trace(substr(x, 0, 12));
+ trace(substr(x, 0, 13));
+ trace(substr(x, 0, 14));
+ exit(0);
+}
+
+ERROR
+{
+ exit(1);
+}
diff --git a/test/unittest/funcs/substr/tst.substr-strsize.r b/test/unittest/funcs/substr/tst.substr-strsize.r
new file mode 100644
index 00000000..d96d12f6
--- /dev/null
+++ b/test/unittest/funcs/substr/tst.substr-strsize.r
@@ -0,0 +1,16 @@
+
+ 0 1 2 3 4 5 6 7 8 9 a b c d e f 0123456789abcdef
+ 0: 00 0d 31 32 33 34 35 36 37 38 39 30 31 32 33 00 ..1234567890123.
+
+ 0 1 2 3 4 5 6 7 8 9 a b c d e f 0123456789abcdef
+ 0: 00 0d 31 32 33 34 35 36 37 38 39 30 31 32 33 00 ..1234567890123.
+
+ 0 1 2 3 4 5 6 7 8 9 a b c d e f 0123456789abcdef
+ 0: 00 0c 31 32 33 34 35 36 37 38 39 30 31 32 00 00 ..123456789012..
+
+ 0 1 2 3 4 5 6 7 8 9 a b c d e f 0123456789abcdef
+ 0: 00 0d 31 32 33 34 35 36 37 38 39 30 31 32 33 00 ..1234567890123.
+
+ 0 1 2 3 4 5 6 7 8 9 a b c d e f 0123456789abcdef
+ 0: 00 0d 31 32 33 34 35 36 37 38 39 30 31 32 33 00 ..1234567890123.
+
--
2.33.0
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