[DTrace-devel] [PATCH 05/14] Support dirname() for addresses that are not DTrace pointers

[eugene.loh at oracle.com]

From: Eugene Loh <eugene.loh at oracle.com>

Signed-off-by: Eugene Loh <eugene.loh at oracle.com>
---
 bpf/dirname.S                             | 17 ++++++++++------
 test/unittest/funcs/tst.dirname_nonDPTR.d | 24 +++++++++++++++++++++++
 test/unittest/funcs/tst.dirname_nonDPTR.r |  2 ++
 3 files changed, 37 insertions(+), 6 deletions(-)
 create mode 100644 test/unittest/funcs/tst.dirname_nonDPTR.d
 create mode 100644 test/unittest/funcs/tst.dirname_nonDPTR.r

diff --git a/bpf/dirname.S b/bpf/dirname.S
index e5795f06..7ff90b47 100644
--- a/bpf/dirname.S
+++ b/bpf/dirname.S
@@ -21,6 +21,11 @@ dt_dirname :
 	mov	SRC, %r1
 	mov	DST, %r2
 
+	/*
+	 * Copy src to dst for two reasons:
+	 *   - to get the string length
+	 *   - to have a copy that we can access directly
+	 */
 	/* r0 = bpf_probe_read_str(dst, STRSZ + 1, src) */
 	mov	%r1, DST
 	lddw	%r2, STRSZ
@@ -49,8 +54,8 @@ dt_dirname :
 	sub	LEN, 1
 	/* if (len s< 0) goto Lslash */
 	jslt	LEN, 0, .Lslash
-	/* if (src[len] == '/') goto L1 */
-	mov	%r0, SRC
+	/* if (dst[len] == '/') goto L1 */
+	mov	%r0, DST
 	add	%r0, LEN
 	ldxb	%r0, [%r0+0]
 	and	%r0, 0xff
@@ -65,8 +70,8 @@ dt_dirname :
 	sub	LEN, 1
 	/* if (len s< 0) goto Ldot */
 	jslt	LEN, 0, .Ldot
-	/* if (src[len] != '/') goto L2 */
-	mov	%r0, SRC
+	/* if (dst[len] != '/') goto L2 */
+	mov	%r0, DST
 	add	%r0, LEN
 	ldxb	%r0, [%r0+0]
 	and	%r0, 0xff
@@ -81,8 +86,8 @@ dt_dirname :
 	sub	LEN, 1
 	/* if (len s< 0) goto Lslash */
 	jslt	LEN, 0, .Lslash
-	/* if (src[len] == '/') goto L3 */
-	mov	%r0, SRC
+	/* if (dst[len] == '/') goto L3 */
+	mov	%r0, DST
 	add	%r0, LEN
 	ldxb	%r0, [%r0+0]
 	and	%r0, 0xff
diff --git a/test/unittest/funcs/tst.dirname_nonDPTR.d b/test/unittest/funcs/tst.dirname_nonDPTR.d
new file mode 100644
index 00000000..dab80655
--- /dev/null
+++ b/test/unittest/funcs/tst.dirname_nonDPTR.d
@@ -0,0 +1,24 @@
+/*
+ * Oracle Linux DTrace.
+ * Copyright (c) 2022, 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 quiet
+#pragma D option destructive
+
+BEGIN
+{
+	/* "/foo/bar///baz/" */
+	system("printf '\x2f\x66\x6f\x6f\x2f\x62\x61\x72\x2f\x2f\x2f\x62\x61\x7a\x2f' > /dev/null 2>&1");
+}
+
+syscall::write:entry
+/ppid == $pid/
+{
+	printf("|%s|\n", dirname((void *)arg1));
+	exit(0);
+}
+
+ERROR { exit(1); }
diff --git a/test/unittest/funcs/tst.dirname_nonDPTR.r b/test/unittest/funcs/tst.dirname_nonDPTR.r
new file mode 100644
index 00000000..bb8afc9d
--- /dev/null
+++ b/test/unittest/funcs/tst.dirname_nonDPTR.r
@@ -0,0 +1,2 @@
+|/foo/bar|
+
-- 
2.18.4