[PATCH] Fix proc:::exec args[0]

[eugene.loh@oracle.com]

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

Reported-by: Kris Van Hees <kris.van.hees@oracle.com>
Signed-off-by: Eugene Loh <eugene.loh@oracle.com>
---
 libdtrace/dt_prov_proc.c                | 12 ++++++
 test/unittest/proc/tst.exec-execve.r    |  4 ++
 test/unittest/proc/tst.exec-execve.sh   | 52 ++++++++++++++++++++++++
 test/unittest/proc/tst.exec-execveat.r  |  4 ++
 test/unittest/proc/tst.exec-execveat.sh | 54 +++++++++++++++++++++++++
 5 files changed, 126 insertions(+)
 create mode 100644 test/unittest/proc/tst.exec-execve.r
 create mode 100755 test/unittest/proc/tst.exec-execve.sh
 create mode 100644 test/unittest/proc/tst.exec-execveat.r
 create mode 100755 test/unittest/proc/tst.exec-execveat.sh

diff --git a/libdtrace/dt_prov_proc.c b/libdtrace/dt_prov_proc.c
index 05ad66346..f7e46a5af 100644
--- a/libdtrace/dt_prov_proc.c
+++ b/libdtrace/dt_prov_proc.c
@@ -118,6 +118,18 @@ static int trampoline(dt_pcb_t *pcb, uint_t exitlbl)
 		emit(dlp, BPF_LOAD(BPF_DW, BPF_REG_0, BPF_REG_7, DMST_ARG(1)));
 		emit(dlp, BPF_BRANCH_IMM(BPF_JEQ, BPF_REG_0, 0, exitlbl));
 		emit(dlp, BPF_STORE(BPF_DW, BPF_REG_7, DMST_ARG(0), BPF_REG_0));
+	} else if (strcmp(prp->desc->prb, "exec") == 0) {
+		dt_probe_t	*uprp = pcb->pcb_parent_probe;
+
+		/*
+		 * If the underlying probe is syscall:vmlinux:execve:entry,
+		 * then the arg0 is already right.  If it is execveat, we have
+		 * to copy arg1 to arg0.
+		 */
+		if (strcmp(uprp->desc->fun, "execveat") == 0) {
+			emit(dlp, BPF_LOAD(BPF_DW, BPF_REG_0, BPF_REG_7, DMST_ARG(1)));
+			emit(dlp, BPF_STORE(BPF_DW, BPF_REG_7, DMST_ARG(0), BPF_REG_0));
+		}
 	} else if (strcmp(prp->desc->prb, "exit") == 0) {
 		ctf_file_t	*cfp = dtp->dt_shared_ctf;
 		ctf_id_t	type;
diff --git a/test/unittest/proc/tst.exec-execve.r b/test/unittest/proc/tst.exec-execve.r
new file mode 100644
index 000000000..09791d5b0
--- /dev/null
+++ b/test/unittest/proc/tst.exec-execve.r
@@ -0,0 +1,4 @@
+execve      bogus_direc/bogus_exec
+proc:::exec bogus_direc/bogus_exec
+exec
+
diff --git a/test/unittest/proc/tst.exec-execve.sh b/test/unittest/proc/tst.exec-execve.sh
new file mode 100755
index 000000000..d3f84e0d2
--- /dev/null
+++ b/test/unittest/proc/tst.exec-execve.sh
@@ -0,0 +1,52 @@
+#!/bin/bash
+#
+# Oracle Linux DTrace.
+# Copyright (c) 2025, 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.
+#
+# This script tests that the proc:::exec probe fires for execve() and
+# produces the correct probe arg.
+
+dtrace=$1
+
+DIRNAME="$tmpdir/exec-execve.$$.$RANDOM"
+mkdir -p $DIRNAME
+cd $DIRNAME
+
+cat << EOF > parent.c
+#include <stdio.h>
+#include <unistd.h>
+
+int main(int c, char **v) {
+  char *argv[] = { "bogus_exec", NULL };
+  char *envp[] = { NULL };
+  int rc;
+
+  printf("exec\n");
+  rc = execve("bogus_direc/bogus_exec", argv, envp);
+
+  return 0;
+}
+EOF
+
+${CC} -o parent.x parent.c
+
+$dtrace $dt_flags -qn '
+BEGIN { dtpid = pid; }
+proc:::exec
+/ppid == dtpid && execname == "parent.x"/
+{
+    printf("proc:::exec %s\n", args[0]);
+}
+syscall::execve:entry
+/ppid == dtpid && execname == "parent.x"/
+{
+    printf("execve      %s\n", stringof(arg0));
+}' -c ./parent.x
+if [ $? -ne 0 ]; then
+    echo ERROR
+    exit 1
+fi
+
+exit 0
diff --git a/test/unittest/proc/tst.exec-execveat.r b/test/unittest/proc/tst.exec-execveat.r
new file mode 100644
index 000000000..696300e0e
--- /dev/null
+++ b/test/unittest/proc/tst.exec-execveat.r
@@ -0,0 +1,4 @@
+execveat    bogus_direc/bogus_exec
+proc:::exec bogus_direc/bogus_exec
+exec
+
diff --git a/test/unittest/proc/tst.exec-execveat.sh b/test/unittest/proc/tst.exec-execveat.sh
new file mode 100755
index 000000000..db68a5043
--- /dev/null
+++ b/test/unittest/proc/tst.exec-execveat.sh
@@ -0,0 +1,54 @@
+#!/bin/bash
+#
+# Oracle Linux DTrace.
+# Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
+# Licensed under the Universal Permissive License v 1.0 as shown at
+# http://oss.oracle.com/licenses/upl.
+#
+# This script tests that the proc:::exec probe fires for execveat() and
+# produces the correct probe arg.
+
+dtrace=$1
+
+DIRNAME="$tmpdir/exec-execveat.$$.$RANDOM"
+mkdir -p $DIRNAME
+cd $DIRNAME
+
+cat << EOF > parent.c
+#include <stdio.h>
+#include <linux/fcntl.h>      /* Definition of AT_* constants */
+#define __USE_GNU             /* so unistd.h will find execveat */
+#include <unistd.h>
+
+int main(int c, char **v) {
+  char *argv[] = { "bogus_exec", NULL };
+  char *envp[] = { NULL };
+  int rc;
+
+  printf("exec\n");
+  rc = execveat(AT_FDCWD, "bogus_direc/bogus_exec", argv, envp, 0);
+
+  return 0;
+}
+EOF
+
+${CC} -o parent.x parent.c
+
+$dtrace $dt_flags -qn '
+BEGIN { dtpid = pid; }
+proc:::exec
+/ppid == dtpid && execname == "parent.x"/
+{
+    printf("proc:::exec %s\n", args[0]);
+}
+syscall::execveat:entry
+/ppid == dtpid && execname == "parent.x"/
+{
+    printf("execveat    %s\n", stringof(arg1));
+}' -c ./parent.x
+if [ $? -ne 0 ]; then
+    echo ERROR
+    exit 1
+fi
+
+exit 0
-- 
2.47.3