[RFC PATCH v2 10/14] selftests/kcov_dataflow: add eight_args_c test module

[Yunseong Kim <yunseong.kim@est.tech>]

C module exercising 1-8 argument functions plus struct pointer.
Verifies register-passed (1-6) and stack-passed (7-8) arguments.

Test:

  make LLVM=1 CC=clang \
    M=tools/testing/selftests/kcov_dataflow/eight_args_c modules
  vng --user root --exec \
    "python3 tools/testing/selftests/kcov_dataflow/trigger-view.py \
      eight_args_c -C 8 --ko \
      tools/testing/selftests/kcov_dataflow/eight_args_c/eight_args_c.ko"

Result:

  # Loaded eight_args_c
  # Captured 6195 words
  # 578 records
  # showing 65 records with context=8 around eight_args_c

  vfs_write(0x0)
  0x0 = full_proxy_write()
  full_proxy_write(0x0, 0x1, 0x0)
  0x8200080 = __debugfs_file_get()
  __debugfs_file_get(0x0)
  0x0 = __debugfs_file_get()
  0x0 = trigger_write [eight_args_c]()
  trigger_write [eight_args_c](0x0, 0x1, 0x0)
    df_func2 [eight_args_c](0x11, 0x22)
    0x33 = df_func2 [eight_args_c]()
    df_func3 [eight_args_c](0x11, 0x22, 0x33)
    0x66 = df_func3 [eight_args_c]()
    df_func4 [eight_args_c](0x11, 0x22, 0x33, 0x44)
    0xaa = df_func4 [eight_args_c]()
    df_func5 [eight_args_c](0x11, 0x22, 0x33, 0x44, 0x55)
    0xff = df_func5 [eight_args_c]()
    df_func6 [eight_args_c](0x11, 0x22, 0x33, 0x44, 0x55, 0x66)
    0x165 = df_func6 [eight_args_c]()
    df_func7 [eight_args_c](0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77)
    0x1dc = df_func7 [eight_args_c]()
    df_func8 [eight_args_c](0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88)
    0x264 = df_func8 [eight_args_c]()
    df_func_struct [eight_args_c](0xaaaa)
    0x16665 = df_func_struct [eight_args_c]()
  0x1 = trigger_write [eight_args_c]()
  0x1 = full_proxy_write()
  0x1 = vfs_write()
  0x1 = ksys_write()
  0x1 = __x64_sys_write()
  0x0 = fpregs_assert_state_consistent()
  0xba5748 = __x64_sys_close()
  file_close_fd(0x4)
  0x0 = file_close_fd()

Cc: Alexander Potapenko <glider@google.com>
Assisted-by: Claude:claude-opus-4-6 [kiro-chat]
Link: https://github.com/yskzalloc/kcov-dataflow/actions
Signed-off-by: Yunseong Kim <yunseong.kim@est.tech>
---
 tools/testing/selftests/kcov_dataflow/Makefile     |  1 +
 tools/testing/selftests/kcov_dataflow/README.rst   |  6 ++
 .../selftests/kcov_dataflow/eight_args_c/Makefile  |  3 +
 .../kcov_dataflow/eight_args_c/eight_args_c.c      | 95 ++++++++++++++++++++++
 .../selftests/kcov_dataflow/run_eight_args_c.sh    | 35 ++++++++
 5 files changed, 140 insertions(+)

diff --git a/tools/testing/selftests/kcov_dataflow/Makefile b/tools/testing/selftests/kcov_dataflow/Makefile
index b9fc1c5f0104..3a42c54e954d 100644
--- a/tools/testing/selftests/kcov_dataflow/Makefile
+++ b/tools/testing/selftests/kcov_dataflow/Makefile
@@ -1,3 +1,4 @@
 # SPDX-License-Identifier: GPL-2.0
 TEST_GEN_PROGS := user_ioctl/user_ioctl
+TEST_PROGS := run_eight_args_c.sh
 include ../lib.mk
diff --git a/tools/testing/selftests/kcov_dataflow/README.rst b/tools/testing/selftests/kcov_dataflow/README.rst
index 8b650a62acb1..e93b4e573504 100644
--- a/tools/testing/selftests/kcov_dataflow/README.rst
+++ b/tools/testing/selftests/kcov_dataflow/README.rst
@@ -35,3 +35,9 @@ trigger-view.py
 
         python3 trigger-view.py <module_name>
         python3 trigger-view.py <module_name> --raw
+
+eight_args_c/
+    C module with 1-8 argument functions + struct pointer::
+
+        make LLVM=1 CC=clang M=tools/testing/selftests/kcov_dataflow/eight_args_c modules
+        python3 trigger-view.py eight_args_c
diff --git a/tools/testing/selftests/kcov_dataflow/eight_args_c/Makefile b/tools/testing/selftests/kcov_dataflow/eight_args_c/Makefile
new file mode 100644
index 000000000000..aad45c7e3863
--- /dev/null
+++ b/tools/testing/selftests/kcov_dataflow/eight_args_c/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-m := eight_args_c.o
+KCOV_DATAFLOW_eight_args_c.o := y
diff --git a/tools/testing/selftests/kcov_dataflow/eight_args_c/eight_args_c.c b/tools/testing/selftests/kcov_dataflow/eight_args_c/eight_args_c.c
new file mode 100644
index 000000000000..09fbbbf8d14b
--- /dev/null
+++ b/tools/testing/selftests/kcov_dataflow/eight_args_c/eight_args_c.c
@@ -0,0 +1,95 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * eight_args_c.c - Verify kcov_dataflow captures 1-8 argument functions.
+ *
+ * Write to /sys/kernel/debug/kcov_dataflow_test/trigger to invoke all
+ * eight functions and a struct-pointer function. Use with the
+ * kcov_dataflow selftest to verify correct capture of register-passed
+ * (1-6) and stack-passed (7-8) arguments on x86_64.
+ */
+#include <linux/module.h>
+#include <linux/debugfs.h>
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("KCOV dataflow 8-argument stress test");
+
+struct pair {
+	u32 x;
+	u32 y;
+};
+
+/* Prototypes */
+u64 df_func1(u64 a1);
+u64 df_func2(u64 a1, u64 a2);
+u64 df_func3(u64 a1, u64 a2, u64 a3);
+u64 df_func4(u64 a1, u64 a2, u64 a3, u64 a4);
+u64 df_func5(u64 a1, u64 a2, u64 a3, u64 a4, u64 a5);
+u64 df_func6(u64 a1, u64 a2, u64 a3, u64 a4, u64 a5, u64 a6);
+u64 df_func7(u64 a1, u64 a2, u64 a3, u64 a4, u64 a5, u64 a6, u64 a7);
+u64 df_func8(u64 a1, u64 a2, u64 a3, u64 a4, u64 a5, u64 a6, u64 a7,
+	     u64 a8);
+u64 df_func_struct(struct pair *p);
+
+/* Implementations - noinline ensures trace callbacks are emitted */
+#define DEF_FUNC(name, ret_expr, ...)				\
+noinline u64 name(__VA_ARGS__) { return (ret_expr); }		\
+EXPORT_SYMBOL(name)
+
+DEF_FUNC(df_func1, a1, u64 a1);
+DEF_FUNC(df_func2, a1 + a2, u64 a1, u64 a2);
+DEF_FUNC(df_func3, a1 + a2 + a3, u64 a1, u64 a2, u64 a3);
+DEF_FUNC(df_func4, a1 + a2 + a3 + a4, u64 a1, u64 a2, u64 a3, u64 a4);
+DEF_FUNC(df_func5, a1 + a2 + a3 + a4 + a5,
+	 u64 a1, u64 a2, u64 a3, u64 a4, u64 a5);
+DEF_FUNC(df_func6, a1 + a2 + a3 + a4 + a5 + a6,
+	 u64 a1, u64 a2, u64 a3, u64 a4, u64 a5, u64 a6);
+DEF_FUNC(df_func7, a1 + a2 + a3 + a4 + a5 + a6 + a7,
+	 u64 a1, u64 a2, u64 a3, u64 a4, u64 a5, u64 a6, u64 a7);
+DEF_FUNC(df_func8, a1 + a2 + a3 + a4 + a5 + a6 + a7 + a8,
+	 u64 a1, u64 a2, u64 a3, u64 a4, u64 a5, u64 a6, u64 a7, u64 a8);
+
+noinline u64 df_func_struct(struct pair *p)
+{
+	return (u64)p->x + (u64)p->y;
+}
+EXPORT_SYMBOL(df_func_struct);
+
+static struct dentry *test_dir;
+
+static ssize_t trigger_write(struct file *f, const char __user *buf,
+			     size_t count, loff_t *ppos)
+{
+	struct pair p = { .x = 0xAAAA, .y = 0xBBBB };
+	volatile u64 sum = 0;
+
+	sum += df_func1(0x11);
+	sum += df_func2(0x11, 0x22);
+	sum += df_func3(0x11, 0x22, 0x33);
+	sum += df_func4(0x11, 0x22, 0x33, 0x44);
+	sum += df_func5(0x11, 0x22, 0x33, 0x44, 0x55);
+	sum += df_func6(0x11, 0x22, 0x33, 0x44, 0x55, 0x66);
+	sum += df_func7(0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77);
+	sum += df_func8(0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88);
+	sum += df_func_struct(&p);
+
+	return count;
+}
+
+static const struct file_operations trigger_fops = {
+	.write = trigger_write,
+};
+
+static int __init eight_args_init(void)
+{
+	test_dir = debugfs_create_dir("kcov_dataflow_test", NULL);
+	debugfs_create_file("trigger", 0200, test_dir, NULL, &trigger_fops);
+	return 0;
+}
+
+static void __exit eight_args_exit(void)
+{
+	debugfs_remove_recursive(test_dir);
+}
+
+module_init(eight_args_init);
+module_exit(eight_args_exit);
diff --git a/tools/testing/selftests/kcov_dataflow/run_eight_args_c.sh b/tools/testing/selftests/kcov_dataflow/run_eight_args_c.sh
new file mode 100755
index 000000000000..d24092e920ff
--- /dev/null
+++ b/tools/testing/selftests/kcov_dataflow/run_eight_args_c.sh
@@ -0,0 +1,35 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Test eight_args_c module capture via kcov_dataflow
+DIR="$(dirname "$0")"
+KO="$DIR/eight_args_c/eight_args_c.ko"
+
+if [ ! -f "$KO" ]; then
+	echo "SKIP: $KO not found"
+	echo "Build: make LLVM=1 CC=clang M=...eight_args_c modules"
+	exit 4  # kselftest SKIP
+fi
+
+if [ ! -e /sys/kernel/debug/kcov_dataflow ]; then
+	echo "SKIP: kcov_dataflow not available"
+	exit 4
+fi
+
+OUTPUT=$(python3 "$DIR/trigger-view.py" eight_args_c --ko "$KO" --raw 2>&1)
+RC=$?
+
+if [ $RC -ne 0 ]; then
+	echo "FAIL: trigger-and-view exited with $RC"
+	echo "$OUTPUT"
+	exit 1
+fi
+
+RECORDS=$(echo "$OUTPUT" | grep -c "^\[ENTRY\]\|^\[RET")
+if [ "$RECORDS" -gt 0 ]; then
+	echo "PASS: captured $RECORDS records from eight_args_c"
+	exit 0
+else
+	echo "FAIL: no records captured"
+	echo "$OUTPUT"
+	exit 1
+fi

-- 
2.43.0