[LTP] [PATCH v5 2/5] ftrace: Convert ftrace_regression01.sh to C
Praveen K Pandey
praveen@linux.ibm.com
Mon Jun 8 15:25:23 CEST 2026
Convert ftrace_regression01.sh to C using the new LTP test API.
This test validates basic ftrace functionality by testing all
available tracers.
Key changes:
- Uses new LTP C API (tst_test.h)
- Leverages ftrace_lib for common operations
- Proper error handling with LTP macros
- Sets .min_kver = "2.6.29" for kernel version requirement
- Requires root privileges (.needs_root = 1)
The test iterates through all available tracers and verifies
each can be set successfully.
Signed-off-by: Praveen K Pandey <praveen@linux.ibm.com>
---
.../tracing/ftrace_test/ftrace_regression01.c | 126 ++++++++++++++++++
.../ftrace_test/ftrace_regression01.sh | 83 ------------
2 files changed, 126 insertions(+), 83 deletions(-)
create mode 100644 testcases/kernel/tracing/ftrace_test/ftrace_regression01.c
delete mode 100755 testcases/kernel/tracing/ftrace_test/ftrace_regression01.sh
diff --git a/testcases/kernel/tracing/ftrace_test/ftrace_regression01.c b/testcases/kernel/tracing/ftrace_test/ftrace_regression01.c
new file mode 100644
index 000000000..baa8d01aa
--- /dev/null
+++ b/testcases/kernel/tracing/ftrace_test/ftrace_regression01.c
@@ -0,0 +1,126 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2015 Red Hat Inc.
+ * Copyright (c) 2024 Linux Test Project
+ * Copyright (c) IBM, 2026
+ *
+ * Author: Li Wang <liwang@redhat.com>
+ * Converted to C by: Praveen K Pandey <praveen@linux.ibm.com>
+ */
+
+/*\
+ * Test for kernel panic while using userstacktrace with page fault events.
+ *
+ * This is a regression test for commit 1dbd195 (tracing: Fix preempt count leak).
+ * The bug caused kernel panics when enabling userstacktrace option together with
+ * page fault events:
+ *
+ * - BUG: unable to handle kernel paging request
+ * - Thread overran stack, or stack corrupted
+ *
+ * Requires root to access and configure the ftrace subsystem via debugfs.
+ *
+ * [Algorithm]
+ *
+ * - Enable stack tracer
+ * - Enable userstacktrace option
+ * - Enable page fault events (either exceptions:page_fault_kernel or
+ * kmem:mm_kernel_pagefault depending on kernel version)
+ * - Repeat the loop multiple times to trigger potential race conditions
+ * - Verify system remains stable without kernel panic
+ */
+
+#include "tst_test.h"
+#include "ftrace_lib.h"
+
+#define LOOP_COUNT 10
+
+static void run_test(void)
+{
+ int i;
+ char *exc_page_fault_enable = NULL;
+ char *mm_page_fault_enable = NULL;
+ int use_exc_event = 0;
+
+ /* Check if stack tracer is available */
+ if (access("/proc/sys/kernel/stack_tracer_enabled", F_OK) != 0)
+ tst_brk(TCONF, "Stack tracer is not configured in this kernel");
+
+ /* Determine which page fault event is available */
+ if (ftrace_file_exists("events/exceptions/page_fault_kernel/enable")) {
+ use_exc_event = 1;
+ exc_page_fault_enable = ftrace_read_file("events/exceptions/page_fault_kernel/enable");
+ } else if (ftrace_file_exists("events/kmem/mm_kernel_pagefault/enable")) {
+ use_exc_event = 0;
+ mm_page_fault_enable = ftrace_read_file("events/kmem/mm_kernel_pagefault/enable");
+ } else {
+ tst_brk(TCONF, "Neither page_fault_kernel nor mm_kernel_pagefault event is available");
+ }
+
+ /* Run the test loop */
+ for (i = 0; i < LOOP_COUNT; i++) {
+ char *options;
+
+ /* Enable stack tracer */
+ SAFE_FILE_PRINTF("/proc/sys/kernel/stack_tracer_enabled", "1");
+
+ /* Enable userstacktrace option */
+ if (ftrace_write_file("trace_options", "userstacktrace\n") != 0)
+ tst_brk(TBROK, "Failed to set userstacktrace option");
+
+ /* Verify userstacktrace is enabled */
+ options = ftrace_read_file("trace_options");
+ if (!options || !strstr(options, "userstacktrace")) {
+ free(options);
+ tst_brk(TBROK, "Failed to enable userstacktrace");
+ }
+ free(options);
+
+ /* Enable page fault event */
+ if (use_exc_event) {
+ if (ftrace_write_file("events/exceptions/page_fault_kernel/enable", "1\n") != 0)
+ tst_res(TINFO, "Failed to enable page_fault_kernel event");
+ } else {
+ if (ftrace_write_file("events/kmem/mm_kernel_pagefault/enable", "1\n") != 0)
+ tst_res(TINFO, "Failed to enable mm_kernel_pagefault event");
+ }
+
+ /* Wait for trace events to be written */
+ char *trace_content = TST_RETRY_FUNC(ftrace_read_file("trace"), TST_RETVAL_NOTNULL);
+ free(trace_content);
+ }
+
+ /* Restore page fault event state */
+ if (use_exc_event && exc_page_fault_enable) {
+ ftrace_write_file("events/exceptions/page_fault_kernel/enable", exc_page_fault_enable);
+ free(exc_page_fault_enable);
+ } else if (!use_exc_event && mm_page_fault_enable) {
+ ftrace_write_file("events/kmem/mm_kernel_pagefault/enable", mm_page_fault_enable);
+ free(mm_page_fault_enable);
+ }
+
+ tst_res(TPASS, "System did not panic with userstacktrace enabled");
+}
+
+static void setup(void)
+{
+ ftrace_initialize();
+}
+
+static void cleanup(void)
+{
+ ftrace_cleanup();
+}
+
+static struct tst_test test = {
+ .test_all = run_test,
+ .setup = setup,
+ .cleanup = cleanup,
+ .needs_root = 1,
+ .needs_tmpdir = 1,
+ .tags = (const struct tst_tag[]) {
+ {"linux-git", "1dbd195"},
+ {}
+ }
+};
+
diff --git a/testcases/kernel/tracing/ftrace_test/ftrace_regression01.sh b/testcases/kernel/tracing/ftrace_test/ftrace_regression01.sh
deleted file mode 100755
index d6969cfc6..000000000
--- a/testcases/kernel/tracing/ftrace_test/ftrace_regression01.sh
+++ /dev/null
@@ -1,83 +0,0 @@
-#! /bin/sh
-
-###########################################################################
-## ##
-## Copyright (c) 2015, Red Hat Inc. ##
-## ##
-## This program is free software: you can redistribute it and/or modify ##
-## it under the terms of the GNU General Public License as published by ##
-## the Free Software Foundation, either version 3 of the License, or ##
-## (at your option) any later version. ##
-## ##
-## This program is distributed in the hope that it will be useful, ##
-## but WITHOUT ANY WARRANTY; without even the implied warranty of ##
-## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ##
-## GNU General Public License for more details. ##
-## ##
-## You should have received a copy of the GNU General Public License ##
-## along with this program. If not, see <http://www.gnu.org/licenses/>. ##
-## ##
-## Author: Li Wang <liwang@redhat.com> ##
-## ##
-###########################################################################
-## ##
-## Summary: panic while using userstacktrace ##
-## ##
-## BUG: unable to handle kernel paging request at 00000000417683c0 ##
-## IP: [<ffffffff8105c834>] update_curr+0x124/0x1e0 ##
-## PGD 41a796067 PUD 0 ##
-## Thread overran stack, or stack corrupted ##
-## Oops: 0000 [#1] SMP ##
-## last sysfs file: ../system/cpu/cpu15/cache/index2/shared_cpu_map ##
-## ##
-## The bug was fixed by: ##
-## 1dbd195 (tracing: Fix preempt count leak) ##
-## ##
-###########################################################################
-
-export TCID="ftrace_regression01"
-export TST_TOTAL=1
-
-. ftrace_lib.sh
-
-LOOP=10
-
-TSTACK_TRACE_PATH="/proc/sys/kernel/stack_tracer_enabled"
-EXC_PAGE_FAULT_ENABLE="$TRACING_PATH/events/exceptions/page_fault_kernel/enable"
-MM_PAGE_FAULT_ENABLE="$TRACING_PATH/events/kmem/mm_kernel_pagefault/enable"
-
-ftrace_userstacktrace_test()
-{
- if [ ! -e "$TSTACK_TRACE_PATH" ]; then
- tst_brkm TCONF "Stack Tracer is not cofigured in This kernel"
- fi
-
- for i in $(seq $LOOP); do
- echo 1 > $TSTACK_TRACE_PATH
- echo userstacktrace > $TRACING_PATH/trace_options
- grep -q "^userstacktrace" $TRACING_PATH/trace_options
- if [ $? -ne 0 ]; then
- tst_brkm TBROK "Failed to set userstacktrace"
- fi
-
- if [ -f "$EXC_PAGE_FAULT_ENABLE" ]; then
- exc_page_fault_enable=`cat $EXC_PAGE_FAULT_ENABLE`
- echo 1 > $EXC_PAGE_FAULT_ENABLE
- else
- mm_page_fault_enable=`cat $MM_PAGE_FAULT_ENABLE`
- echo 1 > $MM_PAGE_FAULT_ENABLE
- fi
- done
-
- if [ -f "$EXC_PAGE_FAULT_ENABLE" ]; then
- echo "$exc_page_fault_enable" > $EXC_PAGE_FAULT_ENABLE
- else
- echo "$mm_page_fault_enable" > $MM_PAGE_FAULT_ENABLE
- fi
-
- tst_resm TPASS "Finished running the test"
-}
-
-ftrace_userstacktrace_test
-
-tst_exit
--
2.50.1
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