[PATCH v2 9/9] selftests/ftrace: Add event filter syntax check test case

["Masami Hiramatsu (Google)" <mhiramat@kernel.org>]

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Add a new ftracetest test case (filter-syntax-check.tc) to verify valid
event filter expressions, error_log caret reporting for malformed filter
expressions (empty filters, missing fields, unbalanced parentheses and
quotes, dangling logical operators, invalid fields/values/cpulists),
newline truncation on multi-line filter input, and error returns on
invalid subsystem filters.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
 .../ftrace/test.d/filter/filter-syntax-check.tc    |   52 ++++++++++++++++++++
 1 file changed, 52 insertions(+)
 create mode 100644 tools/testing/selftests/ftrace/test.d/filter/filter-syntax-check.tc

diff --git a/tools/testing/selftests/ftrace/test.d/filter/filter-syntax-check.tc b/tools/testing/selftests/ftrace/test.d/filter/filter-syntax-check.tc
new file mode 100644
index 000000000000..68c8accc5ffd
--- /dev/null
+++ b/tools/testing/selftests/ftrace/test.d/filter/filter-syntax-check.tc
@@ -0,0 +1,52 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: event filter - test filter syntax error check
+# requires: set_event events/sched/sched_switch/filter error_log
+# flags: instance
+
+check_error() { # command-with-error-pos-by-^
+    ftrace_errlog_check 'event filter parse error' "$1" 'events/sched/sched_switch/filter'
+}
+
+# Valid filter expressions
+echo '(common_pid == 0)' > events/sched/sched_switch/filter
+echo '((common_pid == 0) && (prev_pid == 0))' > events/sched/sched_switch/filter
+echo 'prev_comm ~ "*sh"' > events/sched/sched_switch/filter
+echo 'common_pid == CPUS{0}' > events/sched/sched_switch/filter
+echo 'common_pid != CPUS{0}' > events/sched/sched_switch/filter
+echo 0 > events/sched/sched_switch/filter
+
+# Empty or meaningless filter expressions
+check_error '^()'						# NO_FILTER
+check_error '=^= 1'						# INVALID_FILTER
+
+# Unbalanced parentheses and quotes
+check_error '^(common_pid == 1'					# TOO_MANY_OPEN
+check_error 'common_pid == 1^)'					# TOO_MANY_CLOSE
+check_error 'prev_comm == ^"bash'				# MISSING_QUOTE
+
+# Dangling logical operators
+check_error 'common_pid == 1 &&^'				# TOO_MANY_PREDS
+check_error 'common_pid == 1 ||^'				# TOO_MANY_PREDS
+check_error 'common_pid == 1 || (common_pid == 2 && )^'		# INVALID_FILTER
+
+# Invalid field, operator, or operand value
+check_error 'no_such_field ^== 1'				# FIELD_NOT_FOUND
+check_error 'common_pid == @^'					# INVALID_VALUE
+check_error 'common_pid == CPUS0}^'				# MISSING_BRACE_OPEN
+check_error 'common_pid == CPUS{}^'				# INVALID_CPULIST
+
+# Multi-line input must be truncated at the first newline
+echo > error_log
+! ( printf "common_pid == CPUS{0\n\"} && common_pid == 0 && common_pid == CPUS{0\n\"}" | \
+    dd of=events/sched/sched_switch/filter bs=4096 ) 2> /dev/null
+grep -q "Missing '}'" error_log
+! grep -q "Missing matching quote" error_log
+
+# Subsystem filter must fail on invalid filter expressions
+echo 'common_pid >= 0' > events/sched/filter
+! echo 'no_such_field == 1' > events/sched/filter
+! echo 'common_pid == 1 &&' > events/sched/filter
+echo 0 > events/sched/filter
+
+exit 0