Merge tag 'linux_kselftest-fixes-6.15-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest

Pull kselftest fix from Shuah Khan:
 "Fixes dynevent_limitations.tc test failure on dash by detecting and
  handling bash and dash differences in evaluating \\"

* tag 'linux_kselftest-fixes-6.15-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest:
  selftests/ftrace: Differentiate bash and dash in dynevent_limitations.tc

Author: torvalds

tools/testing/selftests/ftrace/test.d/dynevent/dynevent_limitations.tc

@@ -7,11 +7,32 @@
 MAX_ARGS=128
 EXCEED_ARGS=$((MAX_ARGS + 1))
 
+# bash and dash evaluate variables differently.
+# dash will evaluate '\\' every time it is read whereas bash does not.
+#
+#   TEST_STRING="$TEST_STRING \\$i"
+#   echo $TEST_STRING
+#
+# With i=123
+# On bash, that will print "\123"
+# but on dash, that will print the escape sequence of \123 as the \ will
+# be interpreted again in the echo.
+#
+# Set a variable "bs" to save a double backslash, then echo that
+# to "ts" to see if $ts changed or not. If it changed, it's dash,
+# if not, it's bash, and then bs can equal a single backslash.
+bs='\\'
+ts=`echo $bs`
+if [ "$ts" = '\\' ]; then
+  # this is bash
+  bs='\'
+fi
+
 check_max_args() { # event_header
   TEST_STRING=$1
   # Acceptable
   for i in `seq 1 $MAX_ARGS`; do
-    TEST_STRING="$TEST_STRING \\$i"
+    TEST_STRING="$TEST_STRING $bs$i"
   done
   echo "$TEST_STRING" >> dynamic_events
   echo > dynamic_events