[PATCH] selftests/ftrace: Use printf instead of echo in kprobe syntax error tests

[Seth Forshee <seth.forshee@canonical.com>]

Test cases which use echo to write strings containing backslashes
fail with some shells, as echo's treatment of backslashes in
strings varies between shell implementations. Use printf instead,
as it should behave consistently across different shells. This
requires adjustments to the strings to escape \ and % characters.
ftrace_errlog_check() must also re-escape these characters after
processing them to remove ^ characters.

Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
---
 tools/testing/selftests/ftrace/test.d/functions  |  6 +++---
 .../ftrace/test.d/kprobe/kprobe_syntax_errors.tc | 16 ++++++++--------
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/tools/testing/selftests/ftrace/test.d/functions b/tools/testing/selftests/ftrace/test.d/functions
index 5d4550591ff9..b38c6eb029e8 100644
--- a/tools/testing/selftests/ftrace/test.d/functions
+++ b/tools/testing/selftests/ftrace/test.d/functions
@@ -114,11 +114,11 @@ yield() {
 }
 
 ftrace_errlog_check() { # err-prefix command-with-error-pos-by-^ command-file
-    pos=$(echo -n "${2%^*}" | wc -c) # error position
-    command=$(echo "$2" | tr -d ^)
+    pos=$(printf "${2%^*}" | wc -c) # error position
+    command=$(printf "$2" | sed -e 's/\^//g' -e 's/%/%%/g' -e 's/\\/\\\\/g')
     echo "Test command: $command"
     echo > error_log
-    (! echo "$command" >> "$3" ) 2> /dev/null
+    (! printf "$command" >> "$3" ) 2> /dev/null
     grep "$1: error:" -A 3 error_log
     N=$(tail -n 1 error_log | wc -c)
     # "  Command: " and "^\n" => 13
diff --git a/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_syntax_errors.tc b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_syntax_errors.tc
index ef1e9bafb098..adef694eb740 100644
--- a/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_syntax_errors.tc
+++ b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_syntax_errors.tc
@@ -37,7 +37,7 @@ fi
 
 check_error 'p vfs_read ^$none_var'	# BAD_VAR
 
-check_error 'p vfs_read ^%none_reg'	# BAD_REG_NAME
+check_error 'p vfs_read ^%%none_reg'	# BAD_REG_NAME
 check_error 'p vfs_read ^@12345678abcde'	# BAD_MEM_ADDR
 check_error 'p vfs_read ^@+10'		# FILE_ON_KPROBE
 
@@ -80,7 +80,7 @@ check_error 'p vfs_read arg1=^'			# NO_ARG_BODY
 # instruction boundary check is valid on x86 (at this moment)
 case $(uname -m) in
   x86_64|i[3456]86)
-    echo 'p vfs_read' > kprobe_events
+    printf 'p vfs_read' > kprobe_events
     if grep -q FTRACE ../kprobes/list ; then
 	check_error 'p ^vfs_read+3'		# BAD_INSN_BNDRY (only if function-tracer is enabled)
     fi
@@ -89,13 +89,13 @@ esac
 
 # multiprobe errors
 if grep -q "Create/append/" README && grep -q "imm-value" README; then
-echo 'p:kprobes/testevent _do_fork' > kprobe_events
+printf 'p:kprobes/testevent _do_fork' > kprobe_events
 check_error '^r:kprobes/testevent do_exit'	# DIFF_PROBE_TYPE
-echo 'p:kprobes/testevent _do_fork abcd=\1' > kprobe_events
-check_error 'p:kprobes/testevent _do_fork ^bcd=\1'	# DIFF_ARG_TYPE
-check_error 'p:kprobes/testevent _do_fork ^abcd=\1:u8'	# DIFF_ARG_TYPE
-check_error 'p:kprobes/testevent _do_fork ^abcd=\"foo"'	# DIFF_ARG_TYPE
-check_error '^p:kprobes/testevent _do_fork abcd=\1'	# SAME_PROBE
+printf 'p:kprobes/testevent _do_fork abcd=\\1' > kprobe_events
+check_error 'p:kprobes/testevent _do_fork ^bcd=\\1'	# DIFF_ARG_TYPE
+check_error 'p:kprobes/testevent _do_fork ^abcd=\\1:u8'	# DIFF_ARG_TYPE
+check_error 'p:kprobes/testevent _do_fork ^abcd=\\"foo"'# DIFF_ARG_TYPE
+check_error '^p:kprobes/testevent _do_fork abcd=\\1'	# SAME_PROBE
 fi
 
 exit 0
-- 
2.25.0