[PATCH v3 2/6] perf test trace: Remove set -e and print trace test's error messages

[Howard Chu <howardchu95@gmail.com>]

Currently perf test utilizes the set -e option in shell that exit
immediately if a command exits with a non-zero status, this prevents
further error handling and introduces ambiguity. This patch removes set
-e and prints the error message after invoking perf trace during perf
tests.

In my case, the command that exits with a non-zero status is perf
trace instead of grep, because it can't find the 'timer:hrtimer_setup'
tracepoint, see below.

Before:
    $ sudo /tmp/perf test enum -vv
    107: perf trace enum augmentation tests:
    107: perf trace enum augmentation tests                              : Running
    --- start ---
    test child forked, pid 783533
    Checking if vmlinux exists
    Tracing syscall landlock_add_rule
    Tracing non-syscall tracepoint syscall
    ---- end(-1) ----
    107: perf trace enum augmentation tests                              : FAILED!

After:
    $ sudo /tmp/perf test enum -vv
    107: perf trace enum augmentation tests:
    107: perf trace enum augmentation tests                              : Running
    --- start ---
    test child forked, pid 851658
    Checking if vmlinux exists
    Tracing syscall landlock_add_rule
    Tracing non-syscall tracepoint timer:hrtimer_setup,timer:hrtimer_start
    [tracepoint failure] Failed to trace tracepoint timer:hrtimer_setup,timer:hrtimer_start, output:
    event syntax error: 'timer:hrtimer_setup,timer:hrtimer_start'
			 \___ unknown tracepoint

    Error:  File /sys/kernel/tracing//events/timer/hrtimer_setup not found.
    Hint:   Perhaps this kernel misses some CONFIG_ setting to enable this feature?.

    Run 'perf list' for a list of valid events

     Usage: perf trace [<options>] [<command>]
	or: perf trace [<options>] -- <command> [<options>]
	or: perf trace record [<options>] [<command>]
	or: perf trace record [<options>] -- <command> [<options>]

	-e, --event <event>   event/syscall selector. use 'perf list' to list available events---- end(-1) ----
    107: perf trace enum augmentation tests                              : FAILED!

Signed-off-by: Howard Chu <howardchu95@gmail.com>
---
 tools/perf/tests/shell/trace_btf_enum.sh | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/tools/perf/tests/shell/trace_btf_enum.sh b/tools/perf/tests/shell/trace_btf_enum.sh
index b3775209a0b1..f59ba34fac4c 100755
--- a/tools/perf/tests/shell/trace_btf_enum.sh
+++ b/tools/perf/tests/shell/trace_btf_enum.sh
@@ -3,7 +3,6 @@
 # SPDX-License-Identifier: GPL-2.0
 
 err=0
-set -e
 
 syscall="landlock_add_rule"
 non_syscall="timer:hrtimer_setup,timer:hrtimer_start"
@@ -34,22 +33,24 @@ trace_landlock() {
     return
   fi
 
-  if perf trace -e $syscall $TESTPROG 2>&1 | \
-     grep -q -E ".*landlock_add_rule\(ruleset_fd: 11, rule_type: (LANDLOCK_RULE_PATH_BENEATH|LANDLOCK_RULE_NET_PORT), rule_attr: 0x[a-f0-9]+, flags: 45\) = -1.*"
+  output="$(perf trace -e $syscall $TESTPROG 2>&1)"
+  if echo "$output" | grep -q -E ".*landlock_add_rule\(ruleset_fd: 11, rule_type: (LANDLOCK_RULE_PATH_BENEATH|LANDLOCK_RULE_NET_PORT), rule_attr: 0x[a-f0-9]+, flags: 45\) = -1.*"
   then
     err=0
   else
+	printf "[syscall failure] Failed to trace syscall $syscall, output:\n$output\n"
     err=1
   fi
 }
 
 trace_non_syscall() {
-  echo "Tracing non-syscall tracepoint ${non-syscall}"
-  if perf trace -e $non_syscall --max-events=1 2>&1 | \
-     grep -q -E '.*timer:hrtimer_.*\(.*mode: HRTIMER_MODE_.*\)$'
+  echo "Tracing non-syscall tracepoint ${non_syscall}"
+  output="$(perf trace -e $non_syscall --max-events=1 2>&1)"
+  if echo "$output" | grep -q -E '.*timer:hrtimer_.*\(.*mode: HRTIMER_MODE_.*\)$'
   then
     err=0
   else
+	printf "[tracepoint failure] Failed to trace tracepoint $non_syscall, output:\n$output\n"
     err=1
   fi
 }
-- 
2.45.2