Re: [PATCH 00/15] selftests/seccomp: Refactor change_syscall()

From: Michael Ellerman <mpe@ellerman.id.au>
To: Kees Cook <keescook@chromium.org>
Cc: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>,
	Will Drewry <wad@chromium.org>,
	linux-xtensa@linux-xtensa.org, linux-kernel@vger.kernel.org,
	Andy Lutomirski <luto@amacapital.net>,
	Max Filippov <jcmvbkbc@gmail.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-kselftest@vger.kernel.org, linux-mips@vger.kernel.org,
	linuxppc-dev@lists.ozlabs.org,
	Christian Brauner <christian@brauner.io>
Subject: Re: [PATCH 00/15] selftests/seccomp: Refactor change_syscall()
Date: Tue, 15 Sep 2020 22:52:21 +1000	[thread overview]
Message-ID: <87een3p5h6.fsf@mpe.ellerman.id.au> (raw)
In-Reply-To: <202009141321.366935EF52@keescook>

Kees Cook <keescook@chromium.org> writes:
> On Mon, Sep 14, 2020 at 10:15:18PM +1000, Michael Ellerman wrote:
>> Kees Cook <keescook@chromium.org> writes:
>> > Hi,
>> >
>> > This refactors the seccomp selftest macros used in change_syscall(),
>> > in an effort to remove special cases for mips, arm, arm64, and xtensa,
>> > which paves the way for powerpc fixes.
>> >
>> > I'm not entirely done testing, but all-arch build tests and x86_64
>> > selftests pass. I'll be doing arm, arm64, and i386 selftests shortly,
>> > but I currently don't have an easy way to check xtensa, mips, nor
>> > powerpc. Any help there would be appreciated!
>> 
>> The series builds fine for me, and all the tests pass (see below).
>> 
>> Thanks for picking up those changes to deal with powerpc being oddball.
>> 
>> Tested-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
>
> Awesome; thanks!
>
> However...
>
>> ./seccomp_bpf
>> TAP version 13
>> 1..86
>> # Starting 86 tests from 7 test cases.
>> #  RUN           global.kcmp ...
>> #            OK  global.kcmp
>> ok 1 global.kcmp
>> [...]
>> #  RUN           global.KILL_thread ...
>> TAP version 13
>> 1..86
>> # Starting 86 tests from 7 test cases.
>
> Was this a mis-paste, or has something very very bad happened here in
> global.KILL_one_arg_six finishes?
>
...
>> TAP version 13
>> 1..86
>> # Starting 86 tests from 7 test cases.
>> [...]
>> # PASSED: 86 / 86 tests passed.
>> # Totals: pass:86 fail:0 xfail:0 xpass:0 skip:0 error:0
>
> And after every user_notification test? O_O

Haha, I thought that was normal :)

It's because of redirection, I run the tests with:

  find . -executable -type f -print -execdir '{}' ';' | tee test.log

If I just run it directly on the terminal everything is normal.

It'll be fork() vs libc buffering.

I can fix it with:

$ stdbuf -oL ./seccomp_bpf | tee test.log

Or the patch below.

I can send a proper patch for that tomorrow, I don't know that harness
code, but I think that's the right fix.

cheers

diff --git a/tools/testing/selftests/kselftest_harness.h b/tools/testing/selftests/kselftest_harness.h
index 4f78e4805633..b1bd00ff3d94 100644
--- a/tools/testing/selftests/kselftest_harness.h
+++ b/tools/testing/selftests/kselftest_harness.h
@@ -971,6 +971,7 @@ void __run_test(struct __fixture_metadata *f,
 
 	ksft_print_msg(" RUN           %s%s%s.%s ...\n",
 	       f->name, variant->name[0] ? "." : "", variant->name, t->name);
+	fflush(stdout);
 	t->pid = fork();
 	if (t->pid < 0) {
 		ksft_print_msg("ERROR SPAWNING TEST CHILD\n");

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