linux-kernel - Re: selftests: sigaltstack: sas # exit=1 - # Bail out! SP is not on sigaltstack

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Message-ID: <CA+G9fYtDtUbKr-Kf_ZVF0z_xLsP3_2MVsMrvHmvV1UemXbfe3g@mail.gmail.com>
Date:   Wed, 8 Mar 2023 08:44:11 +0530
From:   Naresh Kamboju <naresh.kamboju@...aro.org>
To:     "Chang S. Bae" <chang.seok.bae@...el.com>, llvm@...ts.linux.dev
Cc:     "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>, linux-api@...r.kernel.org,
        open list <linux-kernel@...r.kernel.org>,
        lkft-triage@...ts.linaro.org, Shuah Khan <shuah@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Len Brown <len.brown@...el.com>, Borislav Petkov <bp@...e.de>,
        Stas Sergeev <stsp@...t.ru>, Arnd Bergmann <arnd@...db.de>,
        Anders Roxell <anders.roxell@...aro.org>,
        Nathan Chancellor <nathan@...nel.org>
Subject: Re: selftests: sigaltstack: sas # exit=1 - # Bail out! SP is not on
 sigaltstack - on clang build

+ LLVM

On Wed, 8 Mar 2023 at 00:58, Chang S. Bae <chang.seok.bae@...el.com> wrote:
>
> On 3/6/2023 10:57 PM, Naresh Kamboju wrote:
> > kselftest: sigaltstack built with clang-16 getting failed but passed with
> > gcc-12 build. Please find more details about test logs on clang-16 and
> > gcc-12 and steps to reproduce locally on your machine by using tuxrun.
> >
> > Reported-by: Linux Kernel Functional Testing <lkft@...aro.org>
> >
> > Test log:
> > ----------
> >
> > Linux version 6.3.0-rc1-next-20230307 (tuxmake@...make) (Debian clang
> > version 16.0.0 (++20230228093516+60692a66ced6-1~exp1~20230228093525.41),
> > Debian LLD 16.0.0) #1 SMP PREEMPT @1678159722
> > ...
> > kselftest: Running tests in sigaltstack
> > TAP version 13
> > 1..1
> > # selftests: sigaltstack: sas
> > # # [NOTE] the stack size is 21104
> > # TAP version 13
> > # 1..3
> > # ok 1 Initial sigaltstack state was SS_DISABLE
> > # Bail out! SP is not on sigaltstack
> > # # Planned tests != run tests (3 != 1)
> > # # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
> > not ok 1 selftests: sigaltstack: sas # exit=1
> <snip>
>
> > Linux version 6.3.0-rc1-next-20230307 (tuxmake@...make)
> > (aarch64-linux-gnu-gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils
> > for Debian) 2.40) #1 SMP PREEMPT @1678159736
> > ...
> > kselftest: Running tests in sigaltstack
> > TAP version 13
> > 1..1
> > # selftests: sigaltstack: sas
> > # # [NOTE] the stack size is 50080
> > # TAP version 13
> > # 1..3
> > # ok 1 Initial sigaltstack state was SS_DISABLE
> > # # [RUN] signal USR1
> > # ok 2 sigaltstack is disabled in sighandler
> > # # [RUN] switched to user ctx
> > # # [RUN] signal USR2
> > # # [OK] Stack preserved
> > # ok 3 sigaltstack is still SS_AUTODISARM after signal
> > # # Totals: pass:3 fail:0 xfail:0 xpass:0 skip:0 error:0
> > ok 1 selftests: sigaltstack: sas
>
> At glance, the log shows the altstack size difference between LLVM and GCC.
>
> But, when I tried with the LLVM that I have,
>
>      $ clang --version
>      clang version 13.0.0 ...
>
> it failed only with this compiler:
>
>      $ rm sas;clang -o sas sas.c;./sas
>      # [NOTE]        the stack size is 8192
>      TAP version 13
>      1..3
>      ok 1 Initial sigaltstack state was SS_DISABLE
>      Bail out! SP is not on sigaltstack
>      # Planned tests != run tests (3 != 1)
>      # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
>
>      $ rm sas;gcc -o sas sas.c;./sas
>      # [NOTE]        the stack size is 8192
>      TAP version 13
>      1..3
>      ok 1 Initial sigaltstack state was SS_DISABLE
>      # [RUN] signal USR1
>      ok 2 sigaltstack is disabled in sighandler
>      # [RUN] switched to user ctx
>      # [RUN] signal USR2
>      # [OK]  Stack preserved
>      ok 3 sigaltstack is still SS_AUTODISARM after signal
>      # Totals: pass:3 fail:0 xfail:0 xpass:0 skip:0 error:0
>
> The same is true with some old versions -- e.g. the one that came with
> commit 0c49ad415512 ("tools/testing/selftests/sigaltstack/sas.c: improve
> output of sigaltstack testcase"):
>
>      $ rm sas;clang -o sas sas.c;./sas
>      [OK]    Initial sigaltstack state was SS_DISABLE
>      [FAIL]  SP is not on sigaltstack
>
>      $ rm sas;gcc -o sas sas.c;./sas
>      [OK]    Initial sigaltstack state was SS_DISABLE
>      [RUN]   signal USR1
>      [OK]    sigaltstack is disabled in sighandler
>      [RUN]   switched to user ctx
>      [RUN]   signal USR2
>      [OK]    Stack preserved
>      [OK]    sigaltstack is still SS_AUTODISARM after signal
>      [OK]    Test passed
>
> So, this test failure appears to have been there for a while. I think
> the LLVM folks need to take a look at it.
>
> Thanks,
> Chang