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SubjectRe: [PATCH 2/4] selftests/sigaltstack: Fix the sas test on old kernels
On May 7, 2016 8:02 AM, "Stas Sergeev" <stsp@list.ru> wrote:
>
> 03.05.2016 20:31, Andy Lutomirski пишет:
>
>> The handling for old kernels was wrong. Fix it.
>>
>> Reported-by: Ingo Molnar <mingo@kernel.org>
>> Cc: Stas Sergeev <stsp@list.ru>
>> Cc: Al Viro <viro@zeniv.linux.org.uk>
>> Cc: Andrew Morton <akpm@linux-foundation.org>
>> Cc: Andy Lutomirski <luto@amacapital.net>
>> Cc: Borislav Petkov <bp@alien8.de>
>> Cc: Brian Gerst <brgerst@gmail.com>
>> Cc: Denys Vlasenko <dvlasenk@redhat.com>
>> Cc: H. Peter Anvin <hpa@zytor.com>
>> Cc: Linus Torvalds <torvalds@linux-foundation.org>
>> Cc: Oleg Nesterov <oleg@redhat.com>
>> Cc: Pavel Emelyanov <xemul@parallels.com>
>> Cc: Peter Zijlstra <peterz@infradead.org>
>> Cc: Shuah Khan <shuahkh@osg.samsung.com>
>> Cc: Thomas Gleixner <tglx@linutronix.de>
>> Cc: linux-api@vger.kernel.org
>> Cc: linux-kernel@vger.kernel.org
>> Signed-off-by: Andy Lutomirski <luto@kernel.org>
>> ---
>> tools/testing/selftests/sigaltstack/sas.c | 21 ++++++++++++++-------
>> 1 file changed, 14 insertions(+), 7 deletions(-)
>>
>> diff --git a/tools/testing/selftests/sigaltstack/sas.c b/tools/testing/selftests/sigaltstack/sas.c
>> index 57da8bfde60b..a98c3ef8141f 100644
>> --- a/tools/testing/selftests/sigaltstack/sas.c
>> +++ b/tools/testing/selftests/sigaltstack/sas.c
>> @@ -15,6 +15,7 @@
>> #include <alloca.h>
>> #include <string.h>
>> #include <assert.h>
>> +#include <errno.h>
>> #ifndef SS_AUTODISARM
>> #define SS_AUTODISARM (1 << 4)
>> @@ -117,13 +118,19 @@ int main(void)
>> stk.ss_flags = SS_ONSTACK | SS_AUTODISARM;
>> err = sigaltstack(&stk, NULL);
>> if (err) {
>> - perror("[FAIL]\tsigaltstack(SS_ONSTACK | SS_AUTODISARM)");
>> - stk.ss_flags = SS_ONSTACK;
>> - }
>> - err = sigaltstack(&stk, NULL);
>> - if (err) {
>> - perror("[FAIL]\tsigaltstack(SS_ONSTACK)");
>> - return EXIT_FAILURE;
>> + if (errno == EINVAL) {
>> + printf("[NOTE]\tThe running kernel doesn't support SS_AUTODISARM\n");
>> + /*
>> + * If test cases for the !SS_AUTODISARM variant were
>> + * added, we could still run them. We don't have any
>> + * test cases like that yet, so just exit and report
>> + * success.
>> + */
>
> But that was the point, please see how it handles the
> old kernels:
>
> $ ./sas
> [FAIL] sigaltstack(SS_ONSTACK | SS_AUTODISARM): Invalid argument
> [RUN] signal USR1
> [FAIL] ss_flags=1, should be SS_DISABLE
> [RUN] switched to user ctx
> [RUN] signal USR2
> [FAIL] sigaltstack re-used
> [FAIL] Stack corrupted
> [RUN] Aborting

This is useful as a demonstration of why the feature is useful, but it
doesn't indicate that anything is wrong with old kernels per she.
That's why I changed it to simply report that the feature is missing.

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