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@linaro.org
Test log:
Linux version 6.3.0-rc1-next-20230307 (tuxmake@tuxmake) (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@tuxmake) (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