----- On Aug 6, 2018, at 7:47 AM, gor gor@xxxxxxxxxxxxx wrote: > While implementing rseq selftest for s390 a glibc problem with tls > variables alignment has been discovered. It turned out to be a general > problem affecting several architectures. The bug opened for this problem: > > https://sourceware.org/bugzilla/show_bug.cgi?id=23403 > > There is no fix yet. On s390 __rseq_abi ends up aligned to 0x10 instead > of 0x20 which makes rseq selftest fail every time. > > The change proposed adds __rseq_abi misalignment check, produces user > friendly message and skips the test. That's a very unfortunate situation. I'm concerned about adding glibc-specific error messages in rseq selftests though. I'm curious to hear what others think about this. I would have thought simply improving rseq registration error handling from having the test program return nonzero to add a perror() in there would be a more generic way to handle this. Regarding the message printed by your check: "you need a fixed version of glibc to run this test". I disagree with it. Someone can effectively run the test on a bogus glibc and it serves its purpose: it reports that glibc is buggy. I would understand adding this kind of test in an user-facing application or library to detect bogus glibc (in fact I've used similar approaches in lttng-ust to detect bogus compilers), but why add this to skip a selftest program, which sole purpose is to test the stack underneath it ? Thanks, Mathieu > > Vasily Gorbik (1): > rseq/selftests: add __rseq_abi misalignment check > > tools/testing/selftests/rseq/rseq.c | 19 +++++++++++++++++++ > .../testing/selftests/rseq/run_param_test.sh | 4 ++-- > 2 files changed, 21 insertions(+), 2 deletions(-) > > -- > 2.18.0.13.gd42ae10 -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com -- To unsubscribe from this list: send the line "unsubscribe linux-kselftest" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
