Rolf Eike Beer <eike-kernel@xxxxxxxxx> writes: > This originally came up as a failure in the testsuite of strace on Gentoo > (T5120, 64 bit kernel, 32 bit userspace) and was reported here: > https://bugs.gentoo.org/643060. This was then reported upstream here: > https://github.com/strace/strace/issues/21 . I'll paste the relevant parts of > those bugs here. > > The test program is as follows (done by Dmitry V. Levin): > > #include <assert.h> > #include <signal.h> > #include <stdio.h> > #include <unistd.h> > > static void > handler(int sig, siginfo_t *info, void *ucontext) > { > > fprintf(stderr, "sig=%d, si_signo=%d, si_pid=%d, si_uid=%d\n", > sig, info->si_signo, info->si_pid, info->si_uid); > } > > static void > setup(int sig, sigset_t *mask) > { > > static const struct sigaction act = { .sa_sigaction = handler, .sa_flags = SA_SIGINFO }; > assert(!sigaction(sig, &act, NULL)); > assert(!sigaddset(mask, sig)); > } > > static void > test(int sig) > { > > assert(!raise(sig)); > assert(!kill(getpid(), sig)); > } > > int > main(void) > { > > sigset_t mask; > assert(!sigemptyset(&mask)); > > setup(SIGFPE, &mask); > setup(SIGTERM, &mask); > > assert(!sigprocmask(SIG_UNBLOCK, &mask, NULL)); > > test(SIGFPE); > test(SIGTERM); > > return 0; > } > > Running this on sparc64 userspace works fine: > > sig=8, si_signo=8, si_pid=135186, si_uid=1008 > sig=8, si_signo=8, si_pid=135186, si_uid=1008 > sig=15, si_signo=15, si_pid=135186, si_uid=1008 > sig=15, si_signo=15, si_pid=135186, si_uid=1008 > > However, on sparc32 things go wrong: > > sig=8, si_signo=8, si_pid=135192, si_uid=1008 > sig=8, si_signo=8, si_pid=1008, si_uid=0 > sig=15, si_signo=15, si_pid=135192, si_uid=1008 > sig=15, si_signo=15, si_pid=135192, si_uid=1008 > > When digging the code up and down I came up with this patch, which fixes the > issue for me: > > diff --git a/arch/sparc/kernel/signal32.c b/arch/sparc/kernel/signal32.c > index 54a6159b9cd8..a05e271e0924 100644 > --- a/arch/sparc/kernel/signal32.c > +++ b/arch/sparc/kernel/signal32.c > @@ -87,7 +87,7 @@ int copy_siginfo_to_user32(compat_siginfo_t __user *to, > err = __put_user(from->si_signo, &to->si_signo); > err |= __put_user(from->si_errno, &to->si_errno); > err |= __put_user(from->si_code, &to->si_code); > - if (from->si_code < 0) > + if (SI_FROMUSER(from)) > err |= __copy_to_user(&to->_sifields._pad, &from->_sifields._pad, SI_PAD_SIZE); > else { > switch (siginfo_layout(from->si_signo, from->si_code)) { > > I suspect it was broken by cc731525f26af85a1c3537da41e0abd1d35e0bdb as it is > reported that it worked in 4.5.0. Looking at that commit other archs (at least > arm64, mips, parisc, powerpc, s390, tile, x86) have the same code, but > different default-cases. From a quick glance arm64, parisc, and x86 do not > have a default case anymore since that commit, while the others do not seem to > have changed their default case. However it could be that siginfo_layout() > behaves slightly different than the mask code used before in the switch > statements. I'm currently building a 4.14.9 kernel for my HP C8000, will > report the test results once that is done. That is definitely the wrong fix. However it does verify that your si_code is SI_USER. The issue is that sparc has ambiguous signal handling, and si_code of 0 combined with the signal SIGFPE could be either a real floating point signal or a signal sent with kill. As it is pointless to send yourself a signal with kill I choose to preserve the floating point signal. That is the test is not actually testing floating point SIGFPE so I don't know that it makes much sense. I do have some further fixes that I was planning on testing and applying but I ran out of time to finish last year so I will see about digging those up. It is definitely wrong to allow sending SIGFPE to yourself whent si_code == SI_USER when SIGFPE_FIXME is defined. I should fix that as well. Ideally someone will go through sparc and look at arch/sparc/kernel/traps_32.c:do_fpe_trap and arch/sparc/kernel/traps_64.c:do_fpe_common and see if they can remove the need for FPE_FIXME (aka SI_USER, aka 0). Eric -- To unsubscribe from this list: send the line "unsubscribe sparclinux" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
