On May 22, 2019 3:42 PM, "Alex Bennée" <alex.ben...@linaro.org> wrote: > > > Aleksandar Markovic <aleksandar.m.m...@gmail.com> writes: > > > On May 22, 2019 2:24 PM, "Cornelia Huck" <coh...@redhat.com> wrote: > >> > >> On Wed, 22 May 2019 14:10:39 +0200 > >> Laurent Vivier <laur...@vivier.eu> wrote: > >> > >> > On 22/05/2019 14:07, Cornelia Huck wrote: > >> > > On Wed, 22 May 2019 13:47:25 +0200 > >> > > Philippe Mathieu-Daudé <phi...@redhat.com> wrote: > >> > > > >> > >> On 5/21/19 5:28 PM, Cornelia Huck wrote: > >> > >>> commit a188339ca5a396acc588e5851ed7e19f66b0ebd9 > >> > >>> > >> > >>> Signed-off-by: Cornelia Huck <coh...@redhat.com> > >> > >>> --- > >> > >> [...] > >> > >>> #define __NR_mq_notify 184 > >> > >>> __SC_COMP(__NR_mq_notify, sys_mq_notify, compat_sys_mq_notify) > >> > >>> #define __NR_mq_getsetattr 185 > >> > >>> @@ -536,8 +567,10 @@ __SC_COMP(__NR_msgsnd, sys_msgsnd, > > compat_sys_msgsnd) > >> > >>> __SYSCALL(__NR_semget, sys_semget) > >> > >>> #define __NR_semctl 191 > >> > >>> __SC_COMP(__NR_semctl, sys_semctl, compat_sys_semctl) > >> > >>> +#if defined(__ARCH_WANT_TIME32_SYSCALLS) || __BITS_PER_LONG != 32 > >> > > > >> > > Eww. It seems only aarch64 sets __ARCH_WANT_TIME32_SYSCALLS, and the > >> > > second condition probably catches others but not mipsel. > >> > > > >> > >>> #define __NR_semtimedop 192 > >> > >>> -__SC_COMP(__NR_semtimedop, sys_semtimedop, compat_sys_semtimedop) > >> > >>> +__SC_COMP(__NR_semtimedop, sys_semtimedop, sys_semtimedop_time32) > >> > >>> +#endif > >> > >>> #define __NR_semop 193 > >> > >>> __SYSCALL(__NR_semop, sys_semop) > >> > >> [...] > >> > >> > >> > >> https://app.shippable.com/github/qemu/qemu/runs/1703/summary/console > >> > >> > >> > >> It seems this commit introduce a regression on mips32: > >> > >> > >> > >> CC mipsel-linux-user/linux-user/syscall.o > >> > >> ./linux-user/syscall.c: In function 'safe_semtimedop': > >> > >> ./linux-user/syscall.c:697:25: error: '__NR_semtimedop' undeclared > >> > >> (first use in this function) > >> > >> return safe_syscall(__NR_##name, arg1, arg2, arg3, arg4); \ > >> > > > >> > > So, we unconditionally deal with this syscall, i.e. we assume it is > >> > > always present? (I'm not sure of the logic in linux-user code.) > >> > > > >> > > >> > linux-user assumes it is present if __NR_msgsnd is present. > >> > >> Hm. The kernel change seems to break that assumption. Does anyone with > >> mips knowledge have an idea whether that was intentional (and the > >> linux-user code needs to be changed), or whether that's an issue on the > >> kernel side? > >> > > > > Hi, Cornelia. > > > > Thanks for your involving into this issue! > > > > It could be that (not-originating-from-MIPS) kernel commit: > > > > https://github.com/torvalds/linux/commit/1a787fc5ba18ac767e635c58d06a0b46876184e3 > > > > made a mess with system call availability for MIPS (I will forward this to > > MIPS kernel maintainer Paul Burton). My impression is that this was not > > intentional, and is a temporary instability of kernel interface. > > I think this stems from 2038 time bomb work. Eventually they want it to > be possible to build non-legacy kernels that don't expose time32 to the > outside world. As part of that new system calls are being introduced > where needed. The IPC syscall which orignally multiplexed a bunch of > these operations on some systems would eventually be potentially phased > out. > > > However, I think that QEMU nevertheless should not make the assumption that > > if __NR_MSGSND, than semtimedop() is present. It could be true, but it is > > still just self-imposed belief in QEMU, kernel never guarantied such things. > > > > The alternative way of invoking via IPCV6 (else part of “ifdef > > __NR_MSGSND”) should work for MIPS in the present stage of headers and > > kernel. > > Yeah I think #ifndef __NR_ipc would work for now. It shouldn't affect > architectures that never had the IPC call. > > > As a side note, perhaps we shoul update kernel headers only off of stable > > kernel releases. > > I guess that's a part of the tension for supporting new kernel APIs > quickly. At least 5.2-rc1 wasn't a random tree - you would expect the > external facing ABI to be stable after the merge window closed. It would > be nice to know what new features were being exposed though. >
Yes, one would expect no intentional changes in ABI kernel headers would happen after RC1. However, one must expect that there could certainly be bugs in RC1 - and there is a larger risk of propagating these bugs to QEMU with header updates from non-stable code. Sincerely, Aleksandar > > > > Regards, > > Aleksandar > > > -- > Alex Bennée
