On Thu, Feb 18, 2021 at 8:54 AM Alex Ghiti <a...@ghiti.fr> wrote: > > Hi Dmitry, > > > On Wed, Feb 17, 2021 at 5:36 PM Alex Ghiti <a...@ghiti.fr> wrote: > >> > >> Le 2/16/21 à 11:42 PM, Dmitry Vyukov a écrit : > >>> On Tue, Feb 16, 2021 at 9:42 PM Alex Ghiti <a...@ghiti.fr> wrote: > >>>> > >>>> Hi Dmitry, > >>>> > >>>> Le 2/16/21 à 6:25 AM, Dmitry Vyukov a écrit : > >>>>> On Tue, Feb 16, 2021 at 12:17 PM Dmitry Vyukov <dvyu...@google.com> > >>>>> wrote: > >>>>>> > >>>>>> On Fri, Jan 29, 2021 at 9:11 AM Dmitry Vyukov <dvyu...@google.com> > >>>>>> wrote: > >>>>>>>> I was fixing KASAN support for my sv48 patchset so I took a look at > >>>>>>>> your > >>>>>>>> issue: I built a kernel on top of the branch riscv/fixes using > >>>>>>>> https://github.com/google/syzkaller/blob/269d24e857a757d09a898086a2fa6fa5d827c3e1/dashboard/config/linux/upstream-riscv64-kasan.config > >>>>>>>> and Buildroot 2020.11. I have the warnings regarding the use of > >>>>>>>> __virt_to_phys on wrong addresses (but that's normal since this > >>>>>>>> function > >>>>>>>> is used in virt_addr_valid) but not the segfaults you describe. > >>>>>>> > >>>>>>> Hi Alex, > >>>>>>> > >>>>>>> Let me try to rebuild buildroot image. Maybe there was something wrong > >>>>>>> with my build, though, I did 'make clean' before doing. But at the > >>>>>>> same time it worked back in June... > >>>>>>> > >>>>>>> Re WARNINGs, they indicate kernel bugs. I am working on setting up a > >>>>>>> syzbot instance on riscv. If there a WARNING during boot then the > >>>>>>> kernel will be marked as broken. No further testing will happen. > >>>>>>> Is it a mis-use of WARN_ON? If so, could anybody please remove it or > >>>>>>> replace it with pr_err. > >>>>>> > >>>>>> > >>>>>> Hi, > >>>>>> > >>>>>> I've localized one issue with riscv/KASAN: > >>>>>> KASAN breaks VDSO and that's I think the root cause of weird faults I > >>>>>> saw earlier. The following patch fixes it. > >>>>>> Could somebody please upstream this fix? I don't know how to add/run > >>>>>> tests for this. > >>>>>> Thanks > >>>>>> > >>>>>> diff --git a/arch/riscv/kernel/vdso/Makefile > >>>>>> b/arch/riscv/kernel/vdso/Makefile > >>>>>> index 0cfd6da784f84..cf3a383c1799d 100644 > >>>>>> --- a/arch/riscv/kernel/vdso/Makefile > >>>>>> +++ b/arch/riscv/kernel/vdso/Makefile > >>>>>> @@ -35,6 +35,7 @@ CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) > >>>>>> -Os > >>>>>> # Disable gcov profiling for VDSO code > >>>>>> GCOV_PROFILE := n > >>>>>> KCOV_INSTRUMENT := n > >>>>>> +KASAN_SANITIZE := n > >>>>>> > >>>>>> # Force dependency > >>>>>> $(obj)/vdso.o: $(obj)/vdso.so > >>>> > >>>> What's weird is that I don't have any issue without this patch with the > >>>> following config whereas it indeed seems required for KASAN. But when > >>>> looking at the segfaults you got earlier, the segfault address is 0xbb0 > >>>> and the cause is an instruction page fault: this address is the PLT base > >>>> address in vdso.so and an instruction page fault would mean that someone > >>>> tried to jump at this address, which is weird. At first sight, that does > >>>> not seem related to your patch above, but clearly I may be wrong. > >>>> > >>>> Tobias, did you observe the same segfaults as Dmitry ? > >>> > >>> > >>> I noticed that not all buildroot images use VDSO, it seems to be > >>> dependent on libc settings (at least I think I changed it in the > >>> past). > >> > >> Ok, I used uClibc but then when using glibc, I have the same segfaults, > >> only when KASAN is enabled. And your patch fixes the problem. I will try > >> to take a look later to better understand the problem. > >> > >>> I also booted an image completely successfully including dhcpd/sshd > >>> start, but then my executable crashed in clock_gettime. The executable > >>> was build on linux/amd64 host with "riscv64-linux-gnu-gcc -static" > >>> (10.2.1). > >>> > >>> > >>>>> Second issue I am seeing seems to be related to text segment size. > >>>>> I check out v5.11 and use this config: > >>>>> https://gist.github.com/dvyukov/6af25474d455437577a84213b0cc9178 > >>>> > >>>> This config gave my laptop a hard time ! Finally I was able to boot > >>>> correctly to userspace, but I realized I used my sv48 branch...Either I > >>>> fixed your issue along the way or I can't reproduce it, I'll give it a > >>>> try tomorrow. > >>> > >>> Where is your branch? I could also test in my setup on your branch. > >>> > >> > >> You can find my branch int/alex/riscv_kernel_end_of_address_space_v2 > >> here: https://github.com/AlexGhiti/riscv-linux.git > > > > No, it does not work for me. > > > > Source is on b61ab6c98de021398cd7734ea5fc3655e51e70f2 (HEAD, > > int/alex/riscv_kernel_end_of_address_space_v2) > > Config is > > https://gist.githubusercontent.com/dvyukov/6af25474d455437577a84213b0cc9178/raw/55b116522c14a8a98a7626d76df740d54f648ce5/gistfile1.txt > > > > riscv64-linux-gnu-gcc -v > > gcc version 10.2.1 20210110 (Debian 10.2.1-6+build1) > > > > qemu-system-riscv64 --version > > QEMU emulator version 5.2.0 (Debian 1:5.2+dfsg-3) > > > > qemu-system-riscv64 \ > > -machine virt -smp 2 -m 2G \ > > -device virtio-blk-device,drive=hd0 \ > > -drive file=image-riscv64,if=none,format=raw,id=hd0 \ > > -kernel arch/riscv/boot/Image \ > > -nographic \ > > -device virtio-rng-device,rng=rng0 -object > > rng-random,filename=/dev/urandom,id=rng0 \ > > -netdev user,id=net0,host=10.0.2.10,hostfwd=tcp::10022-:22 -device > > virtio-net-device,netdev=net0 \ > > -append "root=/dev/vda earlyprintk=serial console=ttyS0 oops=panic > > panic_on_warn=1 panic=86400 earlycon" > > It still works for me but I had to disable CONFIG_DEBUG_INFO_BTF (I > don't think that changes anything at runtime). But your above command > line does not work for me as it appears you do not load any firmware, if > I add -bios images/fw_jump.elf, it works. But then I don't know where > your opensbi output below comes from... > > And regarding your issue with calling clock_gettime 'directly' compared > to using the syscall, I have the same consistent output from both calls. > > I have an older gcc (9.3.0) and the same qemu. I think what is missing > here is your buildroot config, so that we have the exact same > environment: could you post your buildroot config as well ?
I don't think the image is relevant because I don't even get to kernel code. If the kernel will complain about no init later, that's fine. Re bios, this version of qemu already has OpenSBI bios builtin, you can pass -bios default, but that's, well, the default :) Here are more reproducible repro instructions that capture gcc and qemu. I think gcc version may be potentially relevant as I suspect code size. curl https://gist.githubusercontent.com/dvyukov/6af25474d455437577a84213b0cc9178/raw/55b116522c14a8a98a7626d76df740d54f648ce5/gistfile1.txt > $KERNEL_SRC/.config docker pull gcr.io/syzkaller/syzbot docker run -it -v $KERNEL_SRC:/kernel gcr.io/syzkaller/syzbot cd /kernel make -j72 ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- olddefconfig make -j72 ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- qemu-system-riscv64 -machine virt -smp 2 -m 4G -kernel arch/riscv/boot/Image -nographic -append "earlycon earlyprintk=serial console=ttyS0" [this does not, only OpenSBI output] scripts/config -d KASAN_INLINE -e KASAN_OUTLINE -d CC_OPTIMIZE_FOR_PERFORMANCE -e CC_OPTIMIZE_FOR_SIZE make -j72 ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- qemu-system-riscv64 -machine virt -smp 2 -m 4G -kernel arch/riscv/boot/Image -nographic -append "earlycon earlyprintk=serial console=ttyS0" [this boots fine, at least at to starting init process]