Messages in this thread | | | Subject | Re: riscv+KASAN does not boot | From | Alex Ghiti <> | Date | Tue, 9 Mar 2021 14:49:00 -0500 |
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Le 3/9/21 à 12:11 PM, Dmitry Vyukov a écrit : > On Fri, Feb 19, 2021 at 11:26 PM 'Palmer Dabbelt' via syzkaller > <syzkaller@googlegroups.com> wrote: >> >> On Fri, 19 Feb 2021 10:53:43 PST (-0800), dvyukov@google.com wrote: >>> On Fri, Feb 19, 2021 at 6:01 PM Alex Ghiti <alex@ghiti.fr> wrote: >>>> >>>> Hi Dmitry, >>>> >>>> Le 2/18/21 à 6:36 AM, Dmitry Vyukov a écrit : >>>>> On Thu, Feb 18, 2021 at 8:54 AM Alex Ghiti <alex@ghiti.fr> wrote: >>>>>> >>>>>> Hi Dmitry, >>>>>> >>>>>>> On Wed, Feb 17, 2021 at 5:36 PM Alex Ghiti <alex@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 <alex@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 <dvyukov@google.com> wrote: >>>>>>>>>>>> >>>>>>>>>>>> On Fri, Jan 29, 2021 at 9:11 AM Dmitry Vyukov <dvyukov@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] >>>>> >>>> >>>> Indeed the issue was code size, please find the fix below. I will send a >>>> proper patch once I made sure the fix is the right one, but I'm pretty >>>> confident, there's no reason to limit the mapping size to 128MB whereas >>>> we have a whole pgdir. >>> >>> Great you get to the bottom of this! >>> Riscv kernels are going to be YUGE! >> >> IIRC I tried that a while ago and it didn't work. It's possible I was just >> running into some other bug, but I'm just build testing allyesconfig as opposed >> to boot testing it. >> >> If you've got a setup that does boot I'm happy to take a patch, though. It'll >> at least be one step forward. > > > > OK, it's getting better.
Nice :)
> The next issue is called "512 bytes should be enough for everyone!" :) > https://elixir.bootlin.com/linux/v5.12-rc2/source/include/uapi/asm-generic/setup.h#L5 > Most other arches redefine it to something bigger: > https://elixir.bootlin.com/linux/v5.12-rc2/source/arch/s390/include/uapi/asm/setup.h#L10 > even arm32 redefines it. > I am not sure the default is even reasonable anymore.
Some archs override this value to 256, but git blame shows this is (very) old. I agree that 512 as default seems low.
> Failure mode is > also not nice (silent truncation).
Agreed, maybe we could still have the default value and checks the terminating null character is somewhere and bugs if not, I'll take a look.
> We are trying to pass this: > > earlyprintk=serial oops=panic nmi_watchdog=panic panic=86400 > net.ifnames=0 sysctl.kernel.hung_task_all_cpu_backtrace=1 > ima_policy=tcb kvm-intel.nested=1 nf-conntrack-ftp.ports=20000 > nf-conntrack-tftp.ports=20000 nf-conntrack-sip.ports=20000 > nf-conntrack-irc.ports=20000 nf-conntrack-sane.ports=20000 > vivid.n_devs=16 vivid.multiplanar=1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2 > netrom.nr_ndevs=16 rose.rose_ndevs=16 spec_store_bypass_disable=prctl > numa=fake=2 nopcid dummy_hcd.num=8 binder.debug_mask=0 > rcupdate.rcu_expedited=1 watchdog_thresh=165 > workqueue.watchdog_thresh=420 panic_on_warn=1 > > The last part gets truncated and we are getting false workqueue watchdog stalls. > > Could you please increase it?
I will propose a patchset that increases the default value and cleans archs up accordingly too.
Thanks again,
Alex
> > _______________________________________________ > linux-riscv mailing list > linux-riscv@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-riscv >
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