On Fri, Feb 19, 2021 at 6:01 PM Alex Ghiti <a...@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 <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] > > > > 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! > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c > index 9b0592b11a9f..ff2495707edb 100644 > --- a/arch/riscv/mm/init.c > +++ b/arch/riscv/mm/init.c > @@ -287,7 +287,7 @@ pgd_t swapper_pg_dir[PTRS_PER_PGD] __page_aligned_bss; > pgd_t trampoline_pg_dir[PTRS_PER_PGD] __page_aligned_bss; > pte_t fixmap_pte[PTRS_PER_PTE] __page_aligned_bss; > > -#define MAX_EARLY_MAPPING_SIZE SZ_128M > +#define MAX_EARLY_MAPPING_SIZE PGDIR_SIZE > > pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE); > > -- > 2.20.1 > > Thanks, > > Alex > > > 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] > > > > _______________________________________________ > > linux-riscv mailing list > > linux-ri...@lists.infradead.org > > http://lists.infradead.org/mailman/listinfo/linux-riscv > >
