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" OpenSBI v0.8 ____ _____ ____ _____ / __ \ / ____| _ \_ _| | | | |_ __ ___ _ __ | (___ | |_) || | | | | | '_ \ / _ \ '_ \ \___ \| _ < | | | |__| | |_) | __/ | | |____) | |_) || |_ \____/| .__/ \___|_| |_|_____/|____/_____| | | |_| Platform Name : riscv-virtio,qemu Platform Features : timer,mfdeleg Platform HART Count : 2 Boot HART ID : 1 Boot HART ISA : rv64imafdcsu BOOT HART Features : pmp,scounteren,mcounteren,time BOOT HART PMP Count : 16 Firmware Base : 0x80000000 Firmware Size : 104 KB Runtime SBI Version : 0.2 MIDELEG : 0x0000000000000222 MEDELEG : 0x000000000000b109 PMP0 : 0x0000000080000000-0x000000008001ffff (A) no output after this PMP1 : 0x0000000000000000-0xffffffffffffffff (A,R,W,X) > Thanks, > > > > >>> Then trying to boot it using: > >>> QEMU emulator version 5.2.0 (Debian 1:5.2+dfsg-3) > >>> $ qemu-system-riscv64 -machine virt -smp 2 -m 4G ... > >>> > >>> It shows no output from the kernel whatsoever, even though I have > >>> earlycon and output shows very early with other configs. > >>> Kernel boots fine with defconfig and other smaller configs. > >>> > >>> If I enable KASAN_OUTLINE and CC_OPTIMIZE_FOR_SIZE, then this config > >>> also boots fine. Both of these options significantly reduce kernel > >>> size. However, I can also boot the kernel without these 2 configs, if > >>> I disable a whole lot of subsystem configs. This makes me think that > >>> there is an issue related to kernel size somewhere in > >>> qemu/bootloader/kernel bootstrap code. > >>> Does it make sense to you? Can somebody reproduce what I am seeing? > > >> > >> I did not bring any answer to your question, but at least you know I'm > >> working on it, I'll keep you posted. > >> > >> Thanks for taking the time to setup syzkaller. > >> > >> Alex > >> > >>> Thanks > >>> > >>> _______________________________________________ > >>> linux-riscv mailing list > >>> linux-ri...@lists.infradead.org > >>> http://lists.infradead.org/mailman/listinfo/linux-riscv > >>> > > > > _______________________________________________ > > linux-riscv mailing list > > linux-ri...@lists.infradead.org > > http://lists.infradead.org/mailman/listinfo/linux-riscv > >
