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
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 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? Thanks