On Tue, Oct 26, 2021 at 6:48 AM Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote: > > On Tue, 26 Oct 2021 at 06:39, Alexandre Ghiti > <alexandre.ghiti@xxxxxxxxxxxxx> wrote: > > > > Hi, > > > > On Fri, Oct 15, 2021 at 3:08 PM Alexandre ghiti <alex@xxxxxxxx> wrote: > > > > > > On 10/14/21 8:31 PM, Alex Ghiti wrote: > > > > Hi Nathan, > > > > > > > > Le 14/10/2021 à 18:55, Nathan Chancellor a écrit : > > > >> On Fri, Oct 08, 2021 at 11:46:55AM -0700, Palmer Dabbelt wrote: > > > >>> On Thu, 23 Sep 2021 07:59:46 PDT (-0700), nathan@xxxxxxxxxx wrote: > > > >>>> On Thu, Sep 23, 2021 at 12:07:17PM +0200, Marco Elver wrote: > > > >>>>> On Wed, 22 Sept 2021 at 22:55, Nathan Chancellor > > > >>>>> <nathan@xxxxxxxxxx> wrote: > > > >>>>>> Currently, the asan-stack parameter is only passed along if > > > >>>>>> CFLAGS_KASAN_SHADOW is not empty, which requires > > > >>>>>> KASAN_SHADOW_OFFSET to > > > >>>>>> be defined in Kconfig so that the value can be checked. In RISC-V's > > > >>>>>> case, KASAN_SHADOW_OFFSET is not defined in Kconfig, which means > > > >>>>>> that > > > >>>>>> asan-stack does not get disabled with clang even when > > > >>>>>> CONFIG_KASAN_STACK > > > >>>>>> is disabled, resulting in large stack warnings with allmodconfig: > > > >>>>>> > > > >>>>>> drivers/video/fbdev/omap2/omapfb/displays/panel-lgphilips-lb035q02.c:117:12: > > > >>>>>> > > > >>>>>> error: stack frame size (14400) exceeds limit (2048) in function > > > >>>>>> 'lb035q02_connect' [-Werror,-Wframe-larger-than] > > > >>>>>> static int lb035q02_connect(struct omap_dss_device *dssdev) > > > >>>>>> ^ > > > >>>>>> 1 error generated. > > > >>>>>> > > > >>>>>> Ensure that the value of CONFIG_KASAN_STACK is always passed > > > >>>>>> along to > > > >>>>>> the compiler so that these warnings do not happen when > > > >>>>>> CONFIG_KASAN_STACK is disabled. > > > >>>>>> > > > >>>>>> Link: https://github.com/ClangBuiltLinux/linux/issues/1453 > > > >>>>>> References: 6baec880d7a5 ("kasan: turn off asan-stack for clang-8 > > > >>>>>> and earlier") > > > >>>>>> Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx> > > > >>>>> > > > >>>>> Reviewed-by: Marco Elver <elver@xxxxxxxxxx> > > > >>>> > > > >>>> Thanks! > > > >>>> > > > >>>>> [ Which tree are you planning to take it through? ] > > > >>>> > > > >>>> Gah, I was intending for it to go through -mm, then I cc'd neither > > > >>>> Andrew nor linux-mm... :/ Andrew, do you want me to resend or can you > > > >>>> grab it from LKML? > > > >>> > > > >>> Acked-by: Palmer Dabbelt <palmerdabbelt@xxxxxxxxxx> > > > >>> > > > >>> (assuming you still want it through somewhere else) > > > >> > > > >> Thanks, it is now in mainline as commit 19532869feb9 ("kasan: always > > > >> respect CONFIG_KASAN_STACK"). > > > >> > > > >>>>> Note, arch/riscv/include/asm/kasan.h mentions KASAN_SHADOW_OFFSET in > > > >>>>> comment (copied from arm64). Did RISC-V just forget to copy over the > > > >>>>> Kconfig option? > > > >>>> > > > >>>> I do see it defined in that file as well but you are right that > > > >>>> they did > > > >>>> not copy the Kconfig logic, even though it was present in the tree > > > >>>> when > > > >>>> RISC-V KASAN was implemented. Perhaps they should so that they get > > > >>>> access to the other flags in the "else" branch? > > > >>> > > > >>> Ya, looks like we just screwed this up. I'm seeing some warnings like > > > >>> > > > >>> cc1: warning: ‘-fsanitize=kernel-address’ with stack protection > > > >>> is not supported without ‘-fasan-shadow-offset=’ for this target > > > >> > > > >> Hmmm, I thought I did a GCC build with this change but I must not have > > > >> :/ > > > >> > > > >>> which is how I ended up here, I'm assuming that's what you're > > > >>> talking about > > > >>> here? LMK if you were planning on sending along a fix or if you > > > >>> want me to > > > >>> go figure it out. > > > >> > > > >> I took a look at moving the logic into Kconfig like arm64 before sending > > > >> this change and I did not really understand it well enough to do so. I > > > >> think it would be best if you were able to do that so that nothing gets > > > >> messed up. > > > >> > > > > > > > > I'll do it tomorrow, I'm the last one who touched kasan on riscv :) > > > > > > > > > > Adding KASAN_SHADOW_OFFSET config makes kasan kernel fails to boot. > > > It receives a *write* fault at the beginning of a memblock_alloc > > > function while populating the kernel shadow memory: the trap address is > > > in the kasan shadow virtual address range and this corresponds to a > > > kernel address in init_stack. The question is: how do I populate the > > > stack shadow mapping without using memblock API? It's weird, I don't > > > find anything on other architectures. > > > > @kasan: Any idea what we are doing wrong in riscv to encounter the > > above situation? > > Hi Alex, Palmer, > > The patch changes the definition of the KASAN_SHADOW_OFFSET const. > Does it's value change as a result or not? Have you tried to print it > before/after? > If value does not change, then this is more mysterious. If it changes, > then there lots of possible explanations (points to unmapped region, > overlaps with something), but we need to know values before/after to So I debugged a bit more what happened here, and actually the culprit is the call to kasan_populate_early_shadow at the beginning of kasan_init which write-protects the access to kasan_early_shadow_page and hence the write fault later when using memblock. I don't see the point of this call anyway since we populate swapper_pg_dir in kasan_early_init and then we write-protect the access to kasan_early_shadow_page at the end of kasan_init. But that may not be ideal, so I'm open to a better suggestion than just removing the call to kasan_populate_early_shadow. Sorry I did not dig further before asking and thanks for your time, Alex > answer this. > > > > Thanks, > > > > Alex > > > > > > > > And just a short note: I have realized this will break with the sv48 > > > patchset as we decide at runtime the address space width and the kasan > > > shadow start address is different between sv39 and sv48. I will have to > > > do like x86 and move the kasan shadow start at the end of the address > > > space so that it is the same for both sv39 and sv48. > > > > > > Thanks, > > > > > > Alex > > > > > > > > > > Thanks, > > > > > > > > Alex > > > > > > > >> Cheers, > > > >> Nathan > > > >> > > > >> _______________________________________________ > > > >> linux-riscv mailing list > > > >> linux-riscv@xxxxxxxxxxxxxxxxxxx > > > >> http://lists.infradead.org/mailman/listinfo/linux-riscv > > > >> > > > > > > > > _______________________________________________ > > > > linux-riscv mailing list > > > > linux-riscv@xxxxxxxxxxxxxxxxxxx > > > > http://lists.infradead.org/mailman/listinfo/linux-riscv > > > > > > _______________________________________________ > > > linux-riscv mailing list > > > linux-riscv@xxxxxxxxxxxxxxxxxxx > > > http://lists.infradead.org/mailman/listinfo/linux-riscv
