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? 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
