On Thu 09-03-17 14:47:16, Kirill A. Shutemov wrote: > On Thu, Mar 09, 2017 at 10:54:15AM +0100, Michal Hocko wrote: > > On Wed 08-03-17 18:21:30, Kirill A. Shutemov wrote: [...] > > > We can drop the hack once all architectures that support kasan would be > > > converted to pgtable-nop4d.h -- amd64 and x86 at the moment. > > > > But those architectures even do not enable kasan > > $ git grep "select *HAVE_ARCH_KASAN" > > arch/arm64/Kconfig: select HAVE_ARCH_KASAN if SPARSEMEM_VMEMMAP && !(ARM64_16K_PAGES && ARM64_VA_BITS_48) > > arch/x86/Kconfig: select HAVE_ARCH_KASAN if X86_64 && SPARSEMEM_VMEMMAP > > > > both arm64 and x86 (64b) do compile fine without the ifdef... So I guess > > we should be fine without it. > > Have you build the image to the final linking? lm_alias() hides the error > until later. > > x86-64 allmodconfig without the #ifndef: > > MODPOST vmlinux.o > mm/built-in.o: In function `kasan_populate_zero_shadow': > (.init.text+0xb72b): undefined reference to `kasan_zero_p4d' > Makefile:983: recipe for target 'vmlinux' failed > make: *** [vmlinux] Error 1 Interesting arm64 cross compile: $ grep CONFIG_KASAN .config CONFIG_KASAN=y CONFIG_KASAN_OUTLINE=y # CONFIG_KASAN_INLINE is not set Compiling for arm64 with aarch64-linux using gcc 4.9.0 [...] LD vmlinux.o MODPOST vmlinux.o KSYM .tmp_kallsyms1.o KSYM .tmp_kallsyms2.o LD vmlinux SORTEX vmlinux SYSMAP System.map x86_64 crosscompile with the same version to rule out gcc version changes $ grep CONFIG_KASAN .config CONFIG_KASAN_SHADOW_OFFSET=0xdffffc0000000000 CONFIG_KASAN=y CONFIG_KASAN_OUTLINE=y # CONFIG_KASAN_INLINE is not set [...] LD init/built-in.o LD vmlinux.o MODPOST vmlinux.o mm/built-in.o: In function `kasan_populate_zero_shadow': (.init.text+0x84e5): undefined reference to `kasan_zero_p4d' Makefile:983: recipe for target 'vmlinux' failed no idea why arm64 build was OK. Anyway I am not insisting on removing this ifdef it is just too ugly to spread __ARCH_HAS_5LEVEL_HACK outside of the arch code. We have few more in the mm code but those look much more understandable. Maybe a short comment explaining the ifdef would be better. Thanks! -- Michal Hocko SUSE Labs
