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Date: Wed, 27 May 2020 16:24:06 +0100 From: Mark Rutland <mark.rutland@....com> To: Arnd Bergmann <arnd@...db.de>, Nick Desaulniers <ndesaulniers@...gle.com>, Fangrui Song <maskray@...gle.com> Cc: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, Sami Tolvanen <samitolvanen@...gle.com>, Kees Cook <keescook@...omium.org>, clang-built-linux@...glegroups.com, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] arm64: disable -fsanitize=shadow-call-stack for big-endian On Wed, May 27, 2020 at 03:39:46PM +0200, Arnd Bergmann wrote: > clang-11 and earlier do not support -fsanitize=shadow-call-stack > in combination with -mbig-endian, but the Kconfig check does not > pass the endianess flag, so building a big-endian kernel with > this fails at build time: > > clang: error: unsupported option '-fsanitize=shadow-call-stack' for target 'aarch64_be-unknown-linux' > > Change the Kconfig check to let Kconfig figure this out earlier > and prevent the broken configuration. I assume this is a bug > in clang that needs to be fixed, but we also have to work > around existing releases. > > Fixes: 5287569a790d ("arm64: Implement Shadow Call Stack") > Link: https://bugs.llvm.org/show_bug.cgi?id=46076 > Signed-off-by: Arnd Bergmann <arnd@...db.de> I suspect this is similar to the patchable-function-entry issue, and this is an oversight that we'd rather fix toolchain side. Nick, Fangrui, thoughts? Mark. > --- > arch/arm64/Kconfig | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index a82441d6dc36..692e1575a6c8 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -1031,7 +1031,9 @@ config ARCH_ENABLE_SPLIT_PMD_PTLOCK > > # Supported by clang >= 7.0 > config CC_HAVE_SHADOW_CALL_STACK > - def_bool $(cc-option, -fsanitize=shadow-call-stack -ffixed-x18) > + bool > + default $(cc-option, -fsanitize=shadow-call-stack -ffixed-x18 -mbig-endian) if CPU_BIG_ENDIAN > + default $(cc-option, -fsanitize=shadow-call-stack -ffixed-x18 -mlittle-endian) if !CPU_BIG_ENDIAN > > config SECCOMP > bool "Enable seccomp to safely compute untrusted bytecode" > -- > 2.26.2 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@...ts.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
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