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[84.236.113.171]) by smtp.gmail.com with ESMTPSA id r19sm532925wmh.42.2022.01.08.03.49.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 08 Jan 2022 03:49:06 -0800 (PST) Sender: Ingo Molnar Date: Sat, 8 Jan 2022 12:49:04 +0100 From: Ingo Molnar To: Nathan Chancellor Cc: Linus Torvalds , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, Andrew Morton , Peter Zijlstra , Thomas Gleixner , Greg Kroah-Hartman , "David S. Miller" , Ard Biesheuvel , Josh Poimboeuf , Jonathan Corbet , Al Viro , llvm@lists.linux.dev Subject: Re: [PATCH 0000/2297] [ANNOUNCE, RFC] "Fast Kernel Headers" Tree -v1: Eliminate the Linux kernel's "Dependency Hell" Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Nathan Chancellor wrote: > 5. Build error in arch/arm64/kvm/hyp/nvhe with LTO > > With arm64 + CONFIG_LTO_CLANG_THIN=y, I see: > > $ make -skj"$(nproc)" ARCH=arm64 LLVM=1 defconfig > > $ scripts/config -e LTO_CLANG_THIN > > $ make -skj"$(nproc)" ARCH=arm64 LLVM=1 olddefconfig arch/arm64/kvm/hyp/nvhe/ > ld.lld: error: arch/arm64/kvm/hyp/nvhe/hyp.lds:2: unknown directive: .macro > >>> .macro __put, val, name > >>> ^ > make[5]: *** [arch/arm64/kvm/hyp/nvhe/Makefile:51: arch/arm64/kvm/hyp/nvhe/kvm_nvhe.tmp.o] Error 1 > > I was not able to figure out the exact include chain but CONFIG_LTO > causes asm/alternative-macros.h to be included in asm/rwonce.h, which > eventually gets included in either asm/cache.h or asm/memory.h. > > I managed to solve this with the following diff but I am not sure if > there is a better or cleaner way to do that. > > diff --git a/arch/arm64/include/asm/rwonce.h b/arch/arm64/include/asm/rwonce.h > index 1bce62fa908a..e19572a205d0 100644 > --- a/arch/arm64/include/asm/rwonce.h > +++ b/arch/arm64/include/asm/rwonce.h > @@ -5,7 +5,7 @@ > #ifndef __ASM_RWONCE_H > #define __ASM_RWONCE_H > > -#ifdef CONFIG_LTO > +#if defined(CONFIG_LTO) && !defined(LINKER_SCRIPT) > > #include > #include > @@ -66,7 +66,7 @@ > }) > > #endif /* !BUILD_VDSO */ > -#endif /* CONFIG_LTO */ > +#endif /* CONFIG_LTO && !LINKER_SCRIPT */ So the error message suggests that the linker script somehow ends up including asm-generic/export.h: kepler:~/mingo.tip.git> git grep 'macro __put' include/asm-generic/export.h:.macro __put, val, name ? But I'd guess that similar to the __ASSEMBLY__ patterns we have in headers, not including the rwonce.h bits if LINKER_SCRIPT is defined is probably close to the right solution - but it would also know how such a low level header ended up in a linker script. Might have been to pick up some offset or size definition somewhere? I.e. how did the build end up including asm/rwonce.h? You can generally debug such weird dependency chains by putting a debug #warning into the affected header - such as the patch below. This prints a stack of the header dependencies: CC kernel/sched/core.o In file included from ./include/linux/compiler.h:263, from ./include/linux/static_call_types.h:7, from ./include/linux/kernel.h:6, from ./include/linux/highmem.h:5, from kernel/sched/core.c:9: ./arch/arm64/include/asm/rwonce.h:8:2: warning: #warning debug [-Wcpp] 8 | #warning debug ... and should in principle also work in the linker script context. Thanks, Ingo ===============> arch/arm64/include/asm/rwonce.h | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/arm64/include/asm/rwonce.h b/arch/arm64/include/asm/rwonce.h index 1bce62fa908a..5b3305381481 100644 --- a/arch/arm64/include/asm/rwonce.h +++ b/arch/arm64/include/asm/rwonce.h @@ -5,6 +5,8 @@ #ifndef __ASM_RWONCE_H #define __ASM_RWONCE_H +#warning debug + #ifdef CONFIG_LTO #include