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[110.175.254.242]) by smtp.gmail.com with ESMTPSA id v13-20020a17090331cd00b0015e8d4eb247sm1026976ple.145.2022.05.09.23.22.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 09 May 2022 23:22:13 -0700 (PDT) Message-ID: Date: Tue, 10 May 2022 16:22:08 +1000 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:100.0) Gecko/20100101 Thunderbird/100.0 Subject: Re: [PATCH 1/2] powerpc/vdso: Remove unused ENTRY in linker scripts Content-Language: en-US To: Nathan Chancellor , Michael Ellerman Cc: Benjamin Herrenschmidt , Paul Mackerras , Christophe Leroy , Nick Desaulniers , Tom Rix , linuxppc-dev@lists.ozlabs.org, llvm@lists.linux.dev, patches@lists.linux.dev References: <20220509204635.2539549-1-nathan@kernel.org> <20220509204635.2539549-2-nathan@kernel.org> From: Alexey Kardashevskiy In-Reply-To: <20220509204635.2539549-2-nathan@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 5/10/22 06:46, Nathan Chancellor wrote: > When linking vdso{32,64}.so.dbg with ld.lld, there is a warning about > not finding _start for the starting address: > > ld.lld: warning: cannot find entry symbol _start; not setting start address > ld.lld: warning: cannot find entry symbol _start; not setting start address > > Looking at GCC + GNU ld, the entry point address is 0x0: > > $ llvm-readelf -h vdso{32,64}.so.dbg &| rg "(File|Entry point address):" > File: vdso32.so.dbg > Entry point address: 0x0 > File: vdso64.so.dbg > Entry point address: 0x0 > > This matches what ld.lld emits: > > $ powerpc64le-linux-gnu-readelf -p .comment vdso{32,64}.so.dbg > > File: vdso32.so.dbg > > String dump of section '.comment': > [ 0] Linker: LLD 14.0.0 > [ 14] clang version 14.0.0 (Fedora 14.0.0-1.fc37) > > File: vdso64.so.dbg > > String dump of section '.comment': > [ 0] Linker: LLD 14.0.0 > [ 14] clang version 14.0.0 (Fedora 14.0.0-1.fc37) > > $ llvm-readelf -h vdso{32,64}.so.dbg &| rg "(File|Entry point address):" > File: vdso32.so.dbg > Entry point address: 0x0 > File: vdso64.so.dbg > Entry point address: 0x0 > > Remove ENTRY to remove the warning, as it is unnecessary for the vDSO to > function correctly. Sounds more like a bugfix to me - _start is simply not defined, I wonder why ld is not complaining. Tested-by: Alexey Kardashevskiy Reviewed-by: Alexey Kardashevskiy > > Signed-off-by: Nathan Chancellor > --- > arch/powerpc/kernel/vdso/vdso32.lds.S | 1 - > arch/powerpc/kernel/vdso/vdso64.lds.S | 1 - > 2 files changed, 2 deletions(-) > > diff --git a/arch/powerpc/kernel/vdso/vdso32.lds.S b/arch/powerpc/kernel/vdso/vdso32.lds.S > index 58e0099f70f4..e0d19d74455f 100644 > --- a/arch/powerpc/kernel/vdso/vdso32.lds.S > +++ b/arch/powerpc/kernel/vdso/vdso32.lds.S > @@ -13,7 +13,6 @@ OUTPUT_FORMAT("elf32-powerpcle", "elf32-powerpcle", "elf32-powerpcle") > OUTPUT_FORMAT("elf32-powerpc", "elf32-powerpc", "elf32-powerpc") > #endif > OUTPUT_ARCH(powerpc:common) > -ENTRY(_start) > > SECTIONS > { > diff --git a/arch/powerpc/kernel/vdso/vdso64.lds.S b/arch/powerpc/kernel/vdso/vdso64.lds.S > index 0288cad428b0..1a4a7bc4c815 100644 > --- a/arch/powerpc/kernel/vdso/vdso64.lds.S > +++ b/arch/powerpc/kernel/vdso/vdso64.lds.S > @@ -13,7 +13,6 @@ OUTPUT_FORMAT("elf64-powerpcle", "elf64-powerpcle", "elf64-powerpcle") > OUTPUT_FORMAT("elf64-powerpc", "elf64-powerpc", "elf64-powerpc") > #endif > OUTPUT_ARCH(powerpc:common64) > -ENTRY(_start) > > SECTIONS > {