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a=rsa-sha256; c=relaxed/relaxed; d=landley.net; s=dreamhost; t=1751745226; bh=oMtAvX6qZfeuJIf0ta5kkKNYBlAGah2HCzc1WvVT/Fw=; h=Date:Subject:To:Cc:From:Content-Type:Content-Transfer-Encoding; b=fW7jINTJHi5oRDv1NNGtkUycVaclQhMYZPb8AG7b5YNiCYOoWC++dYAhFJ0eY0KaV tPIKTgvos7rmWrqtDC3ENcguoWWMM64g0YXcvv166i4F9X9TrEnb3WSBp6KF2zmoqU jYraDxiBayw1c+uKWl3U10raWwjkq7zL5aUV6//gyqYSTqIH+Bnxy7m/lFV0C0Tdef YjrxLbsPr+cHJV2oI6w+d+Imv4FluzVi9VBI8gTNWZqS/k73KFWQQnYdBdtLPFw31Q Q6kcVp+9pvM/pCyqVMU+DFbk3oaUvglmsyetKasCYgz2vdrjNPO/cOtKlYfg5nsjy6 YWF/+IM5V/enA== Message-ID: Date: Sat, 5 Jul 2025 14:53:43 -0500 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] ARM: Require linker to support KEEP within OVERLAY for DCE To: Nathan Chancellor Cc: Linus Walleij , Russell King , Christian Eggers , Arnd Bergmann , Yuntao Liu , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Rich Felker References: <20250311-arm-fix-vectors-with-linker-dce-v1-0-ec4c382e3bfd@kernel.org> <20250311-arm-fix-vectors-with-linker-dce-v1-1-ec4c382e3bfd@kernel.org> <6739da7d-e555-407a-b5cb-e5681da71056@landley.net> <20250705002402.GA1968690@ax162> Content-Language: en-US From: Rob Landley In-Reply-To: <20250705002402.GA1968690@ax162> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 7/4/25 19:24, Nathan Chancellor wrote: > Hmm, I do see a bug in that change, as it allows DCE to be turned on > with binutils older than 2.36, which should be avoided with something > like > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > index 3072731fe09c..962451e54fdd 100644 > --- a/arch/arm/Kconfig > +++ b/arch/arm/Kconfig > @@ -121,7 +121,7 @@ config ARM > select HAVE_KERNEL_XZ > select HAVE_KPROBES if !XIP_KERNEL && !CPU_ENDIAN_BE32 && !CPU_V7M > select HAVE_KRETPROBES if HAVE_KPROBES > - select HAVE_LD_DEAD_CODE_DATA_ELIMINATION if (LD_VERSION >= 23600 || LD_CAN_USE_KEEP_IN_OVERLAY) > + select HAVE_LD_DEAD_CODE_DATA_ELIMINATION if (LD_VERSION >= 23600 || LD_IS_LLD) && LD_CAN_USE_KEEP_IN_OVERLAY > select HAVE_MOD_ARCH_SPECIFIC > select HAVE_NMI > select HAVE_OPTPROBES if !THUMB2_KERNEL > > but it does not seem like your test configuration enables > CONFIG_LD_DEAD_CODE_DATA_ELIMINATION so I would expect this change to be > a no-op in that case? Does the above change work for you? I won't be > free to validate this until after the weekend. That fixed it, thanks. AS arch/arm/boot/compressed/piggy.o LD arch/arm/boot/compressed/vmlinux OBJCOPY arch/arm/boot/zImage Kernel: arch/arm/boot/zImage is ready $ qemu-system-arm -M virt -nographic -no-reboot -kernel $(find . -name zImage) -append console=ttyAMA0 Booting Linux on physical CPU 0x0 Linux version 6.15.0-dirty (landley@driftwood) (armv7l-linux-musleabihf-gcc (GCC) 11.4.0, GNU ld (GNU Binutils) 2.33.1) #1 Sat Jul 5 14:40:16 CDT 2025 CPU: ARMv7 Processor [414fc0f0] revision 0 (ARMv7), cr=30c53c7d CPU: PIPT / VIPT nonaliasing data cache, PIPT instruction cache OF: fdt: Machine model: linux,dummy-virt ... I note it was a host tool segfaulting. It seems unlikely the host was running an arm binary, maybe something went off into la-la land trying to parse unexpected ELF tables? Appropriately-tagged-by: Rob Landley > Cheers, > Nathan Thanks, Rob