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Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jTQSa-0004Mw-Q6; Tue, 28 Apr 2020 13:39:40 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jTQSX-0004M4-J2 for linux-arm-kernel@lists.infradead.org; Tue, 28 Apr 2020 13:39:39 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id ED1B331B; Tue, 28 Apr 2020 06:39:36 -0700 (PDT) Received: from [10.37.8.217] (unknown [10.37.8.217]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C661F3F68F; Tue, 28 Apr 2020 06:39:35 -0700 (PDT) Subject: Re: arm64 vdso might miss .eh_frame To: Will Deacon References: <20200415092336.GK987@arm.com> <20200428073435.GC4049@willie-the-truck> <152f54d5-2fa9-bc08-d931-ed2f3675da6b@arm.com> <20200428111123.GA15519@C02TD0UTHF1T.local> <20200428115835.GA6791@willie-the-truck> From: Vincenzo Frascino Message-ID: <79f6a780-25eb-d4e7-11ea-f5d9a862f9df@arm.com> Date: Tue, 28 Apr 2020 14:40:35 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20200428115835.GA6791@willie-the-truck> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200428_063937_673469_F69369E8 X-CRM114-Status: GOOD ( 15.32 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Szabolcs Nagy , Tamas Zsoldos , linux-arm-kernel@lists.infradead.org, Catalin Marinas Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 4/28/20 12:58 PM, Will Deacon wrote: > On Tue, Apr 28, 2020 at 12:15:46PM +0100, Vincenzo Frascino wrote: >> On 4/28/20 12:11 PM, Mark Rutland wrote: >>> On Tue, Apr 28, 2020 at 11:54:25AM +0100, Vincenzo Frascino wrote: >>>> On 4/28/20 8:34 AM, Will Deacon wrote: >>>>> On Wed, Apr 15, 2020 at 10:23:36AM +0100, Szabolcs Nagy wrote: >>>>>> On aarch64 linux gcc uses -fasynchronous-unwind-tables -funwind-tables >>>>>> by default since gcc-8, so now the de facto platform ABI is to allow >>>>>> unwinding from async signal handlers. >>>>>> >>>>>> However on bare metal targets (aarch64-none-elf), and on old gcc, >>>>>> async and sync unwind tables are not enabled by default to avoid >>>>>> runtime memory costs. >>>>>> >>>>>> This means if linux is built with a baremetal toolchain the vdso.so >>>>>> may not have unwind tables which breaks our (undocumented) platform >>>>>> ABI guarantee in userspace. So adding -fasynchronous-unwind-tables >>>>>> explicitly to the vgettimeofday.o cflags would be nice (the other >>>>>> objects in the vdso seem to be asm). >>>>>> >>>>>> There was also a report that android clang built linux vdso.so lacks >>>>>> .eh_frame completely, that may be a missing --eh-frame-hdr or different >>>>>> platform ABI on android, Tamas on cc may be able to verify this. >>>>> >>>>> Vincenzo? Looks like this is a regression caused by the move to C -- please >>>>> can you take a look? >>>> >>>> I have already, locally, a patch that addresses the problem presented in this >>>> email, based on Szabolcs comment. I did not post it yet because I was waiting >>>> for Tamas' comment and address everything in one go. >>> >>> Can I suggest that you post the patch as-is here, even if it's not >>> complete, so that we can all review/test in parallel? >>> >> >> Sure, I will write a sensible comment and send it out. > I sent out a patch that addresses the problem reported by Szabolcs [1]. @Tamas, I have few questions: - Could you please provide more details on the problem you are facing? - Does the solution proposed by Szabolcs address it (--eh-frame-hdr)? [1] https://lore.kernel.org/linux-arm-kernel/20200428133411.44092-1-vincenzo.frascino@arm.com/ > Thanks! > > Will > -- Regards, Vincenzo _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel