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Peter Anvin" , , , , , Kefeng Wang , Xie XiuQi , Guohanjun References: <20220528065056.1034168-1-tongtiangen@huawei.com> <20220528065056.1034168-3-tongtiangen@huawei.com> <4371a7c9-8766-9fee-2558-e6f43f06ad19@huawei.com> <0da734f3-5743-3df3-3f90-d92e5bd585ce@huawei.com> From: Tong Tiangen In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.179.234] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To kwepemm600017.china.huawei.com (7.193.23.234) X-CFilter-Loop: Reflected ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf09.hostedemail.com: domain of tongtiangen@huawei.com designates 45.249.212.187 as permitted sender) smtp.mailfrom=tongtiangen@huawei.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1655693959; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ksMNFsTbMNqp6wNY+HsnKiqkntOlNIVUojotKXMMQFY=; b=XsyZg5HFlXVHhOk1TkHNXbauP6lF5GfVvgoLncs/CaGbBQivW2r9C51Ew0RXo0L1n+QRYs OjCUxCUaIQBEq/XCEdl0QmxhX5aT8aJFXktSbcPGu/hO4G0RO2T7khApREI1FTrVrosyxy JWQJLhjcodpBf6bnaxRZI967GHBTRW4= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1655693959; a=rsa-sha256; cv=none; b=RvUZPgWme9L6IYc5wCJRv+qxTbcC6PHhF2kr/B6G2czII2VrLg6/YKf0T07f7XbW6tQ1h4 uytUIvM5BoOQOBlRGj9lp9Bdyf40mPyYz/FTZ5vB0Tj2pdC6YCErJFeclkauQyPFbQFuYv Pv/xM1a9pk87EMidtvYB326PHPVFroc= X-Stat-Signature: ztt86o11ukx3u96snja3ow74w84dqk3i X-Rspamd-Queue-Id: 22D47140019 X-Rspam-User: Authentication-Results: imf09.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf09.hostedemail.com: domain of tongtiangen@huawei.com designates 45.249.212.187 as permitted sender) smtp.mailfrom=tongtiangen@huawei.com X-Rspamd-Server: rspam10 X-HE-Tag: 1655693957-24089 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 在 2022/6/18 20:40, Mark Rutland 写道: > On Sat, Jun 18, 2022 at 04:42:06PM +0800, Tong Tiangen wrote: >>>>> diff --git a/arch/arm64/include/asm/asm-extable.h >>>>> b/arch/arm64/include/asm/asm-extable.h >>>>> index 56ebe183e78b..9c94ac1f082c 100644 >>>>> --- a/arch/arm64/include/asm/asm-extable.h >>>>> +++ b/arch/arm64/include/asm/asm-extable.h >>>>> @@ -28,6 +28,14 @@ >>>>>       __ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_FIXUP, 0) >>>>>       .endm >>>>> +/* >>>>> + * Create an exception table entry for uaccess `insn`, which >>>>> will branch to `fixup` >>>>> + * when an unhandled fault is taken. >>>>> + * ex->data = ~0 means both reg_err and reg_zero is set to wzr(x31). >>>>> + */ >>>>> +    .macro          _asm_extable_uaccess, insn, fixup >>>>> +    __ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_UACCESS_ERR_ZERO, ~0) >>>>> +    .endm >>>> >>>> I'm not too keen on using `~0` here, since that also sets other bits >>>> in the >>>> data field, and its somewhat opaque. >>>> >>>> How painful is it to generate the data fields as with the C version >>>> of this >>>> macro, so that we can pass in wzr explciitly for the two sub-fields? >>>> >>>> Other than that, this looks good to me. >>>> >>>> Thanks, >>>> Mark. >>> >>> ok, will fix next version. >>> >>> Thanks, >>> Tong. >> >> I tried to using data filelds as with C version, but here assembly code we >> can not using operator such as << and |, if we use lsl and orr instructions, >> the gpr will be occupied. >> >> So how about using 0x3ff directly here? it means err register and zero >> register both set to x31. > > I had a go at implementing this, and it seems simple enough. Please see: > > https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/log/?h=arm64/extable/asm-uaccess > I made the following modifications, and the other parts are based on your implementation: arch/arm64/include/asm/asm-extable.h [...] .macro _asm_extable_uaccess, insn, fixup _ASM_EXTABLE_UACCESS(\insn, \fixup) .endm [...] The following errors are reported during compilation: [...] arch/arm64/lib/clear_user.S:45: Error: invalid operands (*ABS* and *UND* sections) for `<<' [...] "<<" is invalid operands in assembly, is there something wrong with me? Thanks, Tong. > Mark. > > .