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Subject: Re: [PATCH v11 25/25] x86/cet/shstk: Add arch_prctl functions for
 shadow stack
To:     Florian Weimer <fweimer@redhat.com>
Cc:     "H.J. Lu" <hjl.tools@gmail.com>, Dave Martin <Dave.Martin@arm.com>,
        Dave Hansen <dave.hansen@intel.com>,
        Andy Lutomirski <luto@kernel.org>, X86 ML <x86@kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
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        LKML <linux-kernel@vger.kernel.org>,
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        Balbir Singh <bsingharora@gmail.com>,
        Borislav Petkov <bp@alien8.de>,
        Cyrill Gorcunov <gorcunov@gmail.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
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        Randy Dunlap <rdunlap@infradead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@intel.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>,
        Weijiang Yang <weijiang.yang@intel.com>
References: <20200825002540.3351-1-yu-cheng.yu@intel.com>
 <20200825002540.3351-26-yu-cheng.yu@intel.com>
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 <73c2211f-8811-2d9f-1930-1c5035e6129c@intel.com>
 <af258a0e-56e9-3747-f765-dfe45ce76bba@intel.com>
 <ef7f9e24-f952-d78c-373e-85435f742688@intel.com>
 <20200826164604.GW6642@arm.com> <87ft892vvf.fsf@oldenburg2.str.redhat.com>
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 <3c12b6ee-7c93-dcf4-fbf7-2698003386dd@intel.com>
 <87o8mpqtcn.fsf@oldenburg2.str.redhat.com>
From:   "Yu, Yu-cheng" <yu-cheng.yu@intel.com>
Message-ID: <b84e6fae-5d51-b0a0-d917-76f86b3186b7@intel.com>
Date:   Tue, 1 Sep 2020 10:58:25 -0700
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On 9/1/2020 10:50 AM, Florian Weimer wrote:
> * Yu-cheng Yu:
> 
>> Like other arch_prctl()'s, this parameter was 'unsigned long'
>> earlier. The idea was, since this arch_prctl is only implemented for
>> the 64-bit kernel, we wanted it to look as 64-bit only.  I will change
>> it back to 'unsigned long'.
> 
> What about x32?  In general, long is rather problematic for x32.

The problem is the size of 'long', right?
Because this parameter is passed in a register, and only the lower bits 
are used, x32 works as well.