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bh=McAYjxOmKyr2U+MmbX1LHXEFqvuYBMpZyHH0i0wmWno=; b=WKnYuzGvAFfqGW8AzanCAxVss4BYeftT4cDoQ3PniqPxrbJ3+UYmQCJI dljGKG2U49O3wb1Xk9yRO9SSqJkQB2G2aCR9kO91x625onUuk9ctjKGWi yBsCwdL7PIVODtHD6jgFpRbpbfrLFyHSYHNDtgln7zIM44MwRiH1pciVU /078qgayea98T+JsvWBcBejPE58wJO1lMTGwiZw/oQSlQ0t0t1vLR8491 79bMG7eiMjq5s09Rb+rkMJspd+zRZmjl+dlrva7bdKfQsIDVo5WHDQMju 4UOhKmT8FnvSIv+Q1vtBwI/Zyu8BnUdE6WcfFr8WXznAa0x7SyED3Kn+x g==; X-IronPort-AV: E=McAfee;i="6600,9927,11013"; a="22742444" X-IronPort-AV: E=Sophos;i="6.07,126,1708416000"; d="scan'208";a="22742444" Received: from fmviesa007.fm.intel.com ([10.60.135.147]) by orvoesa102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Mar 2024 11:30:00 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.07,126,1708416000"; d="scan'208";a="12293846" Received: from laallen-mobl.amr.corp.intel.com (HELO [10.209.21.198]) ([10.209.21.198]) by fmviesa007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Mar 2024 11:30:00 -0700 Message-ID: Date: Thu, 14 Mar 2024 11:30:01 -0700 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: [RFC PATCH] x86/pkeys: update PKRU to enable pkey 0 before XSAVE Content-Language: en-US To: Aruna Ramakrishna Cc: "linux-kernel@vger.kernel.org" , "x86@kernel.org" , "dave.hansen@linux.intel.com" , "tglx@linutronix.de" References: <20240314172920.2708810-1-aruna.ramakrishna@oracle.com> <4bd2aea0-3cea-4ef8-9607-40447cd531e5@intel.com> <349322E5-5E6C-48D5-BA12-1CF47CE82930@oracle.com> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 8bit On 3/14/24 11:14, Aruna Ramakrishna wrote: > I thought the PKRU value being reset in the signal handler was supposed > to be the default behavior. In which case, this is a bug. > > "Signal Handler Behavior > Each time a signal handler is invoked (including nested signals), > the thread is temporarily given a new, default set of protection > key rights that override the rights from the interrupted context.” > > (Ref: https://man7.org/linux/man-pages/man7/pkeys.7.html) As the person who wrote those words, I can honestly say that there were *ZERO* considerations for what the kernel's permissions were while setting up the frame. I was assuming then and assume to this day that it's practically impossible to turn off pkey-0 writes and get sane behavior. If we want to lawyer-word the manpage, I'll just argue that "Each time a signal handler is invoked" literally doesn't apply until the moment that RIP is pointing back to userspace. :) If this is truly about the manpage, then I'll happily amend the manpage to say, "don't turn off pkey 0 access or else". I'd *MUCH* rather do that than add more pkey munging to the kernel. In other words, you're not going to spur me into action my thwapping me with the manpage that I wrote. You've got to convince me that your new use case is valid, this is the best way to support your new use case, and that your implementation of the new feature is sane.