From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 58E583AD51A for ; Mon, 22 Jun 2026 13:35:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782135342; cv=none; b=SwPPVGaA3p9qs16/RHZd81V4ynyBss9Pxt1t04aPVf3J5xjU1kT6FhXh+YdcoxOObx4OQtjDKvoivOPcmOqwh4BAOI81+h2GOcHzXPgB12QwHFSMLTulogiR5Cr1TUGzakQaffeNKPkYhywoDqGKfqnUF60LtKkSBMoRobID5H0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782135342; c=relaxed/simple; bh=HdIQaBeASUC+3PFLFxGv4B8WmaWQ+wKaXj311z4LKwI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=qS2dFEDv9Vbzs6ZNZFFt1EDS3jmsXRFe51BC/nqTXmHAZN0076xTt5wM5cPjs8i0REVz7M2Kkb8ToXwPS/FEdrdier6DhcSP18ZN90bPnAkdYBjKcCP53ZkWF212T8HGWB81buGesoNhuLypmD6/0PqURX7h3wdna/U+Mujzenk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=A0oiP/9d; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="A0oiP/9d" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 702861F000E9; Mon, 22 Jun 2026 13:35:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782135340; bh=2Jl7C8hZl3Y2Ue1UxUAZLEwyJZ1SEzSpD9zwcG7PeIA=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=A0oiP/9dax3cnrR85YE3GH/p08vAcaj1t4upYnIR21AleNPRWY59kwpSnFpgDXQVj ArhXTZ0UJf3iLFCCQFNEOhKGiy+pAsVfZuy7EPViqOENy3GdkgGbUz/C7fIbITvzst 4iuQDWl5CxtBG55dPuLJEtZ0p9gvGbIEOCwPkUAnQhIFdMQtR0M1rJYVvd/HA78bgV lLkeXZ8nbkn5b+fdGJFiuGNVaBD2u18EY2JLL3YW0nNEW4TtITzhnpiKD0HDStzx97 UTevCAlqSzSBGCn5VF1blTB/cOSOSvCIOLxB/tqSQ3bs7OaLBEQpdHk8fnA/Tf/Qpz VazxRbhZNRmbA== Message-ID: Date: Mon, 22 Jun 2026 15:35:31 +0200 Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v8 05/24] arm64: Implement asm/kpkeys.h using POE To: Kevin Brodsky , linux-hardening@vger.kernel.org Cc: Andrew Morton , Andy Lutomirski , Catalin Marinas , Dave Hansen , Ira Weiny , Jann Horn , Jeff Xu , Joey Gouly , Kees Cook , Linus Walleij , Marc Zyngier , Mark Brown , Matthew Wilcox , Maxwell Bland , "Mike Rapoport (IBM)" , Peter Zijlstra , Pierre Langlois , Quentin Perret , Rick Edgecombe , Ryan Roberts , Vlastimil Babka , Will Deacon , Yang Shi , Yeoreum Yun , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, x86@kernel.org, Lorenzo Stoakes , Thomas Gleixner References: <20260526-kpkeys-v8-0-eaaacdacc67c@arm.com> <20260526-kpkeys-v8-5-eaaacdacc67c@arm.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/26/26 13:15, Kevin Brodsky wrote: > Implement the kpkeys interface if CONFIG_ARM64_POE is enabled. > The permissions for KPKEYS_PKEY_DEFAULT (pkey 0) are set to RWX as > this pkey is also used for code mappings. > > To allow to be included from assembly, also add > appropriate #ifdef's to . > > Signed-off-by: Kevin Brodsky > --- > arch/arm64/include/asm/kpkeys.h | 59 +++++++++++++++++++++++++++++++++++++++++ > arch/arm64/include/asm/por.h | 4 +++ > 2 files changed, 63 insertions(+) > > diff --git a/arch/arm64/include/asm/kpkeys.h b/arch/arm64/include/asm/kpkeys.h > new file mode 100644 > index 000000000000..4dbfeb3dfcfe > --- /dev/null > +++ b/arch/arm64/include/asm/kpkeys.h > @@ -0,0 +1,59 @@ > +/* SPDX-License-Identifier: GPL-2.0-only */ > +#ifndef __ASM_KPKEYS_H > +#define __ASM_KPKEYS_H > + > +#include > +#include > +#include > + > +#include > + > +/* > + * Equivalent to por_set_kpkeys_context(0, KPKEYS_CTX_DEFAULT), but can also be > + * used in assembly. > + */ > +#define POR_EL1_INIT POR_ELx_PERM_PREP(KPKEYS_PKEY_DEFAULT, POE_RWX) Okay, this matches #define POR_EL0_INIT POR_ELx_PERM_PREP(0, POE_RWX) Is there a good reason we need KPKEYS_PKEY_DEFAULT at all (and not similarly just hardcode it to 0)? Just wondering, because apparently we didn't care about adding an indicator for user space pkey 0. > + > +#ifndef __ASSEMBLY__ > + > +static inline bool arch_supports_kpkeys(void) > +{ > + return system_supports_poe(); > +} > + > +#ifdef CONFIG_ARM64_POE > + > +static inline u64 por_set_kpkeys_context(u64 por, int ctx) > +{ > + por = por_elx_set_pkey_perms(por, KPKEYS_PKEY_DEFAULT, POE_RWX); > + > + return por; Why not return por_elx_set_pkey_perms(por, KPKEYS_PKEY_DEFAULT, POE_RWX); ? In light of API discussions, it would be nicer if arch_kpkeys_set_context() would just return the old context. But that would mean that restoring the context would require another read_sysreg_s(SYS_POR_EL1); So instead of returning magic register values, that should be wrapped in some arch state struct as mentioned as reply to a previous patch. > +} > + > +static __always_inline void __kpkeys_set_pkey_reg_nosync(u64 pkey_reg) > +{ > + write_sysreg_s(pkey_reg, SYS_POR_EL1); > +} > + > +static __always_inline u64 arch_kpkeys_set_context(int ctx) > +{ > + u64 prev_por = read_sysreg_s(SYS_POR_EL1); > + u64 new_por = por_set_kpkeys_context(prev_por, ctx); Both can be const. But maybe you just use a single "por" variable. > + > + __kpkeys_set_pkey_reg_nosync(new_por); > + isb(); > + > + return prev_por; > +} > + > +static __always_inline void arch_kpkeys_restore_pkey_reg(u64 pkey_reg) > +{ > + __kpkeys_set_pkey_reg_nosync(pkey_reg); > + isb(); Why is that isb() for both callers outside of the function? Do you expect another user that doesn't need the isb? -- Cheers, David