From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 2BFF0C43458 for ; Tue, 30 Jun 2026 09:16:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=cVi0bfnm6CkyWOx2B3ngEmCvXtH++YDEdZa8Kmvr0VI=; b=AFkkyouTejzYPLvcoTw3Vu5t/0 CM5y2zB/xs3qyjVcxm2XgbBs+fa9eAMBkkHD375YR0QS39o7mcZ5ZaVzoY/0A/ZJ0PiUtEATa32E5 cywKCWRKo3YiCUnmLwKvGkf/bAJmKN3fY1tl/6nH0AQegnLEDJX8DQ96NT7ZqI2IHuaFdOgjGRrR1 Q1KMxG/78VwD4JxLTA868aGoFabPuMLPSyhdSykDIE5ScaCNi8iMtpTG2VsYikwiI+Pv2eij4bTxq D/lvgPh3i9MAtbvQlzMLchEZ8nJmCXIMoWwSxMuyLtwQG6Or3vRzE4CbUeiR6hfCtr/Qi54WZaF10 XTsSi0sw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1weUZP-0000000GNOf-22MF; Tue, 30 Jun 2026 09:15:55 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1weUZM-0000000GNNe-178s for linux-arm-kernel@lists.infradead.org; Tue, 30 Jun 2026 09:15:53 +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 579662C1C; Tue, 30 Jun 2026 02:15:46 -0700 (PDT) Received: from [10.57.81.132] (unknown [10.57.81.132]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CDA043FAFB; Tue, 30 Jun 2026 02:15:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1782810950; bh=sVn7JJGwZOLyL4bxlpoMBgAzZBKKk9c/Cy1C3BZSWug=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Hnex8kTIqJvDaCwWDLDms17GUHLABmXpVlHniMOGFY9lEm0cRriX6yLe9fcG0DQqa qEkiKClZ7FQfIJKCVlnr4qWxNJT3I0hCP27j0vIhDQd78gJFmS9Mr/RG6zkIZ1LeLV d0Td8sQg68FW8THEVVnk5GPM4swe7eEP7w7hlH1k= Message-ID: <0554305f-d2a1-4727-bada-0fba203a8af6@arm.com> Date: Tue, 30 Jun 2026 11:15:38 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v8 04/24] arm64: Introduce por_elx_set_pkey_perms() helper To: "David Hildenbrand (Arm)" , 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-v8-4-eaaacdacc67c@arm.com> From: Kevin Brodsky Content-Language: en-GB In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260630_021552_401250_A89B6E28 X-CRM114-Status: GOOD ( 18.99 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 22/06/2026 15:16, David Hildenbrand (Arm) wrote: > On 5/26/26 13:15, Kevin Brodsky wrote: >> Introduce a helper that sets the permissions of a given pkey >> (POIndex) in the POR_ELx format, and make use of it in >> arch_set_user_pkey_access(). >> >> Signed-off-by: Kevin Brodsky >> --- >> arch/arm64/include/asm/por.h | 7 +++++++ >> arch/arm64/mm/mmu.c | 26 ++++++++++---------------- >> 2 files changed, 17 insertions(+), 16 deletions(-) >> >> diff --git a/arch/arm64/include/asm/por.h b/arch/arm64/include/asm/por.h >> index d913d5b529e4..bffb4d2b1246 100644 >> --- a/arch/arm64/include/asm/por.h >> +++ b/arch/arm64/include/asm/por.h >> @@ -31,4 +31,11 @@ static inline bool por_elx_allows_exec(u64 por, u8 pkey) >> return perm & POE_X; >> } >> >> +static inline u64 por_elx_set_pkey_perms(u64 por, u8 pkey, u64 perms) >> +{ >> + u64 shift = POR_ELx_PERM_SHIFT(pkey); >> + >> + return (por & ~(POE_MASK << shift)) | (perms << shift); >> +} >> + >> #endif /* _ASM_ARM64_POR_H */ >> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c >> index dd85e093ffdb..493310cf0486 100644 >> --- a/arch/arm64/mm/mmu.c >> +++ b/arch/arm64/mm/mmu.c >> @@ -2339,8 +2339,8 @@ void __cpu_replace_ttbr1(pgd_t *pgdp, bool cnp) >> #ifdef CONFIG_ARCH_HAS_PKEYS >> int arch_set_user_pkey_access(int pkey, unsigned long init_val) >> { >> - u64 new_por; >> - u64 old_por; >> + u64 new_perms; > You should spell out the renaming of the variable. Sure, will do. > Given that perms is 4bit per key, should we use a u8 for it instead? We could, in fact I'm just noticing that this all very inconsistent right now: the POE_* constants are defined as UL, but por_elx_allows_* and other functions use u8. I'll clean that up in a separate patch and use u8 here. >> + u64 por; >> >> if (!system_supports_poe()) >> return -ENOSPC; >> @@ -2354,25 +2354,19 @@ int arch_set_user_pkey_access(int pkey, unsigned long init_val) >> return -EINVAL; >> >> /* Set the bits we need in POR: */ >> - new_por = POE_RWX; >> + new_perms = POE_RWX; >> if (init_val & PKEY_DISABLE_WRITE) >> - new_por &= ~POE_W; >> + new_perms &= ~POE_W; >> if (init_val & PKEY_DISABLE_ACCESS) >> - new_por &= ~POE_RW; >> + new_perms &= ~POE_RW; >> if (init_val & PKEY_DISABLE_READ) >> - new_por &= ~POE_R; >> + new_perms &= ~POE_R; >> if (init_val & PKEY_DISABLE_EXECUTE) >> - new_por &= ~POE_X; >> + new_perms &= ~POE_X; >> >> - /* Shift the bits in to the correct place in POR for pkey: */ >> - new_por = POR_ELx_PERM_PREP(pkey, new_por); >> - >> - /* Get old POR and mask off any old bits in place: */ >> - old_por = read_sysreg_s(SYS_POR_EL0); >> - old_por &= ~(POE_MASK << POR_ELx_PERM_SHIFT(pkey)); >> - >> - /* Write old part along with new part: */ >> - write_sysreg_s(old_por | new_por, SYS_POR_EL0); >> + por = read_sysreg_s(SYS_POR_EL0); >> + por = por_elx_set_pkey_perms(por, pkey, new_perms); >> + write_sysreg_s(por, SYS_POR_EL0); > Was wondering whether to move reading+writing of the register into the same > helper, but you cannot reuse this exactly the same way for SYS_POR_EL1 as it seems. It wouldn't be useful because the new user of the helper, por_set_kpkeys_context(), doesn't itself read or write the register. > Reviewed-by: David Hildenbrand (Arm) Thanks! - Kevin