From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 6505A313E34 for ; Tue, 30 Jun 2026 09:15:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782810952; cv=none; b=mMND+6CFSywu6XLqrVCQjXhDZx8S5g2Ckv/MxXlrwXm798GJH6/vAALZGWlefBs+6R1NaK+pBftST9jgo60m7l2HcgwlhMvsS71PuvhxCrQPqMVLPP5yCgusryYuwu6zs0zJkIkG3Gst7WK83Qmdwq9lo3fzqqUq+UAkRciGuCE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782810952; c=relaxed/simple; bh=sVn7JJGwZOLyL4bxlpoMBgAzZBKKk9c/Cy1C3BZSWug=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ZTiKbHXQub9ORN3gecjk6SsDyjYi5hzHukjnFtdQRe3sIooMuESVa5NFPOy39JDlelaXW5JktJadBbEgt6G/bjE3lJJjcnU52/PpXxkAZIbRC75sO9SW26D1oRsx1AY2XwlYGabVkKmuFsePyS14a7mAGaOW3JKF+Gd8xtSR3pY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=Hnex8kTI; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="Hnex8kTI" 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 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 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 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