Received-SPF: pass (google.com: domain of linux-kernel+bounces-75735-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:4601:e00::3 as permitted sender) client-ip=2604:1380:4601:e00::3;
Date: Wed, 21 Feb 2024 16:39:57 -0800
From: Deepak Gupta <debug@rivosinc.com>
To: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
Cc: "ajones@ventanamicro.com" <ajones@ventanamicro.com>,
	"bjorn@rivosinc.com" <bjorn@rivosinc.com>,
	"conor.dooley@microchip.com" <conor.dooley@microchip.com>,
	"broonie@kernel.org" <broonie@kernel.org>,
	"keescook@chromium.org" <keescook@chromium.org>,
	"kito.cheng@sifive.com" <kito.cheng@sifive.com>,
	"paul.walmsley@sifive.com" <paul.walmsley@sifive.com>,
	"palmer@dabbelt.com" <palmer@dabbelt.com>,
	"alex@ghiti.fr" <alex@ghiti.fr>,
	"Szabolcs.Nagy@arm.com" <Szabolcs.Nagy@arm.com>,
	"alexghiti@rivosinc.com" <alexghiti@rivosinc.com>,
	"atishp@atishpatra.org" <atishp@atishpatra.org>,
	"cleger@rivosinc.com" <cleger@rivosinc.com>,
	"josh@joshtriplett.org" <josh@joshtriplett.org>,
	"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
	"gerg@kernel.org" <gerg@kernel.org>,
	"linux-kselftest@vger.kernel.org" <linux-kselftest@vger.kernel.org>,
	"bhe@redhat.com" <bhe@redhat.com>,
	"charlie@rivosinc.com" <charlie@rivosinc.com>,
	"david@redhat.com" <david@redhat.com>,
	"samitolvanen@google.com" <samitolvanen@google.com>,
	"heiko@sntech.de" <heiko@sntech.de>,
	"panqinglin2020@iscas.ac.cn" <panqinglin2020@iscas.ac.cn>,
	"mchitale@ventanamicro.com" <mchitale@ventanamicro.com>,
	"corbet@lwn.net" <corbet@lwn.net>,
	"revest@chromium.org" <revest@chromium.org>,
	"mason.huo@starfivetech.com" <mason.huo@starfivetech.com>,
	"ojeda@kernel.org" <ojeda@kernel.org>,
	"baruch@tkos.co.il" <baruch@tkos.co.il>,
	"waylingii@gmail.com" <waylingii@gmail.com>,
	"linux-riscv@lists.infradead.org" <linux-riscv@lists.infradead.org>,
	"joey.gouly@arm.com" <joey.gouly@arm.com>,
	"ancientmodern4@gmail.com" <ancientmodern4@gmail.com>,
	"mathis.salmen@matsal.de" <mathis.salmen@matsal.de>,
	"aou@eecs.berkeley.edu" <aou@eecs.berkeley.edu>,
	"shr@devkernel.io" <shr@devkernel.io>,
	"andy.chiu@sifive.com" <andy.chiu@sifive.com>,
	"shuah@kernel.org" <shuah@kernel.org>,
	"arnd@arndb.de" <arnd@arndb.de>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"vincent.chen@sifive.com" <vincent.chen@sifive.com>,
	"greentime.hu@sifive.com" <greentime.hu@sifive.com>,
	"oleg@redhat.com" <oleg@redhat.com>,
	"willy@infradead.org" <willy@infradead.org>,
	"zhangqing@loongson.cn" <zhangqing@loongson.cn>,
	"jhubbard@nvidia.com" <jhubbard@nvidia.com>,
	"ebiederm@xmission.com" <ebiederm@xmission.com>,
	"Wang, Xiao W" <xiao.w.wang@intel.com>,
	"cuiyunhui@bytedance.com" <cuiyunhui@bytedance.com>,
	"brauner@kernel.org" <brauner@kernel.org>,
	"catalin.marinas@arm.com" <catalin.marinas@arm.com>,
	"ruscur@russell.cc" <ruscur@russell.cc>,
	"shikemeng@huaweicloud.com" <shikemeng@huaweicloud.com>,
	"jszhang@kernel.org" <jszhang@kernel.org>,
	"jeeheng.sia@starfivetech.com" <jeeheng.sia@starfivetech.com>,
	"alx@kernel.org" <alx@kernel.org>,
	"guoren@kernel.org" <guoren@kernel.org>,
	"omosnace@redhat.com" <omosnace@redhat.com>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"evan@rivosinc.com" <evan@rivosinc.com>,
	"bgray@linux.ibm.com" <bgray@linux.ibm.com>,
	"apatel@ventanamicro.com" <apatel@ventanamicro.com>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>
Subject: Re: [RFC PATCH v1 11/28] riscv: Implementing "PROT_SHADOWSTACK" on
 riscv
Message-ID: <ZdaX3ckwaKO7YB2Y@debug.ba.rivosinc.com>
References: <20240125062739.1339782-1-debug@rivosinc.com>
 <20240125062739.1339782-12-debug@rivosinc.com>
 <2914cf78e47010e195d963857b37807e8446e3be.camel@intel.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1; format=flowed
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <2914cf78e47010e195d963857b37807e8446e3be.camel@intel.com>

On Fri, Feb 09, 2024 at 08:44:35PM +0000, Edgecombe, Rick P wrote:
>On Wed, 2024-01-24 at 22:21 -0800, debug@rivosinc.com wrote:
>> +???????/*
>> +??????? * PROT_SHADOWSTACK is a kernel only protection flag on risc-
>> v.
>> +??????? * mmap doesn't expect PROT_SHADOWSTACK to be set by user
>> space.
>> +??????? * User space can rely on `map_shadow_stack` syscall to
>> create
>> +??????? * shadow stack pages.
>> +??????? */
>> +???????if (unlikely(prot & PROT_SHADOWSTACK))
>> +???????????????return -EINVAL;
>
>Are you sure you need PROT_SHADOWSTACK? Since you are passing
>VM_SHADOW_STACK into do_mmap() directly.

Sorry for (very) late response.
In this patch series since VM_SHADOW_STACK was an alias to VM_WRITE.
And that's why I needed PROT_SHADOWSTACK to disambiguate.

I am updating my patches and going with ARCH_5 bit (and thus only 64bit support).
So x86, aarch64 and risc-v will be using same bit position.