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[2003:cb:c743:de00:7030:120f:d1c9:4c3c]) by smtp.gmail.com with ESMTPSA id k2-20020a5d5242000000b00343c0c24a65sm63462wrc.89.2024.04.04.11.58.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 04 Apr 2024 11:58:09 -0700 (PDT) Message-ID: <8fb37319-288c-4f77-9cd7-92f17bb567ee@redhat.com> Date: Thu, 4 Apr 2024 20:58:06 +0200 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 08/29] mm: Define VM_SHADOW_STACK for RISC-V To: Deepak Gupta , paul.walmsley@sifive.com, rick.p.edgecombe@intel.com, broonie@kernel.org, Szabolcs.Nagy@arm.com, kito.cheng@sifive.com, keescook@chromium.org, ajones@ventanamicro.com, conor.dooley@microchip.com, cleger@rivosinc.com, atishp@atishpatra.org, alex@ghiti.fr, bjorn@rivosinc.com, alexghiti@rivosinc.com, samuel.holland@sifive.com, conor@kernel.org Cc: linux-doc@vger.kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-kselftest@vger.kernel.org, corbet@lwn.net, palmer@dabbelt.com, aou@eecs.berkeley.edu, robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org, oleg@redhat.com, akpm@linux-foundation.org, arnd@arndb.de, ebiederm@xmission.com, Liam.Howlett@oracle.com, vbabka@suse.cz, lstoakes@gmail.com, shuah@kernel.org, brauner@kernel.org, andy.chiu@sifive.com, jerry.shih@sifive.com, hankuan.chen@sifive.com, greentime.hu@sifive.com, evan@rivosinc.com, xiao.w.wang@intel.com, charlie@rivosinc.com, apatel@ventanamicro.com, mchitale@ventanamicro.com, dbarboza@ventanamicro.com, sameo@rivosinc.com, shikemeng@huaweicloud.com, willy@infradead.org, vincent.chen@sifive.com, guoren@kernel.org, samitolvanen@google.com, songshuaishuai@tinylab.org, gerg@kernel.org, heiko@sntech.de, bhe@redhat.com, jeeheng.sia@starfivetech.com, cyy@cyyself.name, maskray@google.com, ancientmodern4@gmail.com, mathis.salmen@matsal.de, cuiyunhui@bytedance.com, bgray@linux.ibm.com, mpe@ellerman.id.au, baruch@tkos.co.il, alx@kernel.org, catalin.marinas@arm.com, revest@chromium.org, josh@joshtriplett.org, shr@devkernel.io, deller@gmx.de, omosnace@redhat.com, ojeda@kernel.org, jhubbard@nvidia.com References: <20240403234054.2020347-1-debug@rivosinc.com> <20240403234054.2020347-9-debug@rivosinc.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 04.04.24 01:34, Deepak Gupta wrote: > VM_SHADOW_STACK is defined by x86 as vm flag to mark a shadow stack vma. > > x86 uses VM_HIGH_ARCH_5 bit but that limits shadow stack vma to 64bit only. > arm64 follows same path (see links) > > To keep things simple, RISC-V follows the same. > This patch adds `ss` for shadow stack in process maps. > > Links: > https://lore.kernel.org/lkml/20231009-arm64-gcs-v6-12-78e55deaa4dd@kernel.org/#r > > Signed-off-by: Deepak Gupta > --- > fs/proc/task_mmu.c | 3 +++ > include/linux/mm.h | 11 ++++++++++- > 2 files changed, 13 insertions(+), 1 deletion(-) > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index 3f78ebbb795f..d9d63eb74f0d 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -702,6 +702,9 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma) > #endif /* CONFIG_HAVE_ARCH_USERFAULTFD_MINOR */ > #ifdef CONFIG_X86_USER_SHADOW_STACK > [ilog2(VM_SHADOW_STACK)] = "ss", > +#endif > +#ifdef CONFIG_RISCV_USER_CFI > + [ilog2(VM_SHADOW_STACK)] = "ss", > #endif > }; > size_t i; > diff --git a/include/linux/mm.h b/include/linux/mm.h > index f5a97dec5169..64109f6c70f5 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -352,7 +352,16 @@ extern unsigned int kobjsize(const void *objp); > * for more details on the guard size. > */ > # define VM_SHADOW_STACK VM_HIGH_ARCH_5 > -#else > +#endif > + > +#ifdef CONFIG_RISCV_USER_CFI > +/* > + * RISC-V is going along with using VM_HIGH_ARCH_5 bit position for shadow stack > + */ Wow, really?! I could never have guesses that from the code :P Just drop that comment. Are them semantics the same as for the x86 variant documented? ("VM_SHADOW_STACK should not be set with VM_SHARED because of lack of") I assume so. So it might now make sense to merge both paths #if defined(CONFIG_X86_USER_SHADOW_STACK) || defined(CONFIG_RISCV_USER_CFI) or even introduce some ARCH_HAS_SHADOW_STACK so we can remove these arch-specific thingies here. -- Cheers, David / dhildenb