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Peter Anvin" , Andrew Morton , "Liam R. Howlett" , Lorenzo Stoakes , Paul Walmsley , Palmer Dabbelt , Albert Ou , Conor Dooley , Rob Herring , Krzysztof Kozlowski , Arnd Bergmann , Christian Brauner , Peter Zijlstra , Oleg Nesterov , Eric Biederman , Kees Cook , Jonathan Corbet , Shuah Khan , Jann Horn , Conor Dooley , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, devicetree@vger.kernel.org, linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, alistair.francis@wdc.com, richard.henderson@linaro.org, jim.shu@sifive.com, andybnac@gmail.com, kito.cheng@sifive.com, charlie@rivosinc.com, atishp@rivosinc.com, evan@rivosinc.com, cleger@rivosinc.com, alexghiti@rivosinc.com, samitolvanen@google.com, broonie@kernel.org, rick.p.edgecombe@intel.com Subject: Re: [PATCH v9 01/26] mm: helper `is_shadow_stack_vma` to check shadow stack vma Message-ID: References: <20250204-v5_user_cfi_series-v9-0-b37a49c5205c@rivosinc.com> <20250204-v5_user_cfi_series-v9-1-b37a49c5205c@rivosinc.com> <6543c6b6-da86-4c10-9b8c-e5fe6f6f7da9@suse.cz> Precedence: bulk X-Mailing-List: linux-arch@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <6543c6b6-da86-4c10-9b8c-e5fe6f6f7da9@suse.cz> On Fri, Feb 07, 2025 at 10:27:10AM +0100, Vlastimil Babka wrote: >On 2/5/25 02:21, Deepak Gupta wrote: >> VM_SHADOW_STACK (alias to VM_HIGH_ARCH_5) is used to encode shadow stack > >I see that arm GCS uses VM_HIGH_ARCH_6. > >> VMA on three architectures (x86 shadow stack, arm GCS and RISC-V shadow > >And RISC-V doesn't define it at all, not even in this patchset, or did I >miss it somewhere? > hmm... Something wrong in my workflow and rebasing. Thanks for catching this. >> stack). In case architecture doesn't implement shadow stack, it's VM_NONE >> Introducing a helper `is_shadow_stack_vma` to determine shadow stack vma >> or not. > >This looks like an unfinished sentence. As if it was to continue with "... >will allow us to ..." what? > >I'm not against a helper but this changelog is rather confusing and also >code in arch/x86 and arch/arm64 isn't converted to the helper but testing >VM_SHADOW_STACK still. > >> Signed-off-by: Deepak Gupta >> Reviewed-by: Mark Brown >> --- >> mm/gup.c | 2 +- >> mm/mmap.c | 2 +- >> mm/vma.h | 10 +++++++--- >> 3 files changed, 9 insertions(+), 5 deletions(-) >> >> diff --git a/mm/gup.c b/mm/gup.c >> index 3883b307780e..8c64f3ff34ab 100644 >> --- a/mm/gup.c >> +++ b/mm/gup.c >> @@ -1291,7 +1291,7 @@ static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags) >> !writable_file_mapping_allowed(vma, gup_flags)) >> return -EFAULT; >> >> - if (!(vm_flags & VM_WRITE) || (vm_flags & VM_SHADOW_STACK)) { >> + if (!(vm_flags & VM_WRITE) || is_shadow_stack_vma(vm_flags)) { >> if (!(gup_flags & FOLL_FORCE)) >> return -EFAULT; >> /* >> diff --git a/mm/mmap.c b/mm/mmap.c >> index cda01071c7b1..7b6be4eec35d 100644 >> --- a/mm/mmap.c >> +++ b/mm/mmap.c >> @@ -648,7 +648,7 @@ SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg) >> */ >> static inline unsigned long stack_guard_placement(vm_flags_t vm_flags) >> { >> - if (vm_flags & VM_SHADOW_STACK) >> + if (is_shadow_stack_vma(vm_flags)) >> return PAGE_SIZE; >> >> return 0; >> diff --git a/mm/vma.h b/mm/vma.h >> index a2e8710b8c47..47482a25f5c3 100644 >> --- a/mm/vma.h >> +++ b/mm/vma.h >> @@ -278,7 +278,7 @@ static inline struct vm_area_struct *vma_prev_limit(struct vma_iterator *vmi, >> } >> >> /* >> - * These three helpers classifies VMAs for virtual memory accounting. >> + * These four helpers classifies VMAs for virtual memory accounting. >> */ >> >> /* >> @@ -289,6 +289,11 @@ static inline bool is_exec_mapping(vm_flags_t flags) >> return (flags & (VM_EXEC | VM_WRITE | VM_STACK)) == VM_EXEC; >> } >> >> +static inline bool is_shadow_stack_vma(vm_flags_t vm_flags) >> +{ >> + return !!(vm_flags & VM_SHADOW_STACK); >> +} >> + >> /* >> * Stack area (including shadow stacks) >> * >> @@ -297,7 +302,7 @@ static inline bool is_exec_mapping(vm_flags_t flags) >> */ >> static inline bool is_stack_mapping(vm_flags_t flags) >> { >> - return ((flags & VM_STACK) == VM_STACK) || (flags & VM_SHADOW_STACK); >> + return ((flags & VM_STACK) == VM_STACK) || is_shadow_stack_vma(flags); >> } >> >> /* >> @@ -308,7 +313,6 @@ static inline bool is_data_mapping(vm_flags_t flags) >> return (flags & (VM_WRITE | VM_SHARED | VM_STACK)) == VM_WRITE; >> } >> >> - >> static inline void vma_iter_config(struct vma_iterator *vmi, >> unsigned long index, unsigned long last) >> { >> >