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charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <45d5b98c-bad8-471d-a285-47f47c5b50bb@redhat.com> X-Stat-Signature: amsrki186ugyz6m9oqma693n66y3fggt X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: EF700120008 X-Rspam-User: X-HE-Tag: 1708565581-953107 X-HE-Meta: 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 nht5fBDP 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Feb 13, 2024 at 11:34:59AM +0100, David Hildenbrand wrote: >On 25.01.24 18:07, Deepak Gupta wrote: >>On Thu, Jan 25, 2024 at 09:18:07AM +0100, David Hildenbrand wrote: >>>On 25.01.24 07:21, debug@rivosinc.com wrote: >>>>From: Deepak Gupta >>>> >>>>x86 has used VM_SHADOW_STACK (alias to VM_HIGH_ARCH_5) to encode shadow >>>>stack VMA. VM_SHADOW_STACK is thus not possible on 32bit. Some arches may >>>>need a way to encode shadow stack on 32bit and 64bit both and they may >>>>encode this information differently in VMAs. >>>> >>>>This patch changes checks of VM_SHADOW_STACK flag in generic code to call >>>>to a function `arch_is_shadow_stack` which will return true if arch >>>>supports shadow stack and vma is shadow stack else stub returns false. >>>> >>>>There was a suggestion to name it as `vma_is_shadow_stack`. I preferred to >>>>keep `arch` prefix in there because it's each arch specific. >>>> >>>>Signed-off-by: Deepak Gupta >>>>--- >>>> include/linux/mm.h | 18 +++++++++++++++++- >>>> mm/gup.c | 5 +++-- >>>> mm/internal.h | 2 +- >>>> 3 files changed, 21 insertions(+), 4 deletions(-) >>>> >>>>diff --git a/include/linux/mm.h b/include/linux/mm.h >>>>index dfe0e8118669..15c70fc677a3 100644 >>>>--- a/include/linux/mm.h >>>>+++ b/include/linux/mm.h >>>>@@ -352,6 +352,10 @@ extern unsigned int kobjsize(const void *objp); >>>> * for more details on the guard size. >>>> */ >>>> # define VM_SHADOW_STACK VM_HIGH_ARCH_5 >>>>+static inline bool arch_is_shadow_stack(vm_flags_t vm_flags) >>>>+{ >>>>+ return (vm_flags & VM_SHADOW_STACK); >>>>+} >>>> #endif >>>> #ifdef CONFIG_RISCV_USER_CFI >>>>@@ -362,10 +366,22 @@ extern unsigned int kobjsize(const void *objp); >>>> * with VM_SHARED. >>>> */ >>>> #define VM_SHADOW_STACK VM_WRITE >>>>+ >>>>+static inline bool arch_is_shadow_stack(vm_flags_t vm_flags) >>>>+{ >>>>+ return ((vm_flags & (VM_WRITE | VM_READ | VM_EXEC)) == VM_WRITE); >>>>+} >>>>+ >>> >>>Please no such hacks just to work around the 32bit vmflags limitation. >> >>As I said in another response. Noted. >>And if there're no takers for 32bit on riscv (which highly likely is the case) >>This will go away in next version of patchsets. > >Sorry for the (unusually for me) late reply. Simplifying to riscv64 >sounds great. > >Alternatively, maybe VM_SHADOW_STACK is not even required at all on >riscv if we can teach all code to only stare at arch_is_shadow_stack() >instead. Sorry for late reply. I think for risc-v this can be done, if done in following way static inline bool arch_is_shadow_stack(struct vm_flags_t vm_flags) { return (vm_get_page_prot(vm_flags) == PAGE_SHADOWSTACK); } But doing above will require following - Inventing a new PROT_XXX type (let's call it PROT_SHADOWSTACK) that is only exposed to kernel. PROT_SHADOWSTACK protection flag would allow `do_mmap` to do right thing and setup appropriate protection perms. We wouldn't want to expose this protection type to user mode (because `map_shadow_stack` already exists for that). Current patch series uses PROT_SHADOWSTACK because VM_SHADOW_STACK was aliased to VM_WRITE. - As you said teach all the generic code as well to use arch_is_shadow_stack which might become complicated (can't say for sure) > >... but, just using the same VM_SHADOW_STACK will it all much cleaner. >Eventually, we can just stop playing arch-specific games with >arch_is_shadow_stack and VM_SHADOW_STACK. Yeah for now, looks like easier thing to do. > >-- >Cheers, > >David / dhildenb >