On Mon, Feb 24, 2025 at 10:21 AM Dave Hansen <dave.hansen@xxxxxxxxx> wrote: > > On 2/24/25 09:45, jeffxu@xxxxxxxxxxxx wrote: > > +/* > > + * mseal of userspace process's system mappings. > > + */ > > +#ifdef CONFIG_MSEAL_SYSTEM_MAPPINGS > > +#define MSEAL_SYSTEM_MAPPINGS_VM_FLAG VM_SEALED > > +#else > > +#define MSEAL_SYSTEM_MAPPINGS_VM_FLAG VM_NONE > > +#endif > > This ends up looking pretty wonky in practice: > > > + vm_flags = VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP|VM_PFNMAP; > > + vm_flags |= MSEAL_SYSTEM_MAPPINGS_VM_FLAG; > > because MSEAL_SYSTEM_MAPPINGS_VM_FLAG is so much different from the > other ones. > > Would it really hurt to have > > #ifdef CONFIG_64BIT > /* VM is sealed, in vm_flags */ > #define VM_SEALED _BITUL(63) > +#else > +#define VM_SEALED VM_NONE > #endif > > ? > VM_SEALED isn't defined in 32-bit systems, and mseal.c isn't part of the build. This is intentional. Any 32-bit code trying to use the sealing function or the VM_SEALED flag will immediately fail compilation. This makes it easier to identify incorrect usage. For example: Consider the case below in src/third_party/kernel/v6.6/fs/proc/task_mmu.c, #ifdef CONFIG_64BIT [ilog2(VM_SEALED)] = "sl", #endif Redefining VM_SEALED to VM_NONE for 32 bit won't detect the problem in case that "#ifdef CONFIG_64BIT" line is missing. Please note, this has been like this since the first version of mseal() RFC patch, and I prefer to keep it this way. Thanks -Jeff
