On 1/27/22 6:09 PM, Mike Rapoport wrote: > On Mon, Jan 24, 2022 at 06:26:39PM +0530, Anshuman Khandual wrote: >> protection_map[] maps vm_flags access combinations into page protection >> value as defined by the platform via __PXXX and __SXXX macros. The array >> indices in protection_map[], represents vm_flags access combinations but >> it's not very intuitive to derive. This makes it clear and explicit. > > The protection_map is going to be removed in one of the next patches, why > bother with this patch at all? This makes the transition from protection_map[] into __vm_get_page_prot() more intuitive, where protection_map[] gets dropped. This helps platforms (first ones subscribing ARCH_HAS_VM_GET_PAGE_PROT before this drop) create /formulate the required switch case elements in their vm_get_page_prot(). The existing protection_map[] is not clear in demonstrating how exactly the vm_flags combination is mapped into page protection map. This helps clarify the underlying switch before we move on defining it on platforms. > >> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> >> Cc: linux-mm@xxxxxxxxx >> Cc: linux-kernel@xxxxxxxxxxxxxxx >> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx> >> --- >> mm/mmap.c | 18 ++++++++++++++++-- >> 1 file changed, 16 insertions(+), 2 deletions(-) >> >> diff --git a/mm/mmap.c b/mm/mmap.c >> index 1e8fdb0b51ed..254d716220df 100644 >> --- a/mm/mmap.c >> +++ b/mm/mmap.c >> @@ -102,8 +102,22 @@ static void unmap_region(struct mm_struct *mm, >> * x: (yes) yes >> */ >> pgprot_t protection_map[16] __ro_after_init = { >> - __P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111, >> - __S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111 >> + [VM_NONE] = __P000, >> + [VM_READ] = __P001, >> + [VM_WRITE] = __P010, >> + [VM_READ|VM_WRITE] = __P011, >> + [VM_EXEC] = __P100, >> + [VM_EXEC|VM_READ] = __P101, >> + [VM_EXEC|VM_WRITE] = __P110, >> + [VM_EXEC|VM_READ|VM_WRITE] = __P111, >> + [VM_SHARED] = __S000, >> + [VM_SHARED|VM_READ] = __S001, >> + [VM_SHARED|VM_WRITE] = __S010, >> + [VM_SHARED|VM_READ|VM_WRITE] = __S011, >> + [VM_SHARED|VM_EXEC] = __S100, >> + [VM_SHARED|VM_READ|VM_EXEC] = __S101, >> + [VM_SHARED|VM_WRITE|VM_EXEC] = __S110, >> + [VM_SHARED|VM_READ|VM_WRITE|VM_EXEC] = __S111 >> }; >> >> #ifndef CONFIG_ARCH_HAS_FILTER_PGPROT >> -- >> 2.25.1 >> >> >