diff options
| author | Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> | 2016-04-29 23:25:31 +1000 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2016-05-01 18:32:23 +1000 |
| commit | 73a1441a9b2ae05c15eb7cc90d4de379b44249bf (patch) | |
| tree | f3e91025eaa84ccd36bf71bd9f5fd2e19e2c9a6a | |
| parent | c7d54842deb1fa357cff75b988275a1c9f259140 (diff) | |
| download | linux-73a1441a9b2ae05c15eb7cc90d4de379b44249bf.tar.bz2 | |
powerpc/mm/subpage: Clear RWX bit to indicate no access
Subpage protection used to depend on the _PAGE_USER bit to implement no
access mode. This patch switches that to use _PAGE_RWX. We clear Read,
Write and Execute access from the pte instead of clearing _PAGE_USER
now. This was done so that we can switch to _PAGE_PRIVILEGED in a later
patch.
subpage_protection() returns pte bits that need to be cleared. Instead
of updating the interface to handle no-access in a separate way, it
appears simpler to clear RWX acecss to indicate no access.
We still don't insert hash ptes for no access implied by !_PAGE_RWX.
Hence we should not get PROT_FAULT with change.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
| -rw-r--r-- | arch/powerpc/mm/hash_utils_64.c | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c index ed190e42bbc5..36e00371ba5a 100644 --- a/arch/powerpc/mm/hash_utils_64.c +++ b/arch/powerpc/mm/hash_utils_64.c @@ -921,7 +921,7 @@ void demote_segment_4k(struct mm_struct *mm, unsigned long addr) * Userspace sets the subpage permissions using the subpage_prot system call. * * Result is 0: full permissions, _PAGE_RW: read-only, - * _PAGE_USER or _PAGE_USER|_PAGE_RW: no access. + * _PAGE_RWX: no access. */ static int subpage_protection(struct mm_struct *mm, unsigned long ea) { @@ -947,8 +947,13 @@ static int subpage_protection(struct mm_struct *mm, unsigned long ea) /* extract 2-bit bitfield for this 4k subpage */ spp >>= 30 - 2 * ((ea >> 12) & 0xf); - /* turn 0,1,2,3 into combination of _PAGE_USER and _PAGE_RW */ - spp = ((spp & 2) ? _PAGE_USER : 0) | ((spp & 1) ? _PAGE_RW : 0); + /* + * 0 -> full premission + * 1 -> Read only + * 2 -> no access. + * We return the flag that need to be cleared. + */ + spp = ((spp & 2) ? _PAGE_RWX : 0) | ((spp & 1) ? _PAGE_WRITE : 0); return spp; } |