powerpc ioremap_prot

This adds ioremap_prot and pte_pgprot() so that one can extract protection
bits from a PTE and use them to ioremap_prot() (in order to support ptrace
of VM_IO | VM_PFNMAP as per Rik's patch).

This moves a couple of flag checks around in the ioremap implementations
of arch/powerpc.  There's a side effect of allowing non-cacheable and
non-guarded mappings on ppc32 which before would always have _PAGE_GUARDED
set whenever _PAGE_NO_CACHE is.

(standard ioremap will still set _PAGE_GUARDED, but ioremap_prot will be
capable of setting such a non guarded mapping).

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: Dave Airlie <airlied@linux.ie>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/arch/powerpc/mm/pgtable_64.c b/arch/powerpc/mm/pgtable_64.c
index 3ef0ad2f9ca0..365e61ae5dbc 100644
--- a/arch/powerpc/mm/pgtable_64.c
+++ b/arch/powerpc/mm/pgtable_64.c
@@ -107,9 +107,18 @@ void __iomem * __ioremap_at(phys_addr_t pa, void *ea, unsigned long size,
 {
         unsigned long i;
 
+        /* Make sure we have the base flags */
         if ((flags & _PAGE_PRESENT) == 0)
                 flags |= pgprot_val(PAGE_KERNEL);
 
+        /* Non-cacheable page cannot be coherent */
+        if (flags & _PAGE_NO_CACHE)
+                flags &= ~_PAGE_COHERENT;
+
+        /* We don't support the 4K PFN hack with ioremap */
+        if (flags & _PAGE_4K_PFN)
+                return NULL;
+
         WARN_ON(pa & ~PAGE_MASK);
         WARN_ON(((unsigned long)ea) & ~PAGE_MASK);
         WARN_ON(size & ~PAGE_MASK);
@@ -190,6 +199,13 @@ void __iomem * ioremap(phys_addr_t addr, unsigned long size)
 void __iomem * ioremap_flags(phys_addr_t addr, unsigned long size,
                              unsigned long flags)
 {
+        /* writeable implies dirty for kernel addresses */
+        if (flags & _PAGE_RW)
+                flags |= _PAGE_DIRTY;
+
+        /* we don't want to let _PAGE_USER and _PAGE_EXEC leak out */
+        flags &= ~(_PAGE_USER | _PAGE_EXEC);
+
         if (ppc_md.ioremap)
                 return ppc_md.ioremap(addr, size, flags);
         return __ioremap(addr, size, flags);