mm: Allow architectures to define additional protection bits

This patch allows architectures to define functions to deal with
additional protections bits for mmap() and mprotect().

arch_calc_vm_prot_bits() maps additonal protection bits to vm_flags
arch_vm_get_page_prot() maps additional vm_flags to the vma's vm_page_prot
arch_validate_prot() checks for valid values of the protection bits

Note: vm_get_page_prot() is now pretty ugly, but the generated code
should be identical for architectures that don't define additional
protection bits.

Signed-off-by: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

3 files changed, 32 insertions, 4 deletions

diff --git a/include/linux/mman.h b/include/linux/mman.h
index dab8892e6ff1..30d1073bac3b 100644
--- a/include/linux/mman.h
+++ b/include/linux/mman.h
@@ -34,6 +34,32 @@ static inline void vm_unacct_memory(long pages)
 }
 
 /*
+ * Allow architectures to handle additional protection bits
+ */
+
+#ifndef arch_calc_vm_prot_bits
+#define arch_calc_vm_prot_bits(prot) 0
+#endif
+
+#ifndef arch_vm_get_page_prot
+#define arch_vm_get_page_prot(vm_flags) __pgprot(0)
+#endif
+
+#ifndef arch_validate_prot
+/*
+ * This is called from mprotect().  PROT_GROWSDOWN and PROT_GROWSUP have
+ * already been masked out.
+ *
+ * Returns true if the prot flags are valid
+ */
+static inline int arch_validate_prot(unsigned long prot)
+{
+        return (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM)) == 0;
+}
+#define arch_validate_prot arch_validate_prot
+#endif
+
+/*
  * Optimisation macro.  It is equivalent to:
  *      (x & bit1) ? bit2 : 0
  * but this version is faster.
@@ -51,7 +77,8 @@ calc_vm_prot_bits(unsigned long prot)
 {
         return _calc_vm_trans(prot, PROT_READ,  VM_READ ) |
                _calc_vm_trans(prot, PROT_WRITE, VM_WRITE) |
-               _calc_vm_trans(prot, PROT_EXEC,  VM_EXEC );
+               _calc_vm_trans(prot, PROT_EXEC,  VM_EXEC) |
+               arch_calc_vm_prot_bits(prot);
 }
 
 /*
diff --git a/mm/mmap.c b/mm/mmap.c
index 3354fdd83d4b..1d102b956fd8 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -72,8 +72,9 @@ pgprot_t protection_map[16] = {
 
 pgprot_t vm_get_page_prot(unsigned long vm_flags)
 {
-        return protection_map[vm_flags &
-                                (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)];
+        return __pgprot(pgprot_val(protection_map[vm_flags &
+                                (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) |
+                        pgprot_val(arch_vm_get_page_prot(vm_flags)));
 }
 EXPORT_SYMBOL(vm_get_page_prot);
 
diff --git a/mm/mprotect.c b/mm/mprotect.c
index a5bf31c27375..ecfaa5844b5f 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -239,7 +239,7 @@ sys_mprotect(unsigned long start, size_t len, unsigned long prot)
         end = start + len;
         if (end <= start)
                 return -ENOMEM;
-        if (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM))
+        if (!arch_validate_prot(prot))
                 return -EINVAL;
 
         reqprot = prot;