[patch 1/6] mm: Allow architectures to define additional protection bits

shaggy
2008-06-18T22:32:55Z

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. Suggestions?

Signed-off-by: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
---

include/linux/mman.h | 28 +++++++++++++++++++++++++++-
mm/mmap.c | 5 +++--
mm/mprotect.c | 2 +-
3 files changed, 31 insertions(+), 4 deletions(-)

Index: linux-2.6.26-rc5/include/linux/mman.h
===================================================================
--- linux-2.6.26-rc5.orig/include/linux/mman.h
+++ linux-2.6.26-rc5/include/linux/mman.h
@@ -34,6 +34,31 @@ static inline void vm_unacct_memory(long
}

/*
+ * 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;
+}
+#endif
+
+/*
* Optimisation macro. It is equivalent to:
* (x & bit1) ? bit2 : 0
* but this version is faster.
@@ -51,7 +76,8 @@ 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);
}

/*
Index: linux-2.6.26-rc5/mm/mmap.c
===================================================================
--- linux-2.6.26-rc5.orig/mm/mmap.c
+++ linux-2.6.26-rc5/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);

Index: linux-2.6.26-rc5/mm/mprotect.c
===================================================================
--- linux-2.6.26-rc5.orig/mm/mprotect.c
+++ linux-2.6.26-rc5/mm/mprotect.c
@@ -239,7 +239,7 @@ sys_mprotect(unsigned long start, size_t
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;

--