[PATCH] freepgt: arm26 FIRST_USER_ADDRESS PAGE_SIZE

ARM26 define FIRST_USER_ADDRESS as PAGE_SIZE (beyond the machine vectors when
they are mapped low), and use that definition in place of locally defined
MIN_MAP_ADDR. Previously, ARM26 permitted user mappings at 0 if the machine
vectors were mapped high; but that's inconsistent with ARM, and
FIRST_USER_ADDRESS would then have to be determined at runtime. Let's fix it
at PAGE_SIZE throughout the architecture.

Signed-off-by: Hugh Dickins <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/arm26/kernel/sys_arm.c

···
 	flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
 
 	/*
-	 * If we are doing a fixed mapping, and address < PAGE_SIZE,
+	 * If we are doing a fixed mapping, and address < FIRST_USER_ADDRESS,
 	 * then deny it.
 	 */
-	if (flags & MAP_FIXED && addr < PAGE_SIZE && vectors_base() == 0)
+	if (flags & MAP_FIXED && addr < FIRST_USER_ADDRESS)
 		goto out;
 
 	error = -EBADF;
···
 	unsigned long ret = -EINVAL;
 
 	/*
-	 * If we are doing a fixed mapping, and address < PAGE_SIZE,
+	 * If we are doing a fixed mapping, and address < FIRST_USER_ADDRESS,
 	 * then deny it.
 	 */
-	if (flags & MREMAP_FIXED && new_addr < PAGE_SIZE &&
-	    vectors_base() == 0)
+	if (flags & MREMAP_FIXED && new_addr < FIRST_USER_ADDRESS)
 		goto out;
 
 	down_write(&current->mm->mmap_sem);

include/asm-arm26/pgtable.h

···
 #define PTRS_PER_PMD            1
 #define PTRS_PER_PTE            32
 
+/*
+ * This is the lowest virtual address we can permit any user space
+ * mapping to be mapped at.  This is particularly important for
+ * non-high vector CPUs.
+ */
+#define FIRST_USER_ADDRESS	PAGE_SIZE
+
 #define FIRST_USER_PGD_NR       1
 #define USER_PTRS_PER_PGD       ((TASK_SIZE/PGD_SIZE) - FIRST_USER_PGD_NR)