[PATCH] Inconsistent mmap()/mremap() flags

Thayne Harbaugh
2007-09-28T06:10:03Z

The x86_64 mmap() accepts the MAP_32BIT flag to request 32-bit clean
addresses. It seems to me that for consistency x86_64 mremap() should
also accept this (or an equivalent) flag.

Here is a trivial and untested patch for basis of discussion:

--- linux-source-2.6.22/mm/mremap.c.orig 2007-09-27 23:02:13.000000000 -0600
+++ linux-source-2.6.22/mm/mremap.c 2007-09-27 23:07:29.000000000 -0600
@@ -23,6 +23,11 @@
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>

+/* MAP_32BIT possibly defined in asm/mman.h */
+#ifndef MAP_32BIT
+#define MAP_32BIT 0
+#endif
+
static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
{
pgd_t *pgd;
@@ -255,7 +259,7 @@
unsigned long ret = -EINVAL;
unsigned long charged = 0;

- if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
+ if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE | MAP_32BIT))
goto out;

if (addr & ~PAGE_MASK)
@@ -388,6 +392,9 @@
if (vma->vm_flags & VM_MAYSHARE)
map_flags |= MAP_SHARED;

+ if (flags & MAP_32BIT)
+ map_flags |= MAP_32BIT;
+
new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
vma->vm_pgoff, map_flags);
ret = new_addr;