[PATCH] FRV: Make futex code compilable on nommu [try #2]

Make the futex code compilable and usable on NOMMU by making the attempt to
handle page faults conditional on CONFIG_MMU.  If this is not enabled, then
we can assume that EFAULT returned from futex_atomic_op_inuser() is not
recoverable, and that the address lies outside of valid memory.

handle_mm_fault() is made to BUG if called on NOMMU without attempting to
invoke the actual handler (__handle_mm_fault).

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 26 insertions, 3 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 26f3094911a5..bc01fff3aa01 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -717,12 +717,28 @@ extern int vmtruncate(struct inode * inode, loff_t offset);
 extern int vmtruncate_range(struct inode * inode, loff_t offset, loff_t end);
 extern int install_page(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long addr, struct page *page, pgprot_t prot);
 extern int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long addr, unsigned long pgoff, pgprot_t prot);
-extern int __handle_mm_fault(struct mm_struct *mm,struct vm_area_struct *vma, unsigned long address, int write_access);
 
-static inline int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, int write_access)
+#ifdef CONFIG_MMU
+extern int __handle_mm_fault(struct mm_struct *mm,struct vm_area_struct *vma,
+                        unsigned long address, int write_access);
+
+static inline int handle_mm_fault(struct mm_struct *mm,
+                        struct vm_area_struct *vma, unsigned long address,
+                        int write_access)
 {
-        return __handle_mm_fault(mm, vma, address, write_access) & (~VM_FAULT_WRITE);
+        return __handle_mm_fault(mm, vma, address, write_access) &
+                                (~VM_FAULT_WRITE);
 }
+#else
+static inline int handle_mm_fault(struct mm_struct *mm,
+                        struct vm_area_struct *vma, unsigned long address,
+                        int write_access)
+{
+        /* should never happen if there's no MMU */
+        BUG();
+        return VM_FAULT_SIGBUS;
+}
+#endif
 
 extern int make_pages_present(unsigned long addr, unsigned long end);
 extern int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write);
diff --git a/kernel/futex.c b/kernel/futex.c
index 5e71a6bf6f6b..5efa2f978032 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -356,6 +356,13 @@ retry:
                 if (bh1 != bh2)
                         spin_unlock(&bh2->lock);
 
+#ifndef CONFIG_MMU
+                /* we don't get EFAULT from MMU faults if we don't have an MMU,
+                 * but we might get them from range checking */
+                ret = op_ret;
+                goto out;
+#endif
+
                 if (unlikely(op_ret != -EFAULT)) {
                         ret = op_ret;
                         goto out;