The attached patch makes 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 <[email protected]>
---
warthog>diffstat -p1 frv-futex-2615rc2-2.diff
include/linux/mm.h | 10 ++++++++++
kernel/futex.c | 7 +++++++
2 files changed, 17 insertions(+)
diff -uNrp /warthog/kernels/linux-2.6.15-rc2/include/linux/mm.h linux-2.6.15-rc2-frv/include/linux/mm.h
--- /warthog/kernels/linux-2.6.15-rc2/include/linux/mm.h 2005-11-23 12:09:22.000000000 +0000
+++ linux-2.6.15-rc2-frv/include/linux/mm.h 2005-11-29 20:02:34.000000000 +0000
@@ -708,12 +708,22 @@ static inline void unmap_shared_mapping_
extern int vmtruncate(struct inode * inode, loff_t offset);
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);
+
+#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);
}
+#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 -uNrp /warthog/kernels/linux-2.6.15-rc2/kernel/futex.c linux-2.6.15-rc2-frv/kernel/futex.c
--- /warthog/kernels/linux-2.6.15-rc2/kernel/futex.c 2005-11-23 12:09:23.000000000 +0000
+++ linux-2.6.15-rc2-frv/kernel/futex.c 2005-11-29 20:01:07.000000000 +0000
@@ -365,6 +365,13 @@ 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;
-
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