This patchs adds a utility function install_special_mapping, for creating a
special vma using a fixed set of preallocated pages as backing, such as for
a vDSO. This consolidates some nearly identical code used for vDSO mapping
reimplemented for different architectures.
Signed-off-by: Roland McGrath <[email protected]>
---
include/linux/mm.h | 3 ++
mm/mmap.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 75 insertions(+), 0 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 2d2c08d..bb793a4 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1030,6 +1030,9 @@ extern struct vm_area_struct *copy_vma(s
unsigned long addr, unsigned long len, pgoff_t pgoff);
extern void exit_mmap(struct mm_struct *);
extern int may_expand_vm(struct mm_struct *mm, unsigned long npages);
+extern int install_special_mapping(struct mm_struct *mm,
+ unsigned long addr, unsigned long len,
+ unsigned long flags, struct page **pages);
extern unsigned long get_unmapped_area(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
diff --git a/mm/mmap.c b/mm/mmap.c
index 9717337..b540fb2 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2094,3 +2094,75 @@ int may_expand_vm(struct mm_struct *mm,
return 0;
return 1;
}
+
+
+static struct page *special_mapping_nopage(struct vm_area_struct *vma,
+ unsigned long address, int *type)
+{
+ struct page **pages;
+
+ BUG_ON(address < vma->vm_start || address >= vma->vm_end);
+
+ address -= vma->vm_start;
+ for (pages = vma->vm_private_data; address > 0 && *pages; ++pages)
+ address -= PAGE_SIZE;
+
+ if (*pages) {
+ struct page *page = *pages;
+ get_page(page);
+ return page;
+ }
+
+ return NOPAGE_SIGBUS;
+}
+
+/*
+ * Having a close hook prevents vma merging regardless of flags.
+ */
+static void special_mapping_close(struct vm_area_struct *vma)
+{
+}
+
+static struct vm_operations_struct special_mapping_vmops = {
+ .close = special_mapping_close,
+ .nopage = special_mapping_nopage,
+};
+
+/*
+ * Called with mm->mmap_sem held for writing.
+ * Insert a new vma covering the given region, with the given flags.
+ * Its pages are supplied by the given array of struct page *.
+ * The array can be shorter than len >> PAGE_SHIFT if it's null-terminated.
+ * The region past the last page supplied will always produce SIGBUS.
+ * The array pointer and the pages it points to are assumed to stay alive
+ * for as long as this mapping might exist.
+ */
+int install_special_mapping(struct mm_struct *mm,
+ unsigned long addr, unsigned long len,
+ unsigned long vm_flags, struct page **pages)
+{
+ struct vm_area_struct *vma;
+
+ vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
+ if (unlikely(vma == NULL))
+ return -ENOMEM;
+
+ vma->vm_mm = mm;
+ vma->vm_start = addr;
+ vma->vm_end = addr + len;
+
+ vma->vm_flags = vm_flags | mm->def_flags;
+ vma->vm_page_prot = protection_map[vma->vm_flags & 7];
+
+ vma->vm_ops = &special_mapping_vmops;
+ vma->vm_private_data = pages;
+
+ if (unlikely(insert_vm_struct(mm, vma))) {
+ kmem_cache_free(vm_area_cachep, vma);
+ return -ENOMEM;
+ }
+
+ mm->total_vm += len >> PAGE_SHIFT;
+
+ return 0;
+}
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
