vmalloc: introduce remap_vmalloc_range_partial

We want to allocate ELF note segment buffer on the 2nd kernel in vmalloc
space and remap it to user-space in order to reduce the risk that memory
allocation fails on system with huge number of CPUs and so with huge ELF
note segment that exceeds 11-order block size.

Although there's already remap_vmalloc_range for the purpose of
remapping vmalloc memory to user-space, we need to specify user-space
range via vma.
 Mmap on /proc/vmcore needs to remap range across multiple objects, so
the interface that requires vma to cover full range is problematic.

This patch introduces remap_vmalloc_range_partial that receives user-space
range as a pair of base address and size and can be used for mmap on
/proc/vmcore case.

remap_vmalloc_range is rewritten using remap_vmalloc_range_partial.

[akpm@linux-foundation.org: use PAGE_ALIGNED()]
Signed-off-by: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp>
Cc: Lisa Mitchell <lisa.mitchell@hp.com>
Cc: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 49 insertions, 22 deletions

diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 7d5773a99f20..dd0a2c810529 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -82,6 +82,10 @@ extern void *vmap(struct page **pages, unsigned int count,
                         unsigned long flags, pgprot_t prot);
 extern void vunmap(const void *addr);
 
+extern int remap_vmalloc_range_partial(struct vm_area_struct *vma,
+                                       unsigned long uaddr, void *kaddr,
+                                       unsigned long size);
+
 extern int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
                                                         unsigned long pgoff);
 void vmalloc_sync_all(void);
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 3875fa2f0f60..b7259906a806 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1476,10 +1476,9 @@ static void __vunmap(const void *addr, int deallocate_pages)
         if (!addr)
                 return;
 
-        if ((PAGE_SIZE-1) & (unsigned long)addr) {
-                WARN(1, KERN_ERR "Trying to vfree() bad address (%p)\n", addr);
+        if (WARN(!PAGE_ALIGNED(addr), "Trying to vfree() bad address (%p)\n",
+                        addr));
                 return;
-        }
 
         area = remove_vm_area(addr);
         if (unlikely(!area)) {
@@ -2148,42 +2147,43 @@ finished:
 }
 
 /**
- *      remap_vmalloc_range  -  map vmalloc pages to userspace
- *      @vma:           vma to cover (map full range of vma)
- *      @addr:          vmalloc memory
- *      @pgoff:         number of pages into addr before first page to map
+ *      remap_vmalloc_range_partial  -  map vmalloc pages to userspace
+ *      @vma:           vma to cover
+ *      @uaddr:         target user address to start at
+ *      @kaddr:         virtual address of vmalloc kernel memory
+ *      @size:          size of map area
  *
  *      Returns:        0 for success, -Exxx on failure
  *
- *      This function checks that addr is a valid vmalloc'ed area, and
- *      that it is big enough to cover the vma. Will return failure if
- *      that criteria isn't met.
+ *      This function checks that @kaddr is a valid vmalloc'ed area,
+ *      and that it is big enough to cover the range starting at
+ *      @uaddr in @vma. Will return failure if that criteria isn't
+ *      met.
  *
  *      Similar to remap_pfn_range() (see mm/memory.c)
  */
-int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
-                                                unsigned long pgoff)
+int remap_vmalloc_range_partial(struct vm_area_struct *vma, unsigned long uaddr,
+                                void *kaddr, unsigned long size)
 {
         struct vm_struct *area;
-        unsigned long uaddr = vma->vm_start;
-        unsigned long usize = vma->vm_end - vma->vm_start;
 
-        if ((PAGE_SIZE-1) & (unsigned long)addr)
+        size = PAGE_ALIGN(size);
+
+        if (!PAGE_ALIGNED(uaddr) || !PAGE_ALIGNED(kaddr))
                 return -EINVAL;
 
-        area = find_vm_area(addr);
+        area = find_vm_area(kaddr);
         if (!area)
                 return -EINVAL;
 
         if (!(area->flags & VM_USERMAP))
                 return -EINVAL;
 
-        if (usize + (pgoff << PAGE_SHIFT) > area->size - PAGE_SIZE)
+        if (kaddr + size > area->addr + area->size)
                 return -EINVAL;
 
-        addr += pgoff << PAGE_SHIFT;
         do {
-                struct page *page = vmalloc_to_page(addr);
+                struct page *page = vmalloc_to_page(kaddr);
                 int ret;
 
                 ret = vm_insert_page(vma, uaddr, page);
@@ -2191,14 +2191,37 @@ int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
                         return ret;
 
                 uaddr += PAGE_SIZE;
-                addr += PAGE_SIZE;
-                usize -= PAGE_SIZE;
-        } while (usize > 0);
+                kaddr += PAGE_SIZE;
+                size -= PAGE_SIZE;
+        } while (size > 0);
 
         vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
 
         return 0;
 }
+EXPORT_SYMBOL(remap_vmalloc_range_partial);
+
+/**
+ *      remap_vmalloc_range  -  map vmalloc pages to userspace
+ *      @vma:           vma to cover (map full range of vma)
+ *      @addr:          vmalloc memory
+ *      @pgoff:         number of pages into addr before first page to map
+ *
+ *      Returns:        0 for success, -Exxx on failure
+ *
+ *      This function checks that addr is a valid vmalloc'ed area, and
+ *      that it is big enough to cover the vma. Will return failure if
+ *      that criteria isn't met.
+ *
+ *      Similar to remap_pfn_range() (see mm/memory.c)
+ */
+int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
+                                                unsigned long pgoff)
+{
+        return remap_vmalloc_range_partial(vma, vma->vm_start,
+                                           addr + (pgoff << PAGE_SHIFT),
+                                           vma->vm_end - vma->vm_start);
+}
 EXPORT_SYMBOL(remap_vmalloc_range);
 
 /*