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.

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>

diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 7d5773a99f20690dac2bbf60dbcda274b9c20ae8..dd0a2c810529ed09526d25336a7b2a37d969f6ea 100644 (file)
--- 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 3875fa2f0f603fe37fa069817c086489aab03914..d9a9f4f6ee0767684752a1062a3ee8e20d1917bc 100644 (file)
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2148,42 +2148,44 @@ 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_SIZE-1) & (unsigned long)uaddr) ||
+           ((PAGE_SIZE-1) & (unsigned long)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 +2193,37 @@ 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);
 
 /*