mm: vmalloc: add flag preventing guard hole allocation
For instrumenting global variables KASan will shadow memory backing memory
for modules. So on module loading we will need to allocate memory for
shadow and map it at address in shadow that corresponds to the address
allocated in module_alloc().
__vmalloc_node_range() could be used for this purpose, except it puts a
guard hole after allocated area. Guard hole in shadow memory should be a
problem because at some future point we might need to have a shadow memory
at address occupied by guard hole. So we could fail to allocate shadow
for module_alloc().
Add a new vm_struct flag 'VM_NO_GUARD' indicating that vm area doesn't
have a guard hole.
Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Konstantin Serebryany <kcc@google.com>
Cc: Dmitry Chernenkov <dmitryc@google.com>
Signed-off-by: Andrey Konovalov <adech.fo@gmail.com>
Cc: Yuri Gribov <tetra2005@gmail.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index b87696f..1526fe7 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -16,6 +16,7 @@
#define VM_USERMAP 0x00000008 /* suitable for remap_vmalloc_range */
#define VM_VPAGES 0x00000010 /* buffer for pages was vmalloc'ed */
#define VM_UNINITIALIZED 0x00000020 /* vm_struct is not fully initialized */
+#define VM_NO_GUARD 0x00000040 /* don't add guard page */
/* bits [20..32] reserved for arch specific ioremap internals */
/*
@@ -96,8 +97,12 @@
static inline size_t get_vm_area_size(const struct vm_struct *area)
{
- /* return actual size without guard page */
- return area->size - PAGE_SIZE;
+ if (!(area->flags & VM_NO_GUARD))
+ /* return actual size without guard page */
+ return area->size - PAGE_SIZE;
+ else
+ return area->size;
+
}
extern struct vm_struct *get_vm_area(unsigned long size, unsigned long flags);