From: Andrey Ryabinin a.ryabinin@samsung.com
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 (cherry picked from commit 71394fe50146202f2c8d92cf50f5ebc761acf254) Signed-off-by: Alex Shi alex.shi@linaro.org --- include/linux/vmalloc.h | 9 +++++++-- mm/vmalloc.c | 6 ++---- 2 files changed, 9 insertions(+), 6 deletions(-)
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 @@ struct vm_area_struct; /* vma defining user mapping in mm_types.h */ #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 @@ void vmalloc_sync_all(void);
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); diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 90520af..2658d2c 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -1325,10 +1325,8 @@ static struct vm_struct *__get_vm_area_node(unsigned long size, if (unlikely(!area)) return NULL;
- /* - * We always allocate a guard page. - */ - size += PAGE_SIZE; + if (!(flags & VM_NO_GUARD)) + size += PAGE_SIZE;
va = alloc_vmap_area(size, align, start, end, node, gfp_mask); if (IS_ERR(va)) {