From 71394fe50146202f2c8d92cf50f5ebc761acf254 Mon Sep 17 00:00:00 2001 From: Andrey Ryabinin Date: Fri, 13 Feb 2015 14:40:03 -0800 Subject: 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 Cc: Dmitry Vyukov Cc: Konstantin Serebryany Cc: Dmitry Chernenkov Signed-off-by: Andrey Konovalov Cc: Yuri Gribov Cc: Konstantin Khlebnikov Cc: Sasha Levin Cc: Christoph Lameter Cc: Joonsoo Kim Cc: Dave Hansen Cc: Andi Kleen Cc: Ingo Molnar Cc: Thomas Gleixner Cc: "H. Peter Anvin" Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- 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 b87696fdf06a..1526fe712ca0 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 39c338896416..2e74e99d4cfe 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -1324,10 +1324,8 @@ 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)) { -- cgit v1.2.3-59-g8ed1b