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3c5c3cfb9e
Patch series "kasan: support backing vmalloc space with real shadow
memory", v11.
Currently, vmalloc space is backed by the early shadow page. This means
that kasan is incompatible with VMAP_STACK.
This series provides a mechanism to back vmalloc space with real,
dynamically allocated memory. I have only wired up x86, because that's
the only currently supported arch I can work with easily, but it's very
easy to wire up other architectures, and it appears that there is some
work-in-progress code to do this on arm64 and s390.
This has been discussed before in the context of VMAP_STACK:
- https://bugzilla.kernel.org/show_bug.cgi?id=202009
- https://lkml.org/lkml/2018/7/22/198
- https://lkml.org/lkml/2019/7/19/822
In terms of implementation details:
Most mappings in vmalloc space are small, requiring less than a full
page of shadow space. Allocating a full shadow page per mapping would
therefore be wasteful. Furthermore, to ensure that different mappings
use different shadow pages, mappings would have to be aligned to
KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE.
Instead, share backing space across multiple mappings. Allocate a
backing page when a mapping in vmalloc space uses a particular page of
the shadow region. This page can be shared by other vmalloc mappings
later on.
We hook in to the vmap infrastructure to lazily clean up unused shadow
memory.
Testing with test_vmalloc.sh on an x86 VM with 2 vCPUs shows that:
- Turning on KASAN, inline instrumentation, without vmalloc, introuduces
a 4.1x-4.2x slowdown in vmalloc operations.
- Turning this on introduces the following slowdowns over KASAN:
* ~1.76x slower single-threaded (test_vmalloc.sh performance)
* ~2.18x slower when both cpus are performing operations
simultaneously (test_vmalloc.sh sequential_test_order=1)
This is unfortunate but given that this is a debug feature only, not the
end of the world. The benchmarks are also a stress-test for the vmalloc
subsystem: they're not indicative of an overall 2x slowdown!
This patch (of 4):
Hook into vmalloc and vmap, and dynamically allocate real shadow memory
to back the mappings.
Most mappings in vmalloc space are small, requiring less than a full
page of shadow space. Allocating a full shadow page per mapping would
therefore be wasteful. Furthermore, to ensure that different mappings
use different shadow pages, mappings would have to be aligned to
KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE.
Instead, share backing space across multiple mappings. Allocate a
backing page when a mapping in vmalloc space uses a particular page of
the shadow region. This page can be shared by other vmalloc mappings
later on.
We hook in to the vmap infrastructure to lazily clean up unused shadow
memory.
To avoid the difficulties around swapping mappings around, this code
expects that the part of the shadow region that covers the vmalloc space
will not be covered by the early shadow page, but will be left unmapped.
This will require changes in arch-specific code.
This allows KASAN with VMAP_STACK, and may be helpful for architectures
that do not have a separate module space (e.g. powerpc64, which I am
currently working on). It also allows relaxing the module alignment
back to PAGE_SIZE.
Testing with test_vmalloc.sh on an x86 VM with 2 vCPUs shows that:
- Turning on KASAN, inline instrumentation, without vmalloc, introuduces
a 4.1x-4.2x slowdown in vmalloc operations.
- Turning this on introduces the following slowdowns over KASAN:
* ~1.76x slower single-threaded (test_vmalloc.sh performance)
* ~2.18x slower when both cpus are performing operations
simultaneously (test_vmalloc.sh sequential_test_order=3D1)
This is unfortunate but given that this is a debug feature only, not the
end of the world.
The full benchmark results are:
Performance
No KASAN KASAN original x baseline KASAN vmalloc x baseline x KASAN
fix_size_alloc_test 662004 11404956 17.23 19144610 28.92 1.68
full_fit_alloc_test 710950 12029752 16.92 13184651 18.55 1.10
long_busy_list_alloc_test 9431875 43990172 4.66 82970178 8.80 1.89
random_size_alloc_test 5033626 23061762 4.58 47158834 9.37 2.04
fix_align_alloc_test 1252514 15276910 12.20 31266116 24.96 2.05
random_size_align_alloc_te 1648501 14578321 8.84 25560052 15.51 1.75
align_shift_alloc_test 147 830 5.65 5692 38.72 6.86
pcpu_alloc_test 80732 125520 1.55 140864 1.74 1.12
Total Cycles 119240774314 763211341128 6.40 1390338696894 11.66 1.82
Sequential, 2 cpus
No KASAN KASAN original x baseline KASAN vmalloc x baseline x KASAN
fix_size_alloc_test 1423150
14276550 10.03 27733022 19.49 1.94
full_fit_alloc_test 1754219 14722640 8.39 15030786 8.57 1.02
long_busy_list_alloc_test 11451858 52154973 4.55 107016027 9.34 2.05
random_size_alloc_test 5989020 26735276 4.46 68885923 11.50 2.58
fix_align_alloc_test 2050976 20166900 9.83 50491675 24.62 2.50
random_size_align_alloc_te 2858229 17971700 6.29 38730225 13.55 2.16
align_shift_alloc_test 405 6428 15.87 26253 64.82 4.08
pcpu_alloc_test 127183 151464 1.19 216263 1.70 1.43
Total Cycles 54181269392 308723699764 5.70 650772566394 12.01 2.11
fix_size_alloc_test 1420404 14289308 10.06 27790035 19.56 1.94
full_fit_alloc_test 1736145 14806234 8.53 15274301 8.80 1.03
long_busy_list_alloc_test 11404638 52270785 4.58 107550254 9.43 2.06
random_size_alloc_test 6017006 26650625 4.43 68696127 11.42 2.58
fix_align_alloc_test 2045504 20280985 9.91 50414862 24.65 2.49
random_size_align_alloc_te 2845338 17931018 6.30 38510276 13.53 2.15
align_shift_alloc_test 472 3760 7.97 9656 20.46 2.57
pcpu_alloc_test 118643 132732 1.12 146504 1.23 1.10
Total Cycles 54040011688 309102805492 5.72 651325675652 12.05 2.11
[dja@axtens.net: fixups]
Link: http://lkml.kernel.org/r/20191120052719.7201-1-dja@axtens.net
Link: https://bugzilla.kernel.org/show_bug.cgi?id=3D202009
Link: http://lkml.kernel.org/r/20191031093909.9228-2-dja@axtens.net
Signed-off-by: Mark Rutland <mark.rutland@arm.com> [shadow rework]
Signed-off-by: Daniel Axtens <dja@axtens.net>
Co-developed-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Qian Cai <cai@lca.pw>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
252 lines
7.7 KiB
C
252 lines
7.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_VMALLOC_H
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#define _LINUX_VMALLOC_H
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#include <linux/spinlock.h>
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#include <linux/init.h>
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#include <linux/list.h>
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#include <linux/llist.h>
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#include <asm/page.h> /* pgprot_t */
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#include <linux/rbtree.h>
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#include <linux/overflow.h>
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struct vm_area_struct; /* vma defining user mapping in mm_types.h */
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struct notifier_block; /* in notifier.h */
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/* bits in flags of vmalloc's vm_struct below */
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#define VM_IOREMAP 0x00000001 /* ioremap() and friends */
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#define VM_ALLOC 0x00000002 /* vmalloc() */
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#define VM_MAP 0x00000004 /* vmap()ed pages */
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#define VM_USERMAP 0x00000008 /* suitable for remap_vmalloc_range */
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#define VM_DMA_COHERENT 0x00000010 /* dma_alloc_coherent */
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#define VM_UNINITIALIZED 0x00000020 /* vm_struct is not fully initialized */
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#define VM_NO_GUARD 0x00000040 /* don't add guard page */
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#define VM_KASAN 0x00000080 /* has allocated kasan shadow memory */
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/*
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* VM_KASAN is used slighly differently depending on CONFIG_KASAN_VMALLOC.
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*
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* If IS_ENABLED(CONFIG_KASAN_VMALLOC), VM_KASAN is set on a vm_struct after
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* shadow memory has been mapped. It's used to handle allocation errors so that
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* we don't try to poision shadow on free if it was never allocated.
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*
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* Otherwise, VM_KASAN is set for kasan_module_alloc() allocations and used to
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* determine which allocations need the module shadow freed.
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*/
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/*
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* Memory with VM_FLUSH_RESET_PERMS cannot be freed in an interrupt or with
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* vfree_atomic().
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*/
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#define VM_FLUSH_RESET_PERMS 0x00000100 /* Reset direct map and flush TLB on unmap */
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/* bits [20..32] reserved for arch specific ioremap internals */
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/*
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* Maximum alignment for ioremap() regions.
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* Can be overriden by arch-specific value.
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*/
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#ifndef IOREMAP_MAX_ORDER
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#define IOREMAP_MAX_ORDER (7 + PAGE_SHIFT) /* 128 pages */
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#endif
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struct vm_struct {
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struct vm_struct *next;
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void *addr;
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unsigned long size;
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unsigned long flags;
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struct page **pages;
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unsigned int nr_pages;
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phys_addr_t phys_addr;
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const void *caller;
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};
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struct vmap_area {
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unsigned long va_start;
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unsigned long va_end;
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struct rb_node rb_node; /* address sorted rbtree */
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struct list_head list; /* address sorted list */
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/*
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* The following three variables can be packed, because
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* a vmap_area object is always one of the three states:
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* 1) in "free" tree (root is vmap_area_root)
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* 2) in "busy" tree (root is free_vmap_area_root)
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* 3) in purge list (head is vmap_purge_list)
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*/
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union {
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unsigned long subtree_max_size; /* in "free" tree */
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struct vm_struct *vm; /* in "busy" tree */
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struct llist_node purge_list; /* in purge list */
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};
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};
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/*
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* Highlevel APIs for driver use
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*/
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extern void vm_unmap_ram(const void *mem, unsigned int count);
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extern void *vm_map_ram(struct page **pages, unsigned int count,
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int node, pgprot_t prot);
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extern void vm_unmap_aliases(void);
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#ifdef CONFIG_MMU
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extern void __init vmalloc_init(void);
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extern unsigned long vmalloc_nr_pages(void);
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#else
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static inline void vmalloc_init(void)
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{
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}
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static inline unsigned long vmalloc_nr_pages(void) { return 0; }
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#endif
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extern void *vmalloc(unsigned long size);
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extern void *vzalloc(unsigned long size);
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extern void *vmalloc_user(unsigned long size);
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extern void *vmalloc_node(unsigned long size, int node);
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extern void *vzalloc_node(unsigned long size, int node);
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extern void *vmalloc_user_node_flags(unsigned long size, int node, gfp_t flags);
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extern void *vmalloc_exec(unsigned long size);
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extern void *vmalloc_32(unsigned long size);
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extern void *vmalloc_32_user(unsigned long size);
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extern void *__vmalloc(unsigned long size, gfp_t gfp_mask, pgprot_t prot);
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extern void *__vmalloc_node_range(unsigned long size, unsigned long align,
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unsigned long start, unsigned long end, gfp_t gfp_mask,
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pgprot_t prot, unsigned long vm_flags, int node,
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const void *caller);
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#ifndef CONFIG_MMU
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extern void *__vmalloc_node_flags(unsigned long size, int node, gfp_t flags);
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static inline void *__vmalloc_node_flags_caller(unsigned long size, int node,
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gfp_t flags, void *caller)
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{
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return __vmalloc_node_flags(size, node, flags);
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}
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#else
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extern void *__vmalloc_node_flags_caller(unsigned long size,
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int node, gfp_t flags, void *caller);
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#endif
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extern void vfree(const void *addr);
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extern void vfree_atomic(const void *addr);
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extern void *vmap(struct page **pages, unsigned int count,
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unsigned long flags, pgprot_t prot);
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extern void vunmap(const void *addr);
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extern int remap_vmalloc_range_partial(struct vm_area_struct *vma,
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unsigned long uaddr, void *kaddr,
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unsigned long size);
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extern int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
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unsigned long pgoff);
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void vmalloc_sync_all(void);
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/*
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* Lowlevel-APIs (not for driver use!)
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*/
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static inline size_t get_vm_area_size(const struct vm_struct *area)
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{
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if (!(area->flags & VM_NO_GUARD))
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/* return actual size without guard page */
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return area->size - PAGE_SIZE;
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else
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return area->size;
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}
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extern struct vm_struct *get_vm_area(unsigned long size, unsigned long flags);
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extern struct vm_struct *get_vm_area_caller(unsigned long size,
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unsigned long flags, const void *caller);
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extern struct vm_struct *__get_vm_area(unsigned long size, unsigned long flags,
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unsigned long start, unsigned long end);
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extern struct vm_struct *__get_vm_area_caller(unsigned long size,
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unsigned long flags,
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unsigned long start, unsigned long end,
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const void *caller);
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extern struct vm_struct *remove_vm_area(const void *addr);
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extern struct vm_struct *find_vm_area(const void *addr);
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extern int map_vm_area(struct vm_struct *area, pgprot_t prot,
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struct page **pages);
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#ifdef CONFIG_MMU
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extern int map_kernel_range_noflush(unsigned long start, unsigned long size,
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pgprot_t prot, struct page **pages);
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extern void unmap_kernel_range_noflush(unsigned long addr, unsigned long size);
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extern void unmap_kernel_range(unsigned long addr, unsigned long size);
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static inline void set_vm_flush_reset_perms(void *addr)
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{
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struct vm_struct *vm = find_vm_area(addr);
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if (vm)
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vm->flags |= VM_FLUSH_RESET_PERMS;
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}
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#else
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static inline int
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map_kernel_range_noflush(unsigned long start, unsigned long size,
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pgprot_t prot, struct page **pages)
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{
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return size >> PAGE_SHIFT;
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}
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static inline void
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unmap_kernel_range_noflush(unsigned long addr, unsigned long size)
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{
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}
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static inline void
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unmap_kernel_range(unsigned long addr, unsigned long size)
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{
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}
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static inline void set_vm_flush_reset_perms(void *addr)
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{
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}
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#endif
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/* Allocate/destroy a 'vmalloc' VM area. */
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extern struct vm_struct *alloc_vm_area(size_t size, pte_t **ptes);
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extern void free_vm_area(struct vm_struct *area);
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/* for /dev/kmem */
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extern long vread(char *buf, char *addr, unsigned long count);
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extern long vwrite(char *buf, char *addr, unsigned long count);
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/*
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* Internals. Dont't use..
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*/
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extern struct list_head vmap_area_list;
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extern __init void vm_area_add_early(struct vm_struct *vm);
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extern __init void vm_area_register_early(struct vm_struct *vm, size_t align);
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#ifdef CONFIG_SMP
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# ifdef CONFIG_MMU
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struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets,
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const size_t *sizes, int nr_vms,
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size_t align);
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void pcpu_free_vm_areas(struct vm_struct **vms, int nr_vms);
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# else
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static inline struct vm_struct **
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pcpu_get_vm_areas(const unsigned long *offsets,
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const size_t *sizes, int nr_vms,
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size_t align)
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{
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return NULL;
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}
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static inline void
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pcpu_free_vm_areas(struct vm_struct **vms, int nr_vms)
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{
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}
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# endif
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#endif
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#ifdef CONFIG_MMU
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#define VMALLOC_TOTAL (VMALLOC_END - VMALLOC_START)
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#else
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#define VMALLOC_TOTAL 0UL
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#endif
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int register_vmap_purge_notifier(struct notifier_block *nb);
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int unregister_vmap_purge_notifier(struct notifier_block *nb);
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#endif /* _LINUX_VMALLOC_H */
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