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kasan, page_alloc: allow skipping unpoisoning for HW_TAGS

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Add a new GFP flag __GFP_SKIP_KASAN_UNPOISON that allows skipping KASAN
poisoning for page_alloc allocations.  The flag is only effective with
HW_TAGS KASAN.

This flag will be used by vmalloc code for page_alloc allocations backing
vmalloc() mappings in a following patch.  The reason to skip KASAN
poisoning for these pages in page_alloc is because vmalloc code will be
poisoning them instead.

Also reword the comment for __GFP_SKIP_KASAN_POISON.

Link: https://lkml.kernel.org/r/35c97d77a704f6ff971dd3bfe4be95855744108e.1643047180.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Acked-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andrey Konovalov 2022-03-24 18:11:26 -07:00 committed by Linus Torvalds
parent f49d9c5bb1
commit 53ae233c30
3 changed files with 38 additions and 19 deletions
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21
include/linux/gfp.h
View File

@ -55,12 +55,14 @@ struct vm_area_struct;
#define ___GFP_ACCOUNT 0x400000u
#define ___GFP_ZEROTAGS 0x800000u
#ifdef CONFIG_KASAN_HW_TAGS
#define ___GFP_SKIP_KASAN_POISON 0x1000000u
#define ___GFP_SKIP_KASAN_UNPOISON 0x1000000u
#define ___GFP_SKIP_KASAN_POISON 0x2000000u
#else
#define ___GFP_SKIP_KASAN_UNPOISON 0
#define ___GFP_SKIP_KASAN_POISON 0
#endif
#ifdef CONFIG_LOCKDEP
#define ___GFP_NOLOCKDEP 0x2000000u
#define ___GFP_NOLOCKDEP 0x4000000u
#else
#define ___GFP_NOLOCKDEP 0
#endif
@ -241,22 +243,25 @@ struct vm_area_struct;
* intended for optimization: setting memory tags at the same time as zeroing
* memory has minimal additional performace impact.
*
* %__GFP_SKIP_KASAN_POISON returns a page which does not need to be poisoned
* on deallocation. Typically used for userspace pages. Currently only has an
* effect in HW tags mode.
* %__GFP_SKIP_KASAN_UNPOISON makes KASAN skip unpoisoning on page allocation.
* Only effective in HW_TAGS mode.
*
* %__GFP_SKIP_KASAN_POISON makes KASAN skip poisoning on page deallocation.
* Typically, used for userspace pages. Only effective in HW_TAGS mode.
*/
#define __GFP_NOWARN ((__force gfp_t)___GFP_NOWARN)
#define __GFP_COMP ((__force gfp_t)___GFP_COMP)
#define __GFP_ZERO ((__force gfp_t)___GFP_ZERO)
#define __GFP_ZEROTAGS ((__force gfp_t)___GFP_ZEROTAGS)
#define __GFP_SKIP_KASAN_POISON ((__force gfp_t)___GFP_SKIP_KASAN_POISON)
#define __GFP_SKIP_KASAN_UNPOISON ((__force gfp_t)___GFP_SKIP_KASAN_UNPOISON)
#define __GFP_SKIP_KASAN_POISON ((__force gfp_t)___GFP_SKIP_KASAN_POISON)
/* Disable lockdep for GFP context tracking */
#define __GFP_NOLOCKDEP ((__force gfp_t)___GFP_NOLOCKDEP)
/* Room for N __GFP_FOO bits */
#define __GFP_BITS_SHIFT (24 + \
IS_ENABLED(CONFIG_KASAN_HW_TAGS) + \
#define __GFP_BITS_SHIFT (24 + \
2 * IS_ENABLED(CONFIG_KASAN_HW_TAGS) + \
IS_ENABLED(CONFIG_LOCKDEP))
#define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))

5
include/trace/events/mmflags.h
View File

@ -52,8 +52,9 @@
{(unsigned long)__GFP_ZEROTAGS, "__GFP_ZEROTAGS"} \
#ifdef CONFIG_KASAN_HW_TAGS
#define __def_gfpflag_names_kasan \
, {(unsigned long)__GFP_SKIP_KASAN_POISON, "__GFP_SKIP_KASAN_POISON"}
#define __def_gfpflag_names_kasan , \
{(unsigned long)__GFP_SKIP_KASAN_POISON, "__GFP_SKIP_KASAN_POISON"}, \
{(unsigned long)__GFP_SKIP_KASAN_UNPOISON, "__GFP_SKIP_KASAN_UNPOISON"}
#else
#define __def_gfpflag_names_kasan
#endif

31
mm/page_alloc.c
View File

@ -2343,6 +2343,26 @@ static inline bool check_new_pcp(struct page *page, unsigned int order)
}
#endif /* CONFIG_DEBUG_VM */
static inline bool should_skip_kasan_unpoison(gfp_t flags, bool init_tags)
{
/* Don't skip if a software KASAN mode is enabled. */
if (IS_ENABLED(CONFIG_KASAN_GENERIC) ||
IS_ENABLED(CONFIG_KASAN_SW_TAGS))
return false;
/* Skip, if hardware tag-based KASAN is not enabled. */
if (!kasan_hw_tags_enabled())
return true;
/*
* With hardware tag-based KASAN enabled, skip if either:
*
* 1. Memory tags have already been cleared via tag_clear_highpage().
* 2. Skipping has been requested via __GFP_SKIP_KASAN_UNPOISON.
*/
return init_tags || (flags & __GFP_SKIP_KASAN_UNPOISON);
}
inline void post_alloc_hook(struct page *page, unsigned int order,
gfp_t gfp_flags)
{
@ -2382,15 +2402,8 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
/* Note that memory is already initialized by the loop above. */
init = false;
}
/*
* If either a software KASAN mode is enabled, or,
* in the case of hardware tag-based KASAN,
* if memory tags have not been cleared via tag_clear_highpage().
*/
if (IS_ENABLED(CONFIG_KASAN_GENERIC) ||
IS_ENABLED(CONFIG_KASAN_SW_TAGS) ||
kasan_hw_tags_enabled() && !init_tags) {
/* Mark shadow memory or set memory tags. */
if (!should_skip_kasan_unpoison(gfp_flags, init_tags)) {
/* Unpoison shadow memory or set memory tags. */
kasan_unpoison_pages(page, order, init);
/* Note that memory is already initialized by KASAN. */