Commit 2cb34276 authored by Andrey Konovalov's avatar Andrey Konovalov Committed by Linus Torvalds
Browse files

arm64: kasan: simplify and inline MTE functions 

This change provides a simpler implementation of mte_get_mem_tag(),
mte_get_random_tag(), and mte_set_mem_tag_range().

Simplifications include removing system_supports_mte() checks as these
functions are onlye called from KASAN runtime that had already checked
system_supports_mte().  Besides that, size and address alignment checks
are removed from mte_set_mem_tag_range(), as KASAN now does those.

This change also moves these functions into the asm/mte-kasan.h header and
implements mte_set_mem_tag_range() via inline assembly to avoid
unnecessary functions calls.

[vincenzo.frascino@arm.com: fix warning in mte_get_random_tag()]
  Link: https://lkml.kernel.org/r/20210211152208.23811-1-vincenzo.frascino@arm.com

Link: https://lkml.kernel.org/r/a26121b294fdf76e369cb7a74351d1c03a908930.1612546384.git.andreyknvl@google.com


Co-developed-by: default avatarVincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: default avatarVincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: default avatarAndrey Konovalov <andreyknvl@google.com>
Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Branislav Rankov <Branislav.Rankov@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Marco Elver <elver@google.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent cde8a7eb

arch/arm64/include/asm/cache.h

+0 −1
Original line number Diff line number Diff line
@@ -6,7 +6,6 @@ 
#define __ASM_CACHE_H



#include <asm/cputype.h>

#include <asm/mte-kasan.h>



#define CTR_L1IP_SHIFT		14

#define CTR_L1IP_MASK		3

arch/arm64/include/asm/kasan.h

+1 −0
Original line number Diff line number Diff line
@@ -6,6 +6,7 @@ 


#include <linux/linkage.h>

#include <asm/memory.h>

#include <asm/mte-kasan.h>

#include <asm/pgtable-types.h>



#define arch_kasan_set_tag(addr, tag)	__tag_set(addr, tag)

arch/arm64/include/asm/mte-def.h

+2 −0
Original line number Diff line number Diff line
@@ -11,4 +11,6 @@ 
#define MTE_TAG_SIZE		4

#define MTE_TAG_MASK		GENMASK((MTE_TAG_SHIFT + (MTE_TAG_SIZE - 1)), MTE_TAG_SHIFT)



#define __MTE_PREAMBLE		ARM64_ASM_PREAMBLE ".arch_extension memtag\n"



#endif /* __ASM_MTE_DEF_H  */

arch/arm64/include/asm/mte-kasan.h

+57 −8
Original line number Diff line number Diff line
@@ -11,11 +11,14 @@ 


#include <linux/types.h>



#ifdef CONFIG_ARM64_MTE



/*

 * The functions below are meant to be used only for the

 * KASAN_HW_TAGS interface defined in asm/memory.h.

 * These functions are meant to be only used from KASAN runtime through

 * the arch_*() interface defined in asm/memory.h.

 * These functions don't include system_supports_mte() checks,

 * as KASAN only calls them when MTE is supported and enabled.

 */

#ifdef CONFIG_ARM64_MTE



static inline u8 mte_get_ptr_tag(void *ptr)

{
@@ -25,9 +28,54 @@ static inline u8 mte_get_ptr_tag(void *ptr) 
	return tag;

}



u8 mte_get_mem_tag(void *addr);

u8 mte_get_random_tag(void);

void *mte_set_mem_tag_range(void *addr, size_t size, u8 tag);

/* Get allocation tag for the address. */

static inline u8 mte_get_mem_tag(void *addr)

{

	asm(__MTE_PREAMBLE "ldg %0, [%0]"

		: "+r" (addr));



	return mte_get_ptr_tag(addr);

}



/* Generate a random tag. */

static inline u8 mte_get_random_tag(void)

{

	void *addr;



	asm(__MTE_PREAMBLE "irg %0, %0"

		: "=r" (addr));



	return mte_get_ptr_tag(addr);

}



/*

 * Assign allocation tags for a region of memory based on the pointer tag.

 * Note: The address must be non-NULL and MTE_GRANULE_SIZE aligned and

 * size must be non-zero and MTE_GRANULE_SIZE aligned.

 */

static inline void mte_set_mem_tag_range(void *addr, size_t size, u8 tag)

{

	u64 curr, end;



	if (!size)

		return;



	curr = (u64)__tag_set(addr, tag);

	end = curr + size;



	do {

		/*

		 * 'asm volatile' is required to prevent the compiler to move

		 * the statement outside of the loop.

		 */

		asm volatile(__MTE_PREAMBLE "stg %0, [%0]"

			     :

			     : "r" (curr)

			     : "memory");



		curr += MTE_GRANULE_SIZE;

	} while (curr != end);

}



void mte_enable_kernel(void);

void mte_init_tags(u64 max_tag);
@@ -46,13 +94,14 @@ static inline u8 mte_get_mem_tag(void *addr) 
{

	return 0xFF;

}



static inline u8 mte_get_random_tag(void)

{

	return 0xFF;

}

static inline void *mte_set_mem_tag_range(void *addr, size_t size, u8 tag)



static inline void mte_set_mem_tag_range(void *addr, size_t size, u8 tag)

{

	return addr;

}



static inline void mte_enable_kernel(void)

arch/arm64/include/asm/mte.h

+0 −2
Original line number Diff line number Diff line
@@ -8,8 +8,6 @@ 
#include <asm/compiler.h>

#include <asm/mte-def.h>



#define __MTE_PREAMBLE		ARM64_ASM_PREAMBLE ".arch_extension memtag\n"



#ifndef __ASSEMBLY__



#include <linux/bitfield.h>