Make CONFIG_KASAN_SW_TAGS available for x86 machines if they have
ADDRESS_MASKING enabled (LAM) as that works similarly to Top-Byte Ignore
(TBI) that allows the software tag-based mode on arm64 platform.
Set scale macro based on KASAN mode: in software tag-based mode 16 bytes
of memory map to one shadow byte and 8 in generic mode.
Disable CONFIG_KASAN_INLINE and CONFIG_KASAN_STACK when
CONFIG_KASAN_SW_TAGS is enabled on x86 until the appropriate compiler
support is available.
Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com>
---
Changelog v4:
- Add x86 specific kasan_mem_to_shadow().
- Revert x86 to the older unsigned KASAN_SHADOW_OFFSET. Do the same to
KASAN_SHADOW_START/END.
- Modify scripts/gdb/linux/kasan.py to keep x86 using unsigned offset.
- Disable inline and stack support when software tags are enabled on
x86.
Changelog v3:
- Remove runtime_const from previous patch and merge the rest here.
- Move scale shift definition back to header file.
- Add new kasan offset for software tag based mode.
- Fix patch message typo 32 -> 16, and 16 -> 8.
- Update lib/Kconfig.kasan with x86 now having software tag-based
support.
Changelog v2:
- Remove KASAN dense code.
Documentation/arch/x86/x86_64/mm.rst | 6 ++++--
arch/x86/Kconfig | 4 +++-
arch/x86/boot/compressed/misc.h | 1 +
arch/x86/include/asm/kasan.h | 1 +
arch/x86/kernel/setup.c | 2 ++
lib/Kconfig.kasan | 3 ++-
scripts/gdb/linux/kasan.py | 4 ++--
7 files changed, 15 insertions(+), 6 deletions(-)
diff --git a/Documentation/arch/x86/x86_64/mm.rst b/Documentation/arch/x86/x86_64/mm.rst
index a6cf05d51bd8..ccbdbb4cda36 100644
--- a/Documentation/arch/x86/x86_64/mm.rst
+++ b/Documentation/arch/x86/x86_64/mm.rst
@@ -60,7 +60,8 @@ Complete virtual memory map with 4-level page tables
ffffe90000000000 | -23 TB | ffffe9ffffffffff | 1 TB | ... unused hole
ffffea0000000000 | -22 TB | ffffeaffffffffff | 1 TB | virtual memory map (vmemmap_base)
ffffeb0000000000 | -21 TB | ffffebffffffffff | 1 TB | ... unused hole
- ffffec0000000000 | -20 TB | fffffbffffffffff | 16 TB | KASAN shadow memory
+ ffffec0000000000 | -20 TB | fffffbffffffffff | 16 TB | KASAN shadow memory (generic mode)
+ fffff40000000000 | -8 TB | fffffbffffffffff | 8 TB | KASAN shadow memory (software tag-based mode)
__________________|____________|__________________|_________|____________________________________________________________
|
| Identical layout to the 56-bit one from here on:
@@ -130,7 +131,8 @@ Complete virtual memory map with 5-level page tables
ffd2000000000000 | -11.5 PB | ffd3ffffffffffff | 0.5 PB | ... unused hole
ffd4000000000000 | -11 PB | ffd5ffffffffffff | 0.5 PB | virtual memory map (vmemmap_base)
ffd6000000000000 | -10.5 PB | ffdeffffffffffff | 2.25 PB | ... unused hole
- ffdf000000000000 | -8.25 PB | fffffbffffffffff | ~8 PB | KASAN shadow memory
+ ffdf000000000000 | -8.25 PB | fffffbffffffffff | ~8 PB | KASAN shadow memory (generic mode)
+ ffeffc0000000000 | -6 PB | fffffbffffffffff | 4 PB | KASAN shadow memory (software tag-based mode)
__________________|____________|__________________|_________|____________________________________________________________
|
| Identical layout to the 47-bit one from here on:
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index b8df57ac0f28..f44fec1190b6 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -69,6 +69,7 @@ config X86
select ARCH_CLOCKSOURCE_INIT
select ARCH_CONFIGURES_CPU_MITIGATIONS
select ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
+ select ARCH_DISABLE_KASAN_INLINE if X86_64 && KASAN_SW_TAGS
select ARCH_ENABLE_HUGEPAGE_MIGRATION if X86_64 && HUGETLB_PAGE && MIGRATION
select ARCH_ENABLE_MEMORY_HOTPLUG if X86_64
select ARCH_ENABLE_MEMORY_HOTREMOVE if MEMORY_HOTPLUG
@@ -199,6 +200,7 @@ config X86
select HAVE_ARCH_JUMP_LABEL_RELATIVE
select HAVE_ARCH_KASAN if X86_64
select HAVE_ARCH_KASAN_VMALLOC if X86_64
+ select HAVE_ARCH_KASAN_SW_TAGS if ADDRESS_MASKING
select HAVE_ARCH_KFENCE
select HAVE_ARCH_KMSAN if X86_64
select HAVE_ARCH_KGDB
@@ -403,7 +405,7 @@ config AUDIT_ARCH
config KASAN_SHADOW_OFFSET
hex
- depends on KASAN
+ default 0xeffffc0000000000 if KASAN_SW_TAGS
default 0xdffffc0000000000
config HAVE_INTEL_TXT
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index db1048621ea2..ded92b439ada 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -13,6 +13,7 @@
#undef CONFIG_PARAVIRT_SPINLOCKS
#undef CONFIG_KASAN
#undef CONFIG_KASAN_GENERIC
+#undef CONFIG_KASAN_SW_TAGS
#define __NO_FORTIFY
diff --git a/arch/x86/include/asm/kasan.h b/arch/x86/include/asm/kasan.h
index f3e34a9754d2..385f4e9daab3 100644
--- a/arch/x86/include/asm/kasan.h
+++ b/arch/x86/include/asm/kasan.h
@@ -7,6 +7,7 @@
#include <linux/types.h>
#define KASAN_SHADOW_OFFSET _AC(CONFIG_KASAN_SHADOW_OFFSET, UL)
#ifdef CONFIG_KASAN_SW_TAGS
+#define KASAN_SHADOW_SCALE_SHIFT 4
/*
* LLVM ABI for reporting tag mismatches in inline KASAN mode.
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 1b2edd07a3e1..5b819f84f6db 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1207,6 +1207,8 @@ void __init setup_arch(char **cmdline_p)
kasan_init();
+ kasan_init_sw_tags();
+
/*
* Sync back kernel address range.
*
diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index f82889a830fa..9ddbc6aeb5d5 100644
--- a/lib/Kconfig.kasan
+++ b/lib/Kconfig.kasan
@@ -100,7 +100,8 @@ config KASAN_SW_TAGS
Requires GCC 11+ or Clang.
- Supported only on arm64 CPUs and relies on Top Byte Ignore.
+ Supported on arm64 CPUs that support Top Byte Ignore and on x86 CPUs
+ that support Linear Address Masking.
Consumes about 1/16th of available memory at kernel start and
add an overhead of ~20% for dynamic allocations.
diff --git a/scripts/gdb/linux/kasan.py b/scripts/gdb/linux/kasan.py
index fca39968d308..4b86202b155f 100644
--- a/scripts/gdb/linux/kasan.py
+++ b/scripts/gdb/linux/kasan.py
@@ -7,7 +7,7 @@
#
import gdb
-from linux import constants, mm
+from linux import constants, utils, mm
from ctypes import c_int64 as s64
def help():
@@ -40,7 +40,7 @@ class KasanMemToShadow(gdb.Command):
else:
help()
def kasan_mem_to_shadow(self, addr):
- if constants.CONFIG_KASAN_SW_TAGS:
+ if constants.CONFIG_KASAN_SW_TAGS and not utils.is_target_arch('x86'):
addr = s64(addr)
return (addr >> self.p_ops.KASAN_SHADOW_SCALE_SHIFT) + self.p_ops.KASAN_SHADOW_OFFSET
--
2.50.1On Mon, Aug 25, 2025 at 10:32 PM Maciej Wieczor-Retman
<maciej.wieczor-retman@intel.com> wrote:
>
> Make CONFIG_KASAN_SW_TAGS available for x86 machines if they have
> ADDRESS_MASKING enabled (LAM) as that works similarly to Top-Byte Ignore
> (TBI) that allows the software tag-based mode on arm64 platform.
>
> Set scale macro based on KASAN mode: in software tag-based mode 16 bytes
> of memory map to one shadow byte and 8 in generic mode.
>
> Disable CONFIG_KASAN_INLINE and CONFIG_KASAN_STACK when
> CONFIG_KASAN_SW_TAGS is enabled on x86 until the appropriate compiler
> support is available.
>
> Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com>
> ---
> Changelog v4:
> - Add x86 specific kasan_mem_to_shadow().
> - Revert x86 to the older unsigned KASAN_SHADOW_OFFSET. Do the same to
> KASAN_SHADOW_START/END.
> - Modify scripts/gdb/linux/kasan.py to keep x86 using unsigned offset.
> - Disable inline and stack support when software tags are enabled on
> x86.
>
> Changelog v3:
> - Remove runtime_const from previous patch and merge the rest here.
> - Move scale shift definition back to header file.
> - Add new kasan offset for software tag based mode.
> - Fix patch message typo 32 -> 16, and 16 -> 8.
> - Update lib/Kconfig.kasan with x86 now having software tag-based
> support.
>
> Changelog v2:
> - Remove KASAN dense code.
>
> Documentation/arch/x86/x86_64/mm.rst | 6 ++++--
> arch/x86/Kconfig | 4 +++-
> arch/x86/boot/compressed/misc.h | 1 +
> arch/x86/include/asm/kasan.h | 1 +
> arch/x86/kernel/setup.c | 2 ++
> lib/Kconfig.kasan | 3 ++-
> scripts/gdb/linux/kasan.py | 4 ++--
> 7 files changed, 15 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/arch/x86/x86_64/mm.rst b/Documentation/arch/x86/x86_64/mm.rst
> index a6cf05d51bd8..ccbdbb4cda36 100644
> --- a/Documentation/arch/x86/x86_64/mm.rst
> +++ b/Documentation/arch/x86/x86_64/mm.rst
> @@ -60,7 +60,8 @@ Complete virtual memory map with 4-level page tables
> ffffe90000000000 | -23 TB | ffffe9ffffffffff | 1 TB | ... unused hole
> ffffea0000000000 | -22 TB | ffffeaffffffffff | 1 TB | virtual memory map (vmemmap_base)
> ffffeb0000000000 | -21 TB | ffffebffffffffff | 1 TB | ... unused hole
> - ffffec0000000000 | -20 TB | fffffbffffffffff | 16 TB | KASAN shadow memory
> + ffffec0000000000 | -20 TB | fffffbffffffffff | 16 TB | KASAN shadow memory (generic mode)
> + fffff40000000000 | -8 TB | fffffbffffffffff | 8 TB | KASAN shadow memory (software tag-based mode)
> __________________|____________|__________________|_________|____________________________________________________________
> |
> | Identical layout to the 56-bit one from here on:
> @@ -130,7 +131,8 @@ Complete virtual memory map with 5-level page tables
> ffd2000000000000 | -11.5 PB | ffd3ffffffffffff | 0.5 PB | ... unused hole
> ffd4000000000000 | -11 PB | ffd5ffffffffffff | 0.5 PB | virtual memory map (vmemmap_base)
> ffd6000000000000 | -10.5 PB | ffdeffffffffffff | 2.25 PB | ... unused hole
> - ffdf000000000000 | -8.25 PB | fffffbffffffffff | ~8 PB | KASAN shadow memory
> + ffdf000000000000 | -8.25 PB | fffffbffffffffff | ~8 PB | KASAN shadow memory (generic mode)
> + ffeffc0000000000 | -6 PB | fffffbffffffffff | 4 PB | KASAN shadow memory (software tag-based mode)
> __________________|____________|__________________|_________|____________________________________________________________
> |
> | Identical layout to the 47-bit one from here on:
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index b8df57ac0f28..f44fec1190b6 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -69,6 +69,7 @@ config X86
> select ARCH_CLOCKSOURCE_INIT
> select ARCH_CONFIGURES_CPU_MITIGATIONS
> select ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
> + select ARCH_DISABLE_KASAN_INLINE if X86_64 && KASAN_SW_TAGS
Do you think it would make sense to drop the parts of the series that
add int3 handling, since the inline instrumentation does not work yet
anyway?
> select ARCH_ENABLE_HUGEPAGE_MIGRATION if X86_64 && HUGETLB_PAGE && MIGRATION
> select ARCH_ENABLE_MEMORY_HOTPLUG if X86_64
> select ARCH_ENABLE_MEMORY_HOTREMOVE if MEMORY_HOTPLUG
> @@ -199,6 +200,7 @@ config X86
> select HAVE_ARCH_JUMP_LABEL_RELATIVE
> select HAVE_ARCH_KASAN if X86_64
> select HAVE_ARCH_KASAN_VMALLOC if X86_64
> + select HAVE_ARCH_KASAN_SW_TAGS if ADDRESS_MASKING
> select HAVE_ARCH_KFENCE
> select HAVE_ARCH_KMSAN if X86_64
> select HAVE_ARCH_KGDB
> @@ -403,7 +405,7 @@ config AUDIT_ARCH
>
> config KASAN_SHADOW_OFFSET
> hex
> - depends on KASAN
Line accidentally removed?
> + default 0xeffffc0000000000 if KASAN_SW_TAGS
> default 0xdffffc0000000000
>
> config HAVE_INTEL_TXT
> diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
> index db1048621ea2..ded92b439ada 100644
> --- a/arch/x86/boot/compressed/misc.h
> +++ b/arch/x86/boot/compressed/misc.h
> @@ -13,6 +13,7 @@
> #undef CONFIG_PARAVIRT_SPINLOCKS
> #undef CONFIG_KASAN
> #undef CONFIG_KASAN_GENERIC
> +#undef CONFIG_KASAN_SW_TAGS
>
> #define __NO_FORTIFY
>
> diff --git a/arch/x86/include/asm/kasan.h b/arch/x86/include/asm/kasan.h
> index f3e34a9754d2..385f4e9daab3 100644
> --- a/arch/x86/include/asm/kasan.h
> +++ b/arch/x86/include/asm/kasan.h
> @@ -7,6 +7,7 @@
> #include <linux/types.h>
> #define KASAN_SHADOW_OFFSET _AC(CONFIG_KASAN_SHADOW_OFFSET, UL)
> #ifdef CONFIG_KASAN_SW_TAGS
> +#define KASAN_SHADOW_SCALE_SHIFT 4
>
> /*
> * LLVM ABI for reporting tag mismatches in inline KASAN mode.
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index 1b2edd07a3e1..5b819f84f6db 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -1207,6 +1207,8 @@ void __init setup_arch(char **cmdline_p)
>
> kasan_init();
>
> + kasan_init_sw_tags();
> +
> /*
> * Sync back kernel address range.
> *
> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
> index f82889a830fa..9ddbc6aeb5d5 100644
> --- a/lib/Kconfig.kasan
> +++ b/lib/Kconfig.kasan
> @@ -100,7 +100,8 @@ config KASAN_SW_TAGS
>
> Requires GCC 11+ or Clang.
>
> - Supported only on arm64 CPUs and relies on Top Byte Ignore.
> + Supported on arm64 CPUs that support Top Byte Ignore and on x86 CPUs
> + that support Linear Address Masking.
>
> Consumes about 1/16th of available memory at kernel start and
> add an overhead of ~20% for dynamic allocations.
> diff --git a/scripts/gdb/linux/kasan.py b/scripts/gdb/linux/kasan.py
> index fca39968d308..4b86202b155f 100644
> --- a/scripts/gdb/linux/kasan.py
> +++ b/scripts/gdb/linux/kasan.py
> @@ -7,7 +7,7 @@
> #
>
> import gdb
> -from linux import constants, mm
> +from linux import constants, utils, mm
> from ctypes import c_int64 as s64
>
> def help():
> @@ -40,7 +40,7 @@ class KasanMemToShadow(gdb.Command):
> else:
> help()
> def kasan_mem_to_shadow(self, addr):
> - if constants.CONFIG_KASAN_SW_TAGS:
> + if constants.CONFIG_KASAN_SW_TAGS and not utils.is_target_arch('x86'):
This change seems to belong to the patch that changes how the shadow
memory address is calculated.
> addr = s64(addr)
> return (addr >> self.p_ops.KASAN_SHADOW_SCALE_SHIFT) + self.p_ops.KASAN_SHADOW_OFFSET
>
> --
> 2.50.1
>
On 2025-09-06 at 19:19:33 +0200, Andrey Konovalov wrote:
>On Mon, Aug 25, 2025 at 10:32 PM Maciej Wieczor-Retman
><maciej.wieczor-retman@intel.com> wrote:
>>
>> Make CONFIG_KASAN_SW_TAGS available for x86 machines if they have
>> ADDRESS_MASKING enabled (LAM) as that works similarly to Top-Byte Ignore
>> (TBI) that allows the software tag-based mode on arm64 platform.
>>
>> Set scale macro based on KASAN mode: in software tag-based mode 16 bytes
>> of memory map to one shadow byte and 8 in generic mode.
>>
>> Disable CONFIG_KASAN_INLINE and CONFIG_KASAN_STACK when
>> CONFIG_KASAN_SW_TAGS is enabled on x86 until the appropriate compiler
>> support is available.
>>
>> Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com>
>> ---
>> Changelog v4:
>> - Add x86 specific kasan_mem_to_shadow().
>> - Revert x86 to the older unsigned KASAN_SHADOW_OFFSET. Do the same to
>> KASAN_SHADOW_START/END.
>> - Modify scripts/gdb/linux/kasan.py to keep x86 using unsigned offset.
>> - Disable inline and stack support when software tags are enabled on
>> x86.
>>
>> Changelog v3:
>> - Remove runtime_const from previous patch and merge the rest here.
>> - Move scale shift definition back to header file.
>> - Add new kasan offset for software tag based mode.
>> - Fix patch message typo 32 -> 16, and 16 -> 8.
>> - Update lib/Kconfig.kasan with x86 now having software tag-based
>> support.
>>
>> Changelog v2:
>> - Remove KASAN dense code.
>>
>> Documentation/arch/x86/x86_64/mm.rst | 6 ++++--
>> arch/x86/Kconfig | 4 +++-
>> arch/x86/boot/compressed/misc.h | 1 +
>> arch/x86/include/asm/kasan.h | 1 +
>> arch/x86/kernel/setup.c | 2 ++
>> lib/Kconfig.kasan | 3 ++-
>> scripts/gdb/linux/kasan.py | 4 ++--
>> 7 files changed, 15 insertions(+), 6 deletions(-)
>>
>> diff --git a/Documentation/arch/x86/x86_64/mm.rst b/Documentation/arch/x86/x86_64/mm.rst
>> index a6cf05d51bd8..ccbdbb4cda36 100644
>> --- a/Documentation/arch/x86/x86_64/mm.rst
>> +++ b/Documentation/arch/x86/x86_64/mm.rst
>> @@ -60,7 +60,8 @@ Complete virtual memory map with 4-level page tables
>> ffffe90000000000 | -23 TB | ffffe9ffffffffff | 1 TB | ... unused hole
>> ffffea0000000000 | -22 TB | ffffeaffffffffff | 1 TB | virtual memory map (vmemmap_base)
>> ffffeb0000000000 | -21 TB | ffffebffffffffff | 1 TB | ... unused hole
>> - ffffec0000000000 | -20 TB | fffffbffffffffff | 16 TB | KASAN shadow memory
>> + ffffec0000000000 | -20 TB | fffffbffffffffff | 16 TB | KASAN shadow memory (generic mode)
>> + fffff40000000000 | -8 TB | fffffbffffffffff | 8 TB | KASAN shadow memory (software tag-based mode)
>> __________________|____________|__________________|_________|____________________________________________________________
>> |
>> | Identical layout to the 56-bit one from here on:
>> @@ -130,7 +131,8 @@ Complete virtual memory map with 5-level page tables
>> ffd2000000000000 | -11.5 PB | ffd3ffffffffffff | 0.5 PB | ... unused hole
>> ffd4000000000000 | -11 PB | ffd5ffffffffffff | 0.5 PB | virtual memory map (vmemmap_base)
>> ffd6000000000000 | -10.5 PB | ffdeffffffffffff | 2.25 PB | ... unused hole
>> - ffdf000000000000 | -8.25 PB | fffffbffffffffff | ~8 PB | KASAN shadow memory
>> + ffdf000000000000 | -8.25 PB | fffffbffffffffff | ~8 PB | KASAN shadow memory (generic mode)
>> + ffeffc0000000000 | -6 PB | fffffbffffffffff | 4 PB | KASAN shadow memory (software tag-based mode)
>> __________________|____________|__________________|_________|____________________________________________________________
>> |
>> | Identical layout to the 47-bit one from here on:
>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
>> index b8df57ac0f28..f44fec1190b6 100644
>> --- a/arch/x86/Kconfig
>> +++ b/arch/x86/Kconfig
>> @@ -69,6 +69,7 @@ config X86
>> select ARCH_CLOCKSOURCE_INIT
>> select ARCH_CONFIGURES_CPU_MITIGATIONS
>> select ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
>> + select ARCH_DISABLE_KASAN_INLINE if X86_64 && KASAN_SW_TAGS
>
>Do you think it would make sense to drop the parts of the series that
>add int3 handling, since the inline instrumentation does not work yet
>anyway?
I thought we might as well put it into the kernel, so once the compiler side
gets upstreamed only the Kconfig needs to be modified.
But both options are okay, I thought itd be easy to argument changes to LLVM if
this inline mode is already prepared in the kernel.
>
>> select ARCH_ENABLE_HUGEPAGE_MIGRATION if X86_64 && HUGETLB_PAGE && MIGRATION
>> select ARCH_ENABLE_MEMORY_HOTPLUG if X86_64
>> select ARCH_ENABLE_MEMORY_HOTREMOVE if MEMORY_HOTPLUG
>> @@ -199,6 +200,7 @@ config X86
>> select HAVE_ARCH_JUMP_LABEL_RELATIVE
>> select HAVE_ARCH_KASAN if X86_64
>> select HAVE_ARCH_KASAN_VMALLOC if X86_64
>> + select HAVE_ARCH_KASAN_SW_TAGS if ADDRESS_MASKING
>> select HAVE_ARCH_KFENCE
>> select HAVE_ARCH_KMSAN if X86_64
>> select HAVE_ARCH_KGDB
>> @@ -403,7 +405,7 @@ config AUDIT_ARCH
>>
>> config KASAN_SHADOW_OFFSET
>> hex
>> - depends on KASAN
>
>Line accidentally removed?
Yes, sorry, I'll put it back in.
>
>> + default 0xeffffc0000000000 if KASAN_SW_TAGS
>> default 0xdffffc0000000000
>>
>> config HAVE_INTEL_TXT
>> diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
>> index db1048621ea2..ded92b439ada 100644
>> --- a/arch/x86/boot/compressed/misc.h
>> +++ b/arch/x86/boot/compressed/misc.h
>> @@ -13,6 +13,7 @@
>> #undef CONFIG_PARAVIRT_SPINLOCKS
>> #undef CONFIG_KASAN
>> #undef CONFIG_KASAN_GENERIC
>> +#undef CONFIG_KASAN_SW_TAGS
>>
>> #define __NO_FORTIFY
>>
>> diff --git a/arch/x86/include/asm/kasan.h b/arch/x86/include/asm/kasan.h
>> index f3e34a9754d2..385f4e9daab3 100644
>> --- a/arch/x86/include/asm/kasan.h
>> +++ b/arch/x86/include/asm/kasan.h
>> @@ -7,6 +7,7 @@
>> #include <linux/types.h>
>> #define KASAN_SHADOW_OFFSET _AC(CONFIG_KASAN_SHADOW_OFFSET, UL)
>> #ifdef CONFIG_KASAN_SW_TAGS
>> +#define KASAN_SHADOW_SCALE_SHIFT 4
>>
>> /*
>> * LLVM ABI for reporting tag mismatches in inline KASAN mode.
>> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
>> index 1b2edd07a3e1..5b819f84f6db 100644
>> --- a/arch/x86/kernel/setup.c
>> +++ b/arch/x86/kernel/setup.c
>> @@ -1207,6 +1207,8 @@ void __init setup_arch(char **cmdline_p)
>>
>> kasan_init();
>>
>> + kasan_init_sw_tags();
>> +
>> /*
>> * Sync back kernel address range.
>> *
>> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
>> index f82889a830fa..9ddbc6aeb5d5 100644
>> --- a/lib/Kconfig.kasan
>> +++ b/lib/Kconfig.kasan
>> @@ -100,7 +100,8 @@ config KASAN_SW_TAGS
>>
>> Requires GCC 11+ or Clang.
>>
>> - Supported only on arm64 CPUs and relies on Top Byte Ignore.
>> + Supported on arm64 CPUs that support Top Byte Ignore and on x86 CPUs
>> + that support Linear Address Masking.
>>
>> Consumes about 1/16th of available memory at kernel start and
>> add an overhead of ~20% for dynamic allocations.
>> diff --git a/scripts/gdb/linux/kasan.py b/scripts/gdb/linux/kasan.py
>> index fca39968d308..4b86202b155f 100644
>> --- a/scripts/gdb/linux/kasan.py
>> +++ b/scripts/gdb/linux/kasan.py
>> @@ -7,7 +7,7 @@
>> #
>>
>> import gdb
>> -from linux import constants, mm
>> +from linux import constants, utils, mm
>> from ctypes import c_int64 as s64
>>
>> def help():
>> @@ -40,7 +40,7 @@ class KasanMemToShadow(gdb.Command):
>> else:
>> help()
>> def kasan_mem_to_shadow(self, addr):
>> - if constants.CONFIG_KASAN_SW_TAGS:
>> + if constants.CONFIG_KASAN_SW_TAGS and not utils.is_target_arch('x86'):
>
>This change seems to belong to the patch that changes how the shadow
>memory address is calculated.
Okay, I can move it there.
>
>> addr = s64(addr)
>> return (addr >> self.p_ops.KASAN_SHADOW_SCALE_SHIFT) + self.p_ops.KASAN_SHADOW_OFFSET
>>
>> --
>> 2.50.1
>>
--
Kind regards
Maciej Wieczór-Retman
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