MTE enabled arm64 HW can be configured in synchronous or asynchronous
tagging mode of execution.
In synchronous mode, an exception is triggered if a tag check fault
occurs.
In asynchronous mode, if a tag check fault occurs, the TFSR_EL1 register
is updated asynchronously. The kernel checks the corresponding bits
periodically.
Introduce an API that exposes the mode of execution to the kernel.
Note: This API will be used by KASAN KUNIT tests to forbid the execution
when async mode is enable.
Cc: Catalin Marinas <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Vincenzo Frascino <[email protected]>
---
arch/arm64/include/asm/memory.h | 1 +
arch/arm64/include/asm/mte-kasan.h | 6 ++++++
arch/arm64/kernel/mte.c | 8 ++++++++
3 files changed, 15 insertions(+)
diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index df96b9c10b81..1d4eef519fa6 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -233,6 +233,7 @@ static inline const void *__tag_set(const void *addr, u8 tag)
#ifdef CONFIG_KASAN_HW_TAGS
#define arch_enable_tagging_sync() mte_enable_kernel_sync()
#define arch_enable_tagging_async() mte_enable_kernel_async()
+#define arch_is_mode_sync() mte_is_mode_sync()
#define arch_set_tagging_report_once(state) mte_set_report_once(state)
#define arch_init_tags(max_tag) mte_init_tags(max_tag)
#define arch_get_random_tag() mte_get_random_tag()
diff --git a/arch/arm64/include/asm/mte-kasan.h b/arch/arm64/include/asm/mte-kasan.h
index 76b6a5988ce5..c216160e805c 100644
--- a/arch/arm64/include/asm/mte-kasan.h
+++ b/arch/arm64/include/asm/mte-kasan.h
@@ -31,6 +31,7 @@ void *mte_set_mem_tag_range(void *addr, size_t size, u8 tag);
void mte_enable_kernel_sync(void);
void mte_enable_kernel_async(void);
+bool mte_is_mode_sync(void);
void mte_init_tags(u64 max_tag);
void mte_set_report_once(bool state);
@@ -64,6 +65,11 @@ static inline void mte_enable_kernel_sync(void)
{
}
+static inline bool mte_is_mode_sync(void)
+{
+ return false;
+}
+
static inline void mte_init_tags(u64 max_tag)
{
}
diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
index 7763ac1f2917..1cc3fc173b97 100644
--- a/arch/arm64/kernel/mte.c
+++ b/arch/arm64/kernel/mte.c
@@ -26,6 +26,7 @@
u64 gcr_kernel_excl __ro_after_init;
static bool report_fault_once = true;
+static bool __mte_mode_sync = true;
static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_swap)
{
@@ -169,9 +170,16 @@ void mte_enable_kernel_sync(void)
void mte_enable_kernel_async(void)
{
+ __mte_mode_sync = false;
+
__mte_enable_kernel("asynchronous", SCTLR_ELx_TCF_ASYNC);
}
+bool mte_is_mode_sync(void)
+{
+ return __mte_mode_sync;
+}
+
void mte_set_report_once(bool state)
{
WRITE_ONCE(report_fault_once, state);
--
2.30.0
On Thu, Jan 21, 2021 at 5:40 PM Vincenzo Frascino
<[email protected]> wrote:
>
> MTE enabled arm64 HW can be configured in synchronous or asynchronous
> tagging mode of execution.
> In synchronous mode, an exception is triggered if a tag check fault
> occurs.
> In asynchronous mode, if a tag check fault occurs, the TFSR_EL1 register
> is updated asynchronously. The kernel checks the corresponding bits
> periodically.
>
> Introduce an API that exposes the mode of execution to the kernel.
>
> Note: This API will be used by KASAN KUNIT tests to forbid the execution
> when async mode is enable.
>
> Cc: Catalin Marinas <[email protected]>
> Cc: Will Deacon <[email protected]>
> Signed-off-by: Vincenzo Frascino <[email protected]>
> ---
> arch/arm64/include/asm/memory.h | 1 +
> arch/arm64/include/asm/mte-kasan.h | 6 ++++++
> arch/arm64/kernel/mte.c | 8 ++++++++
> 3 files changed, 15 insertions(+)
>
> diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
> index df96b9c10b81..1d4eef519fa6 100644
> --- a/arch/arm64/include/asm/memory.h
> +++ b/arch/arm64/include/asm/memory.h
> @@ -233,6 +233,7 @@ static inline const void *__tag_set(const void *addr, u8 tag)
> #ifdef CONFIG_KASAN_HW_TAGS
> #define arch_enable_tagging_sync() mte_enable_kernel_sync()
> #define arch_enable_tagging_async() mte_enable_kernel_async()
> +#define arch_is_mode_sync() mte_is_mode_sync()
> #define arch_set_tagging_report_once(state) mte_set_report_once(state)
> #define arch_init_tags(max_tag) mte_init_tags(max_tag)
> #define arch_get_random_tag() mte_get_random_tag()
> diff --git a/arch/arm64/include/asm/mte-kasan.h b/arch/arm64/include/asm/mte-kasan.h
> index 76b6a5988ce5..c216160e805c 100644
> --- a/arch/arm64/include/asm/mte-kasan.h
> +++ b/arch/arm64/include/asm/mte-kasan.h
> @@ -31,6 +31,7 @@ void *mte_set_mem_tag_range(void *addr, size_t size, u8 tag);
>
> void mte_enable_kernel_sync(void);
> void mte_enable_kernel_async(void);
> +bool mte_is_mode_sync(void);
> void mte_init_tags(u64 max_tag);
>
> void mte_set_report_once(bool state);
> @@ -64,6 +65,11 @@ static inline void mte_enable_kernel_sync(void)
> {
> }
>
> +static inline bool mte_is_mode_sync(void)
> +{
> + return false;
> +}
> +
> static inline void mte_init_tags(u64 max_tag)
> {
> }
> diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
> index 7763ac1f2917..1cc3fc173b97 100644
> --- a/arch/arm64/kernel/mte.c
> +++ b/arch/arm64/kernel/mte.c
> @@ -26,6 +26,7 @@
> u64 gcr_kernel_excl __ro_after_init;
>
> static bool report_fault_once = true;
> +static bool __mte_mode_sync = true;
>
> static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_swap)
> {
> @@ -169,9 +170,16 @@ void mte_enable_kernel_sync(void)
>
> void mte_enable_kernel_async(void)
> {
> + __mte_mode_sync = false;
> +
> __mte_enable_kernel("asynchronous", SCTLR_ELx_TCF_ASYNC);
> }
>
> +bool mte_is_mode_sync(void)
> +{
> + return __mte_mode_sync;
> +}
> +
> void mte_set_report_once(bool state)
> {
> WRITE_ONCE(report_fault_once, state);
> --
> 2.30.0
>
(See my comment on patch #6.)