Re: [PATCH v3 2/4] arm64: mte: Add asynchronous mode support
On 1/15/21 3:13 PM, Mark Rutland wrote:
> On Fri, Jan 15, 2021 at 12:00:41PM +, Vincenzo Frascino wrote:
>> MTE provides an asynchronous mode for detecting tag exceptions. In
>> particular instead of triggering a fault the arm64 core updates a
>> register which is checked by the kernel after the asynchronous tag
>> check fault has occurred.
>>
>> Add support for MTE asynchronous mode.
>>
>> The exception handling mechanism will be added with a future patch.
>>
>> Note: KASAN HW activates async mode via kasan.mode kernel parameter.
>> The default mode is set to synchronous.
>> The code that verifies the status of TFSR_EL1 will be added with a
>> future patch.
>>
>> Cc: Catalin Marinas
>> Cc: Will Deacon
>> Signed-off-by: Vincenzo Frascino
>> ---
>> arch/arm64/kernel/mte.c | 26 --
>> 1 file changed, 24 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
>> index 53a6d734e29b..df7a1ae26d7c 100644
>> --- a/arch/arm64/kernel/mte.c
>> +++ b/arch/arm64/kernel/mte.c
>> @@ -153,8 +153,30 @@ void mte_init_tags(u64 max_tag)
>>
>> void mte_enable_kernel(enum kasan_hw_tags_mode mode)
>> {
>> -/* Enable MTE Sync Mode for EL1. */
>> -sysreg_clear_set(sctlr_el1, SCTLR_ELx_TCF_MASK, SCTLR_ELx_TCF_SYNC);
>> +const char *m;
>> +
>> +/* Preset parameter values based on the mode. */
>> +switch (mode) {
>> +case KASAN_HW_TAGS_ASYNC:
>> +/* Enable MTE Async Mode for EL1. */
>> +sysreg_clear_set(sctlr_el1, SCTLR_ELx_TCF_MASK,
>> SCTLR_ELx_TCF_ASYNC);
>> +m = "asynchronous";
>> +break;
>> +case KASAN_HW_TAGS_SYNC:
>> +sysreg_clear_set(sctlr_el1, SCTLR_ELx_TCF_MASK,
>> SCTLR_ELx_TCF_SYNC);
>> +m = "synchronous";
>> +break;
>> +default:
>> +/*
>> + * kasan mode should be always set hence we should
>> + * not reach this condition.
>> + */
>> +WARN_ON_ONCE(1);
>> +return;
>> +}
>> +
>> +pr_info_once("MTE: enabled in %s mode at EL1\n", m);
>> +
>> isb();
>> }
>
> For clarity, we should have that ISB before the pr_info_once().
>
Good point, I will fix it in v4.
> As with my comment on patch 1, I think with separate functions this
> would be much clearer and simpler:
>
> static inline void __mte_enable_kernel(const char *mode, unsigned long tcf)
> {
> sysreg_clear_set(sctlr_el1, SCTLR_ELx_TCF_MASK, tcf);
> isb();
>
> pr_info_once("MTE: enabled in %s mode at EL1\n", mode);
> }
>
> void mte_enable_kernel_sync(void)
> {
> __mte_enable_kernel("synchronous", SCTLR_ELx_TCF_SYNC);
> }
>
> void mte_enable_kernel_async(void)
> {
> __mte_enable_kernel("asynchronous", SCTLR_ELx_TCF_ASYNC);
> }
>
Ok, seems cleaner like this, will adapt my code accordingly.
> Thanks,
> Mark.
>
--
Regards,
Vincenzo
Re: [PATCH v3 2/4] arm64: mte: Add asynchronous mode support
On Fri, Jan 15, 2021 at 12:00:41PM +, Vincenzo Frascino wrote:
> MTE provides an asynchronous mode for detecting tag exceptions. In
> particular instead of triggering a fault the arm64 core updates a
> register which is checked by the kernel after the asynchronous tag
> check fault has occurred.
>
> Add support for MTE asynchronous mode.
>
> The exception handling mechanism will be added with a future patch.
>
> Note: KASAN HW activates async mode via kasan.mode kernel parameter.
> The default mode is set to synchronous.
> The code that verifies the status of TFSR_EL1 will be added with a
> future patch.
>
> Cc: Catalin Marinas
> Cc: Will Deacon
> Signed-off-by: Vincenzo Frascino
> ---
> arch/arm64/kernel/mte.c | 26 --
> 1 file changed, 24 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
> index 53a6d734e29b..df7a1ae26d7c 100644
> --- a/arch/arm64/kernel/mte.c
> +++ b/arch/arm64/kernel/mte.c
> @@ -153,8 +153,30 @@ void mte_init_tags(u64 max_tag)
>
> void mte_enable_kernel(enum kasan_hw_tags_mode mode)
> {
> - /* Enable MTE Sync Mode for EL1. */
> - sysreg_clear_set(sctlr_el1, SCTLR_ELx_TCF_MASK, SCTLR_ELx_TCF_SYNC);
> + const char *m;
> +
> + /* Preset parameter values based on the mode. */
> + switch (mode) {
> + case KASAN_HW_TAGS_ASYNC:
> + /* Enable MTE Async Mode for EL1. */
> + sysreg_clear_set(sctlr_el1, SCTLR_ELx_TCF_MASK,
> SCTLR_ELx_TCF_ASYNC);
> + m = "asynchronous";
> + break;
> + case KASAN_HW_TAGS_SYNC:
> + sysreg_clear_set(sctlr_el1, SCTLR_ELx_TCF_MASK,
> SCTLR_ELx_TCF_SYNC);
> + m = "synchronous";
> + break;
> + default:
> + /*
> + * kasan mode should be always set hence we should
> + * not reach this condition.
> + */
> + WARN_ON_ONCE(1);
> + return;
> + }
> +
> + pr_info_once("MTE: enabled in %s mode at EL1\n", m);
> +
> isb();
> }
For clarity, we should have that ISB before the pr_info_once().
As with my comment on patch 1, I think with separate functions this
would be much clearer and simpler:
static inline void __mte_enable_kernel(const char *mode, unsigned long tcf)
{
sysreg_clear_set(sctlr_el1, SCTLR_ELx_TCF_MASK, tcf);
isb();
pr_info_once("MTE: enabled in %s mode at EL1\n", mode);
}
void mte_enable_kernel_sync(void)
{
__mte_enable_kernel("synchronous", SCTLR_ELx_TCF_SYNC);
}
void mte_enable_kernel_async(void)
{
__mte_enable_kernel("asynchronous", SCTLR_ELx_TCF_ASYNC);
}
Thanks,
Mark.
[PATCH v3 2/4] arm64: mte: Add asynchronous mode support
MTE provides an asynchronous mode for detecting tag exceptions. In
particular instead of triggering a fault the arm64 core updates a
register which is checked by the kernel after the asynchronous tag
check fault has occurred.
Add support for MTE asynchronous mode.
The exception handling mechanism will be added with a future patch.
Note: KASAN HW activates async mode via kasan.mode kernel parameter.
The default mode is set to synchronous.
The code that verifies the status of TFSR_EL1 will be added with a
future patch.
Cc: Catalin Marinas
Cc: Will Deacon
Signed-off-by: Vincenzo Frascino
---
arch/arm64/kernel/mte.c | 26 --
1 file changed, 24 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
index 53a6d734e29b..df7a1ae26d7c 100644
--- a/arch/arm64/kernel/mte.c
+++ b/arch/arm64/kernel/mte.c
@@ -153,8 +153,30 @@ void mte_init_tags(u64 max_tag)
void mte_enable_kernel(enum kasan_hw_tags_mode mode)
{
- /* Enable MTE Sync Mode for EL1. */
- sysreg_clear_set(sctlr_el1, SCTLR_ELx_TCF_MASK, SCTLR_ELx_TCF_SYNC);
+ const char *m;
+
+ /* Preset parameter values based on the mode. */
+ switch (mode) {
+ case KASAN_HW_TAGS_ASYNC:
+ /* Enable MTE Async Mode for EL1. */
+ sysreg_clear_set(sctlr_el1, SCTLR_ELx_TCF_MASK,
SCTLR_ELx_TCF_ASYNC);
+ m = "asynchronous";
+ break;
+ case KASAN_HW_TAGS_SYNC:
+ sysreg_clear_set(sctlr_el1, SCTLR_ELx_TCF_MASK,
SCTLR_ELx_TCF_SYNC);
+ m = "synchronous";
+ break;
+ default:
+ /*
+* kasan mode should be always set hence we should
+* not reach this condition.
+*/
+ WARN_ON_ONCE(1);
+ return;
+ }
+
+ pr_info_once("MTE: enabled in %s mode at EL1\n", m);
+
isb();
}
--
2.30.0
