On 1/21/21 5:34 PM, Andrey Konovalov wrote:
>> +- ``kasan.mode=sync`` or ``=async`` controls whether KASAN is configured in
>> + synchronous or asynchronous mode of execution (default: ``sync``).
>> + ``synchronous mode``: an exception is triggered if a tag check fault
>> occurs.
> Synchronous mode: a bad access is detected immediately when a tag
> check fault occurs.
>
> (No need for `` here, "synchronous mode" is not an inline snippet.)
>
Ok will do in v5.
>> + ``asynchronous mode``: if a tag check fault occurs, the information is
>> stored
>> + asynchronously in hardware (e.g. in the TFSR_EL1 register for arm64). The
>> kernel
>> + checks the hardware location and reports an error if the fault is
>> detected.
> Asynchronous mode: a bad access detection is delayed. When a tag check
> fault occurs, the information is stored in hardware (in the TFSR_EL1
> register for arm64). The kernel periodically checks the hardware and
> only reports tag faults during these checks.
>
Will do in v5.
>> +
>> - ``kasan.stacktrace=off`` or ``=on`` disables or enables alloc and free
>> stack
>> traces collection (default: ``on`` for ``CONFIG_DEBUG_KERNEL=y``,
>> otherwise
>> ``off``).
>> diff --git a/lib/test_kasan.c b/lib/test_kasan.c
>> index d16ec9e66806..7285dcf9fcc1 100644
>> --- a/lib/test_kasan.c
>> +++ b/lib/test_kasan.c
>> @@ -97,7 +97,7 @@ static void kasan_test_exit(struct kunit *test)
>> READ_ONCE(fail_data.report_found)); \
>> if (IS_ENABLED(CONFIG_KASAN_HW_TAGS)) { \
>> if (READ_ONCE(fail_data.report_found)) \
>> - hw_enable_tagging(); \
>> + hw_enable_tagging_sync(); \
>> migrate_enable(); \
>> } \
>> } while (0)
>> diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c
>> index e529428e7a11..224a2187839c 100644
>> --- a/mm/kasan/hw_tags.c
>> +++ b/mm/kasan/hw_tags.c
>> @@ -25,6 +25,11 @@ enum kasan_arg {
>> KASAN_ARG_ON,
>> };
>>
>> +enum kasan_arg_mode {
>> + KASAN_ARG_MODE_SYNC,
>> + KASAN_ARG_MODE_ASYNC,
> For other modes I explicitly added a _DEFAULT option first. It makes
> sense to do this here as well for consistency.
>
Will do in v5.
>> +};
>> +
>> enum kasan_arg_stacktrace {
>> KASAN_ARG_STACKTRACE_DEFAULT,
>> KASAN_ARG_STACKTRACE_OFF,
>> @@ -38,6 +43,7 @@ enum kasan_arg_fault {
>> };
>>
>> static enum kasan_arg kasan_arg __ro_after_init;
>> +static enum kasan_arg_mode kasan_arg_mode __ro_after_init;
>> static enum kasan_arg_stacktrace kasan_arg_stacktrace __ro_after_init;
>> static enum kasan_arg_fault kasan_arg_fault __ro_after_init;
>>
>> @@ -68,6 +74,21 @@ static int __init early_kasan_flag(char *arg)
>> }
>> early_param("kasan", early_kasan_flag);
>>
>> +/* kasan.mode=sync/async */
>> +static int __init early_kasan_mode(char *arg)
>> +{
>> + /* If arg is not set the default mode is sync */
>> + if ((!arg) || !strcmp(arg, "sync"))
>> + kasan_arg_mode = KASAN_ARG_MODE_SYNC;
>> + else if (!strcmp(arg, "async"))
>> + kasan_arg_mode = KASAN_ARG_MODE_ASYNC;
>> + else
>> + return -EINVAL;
>> +
>> + return 0;
>> +}
>> +early_param("kasan.mode", early_kasan_mode);
>> +
>> /* kasan.stacktrace=off/on */
>> static int __init early_kasan_flag_stacktrace(char *arg)
>> {
>> @@ -115,7 +136,11 @@ void kasan_init_hw_tags_cpu(void)
>> return;
>>
>> hw_init_tags(KASAN_TAG_MAX);
>> - hw_enable_tagging();
>> +
> Let's add a comment:
>
> /* Enable async mode only when explicitly requested through the command line.
> */
>
Will do in v5.
--
Regards,
Vincenzo
