On Fri, Jan 15, 2021 at 12:00:41PM +0000, 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 <catalin.mari...@arm.com>
> Cc: Will Deacon <w...@kernel.org>
> Signed-off-by: Vincenzo Frascino <vincenzo.frasc...@arm.com>
> ---
> 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.
