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();
}
--
2.30.0
