Enable MTE support in both secure and non-secure worlds
This patch adds support for the new Memory Tagging Extension arriving in
ARMv8.5. MTE support is now enabled by default on systems that support
at EL0. To enable it at ELx for both the non-secure and the secure
world, the compiler flag CTX_INCLUDE_MTE_REGS includes register saving
and restoring when necessary in order to prevent register leakage
between the worlds.
Change-Id: I2d4ea993d6b11654ea0d4757d00ca20d23acf36c
Signed-off-by: Justin Chadwell <justin.chadwell@arm.com>
diff --git a/lib/el3_runtime/aarch64/context.S b/lib/el3_runtime/aarch64/context.S
index 53dc02e..37bb12c 100644
--- a/lib/el3_runtime/aarch64/context.S
+++ b/lib/el3_runtime/aarch64/context.S
@@ -145,6 +145,17 @@
str x14, [x0, #CTX_CNTKCTL_EL1]
#endif
+ /* Save MTE system registers if the build has instructed so */
+#if CTX_INCLUDE_MTE_REGS
+ mrs x15, TFSRE0_EL1
+ mrs x16, TFSR_EL1
+ stp x15, x16, [x0, #CTX_TFSRE0_EL1]
+
+ mrs x9, RGSR_EL1
+ mrs x10, GCR_EL1
+ stp x9, x10, [x0, #CTX_RGSR_EL1]
+#endif
+
ret
endfunc el1_sysregs_context_save
@@ -229,6 +240,16 @@
ldr x14, [x0, #CTX_CNTKCTL_EL1]
msr cntkctl_el1, x14
#endif
+ /* Restore MTE system registers if the build has instructed so */
+#if CTX_INCLUDE_MTE_REGS
+ ldp x11, x12, [x0, #CTX_TFSRE0_EL1]
+ msr TFSRE0_EL1, x11
+ msr TFSR_EL1, x12
+
+ ldp x13, x14, [x0, #CTX_RGSR_EL1]
+ msr RGSR_EL1, x13
+ msr GCR_EL1, x14
+#endif
/* No explict ISB required here as ERET covers it */
ret
diff --git a/lib/el3_runtime/aarch64/context_mgmt.c b/lib/el3_runtime/aarch64/context_mgmt.c
index bd5b3aa..446d9da 100644
--- a/lib/el3_runtime/aarch64/context_mgmt.c
+++ b/lib/el3_runtime/aarch64/context_mgmt.c
@@ -137,17 +137,30 @@
scr_el3 |= SCR_API_BIT | SCR_APK_BIT;
#endif /* !CTX_INCLUDE_PAUTH_REGS */
- unsigned int mte = get_armv8_5_mte_support();
-
/*
- * Enable MTE support unilaterally for normal world if the CPU supports
- * it.
+ * Enable MTE support. Support is enabled unilaterally for the normal
+ * world, and only for the secure world when CTX_INCLUDE_MTE_REGS is
+ * set.
*/
- if (mte != MTE_UNIMPLEMENTED) {
- if (security_state == NON_SECURE) {
- scr_el3 |= SCR_ATA_BIT;
- }
+ unsigned int mte = get_armv8_5_mte_support();
+#if CTX_INCLUDE_MTE_REGS
+ assert(mte == MTE_IMPLEMENTED_ELX);
+ scr_el3 |= SCR_ATA_BIT;
+#else
+ if (mte == MTE_IMPLEMENTED_EL0) {
+ /*
+ * Can enable MTE across both worlds as no MTE registers are
+ * used
+ */
+ scr_el3 |= SCR_ATA_BIT;
+ } else if (mte == MTE_IMPLEMENTED_ELX && security_state == NON_SECURE) {
+ /*
+ * Can only enable MTE in Non-Secure world without register
+ * saving
+ */
+ scr_el3 |= SCR_ATA_BIT;
}
+#endif
#ifdef IMAGE_BL31
/*