Add support for dynamic mitigation for CVE-2018-3639
Some CPUS may benefit from using a dynamic mitigation approach for
CVE-2018-3639. A new SMC interface is defined to allow software
executing in lower ELs to enable or disable the mitigation for their
execution context.
It should be noted that regardless of the state of the mitigation for
lower ELs, code executing in EL3 is always mitigated against
CVE-2018-3639.
NOTE: This change is a compatibility break for any platform using
the declare_cpu_ops_workaround_cve_2017_5715 macro. Migrate to
the declare_cpu_ops_wa macro instead.
Change-Id: I3509a9337ad217bbd96de9f380c4ff8bf7917013
Signed-off-by: Dimitris Papastamos <dimitris.papastamos@arm.com>
diff --git a/lib/cpus/aarch64/cpu_helpers.S b/lib/cpus/aarch64/cpu_helpers.S
index 78c66e65..69ece8f 100644
--- a/lib/cpus/aarch64/cpu_helpers.S
+++ b/lib/cpus/aarch64/cpu_helpers.S
@@ -316,3 +316,27 @@
mov x0, #ERRATA_NOT_APPLIES
ret
endfunc check_wa_cve_2017_5715
+
+/*
+ * void *wa_cve_2018_3639_get_disable_ptr(void);
+ *
+ * Returns a function pointer which is used to disable mitigation
+ * for CVE-2018-3639.
+ * The function pointer is only returned on cores that employ
+ * dynamic mitigation. If the core uses static mitigation or is
+ * unaffected by CVE-2018-3639 this function returns NULL.
+ *
+ * NOTE: Must be called only after cpu_ops have been initialized
+ * in per-CPU data.
+ */
+ .globl wa_cve_2018_3639_get_disable_ptr
+func wa_cve_2018_3639_get_disable_ptr
+ mrs x0, tpidr_el3
+#if ENABLE_ASSERTIONS
+ cmp x0, #0
+ ASM_ASSERT(ne)
+#endif
+ ldr x0, [x0, #CPU_DATA_CPU_OPS_PTR]
+ ldr x0, [x0, #CPU_EXTRA2_FUNC]
+ ret
+endfunc wa_cve_2018_3639_get_disable_ptr