Add get_current_el_maybe_constant()
There are some cases where we want to run EL-dependent code in the
shared code.
We could use #ifdef, but it leaves slight possibility where we do not
know the exception level at the build-time (e.g. library code).
The counter approach is to use get_current_el(), but it is run-time
detection, so all EL code is linked, some of which might be unneeded.
This commit adds get_current_el_maybe_constant(). This is a static
inline function that returns a constant value if we know the exception
level at build-time. This is mostly the case.
if (get_current_el_maybe_constant() == 1) {
/* do something for EL1 */
} else if (get_current_el_maybe_constant() == 3) {
/* do something for EL3 */
}
If get_current_el_maybe_constant() is build-time constant, the compiler
will optimize out the unreachable code.
If such code is included from the library code, it is not built-time
constant. In this case, it falls back to get_current_el(), so it still
works.
Change-Id: Idb03c20342a5b5173fe2d6b40e1fac7998675ad3
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/include/arch/aarch64/arch_helpers.h b/include/arch/aarch64/arch_helpers.h
index 240c1fb..7c30758 100644
--- a/include/arch/aarch64/arch_helpers.h
+++ b/include/arch/aarch64/arch_helpers.h
@@ -531,6 +531,23 @@
return GET_EL(read_CurrentEl());
}
+static inline unsigned int get_current_el_maybe_constant(void)
+{
+#if defined(IMAGE_AT_EL1)
+ return 1;
+#elif defined(IMAGE_AT_EL2)
+ return 2; /* no use-case in TF-A */
+#elif defined(IMAGE_AT_EL3)
+ return 3;
+#else
+ /*
+ * If we do not know which exception level this is being built for
+ * (e.g. built for library), fall back to run-time detection.
+ */
+ return get_current_el();
+#endif
+}
+
/*
* Check if an EL is implemented from AA64PFR0 register fields.
*/