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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>
This commit is contained in:
Masahiro Yamada 2020-03-26 13:18:48 +09:00
parent d5e97a1d2c
commit fd092be239
1 changed files with 17 additions and 0 deletions
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17
include/arch/aarch64/arch_helpers.h
View File

@ -531,6 +531,23 @@ static inline unsigned int get_current_el(void)
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.
*/