Require GCC for the GCC plugins (part II)

The current result on arm64_full_hardened_5.17_clang.config (clang 12):

[+] Special report mode: show_fail
[+] Kconfig file to check: my/arm64_full_hardened_5.17_clang.config
[+] Detected architecture: ARM64
[+] Detected kernel version: 5.17
=========================================================================================================================
              option name               | type  |desired val | decision |      reason      | check result
=========================================================================================================================
CONFIG_GCC_PLUGINS                      |kconfig|     y      |defconfig | self_protection  | FAIL: CONFIG_CC_IS_GCC not "y"
CONFIG_STACKPROTECTOR_PER_TASK          |kconfig|     y      |defconfig | self_protection  | FAIL: not found
CONFIG_FORTIFY_SOURCE                   |kconfig|     y      |   kspp   | self_protection  | FAIL: not found
CONFIG_GCC_PLUGIN_LATENT_ENTROPY        |kconfig|     y      |   kspp   | self_protection  | FAIL: CONFIG_CC_IS_GCC not "y"
CONFIG_ZERO_CALL_USED_REGS              |kconfig|     y      |   kspp   | self_protection  | FAIL: not found
CONFIG_GCC_PLUGIN_RANDSTRUCT            |kconfig|     y      |   kspp   | self_protection  | FAIL: CONFIG_CC_IS_GCC not "y"
CONFIG_GCC_PLUGIN_STACKLEAK             |kconfig|     y      |   kspp   | self_protection  | FAIL: CONFIG_CC_IS_GCC not "y"
CONFIG_GCC_PLUGIN_RANDSTRUCT_PERFORMANCE|kconfig| is not set |  clipos  | self_protection  | FAIL: CONFIG_CC_IS_GCC not "y"
CONFIG_STACKLEAK_METRICS                |kconfig| is not set |  clipos  | self_protection  | FAIL: CONFIG_CC_IS_GCC not "y"
CONFIG_STACKLEAK_RUNTIME_DISABLE        |kconfig| is not set |  clipos  | self_protection  | FAIL: CONFIG_CC_IS_GCC not "y"

CONFIG_STACKPROTECTOR_PER_TASK, CONFIG_FORTIFY_SOURCE and CONFIG_ZERO_CALL_USED_REGS
will be supported for clang in future (WIP).

kconfig_hardened_check/__init__.py

@@ -462,12 +462,15 @@ def add_kconfig_checks(l, arch):
     l += [KconfigCheck('self_protection', 'clipos', 'RANDOM_TRUST_BOOTLOADER', 'is not set')]
     l += [KconfigCheck('self_protection', 'clipos', 'RANDOM_TRUST_CPU', 'is not set')]
     l += [AND(KconfigCheck('self_protection', 'clipos', 'GCC_PLUGIN_RANDSTRUCT_PERFORMANCE', 'is not set'),
-              randstruct_is_set)]
+              randstruct_is_set,
+              cc_is_gcc)]
     if arch in ('X86_64', 'ARM64', 'X86_32'):
         l += [AND(KconfigCheck('self_protection', 'clipos', 'STACKLEAK_METRICS', 'is not set'),
-                  stackleak_is_set)]
+                  stackleak_is_set,
+                  cc_is_gcc)]
         l += [AND(KconfigCheck('self_protection', 'clipos', 'STACKLEAK_RUNTIME_DISABLE', 'is not set'),
-                  stackleak_is_set)]
+                  stackleak_is_set,
+                  cc_is_gcc)]
     if arch in ('X86_64', 'X86_32'):
         l += [AND(KconfigCheck('self_protection', 'clipos', 'INTEL_IOMMU_DEFAULT_ON', 'y'),
                   iommu_support_is_set)]