diff --git a/arch/arm64/include/arch/asm_macros.h b/arch/arm64/include/arch/asm_macros.h
index 94df594ff2..9fe6c12037 100644
--- a/arch/arm64/include/arch/asm_macros.h
+++ b/arch/arm64/include/arch/asm_macros.h
@@ -36,7 +36,7 @@ ldp \ra, \rb, [sp], #16
 .endif
 .endm
 
-.macro calloc_bootmem_aligned, new_ptr, new_ptr_end, tmp, size_shift, phys_offset=0
+.macro calloc_bootmem_aligned, new_ptr, new_ptr_end, tmp, size_shift, phys_offset
 .if \size_shift < 4
     .error "calloc_bootmem_aligned: Unsupported size_shift, \size_shift"
 .endif
@@ -63,11 +63,9 @@ ldp \ra, \rb, [sp], #16
     mov     x1, #8
     bl      arch_clean_invalidate_cache_range
 
-.if \phys_offset != 0
-    /* clear page */
+    /* calculate virtual address */
     sub     \new_ptr, \new_ptr, \phys_offset
     sub     \new_ptr_end, \new_ptr_end, \phys_offset
-.endif
 
     /* clean and invalidate new page */
     mov     x0, \new_ptr
diff --git a/engine.mk b/engine.mk
index 35f7c296c6..cee2afb936 100644
--- a/engine.mk
+++ b/engine.mk
@@ -64,7 +64,7 @@ GLOBAL_INCLUDES := $(BUILDDIR) $(addsuffix /include,$(LKINC))
 GLOBAL_OPTFLAGS ?= $(ARCH_OPTFLAGS)
 GLOBAL_COMPILEFLAGS := -g -include $(CONFIGHEADER)
 GLOBAL_COMPILEFLAGS += -Wextra -Wall -Werror=return-type -Wshadow -Wdouble-promotion
-GLOBAL_COMPILEFLAGS += -Wno-multichar -Wno-unused-parameter -Wno-unused-function -Wno-unused-label -Wno-nonnull-compare
+GLOBAL_COMPILEFLAGS += -Wno-multichar -Wno-unused-parameter -Wno-unused-function -Wno-unused-label
 GLOBAL_COMPILEFLAGS += -fno-common
 GLOBAL_CFLAGS := --std=gnu11 -Werror-implicit-function-declaration -Wstrict-prototypes -Wwrite-strings
 GLOBAL_CPPFLAGS := --std=c++14 -fno-exceptions -fno-rtti -fno-threadsafe-statics
@@ -181,6 +181,32 @@ ifndef TOOLCHAIN_PREFIX
 $(error TOOLCHAIN_PREFIX not set in the arch rules.mk)
 endif
 
+# default to no ccache
+CCACHE ?=
+CC := $(CCACHE) $(TOOLCHAIN_PREFIX)gcc
+LD := $(TOOLCHAIN_PREFIX)ld
+OBJDUMP := $(TOOLCHAIN_PREFIX)objdump
+OBJCOPY := $(TOOLCHAIN_PREFIX)objcopy
+CPPFILT := $(TOOLCHAIN_PREFIX)c++filt
+SIZE := $(TOOLCHAIN_PREFIX)size
+NM := $(TOOLCHAIN_PREFIX)nm
+STRIP := $(TOOLCHAIN_PREFIX)strip
+
+# Now that CC is defined we can check if warning flags are supported and add
+# them to GLOBAL_COMPILEFLAGS if they are.
+ifeq ($(call is_warning_flag_supported,-Wnonnull-compare),yes)
+GLOBAL_COMPILEFLAGS += -Wno-nonnull-compare
+endif
+# Ideally we would move this check to arm64/rules.mk, but we can only check
+# for supported warning flags once CC is defined.
+ifeq ($(ARCH),arm64)
+# Clang incorrectly diagnoses msr operations as need a 64-bit operand even if
+# the underlying register is actually 32 bits. Silence this common warning.
+ifeq ($(call is_warning_flag_supported,-Wasm-operand-widths),yes)
+ARCH_COMPILEFLAGS += -Wno-asm-operand-widths
+endif
+endif
+
 $(info PROJECT = $(PROJECT))
 $(info PLATFORM = $(PLATFORM))
 $(info TARGET = $(TARGET))
@@ -230,17 +256,6 @@ ifneq ($(DEFINES),)
 $(error DEFINES variable set, please move to GLOBAL_DEFINES: $(DEFINES))
 endif
 
-# default to no ccache
-CCACHE ?=
-CC := $(CCACHE) $(TOOLCHAIN_PREFIX)gcc
-LD := $(TOOLCHAIN_PREFIX)ld
-OBJDUMP := $(TOOLCHAIN_PREFIX)objdump
-OBJCOPY := $(TOOLCHAIN_PREFIX)objcopy
-CPPFILT := $(TOOLCHAIN_PREFIX)c++filt
-SIZE := $(TOOLCHAIN_PREFIX)size
-NM := $(TOOLCHAIN_PREFIX)nm
-STRIP := $(TOOLCHAIN_PREFIX)strip
-
 # try to have the compiler output colorized error messages if available
 export GCC_COLORS ?= 1
 
diff --git a/external/lib/libm/rules.mk b/external/lib/libm/rules.mk
index ca93ce00e2..0ee81f5aa0 100644
--- a/external/lib/libm/rules.mk
+++ b/external/lib/libm/rules.mk
@@ -2,7 +2,10 @@ LOCAL_DIR := $(GET_LOCAL_DIR)
 
 MODULE := $(LOCAL_DIR)
 
-MODULE_CFLAGS += -Wno-unused-variable -Wno-sign-compare -Wno-parentheses -Wno-double-promotion -Wno-maybe-uninitialized
+MODULE_CFLAGS += -Wno-unused-variable -Wno-sign-compare -Wno-parentheses -Wno-double-promotion
+ifeq ($(call is_warning_flag_supported,-Wmaybe-uninitialized),yes)
+MODULE_CFLAGS += -Wno-maybe-uninitialized
+endif
 MODULE_OPTIONS := float
 
 MODULE_SRCS += \
diff --git a/lib/heap/heap_wrapper.c b/lib/heap/heap_wrapper.c
index 162f643c16..2764f4265c 100644
--- a/lib/heap/heap_wrapper.c
+++ b/lib/heap/heap_wrapper.c
@@ -89,6 +89,10 @@ static inline void *HEAP_CALLOC(size_t n, size_t s) {
 #define HEAP_FREE(p) dlfree(p)
 static inline void HEAP_INIT(void) {}
 
+void dump_callback(void *start, void *end, size_t used_bytes, void *arg) {
+    printf("\t\tstart %p end %p used_bytes %zu\n", start, end, used_bytes);
+}
+
 static inline void HEAP_DUMP(void) {
     struct mallinfo minfo = dlmallinfo();
 
@@ -102,9 +106,6 @@ static inline void HEAP_DUMP(void) {
     printf("\t\treleasable space 0x%zx\n", minfo.keepcost);
 
     printf("\theap block list:\n");
-    void dump_callback(void *start, void *end, size_t used_bytes, void *arg) {
-        printf("\t\tstart %p end %p used_bytes %zu\n", start, end, used_bytes);
-    }
 
     dlmalloc_inspect_all(&dump_callback, NULL);
 }
diff --git a/make/build.mk b/make/build.mk
index 84dca4a198..e5fb755c01 100644
--- a/make/build.mk
+++ b/make/build.mk
@@ -24,7 +24,7 @@ $(OUTELF).hex: $(OUTELF)
 $(OUTELF): $(ALLMODULE_OBJS) $(EXTRA_OBJS) $(LINKER_SCRIPT) $(EXTRA_LINKER_SCRIPTS)
 	$(info linking $@)
 	$(NOECHO)$(SIZE) -t --common $(sort $(ALLMODULE_OBJS)) $(EXTRA_OBJS)
-	$(NOECHO)$(LD) $(GLOBAL_LDFLAGS) $(ARCH_LDFLAGS) -dT $(LINKER_SCRIPT) \
+	$(NOECHO)$(LD) $(GLOBAL_LDFLAGS) $(ARCH_LDFLAGS) -d -T $(LINKER_SCRIPT) \
 		$(addprefix -T,$(EXTRA_LINKER_SCRIPTS)) \
 		$(ALLMODULE_OBJS) $(EXTRA_OBJS) $(LIBGCC) -Map=$(OUTELF).map -o $@
 
diff --git a/make/macros.mk b/make/macros.mk
index 39ed24a311..62232d9cf3 100644
--- a/make/macros.mk
+++ b/make/macros.mk
@@ -58,3 +58,17 @@ define MAKECONFIGHEADER
 	echo $3 >> $1.tmp; \
 	$(call TESTANDREPLACEFILE,$1.tmp,$1)
 endef
+
+check_compiler_flag = $(shell $(CC) -c -xc /dev/null -o /dev/null $(1) 2>/dev/null && echo yes || echo no)
+# Due to GCC's behaviour with regard to unknown warning flags this macro can
+# only be used to detect warning-enable options (-Wfoo) but not for warning
+# disable flags such as -Wno-foo.
+# https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#:~:text=When%20an%20unrecognized%20warning%20option%20is%20requested
+is_warning_flag_supported = $(strip \
+    $(if $(findstring -Wno-,$(1)),$(error "Cannot use -Wno- flags here: $(1)"),) \
+	$(if $(CC),,$(error "CC is not set, this macro cannot be used yet!")) \
+	$(if $($(call MAKECVAR,$(1))), \
+	    $(info Using cached result for $(1): $($(call MAKECVAR,$(1)))), \
+	    $(eval $(call MAKECVAR,$(1)) := $(call check_compiler_flag,-Werror -fsyntax-only $(1))) \
+	    $(info Checking if $(1) is supported: $($(call MAKECVAR,$(1)))) \
+	 )$($(call MAKECVAR,$(1))))
diff --git a/top/include/lk/compiler.h b/top/include/lk/compiler.h
index 75c57a4a33..45b1dc81d2 100644
--- a/top/include/lk/compiler.h
+++ b/top/include/lk/compiler.h
@@ -87,19 +87,22 @@
 #define __WARN_UNUSED_RESULT
 #endif
 
-#if (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 1)
+#if defined(__clang__)
+/* Clang does not support externally_visible, used should be similar. */
+#define __EXTERNALLY_VISIBLE __attribute__((used))
+#elif (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 1)
 #define __EXTERNALLY_VISIBLE __attribute__((externally_visible))
 #else
 #define __EXTERNALLY_VISIBLE
 #endif
 
-#if (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5)
+#if (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5) || defined(__clang__)
 #define __UNREACHABLE __builtin_unreachable()
 #else
 #define __UNREACHABLE
 #endif
 
-#if (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)
+#if (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6) || defined(__clang__)
 #ifdef __cplusplus
 #define STATIC_ASSERT(e) static_assert(e, #e)
 #else