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diff --git a/lib/libc/aarch64/Symbol.map b/lib/libc/aarch64/Symbol.map
--- a/lib/libc/aarch64/Symbol.map
+++ b/lib/libc/aarch64/Symbol.map
@@ -11,6 +11,7 @@
/* PSEUDO syscalls */
_exit;
+ .mcount;
_setjmp;
_longjmp;
fabs;
diff --git a/sys/arm64/include/profile.h b/sys/arm64/include/profile.h
--- a/sys/arm64/include/profile.h
+++ b/sys/arm64/include/profile.h
@@ -44,8 +44,51 @@
typedef __uintfptr_t uintfptr_t;
-#define _MCOUNT_DECL void mcount
+#define _MCOUNT_DECL \
+static void _mcount(uintfptr_t frompc, uintfptr_t selfpc) __used; \
+static void _mcount
+
+#ifdef __GNUCLIKE_ASM
+/*
+ * Call into _mcount. On arm64 the .mcount is a function so callers will
+ * handle caller saved registers. As we don't directly touch any callee
+ * saved registers we can just load the two arguments and use a tail call
+ * into the MI _mcount function.
+ *
+ * When building with gcc frompc will be in x0, however this is not the
+ * case on clang. As such we need to load it from the stack. As long as
+ * the caller follows the ABI this will load the correct value.
+ */
+#define MCOUNT __asm( \
+" .text \n" \
+" .align 6 \n" \
+" .type .mcount,#function \n" \
+" .globl .mcount \n" \
+" .mcount: \n" \
+" .cfi_startproc \n" \
+ /* Load the caller return address as frompc */ \
+" ldr x0, [x29, #8] \n" \
+ /* Use our return address as selfpc */ \
+" mov x1, lr \n" \
+" b _mcount \n" \
+" .cfi_endproc \n" \
+" .size .mcount, . - .mcount \n" \
+ );
+#if 0
+/*
+ * If clang passed frompc correctly we could implement it like this, however
+ * all clang versions we care about would need to be fixed before we could
+ * make this change.
+ */
+void
+mcount(uintfptr_t frompc)
+{
+ _mcount(frompc, __builtin_return_address(0));
+}
+#endif
+#else
#define MCOUNT
+#endif
#endif /* !_KERNEL */

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