With CONFIG_CFI_CLANG, the compiler replaces function addresses in
instrumented C code with jump table addresses. This change implements
the function_nocfi() macro, which returns the actual function address
instead.
Signed-off-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Acked-by: Mark Rutland <mark.rutland@xxxxxxx>
Tested-by: Nathan Chancellor <nathan@xxxxxxxxxx>
---
arch/arm64/include/asm/memory.h | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 0aabc3be9a75..3a6f9df63606 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -321,6 +321,22 @@ static inline void *phys_to_virt(phys_addr_t x)
#define virt_to_pfn(x) __phys_to_pfn(__virt_to_phys((unsigned long)(x)))
#define sym_to_pfn(x) __phys_to_pfn(__pa_symbol(x))
+#ifdef CONFIG_CFI_CLANG
+/*
+ * With CONFIG_CFI_CLANG, the compiler replaces function address
+ * references with the address of the function's CFI jump table
+ * entry. The function_nocfi macro always returns the address of the
+ * actual function instead.
+ */
+#define function_nocfi(x) ({ \
+ void *addr; \
+ asm("adrp %0, " __stringify(x) "\n\t" \
+ "add %0, %0, :lo12:" __stringify(x) \
+ : "=r" (addr)); \
+ addr; \
+})
+#endif
+
/*
* virt_to_page(x) convert a _valid_ virtual address to struct page *
* virt_addr_valid(x) indicates whether a virtual address is valid
--
2.31.1.295.g9ea45b61b8-goog
