[PATCH 12/17] arm64: implement __va_function

Sami Tolvanen
2021-03-12T00:50:50Z

With CONFIG_CFI_CLANG, the compiler replaces function addresses in
instrumented C code with jump table addresses. This change implements
the __va_function() macro, which returns the actual function address
instead.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
arch/arm64/include/asm/memory.h | 15 +++++++++++++++
1 file changed, 15 insertions(+)

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index c759faf7a1ff..4defa9dc3cc5 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -321,6 +321,21 @@ 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 __va_function macro always returns the address of the
+ * actual function instead.
+ */
+#define __va_function(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
--
2.31.0.rc2.261.g7f71774620-goog