Commit 4ecfca89 authored by Sami Tolvanen's avatar Sami Tolvanen Committed by Kees Cook
Browse files

arm64: implement function_nocfi 



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: default avatarSami Tolvanen <samitolvanen@google.com>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Acked-by: default avatarMark Rutland <mark.rutland@arm.com>
Tested-by: default avatarNathan Chancellor <nathan@kernel.org>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210408182843.1754385-13-samitolvanen@google.com
parent 167d0da2

arch/arm64/include/asm/memory.h

+16 −0
Original line number Diff line number Diff line
@@ -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