[PATCH v6 12/18] arm64: implement function_nocfi
From: Sami Tolvanen <samitolvanen@google.com>
Date: 2021-04-08 18:30:20
Also in:
bpf, linux-arch, linux-hardening, linux-kbuild, linux-pci, lkml
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
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@google.com> Reviewed-by: Kees Cook <redacted> Acked-by: Mark Rutland <mark.rutland@arm.com> Tested-by: Nathan Chancellor <nathan@kernel.org> --- 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
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