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Date: Wed, 31 Mar 2021 14:27:16 -0700 From: Sami Tolvanen <samitolvanen@...gle.com> To: Kees Cook <keescook@...omium.org> Cc: Nathan Chancellor <nathan@...nel.org>, Nick Desaulniers <ndesaulniers@...gle.com>, Masahiro Yamada <masahiroy@...nel.org>, Will Deacon <will@...nel.org>, Jessica Yu <jeyu@...nel.org>, Arnd Bergmann <arnd@...db.de>, Tejun Heo <tj@...nel.org>, "Paul E. McKenney" <paulmck@...nel.org>, Christoph Hellwig <hch@...radead.org>, Peter Zijlstra <peterz@...radead.org>, Sedat Dilek <sedat.dilek@...il.com>, bpf@...r.kernel.org, linux-hardening@...r.kernel.org, linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, linux-kbuild@...r.kernel.org, linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com, Sami Tolvanen <samitolvanen@...gle.com> Subject: [PATCH v4 12/17] 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: Sami Tolvanen <samitolvanen@...gle.com> Reviewed-by: Kees Cook <keescook@...omium.org> --- 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 0aabc3be9a75..b55410afd3d1 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 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 -- 2.31.0.291.g576ba9dcdaf-goog
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