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Date: Fri, 16 Apr 2021 13:38:34 -0700 From: Sami Tolvanen <samitolvanen@...gle.com> To: x86@...nel.org Cc: Kees Cook <keescook@...omium.org>, Josh Poimboeuf <jpoimboe@...hat.com>, Peter Zijlstra <peterz@...radead.org>, Nathan Chancellor <nathan@...nel.org>, Nick Desaulniers <ndesaulniers@...gle.com>, Sedat Dilek <sedat.dilek@...il.com>, linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com, Sami Tolvanen <samitolvanen@...gle.com> Subject: [PATCH 05/15] x86: 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> --- arch/x86/include/asm/page.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/arch/x86/include/asm/page.h b/arch/x86/include/asm/page.h index 7555b48803a8..5499a05c44fc 100644 --- a/arch/x86/include/asm/page.h +++ b/arch/x86/include/asm/page.h @@ -71,6 +71,20 @@ static inline void copy_user_page(void *to, void *from, unsigned long vaddr, extern bool __virt_addr_valid(unsigned long kaddr); #define virt_addr_valid(kaddr) __virt_addr_valid((unsigned long) (kaddr)) +#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("leaq " __stringify(x) "(%%rip), %0\n\t" : "=r" (addr)); \ + addr; \ +}) +#endif + #endif /* __ASSEMBLY__ */ #include <asm-generic/memory_model.h> -- 2.31.1.368.gbe11c130af-goog
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