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Message-Id: <20210408182843.1754385-13-samitolvanen@google.com>
Date: Thu, 8 Apr 2021 11:28:37 -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>,
Mark Rutland <mark.rutland@....com>,
Catalin Marinas <catalin.marinas@....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 v6 12/18] 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>
Acked-by: Mark Rutland <mark.rutland@....com>
Tested-by: Nathan Chancellor <nathan@...nel.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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