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UPSTREAM: cfi: Use __builtin_function_start

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Clang 14 added support for the __builtin_function_start function,
which allows us to implement the function_nocfi macro without
architecture-specific inline assembly and in a way that also works
with static initializers.

Change CONFIG_CFI_CLANG to depend on Clang >= 14, define
function_nocfi using __builtin_function_start, and remove the arm64
inline assembly implementation.

Link: ec2e26eaf6
Link: https://github.com/ClangBuiltLinux/linux/issues/1353
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Will Deacon <will@kernel.org> # arm64
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>

Bug: 244543039
Bug: 244373730
Link: https://lore.kernel.org/r/20220405221618.633743-1-samitolvanen@google.com
(cherry picked from commit e6f3b3c9c1)
Change-Id: I71d0e805fc66123107ff51f6e30d689948d64fa1
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
This commit is contained in:
Sami Tolvanen
2022-04-05 15:16:18 -07:00
committed by Quentin Perret
parent 0c9fc56eeb
commit c7eab89707
3 changed files with 11 additions and 20 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
arch/Kconfig
View File

@@ -713,10 +713,7 @@ config ARCH_SUPPORTS_CFI_CLANG
config CFI_CLANG
bool "Use Clang's Control Flow Integrity (CFI)"
depends on LTO_CLANG && ARCH_SUPPORTS_CFI_CLANG
# Clang >= 12:
# - https://bugs.llvm.org/show_bug.cgi?id=46258
# - https://bugs.llvm.org/show_bug.cgi?id=47479
depends on CLANG_VERSION >= 120000
depends on CLANG_VERSION >= 140000
select KALLSYMS
help
This option enables Clang’s forward-edge Control Flow Integrity

16
arch/arm64/include/asm/compiler.h
View File

@@ -23,20 +23,4 @@
#define __builtin_return_address(val) \
(void *)(ptrauth_clear_pac((unsigned long)__builtin_return_address(val)))
#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
#endif /* __ASM_COMPILER_H */

10
include/linux/compiler-clang.h
View File

@@ -68,3 +68,13 @@
#define __nocfi __attribute__((__no_sanitize__("cfi")))
#define __cficanonical __attribute__((__cfi_canonical_jump_table__))
#if defined(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) __builtin_function_start(x)
#endif