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From: Sami Tolvanen <samitolvanen@google.com>
To: Kees Cook <keescook@chromium.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	 Masahiro Yamada <masahiroy@kernel.org>,
	Nathan Chancellor <nathan@kernel.org>,
	 Nick Desaulniers <ndesaulniers@google.com>,
	Will Deacon <will@kernel.org>,
	 linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org,  llvm@lists.linux.dev,
	Sami Tolvanen <samitolvanen@google.com>
Subject: [PATCH 1/3] kbuild: Change CFI_CLANG to depend on __builtin_function_start
Date: Fri,  1 Apr 2022 13:19:14 -0700	[thread overview]
Message-ID: <20220401201916.1487500-2-samitolvanen@google.com> (raw)
In-Reply-To: <20220401201916.1487500-1-samitolvanen@google.com>

Clang 14 added support for the __builtin_function_start()
built-in function, which allows us to implement function_nocfi()
without architecture-specific inline assembly. This patch changes
CONFIG_CFI_CLANG to depend on the built-in and effectively upgrades
the minimum supported compiler version for CFI to Clang 14.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 arch/Kconfig | 5 +----
 init/Kconfig | 3 +++
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 29b0167c088b..eecfc2809781 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -723,10 +723,7 @@ 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 CC_HAS_BUILTIN_FUNCTION_START
 	select KALLSYMS
 	help
 	  This option enables Clang’s forward-edge Control Flow Integrity
diff --git a/init/Kconfig b/init/Kconfig
index ddcbefe535e9..f024fd353373 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -86,6 +86,9 @@ config CC_HAS_ASM_INLINE
 config CC_HAS_NO_PROFILE_FN_ATTR
 	def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror)
 
+config CC_HAS_BUILTIN_FUNCTION_START
+	def_bool $(success,echo 'void f(void) {}; void *p = __builtin_function_start(f);' | $(CC) -x c - -c -o /dev/null)
+
 config PAHOLE_VERSION
 	int
 	default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE))
-- 
2.35.0


WARNING: multiple messages have this Message-ID (diff)
From: Sami Tolvanen <samitolvanen@google.com>
To: Kees Cook <keescook@chromium.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	 Masahiro Yamada <masahiroy@kernel.org>,
	Nathan Chancellor <nathan@kernel.org>,
	 Nick Desaulniers <ndesaulniers@google.com>,
	Will Deacon <will@kernel.org>,
	 linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org,  llvm@lists.linux.dev,
	Sami Tolvanen <samitolvanen@google.com>
Subject: [PATCH 1/3] kbuild: Change CFI_CLANG to depend on __builtin_function_start
Date: Fri,  1 Apr 2022 13:19:14 -0700	[thread overview]
Message-ID: <20220401201916.1487500-2-samitolvanen@google.com> (raw)
In-Reply-To: <20220401201916.1487500-1-samitolvanen@google.com>

Clang 14 added support for the __builtin_function_start()
built-in function, which allows us to implement function_nocfi()
without architecture-specific inline assembly. This patch changes
CONFIG_CFI_CLANG to depend on the built-in and effectively upgrades
the minimum supported compiler version for CFI to Clang 14.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 arch/Kconfig | 5 +----
 init/Kconfig | 3 +++
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 29b0167c088b..eecfc2809781 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -723,10 +723,7 @@ 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 CC_HAS_BUILTIN_FUNCTION_START
 	select KALLSYMS
 	help
 	  This option enables Clang’s forward-edge Control Flow Integrity
diff --git a/init/Kconfig b/init/Kconfig
index ddcbefe535e9..f024fd353373 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -86,6 +86,9 @@ config CC_HAS_ASM_INLINE
 config CC_HAS_NO_PROFILE_FN_ATTR
 	def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror)
 
+config CC_HAS_BUILTIN_FUNCTION_START
+	def_bool $(success,echo 'void f(void) {}; void *p = __builtin_function_start(f);' | $(CC) -x c - -c -o /dev/null)
+
 config PAHOLE_VERSION
 	int
 	default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE))
-- 
2.35.0


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  reply	other threads:[~2022-04-01 20:19 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-01 20:19 [PATCH 0/3] cfi: Use __builtin_function_start Sami Tolvanen
2022-04-01 20:19 ` Sami Tolvanen
2022-04-01 20:19 ` Sami Tolvanen [this message]
2022-04-01 20:19   ` [PATCH 1/3] kbuild: Change CFI_CLANG to depend on __builtin_function_start Sami Tolvanen
2022-04-02 13:31   ` Masahiro Yamada
2022-04-02 13:31     ` Masahiro Yamada
2022-04-04 19:40     ` Sami Tolvanen
2022-04-04 19:40       ` Sami Tolvanen
2022-04-04 22:52       ` Nathan Chancellor
2022-04-04 22:52         ` Nathan Chancellor
2022-04-05  2:53         ` Kees Cook
2022-04-05  2:53           ` Kees Cook
2022-04-01 20:19 ` [PATCH 2/3] linux/compiler-clang.h: define function_nocfi Sami Tolvanen
2022-04-01 20:19   ` Sami Tolvanen
2022-04-05 16:16   ` Mark Rutland
2022-04-05 16:16     ` Mark Rutland
2022-04-01 20:19 ` [PATCH 3/3] arm64: Drop the inline assembly implementation of function_nocfi Sami Tolvanen
2022-04-01 20:19   ` Sami Tolvanen
2022-04-04  9:03   ` Will Deacon
2022-04-04  9:03     ` Will Deacon
2022-04-05 16:23   ` Mark Rutland
2022-04-05 16:23     ` Mark Rutland
2022-04-01 20:49 ` [PATCH 0/3] cfi: Use __builtin_function_start Nick Desaulniers
2022-04-01 20:49   ` Nick Desaulniers

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