Commit 3b446c7d authored Mar 19, 2020 by Nick Desaulniers Committed by Catalin Marinas Mar 20, 2020

arm64: Kconfig: verify binutils support for ARM64_PTR_AUTH

Clang relies on GNU as from binutils to assemble the Linux kernel,
currently. A recent patch to enable the armv8.3-a extension for pointer
authentication checked for compiler support of the relevant flags.
Everything works with binutils 2.34+, but for older versions we observe
assembler errors:

/tmp/vgettimeofday-36a54b.s: Assembler messages:
/tmp/vgettimeofday-36a54b.s:40: Error: unknown pseudo-op: `.cfi_negate_ra_state'

When compiling with Clang, require the assembler to support
.cfi_negate_ra_state directives, in order to support CONFIG_ARM64_PTR_AUTH.

Link: https://github.com/ClangBuiltLinux/linux/issues/938


Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>

parent 6cb6982f

arch/arm64/Kconfig

+4 −0

Original line number	Diff line number	Diff line
		@@ -1500,6 +1500,7 @@ config ARM64_PTR_AUTH
		default y
		depends on !KVM \|\| ARM64_VHE
		depends on (CC_HAS_SIGN_RETURN_ADDRESS \|\| CC_HAS_BRANCH_PROT_PAC_RET) && AS_HAS_PAC
		depends on CC_IS_GCC \|\| (CC_IS_CLANG && AS_HAS_CFI_NEGATE_RA_STATE)
		depends on (!FUNCTION_GRAPH_TRACER \|\| DYNAMIC_FTRACE_WITH_REGS)
		help
		Pointer authentication (part of the ARMv8.3 Extensions) provides
		@@ -1544,6 +1545,9 @@ config CC_HAS_SIGN_RETURN_ADDRESS
		config AS_HAS_PAC
		def_bool $(as-option,-Wa$(comma)-march=armv8.3-a)

		config AS_HAS_CFI_NEGATE_RA_STATE
		def_bool $(as-instr,.cfi_startproc\n.cfi_negate_ra_state\n.cfi_endproc\n)

		endmenu

		menu "ARMv8.5 architectural features"

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