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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>
This commit is contained in:
Nick Desaulniers 2020-03-19 11:19:51 -07:00 committed by Catalin Marinas
parent 6cb6982f42
commit 3b446c7d27
1 changed files with 4 additions and 0 deletions
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4
arch/arm64/Kconfig
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@ -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"