Hi Catalin, On 03/10/2019 17:16, Catalin Marinas wrote: > On Thu, Oct 03, 2019 at 05:00:41PM +0100, Catalin Marinas wrote: >> On Wed, Oct 02, 2019 at 03:41:51PM +0100, Vincenzo Frascino wrote: >>> diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile >>> index 84a3d502c5a5..dfa6a5cb99e4 100644 >>> --- a/arch/arm64/Makefile >>> +++ b/arch/arm64/Makefile >>> @@ -53,20 +53,12 @@ $(warning Detected assembler with broken .inst; disassembly will be unreliable) >>> endif >>> endif >>> >>> +COMPATCC ?= $(CROSS_COMPILE_COMPAT)gcc >>> +export COMPATCC >>> + >>> ifeq ($(CONFIG_GENERIC_COMPAT_VDSO), y) >>> - CROSS_COMPILE_COMPAT ?= $(CONFIG_CROSS_COMPILE_COMPAT_VDSO:"%"=%) >>> - >>> - ifeq ($(CONFIG_CC_IS_CLANG), y) >>> - $(warning CROSS_COMPILE_COMPAT is clang, the compat vDSO will not be built) >>> - else ifeq ($(strip $(CROSS_COMPILE_COMPAT)),) >>> - $(warning CROSS_COMPILE_COMPAT not defined or empty, the compat vDSO will not be built) >>> - else ifeq ($(shell which $(CROSS_COMPILE_COMPAT)gcc 2> /dev/null),) >>> - $(error $(CROSS_COMPILE_COMPAT)gcc not found, check CROSS_COMPILE_COMPAT) >>> - else >>> - export CROSS_COMPILE_COMPAT >>> - export CONFIG_COMPAT_VDSO := y >>> - compat_vdso := -DCONFIG_COMPAT_VDSO=1 >>> - endif >>> + export CONFIG_COMPAT_VDSO := y >>> + compat_vdso := -DCONFIG_COMPAT_VDSO=1 >>> endif >> >> With this change, if I don't have any CROSS_COMPILE_COMPAT in my >> environment, the kernel fails to build because COMPATCC becomes gcc >> which cannot build the vdso32. What I really want is not to warn me, nor >> fail to build the kernel when I don't care about the compat vDSO (e.g. I >> have a 64-bit only machine). >> >> What saved us before was the COMPATCC_IS_ARM_GCC check and a selection >> of the GENERIC_COMPAT_VDSO dependent on this check. This was now dropped >> from the previous version of the patch. We could add something like >> COMPATCC_CAN_LINK. > > Ah, the COMPATCC_CAN_LINK idea doesn't help because an x86 gcc can still > link. Maybe only enable CONFIG_COMPAT_VDSO above if CROSS_COMPILE_COMPAT > was set. You could move the COMPATCC setting and export under the > same 'if' block in the Makefile. > The snippet below the scissors solves the problem for me. I am going to re-post a new version of the patches that contains it. --->8--- diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 37c610963eee..b4cc8fb5344c 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -110,7 +110,7 @@ config ARM64 select GENERIC_STRNLEN_USER select GENERIC_TIME_VSYSCALL select GENERIC_GETTIMEOFDAY - select GENERIC_COMPAT_VDSO if (!CPU_BIG_ENDIAN && COMPAT) + select GENERIC_COMPAT_VDSO if (!CPU_BIG_ENDIAN && COMPAT && !COMPATCC_EMPTY) select HANDLE_DOMAIN_IRQ select HARDIRQS_SW_RESEND select HAVE_PCI @@ -313,6 +313,9 @@ config KASAN_SHADOW_OFFSET default 0xeffffff900000000 if ARM64_VA_BITS_36 && KASAN_SW_TAGS default 0xffffffffffffffff +config COMPATCC_EMPTY + def_bool $(success,test -z "${CROSS_COMPILE_COMPAT}") + source "arch/arm64/Kconfig.platforms" menu "Kernel Features" -- Regards, Vincenzo