Re: [PATCH 3/3] isystem: delete global -isystem compile option

[Nathan Chancellor <nathan@kernel.org>]

On Sun, Aug 01, 2021 at 11:13:36PM +0300, Alexey Dobriyan wrote:
> In theory, it enables "leakage" of userspace headers into kernel which
> may present licensing problem.
> 
> In practice, only stdarg.h was used, stdbool.h is trivial and SIMD
> intrinsics are contained to a few architectures and aren't global
> problem.
> 
> In general, kernel is very self contained code and -isystem removal
> will further isolate it from Ring Threeland influence.
> 
> nds32 keeps -isystem globally due to intrisics used in entrenched header.
> 
> -isystem is selectively reenabled for some files.
> 
> Not compile tested on hexagon.

With this series on top of v5.14-rc4 and a tangential patch to fix
another issue, ARCH=hexagon defconfig and allmodconfig show no issues.

Tested-by: Nathan Chancellor <nathan@kernel> # build (hexagon)

> Compile tested on:
> 
> alpha-allmodconfig alpha-allnoconfig alpha-defconfig arm64-allmodconfig
> arm64-allnoconfig arm64-defconfig arm-am200epdkit arm-aspeed_g4
> arm-aspeed_g5 arm-assabet arm-at91_dt arm-axm55xx arm-badge4 arm-bcm2835
> arm-cerfcube arm-clps711x arm-cm_x300 arm-cns3420vb arm-colibri_pxa270
> arm-colibri_pxa300 arm-collie arm-corgi arm-davinci_all arm-dove
> arm-ep93xx arm-eseries_pxa arm-exynos arm-ezx arm-footbridge arm-gemini
> arm-h3600 arm-h5000 arm-hackkit arm-hisi arm-imote2 arm-imx_v4_v5
> arm-imx_v6_v7 arm-integrator arm-iop32x arm-ixp4xx arm-jornada720
> arm-keystone arm-lart arm-lpc18xx arm-lpc32xx arm-lpd270 arm-lubbock
> arm-magician arm-mainstone arm-milbeaut_m10v arm-mini2440 arm-mmp2
> arm-moxart arm-mps2 arm-multi_v4t arm-multi_v5 arm-multi_v7 arm-mv78xx0
> arm-mvebu_v5 arm-mvebu_v7 arm-mxs arm-neponset arm-netwinder arm-nhk8815
> arm-omap1 arm-omap2plus arm-orion5x arm-oxnas_v6 arm-palmz72 arm-pcm027
> arm-pleb arm-pxa arm-pxa168 arm-pxa255-idp arm-pxa3xx arm-pxa910
> arm-qcom arm-realview arm-rpc arm-s3c2410 arm-s3c6400 arm-s5pv210
> arm-sama5 arm-shannon arm-shmobile arm-simpad arm-socfpga arm-spear13xx
> arm-spear3xx arm-spear6xx arm-spitz arm-stm32 arm-sunxi arm-tct_hammer
> arm-tegra arm-trizeps4 arm-u8500 arm-versatile arm-vexpress arm-vf610m4
> arm-viper arm-vt8500_v6_v7 arm-xcep arm-zeus csky-allmodconfig
> csky-allnoconfig csky-defconfig h8300-edosk2674 h8300-h8300h-sim
> h8300-h8s-sim i386-allmodconfig i386-allnoconfig i386-defconfig
> ia64-allmodconfig ia64-allnoconfig ia64-bigsur ia64-generic ia64-gensparse
> ia64-tiger ia64-zx1 m68k-amcore m68k-amiga m68k-apollo m68k-atari
> m68k-bvme6000 m68k-hp300 m68k-m5208evb m68k-m5249evb m68k-m5272c3
> m68k-m5275evb m68k-m5307c3 m68k-m5407c3 m68k-m5475evb m68k-mac
> m68k-multi m68k-mvme147 m68k-mvme16x m68k-q40 m68k-stmark2 m68k-sun3
> m68k-sun3x microblaze-allmodconfig microblaze-allnoconfig microblaze-mmu
> mips-ar7 mips-ath25 mips-ath79 mips-bcm47xx mips-bcm63xx mips-bigsur
> mips-bmips_be mips-bmips_stb mips-capcella mips-cavium_octeon mips-ci20
> mips-cobalt mips-cu1000-neo mips-cu1830-neo mips-db1xxx mips-decstation
> mips-decstation_64 mips-decstation_r4k mips-e55 mips-fuloong2e
> mips-gcw0 mips-generic mips-gpr mips-ip22 mips-ip27 mips-ip28 mips-ip32
> mips-jazz mips-jmr3927 mips-lemote2f mips-loongson1b mips-loongson1c
> mips-loongson2k mips-loongson3 mips-malta mips-maltaaprp mips-malta_kvm
> mips-malta_qemu_32r6 mips-maltasmvp mips-maltasmvp_eva mips-maltaup
> mips-maltaup_xpa mips-mpc30x mips-mtx1 mips-nlm_xlp mips-nlm_xlr
> mips-omega2p mips-pic32mzda mips-pistachio mips-qi_lb60 mips-rb532
> mips-rbtx49xx mips-rm200 mips-rs90 mips-rt305x mips-sb1250_swarm
> mips-tb0219 mips-tb0226 mips-tb0287 mips-vocore2 mips-workpad mips-xway
> nds32-allmodconfig nds32-allnoconfig nds32-defconfig nios2-10m50
> nios2-3c120 nios2-allmodconfig nios2-allnoconfig openrisc-allmodconfig
> openrisc-allnoconfig openrisc-or1klitex openrisc-or1ksim
> openrisc-simple_smp parisc-allnoconfig parisc-generic-32bit
> parisc-generic-64bit powerpc-acadia powerpc-adder875 powerpc-akebono
> powerpc-amigaone powerpc-arches powerpc-asp8347 powerpc-bamboo
> powerpc-bluestone powerpc-canyonlands powerpc-cell powerpc-chrp32
> powerpc-cm5200 powerpc-currituck powerpc-ebony powerpc-eiger
> powerpc-ep8248e powerpc-ep88xc powerpc-fsp2 powerpc-g5 powerpc-gamecube
> powerpc-ge_imp3a powerpc-holly powerpc-icon powerpc-iss476-smp
> powerpc-katmai powerpc-kilauea powerpc-klondike powerpc-kmeter1
> powerpc-ksi8560 powerpc-linkstation powerpc-lite5200b powerpc-makalu
> powerpc-maple powerpc-mgcoge powerpc-microwatt powerpc-motionpro
> powerpc-mpc512x powerpc-mpc5200 powerpc-mpc7448_hpc2 powerpc-mpc8272_ads
> powerpc-mpc8313_rdb powerpc-mpc8315_rdb powerpc-mpc832x_mds
> powerpc-mpc832x_rdb powerpc-mpc834x_itx powerpc-mpc834x_itxgp
> powerpc-mpc834x_mds powerpc-mpc836x_mds powerpc-mpc836x_rdk
> powerpc-mpc837x_mds powerpc-mpc837x_rdb powerpc-mpc83xx
> powerpc-mpc8540_ads powerpc-mpc8560_ads powerpc-mpc85xx_cds
> powerpc-mpc866_ads powerpc-mpc885_ads powerpc-mvme5100 powerpc-obs600
> powerpc-pasemi powerpc-pcm030 powerpc-pmac32 powerpc-powernv
> powerpc-ppa8548 powerpc-ppc40x powerpc-ppc44x powerpc-ppc64
> powerpc-ppc64e powerpc-ppc6xx powerpc-pq2fads powerpc-ps3
> powerpc-pseries powerpc-rainier powerpc-redwood powerpc-sam440ep
> powerpc-sbc8548 powerpc-sequoia powerpc-skiroot powerpc-socrates
> powerpc-storcenter powerpc-stx_gp3 powerpc-taishan powerpc-tqm5200
> powerpc-tqm8540 powerpc-tqm8541 powerpc-tqm8548 powerpc-tqm8555
> powerpc-tqm8560 powerpc-tqm8xx powerpc-walnut powerpc-warp powerpc-wii
> powerpc-xes_mpc85xx riscv-allmodconfig riscv-allnoconfig riscv-nommu_k210
> riscv-nommu_k210_sdcard riscv-nommu_virt riscv-rv32 s390-allmodconfig
> s390-allnoconfig s390-debug s390-zfcpdump sh-ap325rxa sh-apsh4a3a
> sh-apsh4ad0a sh-dreamcast sh-ecovec24 sh-ecovec24-romimage sh-edosk7705
> sh-edosk7760 sh-espt sh-hp6xx sh-j2 sh-kfr2r09 sh-kfr2r09-romimage
> sh-landisk sh-lboxre2 sh-magicpanelr2 sh-microdev sh-migor sh-polaris
> sh-r7780mp sh-r7785rp sh-rsk7201 sh-rsk7203 sh-rsk7264 sh-rsk7269
> sh-rts7751r2d1 sh-rts7751r2dplus sh-sdk7780 sh-sdk7786 sh-se7206 sh-se7343
> sh-se7619 sh-se7705 sh-se7712 sh-se7721 sh-se7722 sh-se7724 sh-se7750
> sh-se7751 sh-se7780 sh-secureedge5410 sh-sh03 sh-sh2007 sh-sh7710voipgw
> sh-sh7724_generic sh-sh7757lcr sh-sh7763rdp sh-sh7770_generic sh-sh7785lcr
> sh-sh7785lcr_32bit sh-shmin sh-shx3 sh-titan sh-ul2 sh-urquell
> sparc-allmodconfig sparc-allnoconfig sparc-sparc32 sparc-sparc64
> um-i386-allmodconfig um-i386-allnoconfig um-i386-defconfig
> um-x86_64-allmodconfig um-x86_64-allnoconfig x86_64-allmodconfig
> x86_64-allnoconfig x86_64-defconfig xtensa-allmodconfig xtensa-allnoconfig
> xtensa-audio_kc705 xtensa-cadence_csp xtensa-common xtensa-generic_kc705
> xtensa-iss xtensa-nommu_kc705 xtensa-smp_lx200 xtensa-virt
> xtensa-xip_kc705
> 
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: linuxppc-dev@lists.ozlabs.org
> Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
> ---
>  Makefile                  | 2 +-
>  arch/arm64/lib/Makefile   | 2 ++
>  arch/nds32/Makefile       | 2 ++
>  arch/powerpc/lib/Makefile | 2 ++
>  crypto/Makefile           | 2 ++
>  lib/raid6/Makefile        | 4 ++++
>  6 files changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/Makefile b/Makefile
> index 6b555f64df06..b59053ec457a 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -979,7 +979,7 @@ KBUILD_CFLAGS += -falign-functions=64
>  endif
>  
>  # arch Makefile may override CC so keep this after arch Makefile is included
> -NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include)
> +NOSTDINC_FLAGS += -nostdinc
>  
>  # warn about C99 declaration after statement
>  KBUILD_CFLAGS += -Wdeclaration-after-statement
> diff --git a/arch/arm64/lib/Makefile b/arch/arm64/lib/Makefile
> index 6dd56a49790a..dcad998f12d7 100644
> --- a/arch/arm64/lib/Makefile
> +++ b/arch/arm64/lib/Makefile
> @@ -9,6 +9,8 @@ ifeq ($(CONFIG_KERNEL_MODE_NEON), y)
>  obj-$(CONFIG_XOR_BLOCKS)	+= xor-neon.o
>  CFLAGS_REMOVE_xor-neon.o	+= -mgeneral-regs-only
>  CFLAGS_xor-neon.o		+= -ffreestanding
> +# Enable <arm_neon.h>
> +CFLAGS_xor-neon.o		+= -isystem $(shell $(CC) -print-file-name=include)
>  endif
>  
>  lib-$(CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE) += uaccess_flushcache.o
> diff --git a/arch/nds32/Makefile b/arch/nds32/Makefile
> index ccdca7142020..c17fc3a755c3 100644
> --- a/arch/nds32/Makefile
> +++ b/arch/nds32/Makefile
> @@ -9,6 +9,8 @@ endif
>  # Avoid generating FPU instructions
>  arch-y  += -mno-ext-fpu-sp -mno-ext-fpu-dp -mfloat-abi=soft
>  
> +# Enable <nds32_intrinsic.h>
> +KBUILD_CFLAGS	+= -isystem $(shell $(CC) -print-file-name=include)
>  KBUILD_CFLAGS	+= $(call cc-option, -mno-sched-prolog-epilog)
>  KBUILD_CFLAGS	+= -mcmodel=large
>  
> diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile
> index 99a7c9132422..9e5d0f413b71 100644
> --- a/arch/powerpc/lib/Makefile
> +++ b/arch/powerpc/lib/Makefile
> @@ -65,5 +65,7 @@ obj-$(CONFIG_FTR_FIXUP_SELFTEST) += feature-fixups-test.o
>  
>  obj-$(CONFIG_ALTIVEC)	+= xor_vmx.o xor_vmx_glue.o
>  CFLAGS_xor_vmx.o += -maltivec $(call cc-option,-mabi=altivec)
> +# Enable <altivec.h>
> +CFLAGS_xor_vmx.o += -isystem $(shell $(CC) -print-file-name=include)
>  
>  obj-$(CONFIG_PPC64) += $(obj64-y)
> diff --git a/crypto/Makefile b/crypto/Makefile
> index 10526d4559b8..75ad9b040506 100644
> --- a/crypto/Makefile
> +++ b/crypto/Makefile
> @@ -117,6 +117,8 @@ aegis128-cflags-$(CONFIG_CC_IS_GCC) += -ffixed-q16 -ffixed-q17 -ffixed-q18 \
>  				       -ffixed-q28 -ffixed-q29 -ffixed-q30 \
>  				       -ffixed-q31
>  CFLAGS_aegis128-neon-inner.o += $(aegis128-cflags-y)
> +# Enable <arm_neon.h>
> +CFLAGS_aegis128-neon-inner.o += -isystem $(shell $(CC) -print-file-name=include)
>  CFLAGS_REMOVE_aegis128-neon-inner.o += -mgeneral-regs-only
>  aegis128-$(CONFIG_CRYPTO_AEGIS128_SIMD) += aegis128-neon.o aegis128-neon-inner.o
>  endif
> diff --git a/lib/raid6/Makefile b/lib/raid6/Makefile
> index c770570bfe4f..45e17619422b 100644
> --- a/lib/raid6/Makefile
> +++ b/lib/raid6/Makefile
> @@ -14,6 +14,8 @@ hostprogs	+= mktables
>  
>  ifeq ($(CONFIG_ALTIVEC),y)
>  altivec_flags := -maltivec $(call cc-option,-mabi=altivec)
> +# Enable <altivec.h>
> +altivec_flags += -isystem $(shell $(CC) -print-file-name=include)
>  
>  ifdef CONFIG_CC_IS_CLANG
>  # clang ppc port does not yet support -maltivec when -msoft-float is
> @@ -34,6 +36,8 @@ endif
>  # ARM/NEON intrinsics in a non C99-compliant environment (such as the kernel)
>  ifeq ($(CONFIG_KERNEL_MODE_NEON),y)
>  NEON_FLAGS := -ffreestanding
> +# Enable <arm_neon.h>
> +NEON_FLAGS += -isystem $(shell $(CC) -print-file-name=include)
>  ifeq ($(ARCH),arm)
>  NEON_FLAGS += -march=armv7-a -mfloat-abi=softfp -mfpu=neon
>  endif
> -- 
> 2.31.1
>