FS#1282 - "CONFIG_STRIP_KERNEL_EXPORTS" breaks kernel compilation for Raspberry PI3 (arm64)

[aparcar]

torte71:

Target: brcm2708_bcm2710 (rpi-3) Affected openwrt revision: git-head (26045049baf646aa2ce3dce78106da5acf4936ea) (openwrt-17.01 is not affected)

• Reproducing git clone https://git.openwrt.org/openwrt/openwrt.git ; cd openwrt make menuconfig

  Select:

  Target: Broadcom BCM27xx

  Subtarget: BCM2710 64 bit based boards

  Global build settings ---> Strip unnecessary exports from the kernel image: Enabled

  make -j 1 V=s

• Build log make -C /home/torte/openwrt/nfs/openwrt/build_dir/target-aarch64_cortex-a53_musl/linux-brcm2708_bcm2710/linux-4.9.76 HOSTCFLAGS="-O2 -I/home/torte/openwrt/nfs/openwrt/staging_dir/host/include -Wall -Wmissing-prototypes -Wstrict-prototypes" CROSS_COMPILE="aarch64-openwrt-linux-musl-" ARCH="arm64" KBUILD_HAVE_NLS=no KBUILD_BUILD_USER="" KBUILD_BUILD_HOST="" KBUILD_BUILD_TIMESTAMP="Thu Jan 18 10:39:42 2018" KBUILD_BUILD_VERSION="0" HOST_LOADLIBES="-L/home/torte/openwrt/nfs/openwrt/staging_dir/host/lib" CONFIG_SHELL="bash" V='' cmd_syscalls= KERNELRELEASE=4.9.76 EXTRA_LDSFLAGS="-I/home/torte/openwrt/nfs/openwrt/build_dir/target-aarch64_cortex-a53_musl/linux-brcm2708_bcm2710 -include symtab.h" CC="aarch64-openwrt-linux-musl-gcc" modules make[5]: Entering directory '/home/torte/openwrt/nfs/openwrt/build_dir/target-aarch64_cortex-a53_musl/linux-brcm2708_bcm2710/linux-4.9.76' CHK include/config/kernel.release CHK include/generated/uapi/linux/version.h CHK include/generated/utsrelease.h CHK include/generated/bounds.h CHK include/generated/timeconst.h CHK include/generated/asm-offsets.h CALL scripts/checksyscalls.sh LDS arch/arm64/kernel/vdso/vdso.lds cc1: fatal error: symtab.h: No such file or directory compilation terminated. scripts/Makefile.build:405: recipe for target 'arch/arm64/kernel/vdso/vdso.lds' failed make[6]: [arch/arm64/kernel/vdso/vdso.lds] Error 1 arch/arm64/Makefile:145: recipe for target 'vdso_prepare' failed make[5]: [vdso_prepare] Error 2

• Details The option CONFIG_STRIP_KERNEL_EXPORTS adds "-include symtab.h" for all linker script invokations. See openwrt/include/kernel-defaults.mk: ifdef CONFIG_STRIP_KERNEL_EXPORTS KERNEL_MAKEOPTS += \ EXTRA_LDSFLAGS="-I$(KERNEL_BUILD_DIR) -include symtab.h" endif

On recent kernels (4.9.x, arm64 build), linker scripts are used to generate "vdso.lds" at the "make modules" stage. But the file "symtab.h" is generated later (at the install/image generation stage). See openwrt/include/kernel-build.mk: $(LINUX_DIR)/.image: $(STAMP_CONFIGURED) $(if $(CONFIG_STRIP_KERNEL_EXPORTS),$(KERNEL_BUILD_DIR)/symtab.h) FORCE $(Kernel/CompileImage) $(Kernel/CollectDebug) touch $$@ As a result, kernel compilation fails.

• Sidenotes:
  • 32bit arm (brcm2708_bcm2708) is not affected, the vdso stuff is generated by normal .c files

• On arm64 4.4 kernels, the vdso stuff is not compiled for reasons, that I don't know. Anyway, openwrt-17.01 is not affected

[aparcar]

Amineahd:

I opened PR#696 to fix this