tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master head: f8e6dfc64f6135d1b6c5215c14cd30b9b60a0008 commit: c28762070ca651fe7a981b8f31d972c9b7d2c386 arm64: Rewrite Spectre-v4 mitigation code date: 11 months ago config: arm64-randconfig-r013-20210814 (attached as .config) compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 62df4df41c939205b2dc0a2a3bfb75b8c1ed74fa) reproduce (this is a W=1 build): wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit... git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git git fetch --no-tags linus master git checkout c28762070ca651fe7a981b8f31d972c9b7d2c386 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=arm64 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>): arch/arm64/kernel/proton-pack.c:288:2: error: implicit declaration of function 'install_bp_hardening_cb' [-Werror,-Wimplicit-function-declaration] install_bp_hardening_cb(cb); ^ arch/arm64/kernel/proton-pack.c:304:2: error: implicit declaration of function 'install_bp_hardening_cb' [-Werror,-Wimplicit-function-declaration] install_bp_hardening_cb(qcom_link_stack_sanitisation); ^ void __init spectre_v4_patch_fw_mitigation_enable(struct alt_instr *alt, ^ arch/arm64/kernel/proton-pack.c:558:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void __init spectre_v4_patch_fw_mitigation_enable(struct alt_instr *alt, ^ static void __init spectre_v4_patch_fw_mitigation_conduit(struct alt_instr *alt, ^ arch/arm64/kernel/proton-pack.c:578:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void __init spectre_v4_patch_fw_mitigation_conduit(struct alt_instr *alt, ^ static 2 warnings and 2 errors generated. vim +/spectre_v4_patch_fw_mitigation_enable +558 arch/arm64/kernel/proton-pack.c 553 554 /* 555 * Patch a branch over the Spectre-v4 mitigation code with a NOP so that 556 * we fallthrough and check whether firmware needs to be called on this CPU. 557 */ 559 __le32 *origptr, 560 __le32 *updptr, int nr_inst) 561 { 562 BUG_ON(nr_inst != 1); /* Branch -> NOP */ 563 564 if (spectre_v4_mitigations_off()) 565 return; 566 567 if (cpus_have_final_cap(ARM64_SSBS)) 568 return; 569 570 if (spectre_v4_mitigations_dynamic()) 571 *updptr = cpu_to_le32(aarch64_insn_gen_nop()); 572 } 573 574 /* 575 * Patch a NOP in the Spectre-v4 mitigation code with an SMC/HVC instruction 576 * to call into firmware to adjust the mitigation state. 577 */ 579 __le32 *origptr, 580 __le32 *updptr, int nr_inst) 581 { 582 u32 insn; 583 584 BUG_ON(nr_inst != 1); /* NOP -> HVC/SMC */ 585 586 switch (arm_smccc_1_1_get_conduit()) { 587 case SMCCC_CONDUIT_HVC: 588 insn = aarch64_insn_get_hvc_value(); 589 break; 590 case SMCCC_CONDUIT_SMC: 591 insn = aarch64_insn_get_smc_value(); 592 break; 593 default: 594 return; 595 } 596 597 *updptr = cpu_to_le32(insn); 598 } 599 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org