[ammarfaizi2-block:tglx/devel/depthtracking 2/45] arch/x86/kernel/cpu/common.c:760:23: error: call to undeclared function 'cpu_kernelmode_gs_base'; ISO C99 and later do not support implicit function declarations

kernel test robot
2022-07-21T10:11:55Z

tree: https://github.com/ammarfaizi2/linux-block tglx/devel/depthtracking
head: 714d29e3e7e3faac27142424ae2533163ddd3a46
commit: 3adc8d7057cc2f5e8dbbaa4b7d8b68f94dadb6ad [2/45] x86/cpu: Remove segment load from switch_to_new_gdt()
config: i386-randconfig-a003-20220718 (https://download.01.org/0day-ci/archive/20220721/202207211807.FC1G4J9o-lkp@intel.com/config)
compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project dd5635541cd7bbd62cd59b6694dfb759b6e9a0d8)
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://github.com/ammarfaizi2/linux-block/commit/3adc8d7057cc2f5e8dbbaa4b7d8b68f94dadb6ad
git remote add ammarfaizi2-block https://github.com/ammarfaizi2/linux-block
git fetch --no-tags ammarfaizi2-block tglx/devel/depthtracking
git checkout 3adc8d7057cc2f5e8dbbaa4b7d8b68f94dadb6ad
# save the config file
mkdir build_dir && cp config build_dir/.config
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=i386 SHELL=/bin/bash arch/x86/

If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

>> arch/x86/kernel/cpu/common.c:760:23: error: call to undeclared function 'cpu_kernelmode_gs_base'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
wrmsrl(MSR_GS_BASE, cpu_kernelmode_gs_base(cpu));
^
1 error generated.

vim +/cpu_kernelmode_gs_base +760 arch/x86/kernel/cpu/common.c

730
731 /**
732 * switch_to_new_gdt - Switch form early GDT to the direct one
733 * @cpu: The CPU number for which this is invoked
734 *
735 * Invoked during early boot to switch from early GDT and early per CPU
736 * (%fs on 32bit, GS_BASE on 64bit) to the direct GDT and the runtime per
737 * CPU area.
738 */
739 void switch_to_new_gdt(int cpu)
740 {
741 load_direct_gdt(cpu);
742
743 /*
744 * No need to load the %gs (%fs for 32bit) segment. It is already
745 * correct, %gs is 0 on 64bit and %fs is __KERNEL_PERCPU on 32 bit.
746 *
747 * Writing %gs on 64bit would zero GSBASE which would make any per
748 * CPU operation up to the point of the wrmsrl() fault.
749 *
750 * 64bit requires to point GSBASE to the new offset. Until the
751 * wrmsrl() happens the early mapping is still valid. That means
752 * the GSBASE update will lose any prior per CPU data which was
753 * not copied over in setup_per_cpu_areas().
754 *
755 * For secondary CPUs this is not a problem because they start
756 * already with the direct GDT and the real GSBASE. This invocation
757 * is pointless and will be removed in a subsequent step.
758 */
759 if (IS_ENABLED(CONFIG_X86_64))
> 760 wrmsrl(MSR_GS_BASE, cpu_kernelmode_gs_base(cpu));
761 }
762

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