linux-kernel - [tglx-devel:x86/fpu 42/78] arch/x86/kernel/fpu/core.c:372:11: warning: variable 'fpdst' is uninitialized when used here

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Date:   Tue, 12 Oct 2021 05:45:45 +0800
From:   kernel test robot <lkp@...el.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     llvm@...ts.linux.dev, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org
Subject: [tglx-devel:x86/fpu 42/78] arch/x86/kernel/fpu/core.c:372:11:
 warning: variable 'fpdst' is uninitialized when used here

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git x86/fpu
head:   cdb8206630ccd0c990e4af058d271f034dfd47de
commit: ec2658e1e6a67104db59576b35507b3cc4567dcb [42/78] x86/fpu: Use fpstate::size
config: i386-randconfig-r034-20211011 (attached as .config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 7ae8f392a1610992c9a925c867fd7238c70d3ce0)
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/tglx/devel.git/commit/?id=ec2658e1e6a67104db59576b35507b3cc4567dcb
        git remote add tglx-devel https://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git
        git fetch --no-tags tglx-devel x86/fpu
        git checkout ec2658e1e6a67104db59576b35507b3cc4567dcb
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 ARCH=i386 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@...el.com>

All warnings (new ones prefixed by >>):

>> arch/x86/kernel/fpu/core.c:372:11: warning: variable 'fpdst' is uninitialized when used here [-Wuninitialized]
                   memcpy(&fpdst->regs, &fpsrc->regs, fpdst->size);
                           ^~~~~
   arch/x86/kernel/fpu/core.c:353:23: note: initialize the variable 'fpdst' to silence this warning
           struct fpstate *fpdst, *fpsrc = current->thread.fpu.fpstate;
                                ^
                                 = NULL
   1 warning generated.


vim +/fpdst +372 arch/x86/kernel/fpu/core.c

   349	
   350	/* Clone current's FPU state on fork */
   351	int fpu_clone(struct task_struct *dst_tsk)
   352	{
   353		struct fpstate *fpdst, *fpsrc = current->thread.fpu.fpstate;
   354		struct fpu *src_fpu = &current->thread.fpu;
   355		struct fpu *dst_fpu = &dst_tsk->thread.fpu;
   356	
   357		/* The new task's FPU state cannot be valid in the hardware. */
   358		dst_fpu->last_cpu = -1;
   359	
   360		fpstate_reset(dst_fpu);
   361	
   362		if (!cpu_feature_enabled(X86_FEATURE_FPU))
   363			return 0;
   364	
   365		/*
   366		 * If the FPU registers are not owned by current just memcpy() the
   367		 * state.  Otherwise save the FPU registers directly into the
   368		 * child's FPU context, without any memory-to-memory copying.
   369		 */
   370		fpregs_lock();
   371		if (test_thread_flag(TIF_NEED_FPU_LOAD))
 > 372			memcpy(&fpdst->regs, &fpsrc->regs, fpdst->size);
   373		else
   374			save_fpregs_to_fpstate(dst_fpu);
   375		fpregs_unlock();
   376	
   377		set_tsk_thread_flag(dst_tsk, TIF_NEED_FPU_LOAD);
   378	
   379		trace_x86_fpu_copy_src(src_fpu);
   380		trace_x86_fpu_copy_dst(dst_fpu);
   381	
   382		return 0;
   383	}
   384	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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