tree:   git://git.infradead.org/users/hch/misc.git maccess-fixups.3
head:   ffc491b4d7cbc956087e89dbd171863c411f3868
commit: 5de7b23a3f5410a896ab792fd3e580d5f0e54258 [15/18] x86: use non-set_fs based maccess routines
config: x86_64-randconfig-a005-20200513 (attached as .config)
compiler: gcc-7 (Ubuntu 7.5.0-6ubuntu2) 7.5.0
reproduce:
        git checkout 5de7b23a3f5410a896ab792fd3e580d5f0e54258
        # save the attached .config to linux build tree
        make ARCH=x86_64 

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

All errors (new ones prefixed by >>):

ld: kernel/trace/bpf_trace.o: in function `bpf_probe_read_kernel_str_common':
>> kernel/trace/bpf_trace.c:252: undefined reference to `strncpy_from_kernel_nofault'
>> ld: kernel/trace/bpf_trace.c:252: undefined reference to `strncpy_from_kernel_nofault'
ld: kernel/trace/bpf_trace.o: in function `bpf_strncpy':
kernel/trace/bpf_trace.c:344: undefined reference to `strncpy_from_kernel_nofault'

vim +252 kernel/trace/bpf_trace.c

6ae08ae3dea2cfa Daniel Borkmann    2019-11-02  232  
6ae08ae3dea2cfa Daniel Borkmann    2019-11-02  233  static __always_inline int
6ae08ae3dea2cfa Daniel Borkmann    2019-11-02  234  bpf_probe_read_kernel_str_common(void *dst, u32 size, const void *unsafe_ptr,
6ae08ae3dea2cfa Daniel Borkmann    2019-11-02  235  				 const bool compat)
6ae08ae3dea2cfa Daniel Borkmann    2019-11-02  236  {
334a11cc65f45f1 Christoph Hellwig  2020-05-13  237  	const void __user *user_ptr = (__force const void __user *)unsafe_ptr;
6ae08ae3dea2cfa Daniel Borkmann    2019-11-02  238  	int ret = security_locked_down(LOCKDOWN_BPF_READ);
6ae08ae3dea2cfa Daniel Borkmann    2019-11-02  239  
6ae08ae3dea2cfa Daniel Borkmann    2019-11-02  240  	if (unlikely(ret < 0))
334a11cc65f45f1 Christoph Hellwig  2020-05-13  241  		goto fail;
334a11cc65f45f1 Christoph Hellwig  2020-05-13  242  
6ae08ae3dea2cfa Daniel Borkmann    2019-11-02  243  	/*
334a11cc65f45f1 Christoph Hellwig  2020-05-13  244  	 * The strncpy_from_*_nofault() calls will likely not fill the entire
6ae08ae3dea2cfa Daniel Borkmann    2019-11-02  245  	 * buffer, but that's okay in this circumstance as we're probing
6ae08ae3dea2cfa Daniel Borkmann    2019-11-02  246  	 * arbitrary memory anyway similar to bpf_probe_read_*() and might
6ae08ae3dea2cfa Daniel Borkmann    2019-11-02  247  	 * as well probe the stack. Thus, memory is explicitly cleared
6ae08ae3dea2cfa Daniel Borkmann    2019-11-02  248  	 * only in error case, so that improper users ignoring return
6ae08ae3dea2cfa Daniel Borkmann    2019-11-02  249  	 * code altogether don't copy garbage; otherwise length of string
6ae08ae3dea2cfa Daniel Borkmann    2019-11-02  250  	 * is returned that can be used for bpf_perf_event_output() et al.
6ae08ae3dea2cfa Daniel Borkmann    2019-11-02  251  	 */
334a11cc65f45f1 Christoph Hellwig  2020-05-13 @252  	ret = strncpy_from_kernel_nofault(dst, unsafe_ptr, size);
334a11cc65f45f1 Christoph Hellwig  2020-05-13  253  	if (unlikely(ret < 0)) {
334a11cc65f45f1 Christoph Hellwig  2020-05-13  254  		if (compat)
334a11cc65f45f1 Christoph Hellwig  2020-05-13  255  			ret = strncpy_from_user_nofault(dst, user_ptr, size);
6ae08ae3dea2cfa Daniel Borkmann    2019-11-02  256  		if (unlikely(ret < 0))
334a11cc65f45f1 Christoph Hellwig  2020-05-13  257  			goto fail;
334a11cc65f45f1 Christoph Hellwig  2020-05-13  258  	}
334a11cc65f45f1 Christoph Hellwig  2020-05-13  259  	return 0;
334a11cc65f45f1 Christoph Hellwig  2020-05-13  260  fail:
6ae08ae3dea2cfa Daniel Borkmann    2019-11-02  261  	memset(dst, 0, size);
074f528eed408b4 Daniel Borkmann    2016-04-13  262  	return ret;
2541517c32be253 Alexei Starovoitov 2015-03-25  263  }
2541517c32be253 Alexei Starovoitov 2015-03-25  264  

:::::: The code@line 252 was first introduced by commit
:::::: 334a11cc65f45f12f7fb8929928e68f7fb63d26d maccess: remove strncpy_from_unsafe

:::::: TO: Christoph Hellwig <hch@lst.de>
:::::: CC: Christoph Hellwig <hch@lst.de>

---
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