Hi Andrii,

I love your patch! Perhaps something to improve:

[auto build test WARNING on bpf-next/master]

url:    https://github.com/0day-ci/linux/commits/Andrii-Nakryiko/Integrate-kernel-module-BTF-support/20201110-095309
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
config: mips-randconfig-r002-20201110 (attached as .config)
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project 4d81c8adb6ed9840257f6cb6b93f60856d422a15)
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
        # install mips cross compiling tool for clang build
        # apt-get install binutils-mips-linux-gnu
        # https://github.com/0day-ci/linux/commit/dcd763b7808fdc01ebf70bbe07ba92388df4d20d
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Andrii-Nakryiko/Integrate-kernel-module-BTF-support/20201110-095309
        git checkout dcd763b7808fdc01ebf70bbe07ba92388df4d20d
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=mips 

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

All warnings (new ones prefixed by >>):

>> kernel/bpf/btf.c:4481:20: warning: unused function 'btf_parse_module'
   static struct btf char const void unsigned int data_size)
   ^
   fatal error: error in backend: Nested variants found in inline asm string: ' .set push
   .set mips64r2
   .if ( 0x00 ) != -1)) 0x00 ) != -1)) : ($( static struct ftrace_branch_data __attribute__((__aligned__(4))) __attribute__((__section__("_ftrace_branch"))) __if_trace = $( .func = __func__, .file = "arch/mips/include/asm/atomic.h", .line = 154, $); 0x00 ) != -1)) : $))) ) && ( 0 ); .set push; .set mips64r2; .rept 1; sync 0x00; .endr; .set pop; .else; ; .endif
   1: ll $1, $2 # atomic_fetch_sub
   subu $0, $1, $3
   sc $0, $2
   beqz $0, 1b
   .set pop
   move $0, $1
   '
   clang-12: error: clang frontend command failed with exit code 70 (use -v to see invocation)
   clang version 12.0.0 (git://gitmirror/llvm_project 874b0a0b9db93f5d3350ffe6b5efda2d908415d0)
   Target: mipsel-unknown-linux-gnu
   Thread model: posix
   InstalledDir: /opt/cross/clang-874b0a0b9d/bin
   clang-12: note: diagnostic msg:
   Makefile arch drivers include kernel mm scripts source usr

vim +/btf_parse_module +4481 kernel/bpf/btf.c

  4480	
> 4481	static struct btf *btf_parse_module(const char *module_name, const void *data, unsigned int data_size)
  4482	{
  4483		struct btf_verifier_env *env = NULL;
  4484		struct bpf_verifier_log *log;
  4485		struct btf *btf = NULL, *base_btf;
  4486		int err;
  4487	
  4488		base_btf = bpf_get_btf_vmlinux();
  4489		if (IS_ERR(base_btf))
  4490			return base_btf;
  4491		if (!base_btf)
  4492			return ERR_PTR(-EINVAL);
  4493	
  4494		env = kzalloc(sizeof(*env), GFP_KERNEL | __GFP_NOWARN);
  4495		if (!env)
  4496			return ERR_PTR(-ENOMEM);
  4497	
  4498		log = &env->log;
  4499		log->level = BPF_LOG_KERNEL;
  4500	
  4501		btf = kzalloc(sizeof(*btf), GFP_KERNEL | __GFP_NOWARN);
  4502		if (!btf) {
  4503			err = -ENOMEM;
  4504			goto errout;
  4505		}
  4506		env->btf = btf;
  4507	
  4508		btf->base_btf = base_btf;
  4509		btf->start_id = base_btf->nr_types;
  4510		btf->start_str_off = base_btf->hdr.str_len;
  4511		btf->kernel_btf = true;
  4512		snprintf(btf->name, sizeof(btf->name), "%s", module_name);
  4513	
  4514		btf->data = kvmalloc(data_size, GFP_KERNEL | __GFP_NOWARN);
  4515		if (!btf->data) {
  4516			err = -ENOMEM;
  4517			goto errout;
  4518		}
  4519		memcpy(btf->data, data, data_size);
  4520		btf->data_size = data_size;
  4521	
  4522		err = btf_parse_hdr(env);
  4523		if (err)
  4524			goto errout;
  4525	
  4526		btf->nohdr_data = btf->data + btf->hdr.hdr_len;
  4527	
  4528		err = btf_parse_str_sec(env);
  4529		if (err)
  4530			goto errout;
  4531	
  4532		err = btf_check_all_metas(env);
  4533		if (err)
  4534			goto errout;
  4535	
  4536		btf_verifier_env_free(env);
  4537		refcount_set(&btf->refcnt, 1);
  4538		return btf;
  4539	
  4540	errout:
  4541		btf_verifier_env_free(env);
  4542		if (btf) {
  4543			kvfree(btf->data);
  4544			kvfree(btf->types);
  4545			kfree(btf);
  4546		}
  4547		return ERR_PTR(err);
  4548	}
  4549	

---
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