linux-kernel - Re: [PATCH hid v11 04/14] HID: bpf jmp table: simplify the logic of cleaning up programs

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Date:   Fri, 28 Oct 2022 11:13:52 +0800
From:   kernel test robot <lkp@...el.com>
To:     Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Greg KH <greg@...ah.com>, Jiri Kosina <jikos@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Shuah Khan <skhan@...uxfoundation.org>
Cc:     llvm@...ts.linux.dev, oe-kbuild-all@...ts.linux.dev,
        Tero Kristo <tero.kristo@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
        bpf@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-doc@...r.kernel.org,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>
Subject: Re: [PATCH hid v11 04/14] HID: bpf jmp table: simplify the logic of
 cleaning up programs

Hi Benjamin,

I love your patch! Perhaps something to improve:

[auto build test WARNING on hid/master]

url:    https://github.com/intel-lab-lkp/linux/commits/Benjamin-Tissoires/Introduce-eBPF-support-for-HID-devices/20221025-173852
base:   https://git.kernel.org/pub/scm/linux/kernel/git/hid/hid.git master
patch link:    https://lore.kernel.org/r/20221025093458.457089-5-benjamin.tissoires%40redhat.com
patch subject: [PATCH hid v11 04/14] HID: bpf jmp table: simplify the logic of cleaning up programs
config: arm64-randconfig-r015-20221027
compiler: clang version 16.0.0 (https://github.com/llvm/llvm-project 791a7ae1ba3efd6bca96338e10ffde557ba83920)
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 arm64 cross compiling tool for clang build
        # apt-get install binutils-aarch64-linux-gnu
        # https://github.com/intel-lab-lkp/linux/commit/e16299dd3103acbce798add51a7595b8c59ecb9e
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Benjamin-Tissoires/Introduce-eBPF-support-for-HID-devices/20221025-173852
        git checkout e16299dd3103acbce798add51a7595b8c59ecb9e
        # 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=arm64 SHELL=/bin/bash drivers/hid/bpf/ fs/

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

All warnings (new ones prefixed by >>):

>> drivers/hid/bpf/hid_bpf_jmp_table.c:288:9: warning: variable 'cnt' set but not used [-Wunused-but-set-variable]
           int i, cnt, index = -1, map_fd = -1, err = -EINVAL;
                  ^
   1 warning generated.


vim +/cnt +288 drivers/hid/bpf/hid_bpf_jmp_table.c

   281	
   282	/*
   283	 * Insert the given BPF program represented by its fd in the jmp table.
   284	 * Returns the index in the jump table or a negative error.
   285	 */
   286	static int hid_bpf_insert_prog(int prog_fd, struct bpf_prog *prog)
   287	{
 > 288		int i, cnt, index = -1, map_fd = -1, err = -EINVAL;
   289	
   290		/* retrieve a fd of our prog_array map in BPF */
   291		map_fd = skel_map_get_fd_by_id(jmp_table.map->id);
   292	
   293		if (map_fd < 0) {
   294			err = -EINVAL;
   295			goto out;
   296		}
   297	
   298		cnt = 0;
   299		/* find the first available index in the jmp_table
   300		 * and count how many time this program has been inserted
   301		 */
   302		for (i = 0; i < HID_BPF_MAX_PROGS; i++) {
   303			if (!jmp_table.progs[i] && index < 0) {
   304				/* mark the index as used */
   305				jmp_table.progs[i] = prog;
   306				index = i;
   307				__set_bit(i, jmp_table.enabled);
   308				cnt++;
   309			} else {
   310				if (jmp_table.progs[i] == prog)
   311					cnt++;
   312			}
   313		}
   314		if (index < 0) {
   315			err = -ENOMEM;
   316			goto out;
   317		}
   318	
   319		/* insert the program in the jump table */
   320		err = skel_map_update_elem(map_fd, &index, &prog_fd, 0);
   321		if (err)
   322			goto out;
   323	
   324		/*
   325		 * The program has been safely inserted, decrement the reference count
   326		 * so it doesn't interfere with the number of actual user handles.
   327		 * This is safe to do because:
   328		 * - we overrite the put_ptr in the prog fd map
   329		 * - we also have a cleanup function that monitors when a program gets
   330		 *   released and we manually do the cleanup in the prog fd map
   331		 */
   332		bpf_prog_sub(prog, 1);
   333	
   334		/* return the index */
   335		err = index;
   336	
   337	 out:
   338		if (err < 0)
   339			__hid_bpf_do_release_prog(map_fd, index);
   340		if (map_fd >= 0)
   341			close_fd(map_fd);
   342		return err;
   343	}
   344	

-- 
0-DAY CI Kernel Test Service
https://01.org/lkp

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