Re:Re: [PATCH] trace/trace_uprobe: Only invoke uprobe ebpf handler when event matches.

[David Wang]

Fix compile warning: unused variable trace_event_match
    
`trace_event_match` is used to indicate whether
current event matches any registered event. For
now, this variable is only used for ebpf handler
and CONFIG_BPF_EVENTS is needed, otherwise a compile
warning would be generated about unused variable.
    
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Signed-off-by: David Wang <00107082@xxxxxxx>
--
diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index 6f13163c0c0f..0548c651699e 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -1346,13 +1346,17 @@ static void __uprobe_perf_func(struct trace_uprobe *tu,
        void *data;
        int size, esize;
        int rctx;
+#ifdef CONFIG_BPF_EVENTS
        bool trace_event_match = true;
+#endif /* CONFIG_BPF_EVENTS */
 
 
        preempt_disable();
        head = this_cpu_ptr(call->perf_events);
        if (hlist_empty(head)) {
+#ifdef CONFIG_BPF_EVENTS
                trace_event_match = false;
+#endif /* CONFIG_BPF_EVENTS */
                goto out;
        }
 
--

















At 2022-11-05 05:30:37, "kernel test robot" <lkp@xxxxxxxxx> wrote:
>Hi David,
>
>Thank you for the patch! Perhaps something to improve:
>
>[auto build test WARNING on linus/master]
>[also build test WARNING on v6.1-rc3 next-20221104]
>[If your patch is applied to the wrong git tree, kindly drop us a note.
>And when submitting patch, we suggest to use '--base' as documented in
>https://git-scm.com/docs/git-format-patch#_base_tree_information]
>
>url:    https://github.com/intel-lab-lkp/linux/commits/David-Wang/trace-trace_uprobe-Only-invoke-uprobe-ebpf-handler-when-event-matches/20221104-210925
>patch link:    https://lore.kernel.org/r/41828b90.5798.18442c10017.Coremail.00107082%40163.com
>patch subject: [PATCH] trace/trace_uprobe: Only invoke uprobe ebpf handler when event matches.
>config: i386-defconfig
>compiler: gcc-11 (Debian 11.3.0-8) 11.3.0
>reproduce (this is a W=1 build):
>        # https://github.com/intel-lab-lkp/linux/commit/6c778c475c0a6c8a11c1a74705a5856681cf6cf0
>        git remote add linux-review https://github.com/intel-lab-lkp/linux
>        git fetch --no-tags linux-review David-Wang/trace-trace_uprobe-Only-invoke-uprobe-ebpf-handler-when-event-matches/20221104-210925
>        git checkout 6c778c475c0a6c8a11c1a74705a5856681cf6cf0
>        # save the config file
>        mkdir build_dir && cp config build_dir/.config
>        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash kernel/trace/
>
>If you fix the issue, kindly add following tag where applicable
>| Reported-by: kernel test robot <lkp@xxxxxxxxx>
>
>All warnings (new ones prefixed by >>):
>
>   kernel/trace/trace_uprobe.c: In function '__uprobe_perf_func':
>>> kernel/trace/trace_uprobe.c:1349:14: warning: variable 'trace_event_match' set but not used [-Wunused-but-set-variable]
>    1349 |         bool trace_event_match = true;
>         |              ^~~~~~~~~~~~~~~~~
>
>
>vim +/trace_event_match +1349 kernel/trace/trace_uprobe.c
>
>  1338	
>  1339	static void __uprobe_perf_func(struct trace_uprobe *tu,
>  1340				       unsigned long func, struct pt_regs *regs,
>  1341				       struct uprobe_cpu_buffer *ucb, int dsize)
>  1342	{
>  1343		struct trace_event_call *call = trace_probe_event_call(&tu->tp);
>  1344		struct uprobe_trace_entry_head *entry;
>  1345		struct hlist_head *head;
>  1346		void *data;
>  1347		int size, esize;
>  1348		int rctx;
>> 1349		bool trace_event_match = true;
>  1350	
>  1351	
>  1352		preempt_disable();
>  1353		head = this_cpu_ptr(call->perf_events);
>  1354		if (hlist_empty(head)) {
>  1355			trace_event_match = false;
>  1356			goto out;
>  1357		}
>  1358	
>  1359		esize = SIZEOF_TRACE_ENTRY(is_ret_probe(tu));
>  1360		size = esize + tu->tp.size + dsize;
>  1361		size = ALIGN(size + sizeof(u32), sizeof(u64)) - sizeof(u32);
>  1362		if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE, "profile buffer not large enough"))
>  1363			goto out;
>  1364	
>  1365		entry = perf_trace_buf_alloc(size, NULL, &rctx);
>  1366		if (!entry)
>  1367			goto out;
>  1368	
>  1369		if (is_ret_probe(tu)) {
>  1370			entry->vaddr[0] = func;
>  1371			entry->vaddr[1] = instruction_pointer(regs);
>  1372			data = DATAOF_TRACE_ENTRY(entry, true);
>  1373		} else {
>  1374			entry->vaddr[0] = instruction_pointer(regs);
>  1375			data = DATAOF_TRACE_ENTRY(entry, false);
>  1376		}
>  1377	
>  1378		memcpy(data, ucb->buf, tu->tp.size + dsize);
>  1379	
>  1380		if (size - esize > tu->tp.size + dsize) {
>  1381			int len = tu->tp.size + dsize;
>  1382	
>  1383			memset(data + len, 0, size - esize - len);
>  1384		}
>  1385		perf_trace_buf_submit(entry, size, rctx, call->event.type, 1, regs,
>  1386				      head, NULL);
>  1387	 out:
>  1388		preempt_enable();
>  1389	
>
>-- 
>0-DAY CI Kernel Test Service
>https://01.org/lkp