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Mon, 14 Apr 2025 04:43:42 -0700 (PDT) Received: from krava ([2a00:102a:4007:73e1:1681:405:90b2:869b]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43f2338db88sm176345815e9.6.2025.04.14.04.43.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Apr 2025 04:43:41 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Mon, 14 Apr 2025 13:43:38 +0200 To: Feng Yang Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, hengqi.chen@gmail.com, bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 bpf-next 1/3] libbpf: Fix event name too long error Message-ID: References: <20250414093402.384872-1-yangfeng59949@163.com> <20250414093402.384872-2-yangfeng59949@163.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250414093402.384872-2-yangfeng59949@163.com> On Mon, Apr 14, 2025 at 05:34:00PM +0800, Feng Yang wrote: > From: Feng Yang > > When the binary path is excessively long, the generated probe_name in libbpf > exceeds the kernel's MAX_EVENT_NAME_LEN limit (64 bytes). > This causes legacy uprobe event attachment to fail with error code -22. > > Before Fix: > ./test_progs -t attach_probe/kprobe-long_name > ...... > libbpf: failed to add legacy kprobe event for 'bpf_kfunc_looooooooooooooooooooooooooooooong_name+0x0': -EINVAL > libbpf: prog 'handle_kprobe': failed to create kprobe 'bpf_kfunc_looooooooooooooooooooooooooooooong_name+0x0' perf event: -EINVAL > test_attach_kprobe_long_event_name:FAIL:attach_kprobe_long_event_name unexpected error: -22 > test_attach_probe:PASS:uprobe_ref_ctr_cleanup 0 nsec > #13/11 attach_probe/kprobe-long_name:FAIL > #13 attach_probe:FAIL > > ./test_progs -t attach_probe/uprobe-long_name > ...... > libbpf: failed to add legacy uprobe event for /root/linux-bpf/bpf-next/tools/testing/selftests/bpf/test_progs:0x13efd9: -EINVAL > libbpf: prog 'handle_uprobe': failed to create uprobe '/root/linux-bpf/bpf-next/tools/testing/selftests/bpf/test_progs:0x13efd9' perf event: -EINVAL > test_attach_uprobe_long_event_name:FAIL:attach_uprobe_long_event_name unexpected error: -22 > #13/10 attach_probe/uprobe-long_name:FAIL > #13 attach_probe:FAIL > After Fix: > ./test_progs -t attach_probe/uprobe-long_name > #13/10 attach_probe/uprobe-long_name:OK > #13 attach_probe:OK > Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED > > ./test_progs -t attach_probe/kprobe-long_name > #13/11 attach_probe/kprobe-long_name:OK > #13 attach_probe:OK > Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED > > Fixes: 46ed5fc33db9 ("libbpf: Refactor and simplify legacy kprobe code") > Fixes: cc10623c6810 ("libbpf: Add legacy uprobe attaching support") > Signed-off-by: Hengqi Chen > Signed-off-by: Feng Yang > --- > tools/lib/bpf/libbpf.c | 19 ++++++++++++------- > 1 file changed, 12 insertions(+), 7 deletions(-) > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index b2591f5cab65..9e047641e001 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -60,6 +60,8 @@ > #define BPF_FS_MAGIC 0xcafe4a11 > #endif > > +#define MAX_EVENT_NAME_LEN 64 > + > #define BPF_FS_DEFAULT_PATH "/sys/fs/bpf" > > #define BPF_INSN_SZ (sizeof(struct bpf_insn)) > @@ -11142,10 +11144,10 @@ static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz, > static int index = 0; > int i; > > - snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx_%d", getpid(), kfunc_name, offset, > - __sync_fetch_and_add(&index, 1)); > + snprintf(buf, buf_sz, "libbpf_%u_%d_%s_0x%zx", getpid(), > + __sync_fetch_and_add(&index, 1), kfunc_name, offset); so the fix is to move unique id before kfunc_name to make sure it gets to the event name right? would be great to have it in changelog > > - /* sanitize binary_path in the probe name */ > + /* sanitize kfunc_name in the probe name */ > for (i = 0; buf[i]; i++) { > if (!isalnum(buf[i])) > buf[i] = '_'; > @@ -11270,7 +11272,7 @@ int probe_kern_syscall_wrapper(int token_fd) > > return pfd >= 0 ? 1 : 0; > } else { /* legacy mode */ > - char probe_name[128]; > + char probe_name[MAX_EVENT_NAME_LEN]; > > gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name), syscall_name, 0); > if (add_kprobe_event_legacy(probe_name, false, syscall_name, 0) < 0) > @@ -11328,7 +11330,7 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog, > func_name, offset, > -1 /* pid */, 0 /* ref_ctr_off */); > } else { > - char probe_name[256]; > + char probe_name[MAX_EVENT_NAME_LEN]; > > gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name), > func_name, offset); > @@ -11878,9 +11880,12 @@ static int attach_uprobe_multi(const struct bpf_program *prog, long cookie, stru > static void gen_uprobe_legacy_event_name(char *buf, size_t buf_sz, > const char *binary_path, uint64_t offset) > { > + static int index = 0; > int i; > > - snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx", getpid(), binary_path, (size_t)offset); > + snprintf(buf, buf_sz, "libbpf_%u_%d_%s_0x%zx", getpid(), > + __sync_fetch_and_add(&index, 1), > + basename((void *)binary_path), (size_t)offset); gen_kprobe_legacy_event_name and gen_uprobe_legacy_event_name seem to be identical now, maybe we can have just one ? thanks, jirka > > /* sanitize binary_path in the probe name */ > for (i = 0; buf[i]; i++) { > @@ -12312,7 +12317,7 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid, > pfd = perf_event_open_probe(true /* uprobe */, retprobe, binary_path, > func_offset, pid, ref_ctr_off); > } else { > - char probe_name[PATH_MAX + 64]; > + char probe_name[MAX_EVENT_NAME_LEN]; > > if (ref_ctr_off) > return libbpf_err_ptr(-EINVAL); > -- > 2.43.0 >