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Tue, 24 Feb 2026 05:12:32 -0800 (PST) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Tue, 24 Feb 2026 14:12:30 +0100 To: Andrey Grodzovsky Cc: bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, rostedt@goodmis.org, linux-trace-kernel@vger.kernel.org, linux-open-source@crowdstrike.com Subject: Re: [RFC PATCH bpf-next 3/3] selftests/bpf: add tests for kprobe.session optimization Message-ID: References: <20260223215113.924599-1-andrey.grodzovsky@crowdstrike.com> <20260223215113.924599-4-andrey.grodzovsky@crowdstrike.com> Precedence: bulk X-Mailing-List: linux-trace-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: <20260223215113.924599-4-andrey.grodzovsky@crowdstrike.com> On Mon, Feb 23, 2026 at 04:51:13PM -0500, Andrey Grodzovsky wrote: > Add two new subtests to kprobe_multi_test to validate the > kprobe.session exact function name optimization: SNIP > +static void test_session_errors(void) > +{ > + struct kprobe_multi_session_errors *skel = NULL; > + struct bpf_link *link_wildcard = NULL; > + struct bpf_link *link_exact = NULL; > + int err_wildcard, err_exact; > + > + skel = kprobe_multi_session_errors__open_and_load(); > + if (!ASSERT_OK_PTR(skel, "kprobe_multi_session_errors__open_and_load")) > + return; > + > + /* > + * Test error code consistency: both wildcard (slow path) and exact name > + * (fast path) should return the same error code (ENOENT) for non-existent > + * functions. This protects against future kernel changes that might alter > + * error return values. > + */ > + > + /* Try to attach with non-existent wildcard pattern (slow path) */ > + link_wildcard = bpf_program__attach(skel->progs.test_nonexistent_wildcard); > + err_wildcard = -errno; > + ASSERT_ERR_PTR(link_wildcard, "attach_nonexistent_wildcard"); > + ASSERT_EQ(err_wildcard, -ENOENT, "wildcard_error_enoent"); > + > + /* Try to attach with non-existent exact name (fast path) */ > + link_exact = bpf_program__attach(skel->progs.test_nonexistent_exact); > + err_exact = -errno; > + ASSERT_ERR_PTR(link_exact, "attach_nonexistent_exact"); > + ASSERT_EQ(err_exact, -ENOENT, "exact_error_enoent"); > + > + /* > + * Verify both paths return identical error codes - this is critical for > + * API consistency and prevents user code from breaking when switching > + * between wildcard patterns and exact function names. > + */ > + ASSERT_EQ(err_wildcard, err_exact, "error_consistency"); > + > + kprobe_multi_session_errors__destroy(skel); there's already subtest for attach failures (test_attach_api_fails), so maybe let's put this over there? SNIP > diff --git a/tools/testing/selftests/bpf/progs/kprobe_multi_session_syms.c b/tools/testing/selftests/bpf/progs/kprobe_multi_session_syms.c > new file mode 100644 > index 000000000000..6a4bd57af1fc > --- /dev/null > +++ b/tools/testing/selftests/bpf/progs/kprobe_multi_session_syms.c > @@ -0,0 +1,45 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* Test kprobe.session with exact function names to verify syms[] optimization */ > +#include > +#include > +#include > +#include > + > +char _license[] SEC("license") = "GPL"; > + > +int pid = 0; > + > +/* Results for each function: incremented on entry and return */ > +__u64 test1_count = 0; > + > +/* Track entry vs return */ > +bool test1_return = false; > + > +/* > + * No tests in here, just to trigger 'bpf_fentry_test*' > + * through tracing test_run > + */ > +SEC("fentry/bpf_modify_return_test") > +int BPF_PROG(trigger) > +{ > + return 0; > +} > + > +/* > + * Test 1: Exact function name (no wildcards) - uses fast syms[] path > + * This should attach via opts.syms array, bypassing kallsyms parsing > + */ > +SEC("kprobe.session/bpf_fentry_test1") > +int test_kprobe_syms_1(struct pt_regs *ctx) perhaps we could execute this as part of test_session_skel_api test? seems like we could put this directly to progs/kprobe_multi_session.c and call session_check(ctx) and change test_results validation accordingly thanks, jirka > +{ > + if (bpf_get_current_pid_tgid() >> 32 != pid) > + return 0; > + > + test1_count++; > + > + /* Check if this is return probe */ > + if (bpf_session_is_return(ctx)) > + test1_return = true; > + > + return 0; /* Always execute return probe */ > +} > -- > 2.34.1 >