From patchwork Sat Jan 16 18:21:32 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Qais Yousef X-Patchwork-Id: 12025003 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A8E88C433E0 for ; Sat, 16 Jan 2021 18:23:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8161F229C4 for ; Sat, 16 Jan 2021 18:23:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727926AbhAPSW5 (ORCPT ); Sat, 16 Jan 2021 13:22:57 -0500 Received: from foss.arm.com ([217.140.110.172]:56652 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727867AbhAPSWw (ORCPT ); Sat, 16 Jan 2021 13:22:52 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 14F1AED1; Sat, 16 Jan 2021 10:22:07 -0800 (PST) Received: from e107158-lin.cambridge.arm.com (e107158-lin.cambridge.arm.com [10.1.194.78]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B9AC73F70D; Sat, 16 Jan 2021 10:22:05 -0800 (PST) From: Qais Yousef To: netdev@vger.kernel.org, bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Yonghong Song , Steven Rostedt , "Peter Zijlstra (Intel)" , linux-kernel@vger.kernel.org, Qais Yousef Subject: [PATCH v2 bpf-next 1/2] trace: bpf: Allow bpf to attach to bare tracepoints Date: Sat, 16 Jan 2021 18:21:32 +0000 Message-Id: <20210116182133.2286884-2-qais.yousef@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210116182133.2286884-1-qais.yousef@arm.com> References: <20210116182133.2286884-1-qais.yousef@arm.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net Some subsystems only have bare tracepoints (a tracepoint with no associated trace event) to avoid the problem of trace events being an ABI that can't be changed. From bpf presepective, bare tracepoints are what it calls RAW_TRACEPOINT(). Since bpf assumed there's 1:1 mapping, it relied on hooking to DEFINE_EVENT() macro to create bpf mapping of the tracepoints. Since bare tracepoints use DECLARE_TRACE() to create the tracepoint, bpf had no knowledge about their existence. By teaching bpf_probe.h to parse DECLARE_TRACE() in a similar fashion to DEFINE_EVENT(), bpf can find and attach to the new raw tracepoints. Enabling that comes with the contract that changes to raw tracepoints don't constitute a regression if they break existing bpf programs. We need the ability to continue to morph and modify these raw tracepoints without worrying about any ABI. Update Documentation/bpf/bpf_design_QA.rst to document this contract. Signed-off-by: Qais Yousef Acked-by: Yonghong Song --- Documentation/bpf/bpf_design_QA.rst | 6 ++++++ include/trace/bpf_probe.h | 12 ++++++++++-- 2 files changed, 16 insertions(+), 2 deletions(-) diff --git a/Documentation/bpf/bpf_design_QA.rst b/Documentation/bpf/bpf_design_QA.rst index 2df7b067ab93..0e15f9b05c9d 100644 --- a/Documentation/bpf/bpf_design_QA.rst +++ b/Documentation/bpf/bpf_design_QA.rst @@ -208,6 +208,12 @@ data structures and compile with kernel internal headers. Both of these kernel internals are subject to change and can break with newer kernels such that the program needs to be adapted accordingly. +Q: Are tracepoints part of the stable ABI? +------------------------------------------ +A: NO. Tracepoints are tied to internal implementation details hence they are +subject to change and can break with newer kernels. BPF programs need to change +accordingly when this happens. + Q: How much stack space a BPF program uses? ------------------------------------------- A: Currently all program types are limited to 512 bytes of stack diff --git a/include/trace/bpf_probe.h b/include/trace/bpf_probe.h index cd74bffed5c6..a23be89119aa 100644 --- a/include/trace/bpf_probe.h +++ b/include/trace/bpf_probe.h @@ -55,8 +55,7 @@ /* tracepoints with more than 12 arguments will hit build error */ #define CAST_TO_U64(...) CONCATENATE(__CAST, COUNT_ARGS(__VA_ARGS__))(__VA_ARGS__) -#undef DECLARE_EVENT_CLASS -#define DECLARE_EVENT_CLASS(call, proto, args, tstruct, assign, print) \ +#define __BPF_DECLARE_TRACE(call, proto, args) \ static notrace void \ __bpf_trace_##call(void *__data, proto) \ { \ @@ -64,6 +63,10 @@ __bpf_trace_##call(void *__data, proto) \ CONCATENATE(bpf_trace_run, COUNT_ARGS(args))(prog, CAST_TO_U64(args)); \ } +#undef DECLARE_EVENT_CLASS +#define DECLARE_EVENT_CLASS(call, proto, args, tstruct, assign, print) \ + __BPF_DECLARE_TRACE(call, PARAMS(proto), PARAMS(args)) + /* * This part is compiled out, it is only here as a build time check * to make sure that if the tracepoint handling changes, the @@ -111,6 +114,11 @@ __DEFINE_EVENT(template, call, PARAMS(proto), PARAMS(args), size) #define DEFINE_EVENT_PRINT(template, name, proto, args, print) \ DEFINE_EVENT(template, name, PARAMS(proto), PARAMS(args)) +#undef DECLARE_TRACE +#define DECLARE_TRACE(call, proto, args) \ + __BPF_DECLARE_TRACE(call, PARAMS(proto), PARAMS(args)) \ + __DEFINE_EVENT(call, call, PARAMS(proto), PARAMS(args), 0) + #include TRACE_INCLUDE(TRACE_INCLUDE_FILE) #undef DEFINE_EVENT_WRITABLE From patchwork Sat Jan 16 18:21:33 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Qais Yousef X-Patchwork-Id: 12025005 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C471CC433E9 for ; Sat, 16 Jan 2021 18:23:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 95C53229F0 for ; Sat, 16 Jan 2021 18:23:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727883AbhAPSW5 (ORCPT ); Sat, 16 Jan 2021 13:22:57 -0500 Received: from foss.arm.com ([217.140.110.172]:56668 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727868AbhAPSWz (ORCPT ); Sat, 16 Jan 2021 13:22:55 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 92A97101E; Sat, 16 Jan 2021 10:22:09 -0800 (PST) Received: from e107158-lin.cambridge.arm.com (e107158-lin.cambridge.arm.com [10.1.194.78]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 4415C3F70D; Sat, 16 Jan 2021 10:22:08 -0800 (PST) From: Qais Yousef To: netdev@vger.kernel.org, bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Yonghong Song , Steven Rostedt , "Peter Zijlstra (Intel)" , linux-kernel@vger.kernel.org, Qais Yousef Subject: [PATCH v2 bpf-next 2/2] selftests: bpf: Add a new test for bare tracepoints Date: Sat, 16 Jan 2021 18:21:33 +0000 Message-Id: <20210116182133.2286884-3-qais.yousef@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210116182133.2286884-1-qais.yousef@arm.com> References: <20210116182133.2286884-1-qais.yousef@arm.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net Reuse module_attach infrastructure to add a new bare tracepoint to check we can attach to it as a raw tracepoint. Signed-off-by: Qais Yousef --- .../bpf/bpf_testmod/bpf_testmod-events.h | 6 +++++ .../selftests/bpf/bpf_testmod/bpf_testmod.c | 21 ++++++++++++++- .../selftests/bpf/bpf_testmod/bpf_testmod.h | 6 +++++ .../selftests/bpf/prog_tests/module_attach.c | 27 +++++++++++++++++++ .../selftests/bpf/progs/test_module_attach.c | 10 +++++++ 5 files changed, 69 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod-events.h b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod-events.h index b83ea448bc79..89c6d58e5dd6 100644 --- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod-events.h +++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod-events.h @@ -28,6 +28,12 @@ TRACE_EVENT(bpf_testmod_test_read, __entry->pid, __entry->comm, __entry->off, __entry->len) ); +/* A bare tracepoint with no event associated with it */ +DECLARE_TRACE(bpf_testmod_test_write_bare, + TP_PROTO(struct task_struct *task, struct bpf_testmod_test_write_ctx *ctx), + TP_ARGS(task, ctx) +); + #endif /* _BPF_TESTMOD_EVENTS_H */ #undef TRACE_INCLUDE_PATH diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c index 2df19d73ca49..e900adad2276 100644 --- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c +++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c @@ -28,9 +28,28 @@ bpf_testmod_test_read(struct file *file, struct kobject *kobj, EXPORT_SYMBOL(bpf_testmod_test_read); ALLOW_ERROR_INJECTION(bpf_testmod_test_read, ERRNO); +noinline ssize_t +bpf_testmod_test_write(struct file *file, struct kobject *kobj, + struct bin_attribute *bin_attr, + char *buf, loff_t off, size_t len) +{ + struct bpf_testmod_test_write_ctx ctx = { + .buf = buf, + .off = off, + .len = len, + }; + + trace_bpf_testmod_test_write_bare(current, &ctx); + + return -EIO; /* always fail */ +} +EXPORT_SYMBOL(bpf_testmod_test_write); +ALLOW_ERROR_INJECTION(bpf_testmod_test_write, ERRNO); + static struct bin_attribute bin_attr_bpf_testmod_file __ro_after_init = { - .attr = { .name = "bpf_testmod", .mode = 0444, }, + .attr = { .name = "bpf_testmod", .mode = 0666, }, .read = bpf_testmod_test_read, + .write = bpf_testmod_test_write, }; static int bpf_testmod_init(void) diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h index b81adfedb4f6..b3892dc40111 100644 --- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h +++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h @@ -11,4 +11,10 @@ struct bpf_testmod_test_read_ctx { size_t len; }; +struct bpf_testmod_test_write_ctx { + char *buf; + loff_t off; + size_t len; +}; + #endif /* _BPF_TESTMOD_H */ diff --git a/tools/testing/selftests/bpf/prog_tests/module_attach.c b/tools/testing/selftests/bpf/prog_tests/module_attach.c index 50796b651f72..e4605c0b5af1 100644 --- a/tools/testing/selftests/bpf/prog_tests/module_attach.c +++ b/tools/testing/selftests/bpf/prog_tests/module_attach.c @@ -21,9 +21,34 @@ static int trigger_module_test_read(int read_sz) return 0; } +static int trigger_module_test_write(int write_sz) +{ + int fd, err; + char *buf = malloc(write_sz); + + if (!buf) + return -ENOMEM; + + memset(buf, 'a', write_sz); + buf[write_sz-1] = '\0'; + + fd = open("/sys/kernel/bpf_testmod", O_WRONLY); + err = -errno; + if (CHECK(fd < 0, "testmod_file_open", "failed: %d\n", err)) + goto out; + + write(fd, buf, write_sz); + close(fd); +out: + free(buf); + + return 0; +} + void test_module_attach(void) { const int READ_SZ = 456; + const int WRITE_SZ = 457; struct test_module_attach* skel; struct test_module_attach__bss *bss; int err; @@ -48,8 +73,10 @@ void test_module_attach(void) /* trigger tracepoint */ ASSERT_OK(trigger_module_test_read(READ_SZ), "trigger_read"); + ASSERT_OK(trigger_module_test_write(WRITE_SZ), "trigger_write"); ASSERT_EQ(bss->raw_tp_read_sz, READ_SZ, "raw_tp"); + ASSERT_EQ(bss->raw_tp_bare_write_sz, WRITE_SZ, "raw_tp_bare"); ASSERT_EQ(bss->tp_btf_read_sz, READ_SZ, "tp_btf"); ASSERT_EQ(bss->fentry_read_sz, READ_SZ, "fentry"); ASSERT_EQ(bss->fentry_manual_read_sz, READ_SZ, "fentry_manual"); diff --git a/tools/testing/selftests/bpf/progs/test_module_attach.c b/tools/testing/selftests/bpf/progs/test_module_attach.c index efd1e287ac17..bd37ceec5587 100644 --- a/tools/testing/selftests/bpf/progs/test_module_attach.c +++ b/tools/testing/selftests/bpf/progs/test_module_attach.c @@ -17,6 +17,16 @@ int BPF_PROG(handle_raw_tp, return 0; } +__u32 raw_tp_bare_write_sz = 0; + +SEC("raw_tp/bpf_testmod_test_write_bare") +int BPF_PROG(handle_raw_tp_bare, + struct task_struct *task, struct bpf_testmod_test_write_ctx *write_ctx) +{ + raw_tp_bare_write_sz = BPF_CORE_READ(write_ctx, len); + return 0; +} + __u32 tp_btf_read_sz = 0; SEC("tp_btf/bpf_testmod_test_read")