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[2001:1ae9:1c2:4c00:726e:c10f:8833:ff22]) by smtp.gmail.com with ESMTPSA id o21-20020aa7c515000000b0052576969ef8sm813790edq.14.2023.08.31.06.52.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 31 Aug 2023 06:52:05 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Thu, 31 Aug 2023 15:52:02 +0200 To: Rong Tao Cc: olsajiri@gmail.com, andrii@kernel.org, daniel@iogearbox.net, sdf@google.com, Rong Tao , Alexei Starovoitov , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Hao Luo , Mykola Lysenko , Shuah Khan , Maxime Coquelin , Alexandre Torgue , Ilya Leoshkevich , Yafang Shao , Daniel =?iso-8859-1?Q?M=FCller?= , Manu Bretelle , Xu Kuohai , Ross Zwisler , Eduard Zingerman , "open list:BPF [GENERAL] (Safe Dynamic Programs and Tools)" , open list , "open list:KERNEL SELFTEST FRAMEWORK" , "moderated list:ARM/STM32 ARCHITECTURE" , "moderated list:ARM/STM32 ARCHITECTURE" Subject: Re: [PATCH bpf-next v9] selftests/bpf: trace_helpers.c: optimize kallsyms cache Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On Tue, Aug 29, 2023 at 10:14:01PM +0800, Rong Tao wrote: > From: Rong Tao > > Static ksyms often have problems because the number of symbols exceeds the > MAX_SYMS limit. Like changing the MAX_SYMS from 300000 to 400000 in > commit e76a014334a6("selftests/bpf: Bump and validate MAX_SYMS") solves > the problem somewhat, but it's not the perfect way. > > This commit uses dynamic memory allocation, which completely solves the > problem caused by the limitation of the number of kallsyms. > > Acked-by: Stanislav Fomichev > Signed-off-by: Rong Tao > --- > v9: Add load_kallsyms_local,ksym_search_local,ksym_get_addr_local functions. > v8: https://lore.kernel.org/lkml/tencent_6D23FE187408D965E95DFAA858BC7E8C760A@qq.com/ > Resolves inter-thread contention for ksyms global variables. > v7: https://lore.kernel.org/lkml/tencent_BD6E19C00BF565CD5C36A9A0BD828CFA210A@qq.com/ > Fix __must_check macro. > v6: https://lore.kernel.org/lkml/tencent_4A09A36F883A06EA428A593497642AF8AF08@qq.com/ > Apply libbpf_ensure_mem() > v5: https://lore.kernel.org/lkml/tencent_0E9E1A1C0981678D5E7EA9E4BDBA8EE2200A@qq.com/ > Release the allocated memory once the load_kallsyms_refresh() upon error > given it's dynamically allocated. > v4: https://lore.kernel.org/lkml/tencent_59C74613113F0C728524B2A82FE5540A5E09@qq.com/ > Make sure most cases we don't need the realloc() path to begin with, > and check strdup() return value. > v3: https://lore.kernel.org/lkml/tencent_50B4B2622FE7546A5FF9464310650C008509@qq.com/ > Do not use structs and judge ksyms__add_symbol function return value. > v2: https://lore.kernel.org/lkml/tencent_B655EE5E5D463110D70CD2846AB3262EED09@qq.com/ > Do the usual len/capacity scheme here to amortize the cost of realloc, and > don't free symbols. > v1: https://lore.kernel.org/lkml/tencent_AB461510B10CD484E0B2F62E3754165F2909@qq.com/ > --- > samples/bpf/Makefile | 4 + > .../selftests/bpf/prog_tests/bpf_cookie.c | 9 +- > .../selftests/bpf/prog_tests/fill_link_info.c | 9 +- > .../bpf/prog_tests/get_stack_raw_tp.c | 10 +- > .../bpf/prog_tests/kprobe_multi_test.c | 15 +- > .../prog_tests/kprobe_multi_testmod_test.c | 19 ++- > tools/testing/selftests/bpf/trace_helpers.c | 142 +++++++++++++----- > tools/testing/selftests/bpf/trace_helpers.h | 8 + > 8 files changed, 159 insertions(+), 57 deletions(-) > > diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile > index 4ccf4236031c..6c707ebcebb9 100644 > --- a/samples/bpf/Makefile > +++ b/samples/bpf/Makefile > @@ -175,6 +175,7 @@ TPROGS_CFLAGS += -I$(srctree)/tools/testing/selftests/bpf/ > TPROGS_CFLAGS += -I$(LIBBPF_INCLUDE) > TPROGS_CFLAGS += -I$(srctree)/tools/include > TPROGS_CFLAGS += -I$(srctree)/tools/perf > +TPROGS_CFLAGS += -I$(srctree)/tools/lib > TPROGS_CFLAGS += -DHAVE_ATTR_TEST=0 > > ifdef SYSROOT > @@ -314,6 +315,9 @@ XDP_SAMPLE_CFLAGS += -Wall -O2 \ > > $(obj)/$(XDP_SAMPLE): TPROGS_CFLAGS = $(XDP_SAMPLE_CFLAGS) > $(obj)/$(XDP_SAMPLE): $(src)/xdp_sample_user.h $(src)/xdp_sample_shared.h > +# Override includes for trace_helpers.o because __must_check won't be defined > +# in our include path. > +$(obj)/$(TRACE_HELPERS): TPROGS_CFLAGS := $(TPROGS_CFLAGS) -D__must_check= > > -include $(BPF_SAMPLES_PATH)/Makefile.target > > diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c b/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c > index 1454cebc262b..4ed47dc75669 100644 > --- a/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c > +++ b/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c > @@ -104,8 +104,10 @@ static void kprobe_multi_link_api_subtest(void) > LIBBPF_OPTS(bpf_link_create_opts, opts); > unsigned long long addrs[8]; > __u64 cookies[8]; > + struct ksyms *ksyms; > > - if (!ASSERT_OK(load_kallsyms(), "load_kallsyms")) > + ksyms = load_kallsyms_local(); > + if (!ASSERT_OK(ksyms != NULL, "load_kallsyms_local")) > goto cleanup; hum, this wont work right? I think you should use ASSERT_OK_PTR in here and ther similar places below > > skel = kprobe_multi__open_and_load(); > @@ -116,8 +118,8 @@ static void kprobe_multi_link_api_subtest(void) > skel->bss->test_cookie = true; > > #define GET_ADDR(__sym, __addr) ({ \ > - __addr = ksym_get_addr(__sym); \ > - if (!ASSERT_NEQ(__addr, 0, "ksym_get_addr " #__sym)) \ > + __addr = ksym_get_addr_local(ksyms, __sym); \ > + if (!ASSERT_NEQ(__addr, 0, "ksym_get_addr_local " #__sym)) \ > goto cleanup; \ > }) > > @@ -171,6 +173,7 @@ static void kprobe_multi_link_api_subtest(void) > cleanup: > close(link1_fd); > close(link2_fd); > + free_kallsyms_local(ksyms); I think we don't need to change any test that's calling load_kallsyms, it should use load_kallsyms and global ksyms data the load_kallsyms_local would be used in tests that use load_kallsyms_refresh and need updated ksyms data for bpf_testmod symbols we just need to make sure that global ksyms initialization won't race, like with: +static pthread_mutex_t ksyms_mutex = PTHREAD_MUTEX_INITIALIZER; + int load_kallsyms(void) { - /* - * This is called/used from multiplace places, - * load symbols just once. - */ - if (sym_cnt) - return 0; - return load_kallsyms_refresh(); + pthread_mutex_lock(&ksyms_mutex); + if (!ksyms) + ksyms = load_kallsyms_local(); + pthread_mutex_unlock(&ksyms_mutex); + return ksyms ? 0 : 1; } it could be in separate patch perhaps, because currently there's the same race > kprobe_multi__destroy(skel); > } > > diff --git a/tools/testing/selftests/bpf/prog_tests/fill_link_info.c b/tools/testing/selftests/bpf/prog_tests/fill_link_info.c > index 9d768e083714..154aaa08761f 100644 > --- a/tools/testing/selftests/bpf/prog_tests/fill_link_info.c > +++ b/tools/testing/selftests/bpf/prog_tests/fill_link_info.c > @@ -302,16 +302,18 @@ void test_fill_link_info(void) > { > struct test_fill_link_info *skel; > int i; > + struct ksyms *ksyms; > > skel = test_fill_link_info__open_and_load(); > if (!ASSERT_OK_PTR(skel, "skel_open")) > return; > > /* load kallsyms to compare the addr */ > - if (!ASSERT_OK(load_kallsyms_refresh(), "load_kallsyms_refresh")) > + ksyms = load_kallsyms_refresh_local(NULL); > + if (!ASSERT_OK(ksyms != NULL, "load_kallsyms_refresh_local")) ASSERT_OK_PTR SNIP > -int load_kallsyms_refresh(void) > +struct ksyms *load_kallsyms_refresh_local(struct ksyms *ksyms) > { > FILE *f; > char func[256], buf[256]; > char symbol; > void *addr; > - int i = 0; > + int ret; > > - sym_cnt = 0; > + /* flush kallsyms, free the previously allocated dynamic memory */ > + free_kallsyms_local(ksyms); > > f = fopen("/proc/kallsyms", "r"); > if (!f) > - return -ENOENT; > + return NULL; > + > + ksyms = calloc(1, sizeof(struct ksyms)); > + if (!ksyms) > + return NULL; > > while (fgets(buf, sizeof(buf), f)) { > if (sscanf(buf, "%p %c %s", &addr, &symbol, func) != 3) > break; > if (!addr) > continue; > - if (i >= MAX_SYMS) > - return -EFBIG; > > - syms[i].addr = (long) addr; > - syms[i].name = strdup(func); > - i++; > + ret = libbpf_ensure_mem((void **) &ksyms->syms, &ksyms->sym_cap, > + sizeof(struct ksym), ksyms->sym_cnt + 1); > + if (ret) > + goto error; > + ret = ksyms__add_symbol(ksyms, func, (unsigned long)addr); > + if (ret) > + goto error; > } > fclose(f); > - sym_cnt = i; > - qsort(syms, sym_cnt, sizeof(struct ksym), ksym_cmp); > - return 0; > + qsort(ksyms->syms, ksyms->sym_cnt, sizeof(struct ksym), ksym_cmp); > + return ksyms; > + > +error: > + free_kallsyms_local(ksyms); > + return NULL; > +} > + > +int load_kallsyms_refresh(void) > +{ > + ksyms = load_kallsyms_refresh_local(NULL); > + return ksyms ? 0 : 1; > +} > + > +struct ksyms *load_kallsyms_local(void) > +{ > + return load_kallsyms_refresh_local(NULL); > } do we need to have load_kallsyms_refresh_local? we could have ksyms arg passed directly to load_kallsyms_local struct ksyms *load_kallsyms_local(struct ksyms *old); it would return fresh ksyms and release old ksyms if it's passed as an argument basically I mean just to drop load_kallsyms_local above and rename load_kallsyms_refresh_local to load_kallsyms_local jirka