From ad8848535e97f4a5374fc68f7a5d16e2565940cc Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Wed, 15 Jun 2022 13:21:15 +0200 Subject: [PATCH 1/4] selftests/bpf: Shuffle cookies symbols in kprobe multi test There's a kernel bug that causes cookies to be misplaced and the reason we did not catch this with this test is that we provide bpf_fentry_test* functions already sorted by name. Shuffling function bpf_fentry_test2 deeper in the list and keeping the current cookie values as before will trigger the bug. The kernel fix is coming in following changes. Acked-by: Song Liu Signed-off-by: Jiri Olsa Link: https://lore.kernel.org/r/20220615112118.497303-2-jolsa@kernel.org Signed-off-by: Alexei Starovoitov --- .../selftests/bpf/prog_tests/bpf_cookie.c | 78 +++++++++---------- .../selftests/bpf/progs/kprobe_multi.c | 24 +++--- 2 files changed, 51 insertions(+), 51 deletions(-) diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c b/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c index 83ef55e3caa4..2974b44f80fa 100644 --- a/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c +++ b/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c @@ -121,24 +121,24 @@ static void kprobe_multi_link_api_subtest(void) }) GET_ADDR("bpf_fentry_test1", addrs[0]); - GET_ADDR("bpf_fentry_test2", addrs[1]); - GET_ADDR("bpf_fentry_test3", addrs[2]); - GET_ADDR("bpf_fentry_test4", addrs[3]); - GET_ADDR("bpf_fentry_test5", addrs[4]); - GET_ADDR("bpf_fentry_test6", addrs[5]); - GET_ADDR("bpf_fentry_test7", addrs[6]); + GET_ADDR("bpf_fentry_test3", addrs[1]); + GET_ADDR("bpf_fentry_test4", addrs[2]); + GET_ADDR("bpf_fentry_test5", addrs[3]); + GET_ADDR("bpf_fentry_test6", addrs[4]); + GET_ADDR("bpf_fentry_test7", addrs[5]); + GET_ADDR("bpf_fentry_test2", addrs[6]); GET_ADDR("bpf_fentry_test8", addrs[7]); #undef GET_ADDR - cookies[0] = 1; - cookies[1] = 2; - cookies[2] = 3; - cookies[3] = 4; - cookies[4] = 5; - cookies[5] = 6; - cookies[6] = 7; - cookies[7] = 8; + cookies[0] = 1; /* bpf_fentry_test1 */ + cookies[1] = 2; /* bpf_fentry_test3 */ + cookies[2] = 3; /* bpf_fentry_test4 */ + cookies[3] = 4; /* bpf_fentry_test5 */ + cookies[4] = 5; /* bpf_fentry_test6 */ + cookies[5] = 6; /* bpf_fentry_test7 */ + cookies[6] = 7; /* bpf_fentry_test2 */ + cookies[7] = 8; /* bpf_fentry_test8 */ opts.kprobe_multi.addrs = (const unsigned long *) &addrs; opts.kprobe_multi.cnt = ARRAY_SIZE(addrs); @@ -149,14 +149,14 @@ static void kprobe_multi_link_api_subtest(void) if (!ASSERT_GE(link1_fd, 0, "link1_fd")) goto cleanup; - cookies[0] = 8; - cookies[1] = 7; - cookies[2] = 6; - cookies[3] = 5; - cookies[4] = 4; - cookies[5] = 3; - cookies[6] = 2; - cookies[7] = 1; + cookies[0] = 8; /* bpf_fentry_test1 */ + cookies[1] = 7; /* bpf_fentry_test3 */ + cookies[2] = 6; /* bpf_fentry_test4 */ + cookies[3] = 5; /* bpf_fentry_test5 */ + cookies[4] = 4; /* bpf_fentry_test6 */ + cookies[5] = 3; /* bpf_fentry_test7 */ + cookies[6] = 2; /* bpf_fentry_test2 */ + cookies[7] = 1; /* bpf_fentry_test8 */ opts.kprobe_multi.flags = BPF_F_KPROBE_MULTI_RETURN; prog_fd = bpf_program__fd(skel->progs.test_kretprobe); @@ -181,12 +181,12 @@ static void kprobe_multi_attach_api_subtest(void) struct kprobe_multi *skel = NULL; const char *syms[8] = { "bpf_fentry_test1", - "bpf_fentry_test2", "bpf_fentry_test3", "bpf_fentry_test4", "bpf_fentry_test5", "bpf_fentry_test6", "bpf_fentry_test7", + "bpf_fentry_test2", "bpf_fentry_test8", }; __u64 cookies[8]; @@ -198,14 +198,14 @@ static void kprobe_multi_attach_api_subtest(void) skel->bss->pid = getpid(); skel->bss->test_cookie = true; - cookies[0] = 1; - cookies[1] = 2; - cookies[2] = 3; - cookies[3] = 4; - cookies[4] = 5; - cookies[5] = 6; - cookies[6] = 7; - cookies[7] = 8; + cookies[0] = 1; /* bpf_fentry_test1 */ + cookies[1] = 2; /* bpf_fentry_test3 */ + cookies[2] = 3; /* bpf_fentry_test4 */ + cookies[3] = 4; /* bpf_fentry_test5 */ + cookies[4] = 5; /* bpf_fentry_test6 */ + cookies[5] = 6; /* bpf_fentry_test7 */ + cookies[6] = 7; /* bpf_fentry_test2 */ + cookies[7] = 8; /* bpf_fentry_test8 */ opts.syms = syms; opts.cnt = ARRAY_SIZE(syms); @@ -216,14 +216,14 @@ static void kprobe_multi_attach_api_subtest(void) if (!ASSERT_OK_PTR(link1, "bpf_program__attach_kprobe_multi_opts")) goto cleanup; - cookies[0] = 8; - cookies[1] = 7; - cookies[2] = 6; - cookies[3] = 5; - cookies[4] = 4; - cookies[5] = 3; - cookies[6] = 2; - cookies[7] = 1; + cookies[0] = 8; /* bpf_fentry_test1 */ + cookies[1] = 7; /* bpf_fentry_test3 */ + cookies[2] = 6; /* bpf_fentry_test4 */ + cookies[3] = 5; /* bpf_fentry_test5 */ + cookies[4] = 4; /* bpf_fentry_test6 */ + cookies[5] = 3; /* bpf_fentry_test7 */ + cookies[6] = 2; /* bpf_fentry_test2 */ + cookies[7] = 1; /* bpf_fentry_test8 */ opts.retprobe = true; diff --git a/tools/testing/selftests/bpf/progs/kprobe_multi.c b/tools/testing/selftests/bpf/progs/kprobe_multi.c index 93510f4f0f3a..08f95a8155d1 100644 --- a/tools/testing/selftests/bpf/progs/kprobe_multi.c +++ b/tools/testing/selftests/bpf/progs/kprobe_multi.c @@ -54,21 +54,21 @@ static void kprobe_multi_check(void *ctx, bool is_return) if (is_return) { SET(kretprobe_test1_result, &bpf_fentry_test1, 8); - SET(kretprobe_test2_result, &bpf_fentry_test2, 7); - SET(kretprobe_test3_result, &bpf_fentry_test3, 6); - SET(kretprobe_test4_result, &bpf_fentry_test4, 5); - SET(kretprobe_test5_result, &bpf_fentry_test5, 4); - SET(kretprobe_test6_result, &bpf_fentry_test6, 3); - SET(kretprobe_test7_result, &bpf_fentry_test7, 2); + SET(kretprobe_test2_result, &bpf_fentry_test2, 2); + SET(kretprobe_test3_result, &bpf_fentry_test3, 7); + SET(kretprobe_test4_result, &bpf_fentry_test4, 6); + SET(kretprobe_test5_result, &bpf_fentry_test5, 5); + SET(kretprobe_test6_result, &bpf_fentry_test6, 4); + SET(kretprobe_test7_result, &bpf_fentry_test7, 3); SET(kretprobe_test8_result, &bpf_fentry_test8, 1); } else { SET(kprobe_test1_result, &bpf_fentry_test1, 1); - SET(kprobe_test2_result, &bpf_fentry_test2, 2); - SET(kprobe_test3_result, &bpf_fentry_test3, 3); - SET(kprobe_test4_result, &bpf_fentry_test4, 4); - SET(kprobe_test5_result, &bpf_fentry_test5, 5); - SET(kprobe_test6_result, &bpf_fentry_test6, 6); - SET(kprobe_test7_result, &bpf_fentry_test7, 7); + SET(kprobe_test2_result, &bpf_fentry_test2, 7); + SET(kprobe_test3_result, &bpf_fentry_test3, 2); + SET(kprobe_test4_result, &bpf_fentry_test4, 3); + SET(kprobe_test5_result, &bpf_fentry_test5, 4); + SET(kprobe_test6_result, &bpf_fentry_test6, 5); + SET(kprobe_test7_result, &bpf_fentry_test7, 6); SET(kprobe_test8_result, &bpf_fentry_test8, 8); } From eb1b2985fe5c5f02e43e4c0d47bbe7ed835007f3 Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Wed, 15 Jun 2022 13:21:16 +0200 Subject: [PATCH 2/4] ftrace: Keep address offset in ftrace_lookup_symbols We want to store the resolved address on the same index as the symbol string, because that's the user (bpf kprobe link) code assumption. Also making sure we don't store duplicates that might be present in kallsyms. Acked-by: Song Liu Acked-by: Steven Rostedt (Google) Fixes: bed0d9a50dac ("ftrace: Add ftrace_lookup_symbols function") Signed-off-by: Jiri Olsa Link: https://lore.kernel.org/r/20220615112118.497303-3-jolsa@kernel.org Signed-off-by: Alexei Starovoitov --- kernel/trace/ftrace.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index e750fe141a60..601ccf1b2f09 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -8029,15 +8029,23 @@ static int kallsyms_callback(void *data, const char *name, struct module *mod, unsigned long addr) { struct kallsyms_data *args = data; + const char **sym; + int idx; - if (!bsearch(&name, args->syms, args->cnt, sizeof(*args->syms), symbols_cmp)) + sym = bsearch(&name, args->syms, args->cnt, sizeof(*args->syms), symbols_cmp); + if (!sym) + return 0; + + idx = sym - args->syms; + if (args->addrs[idx]) return 0; addr = ftrace_location(addr); if (!addr) return 0; - args->addrs[args->found++] = addr; + args->addrs[idx] = addr; + args->found++; return args->found == args->cnt ? 1 : 0; } @@ -8062,6 +8070,7 @@ int ftrace_lookup_symbols(const char **sorted_syms, size_t cnt, unsigned long *a struct kallsyms_data args; int err; + memset(addrs, 0, sizeof(*addrs) * cnt); args.addrs = addrs; args.syms = sorted_syms; args.cnt = cnt; From eb5fb0325698d05f0bf78d322de82c451a3685a2 Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Wed, 15 Jun 2022 13:21:17 +0200 Subject: [PATCH 3/4] bpf: Force cookies array to follow symbols sorting When user specifies symbols and cookies for kprobe_multi link interface it's very likely the cookies will be misplaced and returned to wrong functions (via get_attach_cookie helper). The reason is that to resolve the provided functions we sort them before passing them to ftrace_lookup_symbols, but we do not do the same sort on the cookie values. Fixing this by using sort_r function with custom swap callback that swaps cookie values as well. Fixes: 0236fec57a15 ("bpf: Resolve symbols with ftrace_lookup_symbols for kprobe multi link") Signed-off-by: Jiri Olsa Link: https://lore.kernel.org/r/20220615112118.497303-4-jolsa@kernel.org Signed-off-by: Alexei Starovoitov --- kernel/trace/bpf_trace.c | 70 ++++++++++++++++++++++++++++------------ 1 file changed, 50 insertions(+), 20 deletions(-) diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 7a13e6ac6327..88589d74a892 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -2423,7 +2423,7 @@ kprobe_multi_link_handler(struct fprobe *fp, unsigned long entry_ip, kprobe_multi_link_prog_run(link, entry_ip, regs); } -static int symbols_cmp(const void *a, const void *b) +static int symbols_cmp_r(const void *a, const void *b, const void *priv) { const char **str_a = (const char **) a; const char **str_b = (const char **) b; @@ -2431,6 +2431,28 @@ static int symbols_cmp(const void *a, const void *b) return strcmp(*str_a, *str_b); } +struct multi_symbols_sort { + const char **funcs; + u64 *cookies; +}; + +static void symbols_swap_r(void *a, void *b, int size, const void *priv) +{ + const struct multi_symbols_sort *data = priv; + const char **name_a = a, **name_b = b; + + swap(*name_a, *name_b); + + /* If defined, swap also related cookies. */ + if (data->cookies) { + u64 *cookie_a, *cookie_b; + + cookie_a = data->cookies + (name_a - data->funcs); + cookie_b = data->cookies + (name_b - data->funcs); + swap(*cookie_a, *cookie_b); + } +} + int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) { struct bpf_kprobe_multi_link *link = NULL; @@ -2468,25 +2490,6 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr if (!addrs) return -ENOMEM; - if (uaddrs) { - if (copy_from_user(addrs, uaddrs, size)) { - err = -EFAULT; - goto error; - } - } else { - struct user_syms us; - - err = copy_user_syms(&us, usyms, cnt); - if (err) - goto error; - - sort(us.syms, cnt, sizeof(*us.syms), symbols_cmp, NULL); - err = ftrace_lookup_symbols(us.syms, cnt, addrs); - free_user_syms(&us); - if (err) - goto error; - } - ucookies = u64_to_user_ptr(attr->link_create.kprobe_multi.cookies); if (ucookies) { cookies = kvmalloc_array(cnt, sizeof(*addrs), GFP_KERNEL); @@ -2500,6 +2503,33 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr } } + if (uaddrs) { + if (copy_from_user(addrs, uaddrs, size)) { + err = -EFAULT; + goto error; + } + } else { + struct multi_symbols_sort data = { + .cookies = cookies, + }; + struct user_syms us; + + err = copy_user_syms(&us, usyms, cnt); + if (err) + goto error; + + if (cookies) + data.funcs = us.syms; + + sort_r(us.syms, cnt, sizeof(*us.syms), symbols_cmp_r, + symbols_swap_r, &data); + + err = ftrace_lookup_symbols(us.syms, cnt, addrs); + free_user_syms(&us); + if (err) + goto error; + } + link = kzalloc(sizeof(*link), GFP_KERNEL); if (!link) { err = -ENOMEM; From 730067022c0137691b27726377c2d088f7f8e33c Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Wed, 15 Jun 2022 13:21:18 +0200 Subject: [PATCH 4/4] selftest/bpf: Fix kprobe_multi bench test With [1] the available_filter_functions file contains records starting with __ftrace_invalid_address___ and marking disabled entries. We need to filter them out for the bench test to pass only resolvable symbols to kernel. [1] commit b39181f7c690 ("ftrace: Add FTRACE_MCOUNT_MAX_OFFSET to avoid adding weak function") Fixes: b39181f7c690 ("ftrace: Add FTRACE_MCOUNT_MAX_OFFSET to avoid adding weak function") Signed-off-by: Jiri Olsa Link: https://lore.kernel.org/r/20220615112118.497303-5-jolsa@kernel.org Signed-off-by: Alexei Starovoitov --- tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c index 586dc52d6fb9..5b93d5d0bd93 100644 --- a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c +++ b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c @@ -364,6 +364,9 @@ static int get_syms(char ***symsp, size_t *cntp) continue; if (!strncmp(name, "rcu_", 4)) continue; + if (!strncmp(name, "__ftrace_invalid_address__", + sizeof("__ftrace_invalid_address__") - 1)) + continue; err = hashmap__add(map, name, NULL); if (err) { free(name);