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Fri, 11 Mar 2022 12:11:09 +0000 From: Alan Maguire To: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org Cc: kafai@fb.com, songliubraving@fb.com, yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org, toke@redhat.com, sunyucong@gmail.com, netdev@vger.kernel.org, bpf@vger.kernel.org, Alan Maguire Subject: [PATCH v4 bpf-next 3/5] libbpf: add auto-attach for uprobes based on section name Date: Fri, 11 Mar 2022 12:10:56 +0000 Message-Id: <1647000658-16149-4-git-send-email-alan.maguire@oracle.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1647000658-16149-1-git-send-email-alan.maguire@oracle.com> References: <1647000658-16149-1-git-send-email-alan.maguire@oracle.com> Content-Type: text/plain X-ClientProxiedBy: LO4P123CA0335.GBRP123.PROD.OUTLOOK.COM (2603:10a6:600:18c::16) To BLAPR10MB5267.namprd10.prod.outlook.com (2603:10b6:208:30e::22) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 0274200e-88c4-4b73-bc6d-08da03583a3a X-MS-TrafficTypeDiagnostic: SJ0PR10MB4784:EE_ X-Microsoft-Antispam-PRVS: X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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The format proposed is SEC("u[ret]probe/prog:[raw_offset|[function_name[+offset]]") For example, to trace malloc() in libc: SEC("uprobe/libc.so.6:malloc") ...or to trace function foo2 in /usr/bin/foo: SEC("uprobe//usr/bin/foo:foo2") Auto-attach is done for all tasks (pid -1). prog can be an absolute path or simply a program/library name; in the latter case, we use PATH/LD_LIBRARY_PATH to resolve the full path, falling back to standard locations (/usr/bin:/usr/sbin or /usr/lib64:/usr/lib) if the file is not found via environment-variable specified locations. Signed-off-by: Alan Maguire --- tools/lib/bpf/libbpf.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 66 insertions(+), 2 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 2b50b01..0dcbca8 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -8593,6 +8593,7 @@ int bpf_program__set_log_buf(struct bpf_program *prog, char *log_buf, size_t log } static int attach_kprobe(const struct bpf_program *prog, long cookie, struct bpf_link **link); +static int attach_uprobe(const struct bpf_program *prog, long cookie, struct bpf_link **link); static int attach_tp(const struct bpf_program *prog, long cookie, struct bpf_link **link); static int attach_raw_tp(const struct bpf_program *prog, long cookie, struct bpf_link **link); static int attach_trace(const struct bpf_program *prog, long cookie, struct bpf_link **link); @@ -8604,9 +8605,9 @@ int bpf_program__set_log_buf(struct bpf_program *prog, char *log_buf, size_t log SEC_DEF("sk_reuseport/migrate", SK_REUSEPORT, BPF_SK_REUSEPORT_SELECT_OR_MIGRATE, SEC_ATTACHABLE | SEC_SLOPPY_PFX), SEC_DEF("sk_reuseport", SK_REUSEPORT, BPF_SK_REUSEPORT_SELECT, SEC_ATTACHABLE | SEC_SLOPPY_PFX), SEC_DEF("kprobe/", KPROBE, 0, SEC_NONE, attach_kprobe), - SEC_DEF("uprobe/", KPROBE, 0, SEC_NONE), + SEC_DEF("uprobe/", KPROBE, 0, SEC_NONE, attach_uprobe), SEC_DEF("kretprobe/", KPROBE, 0, SEC_NONE, attach_kprobe), - SEC_DEF("uretprobe/", KPROBE, 0, SEC_NONE), + SEC_DEF("uretprobe/", KPROBE, 0, SEC_NONE, attach_uprobe), SEC_DEF("tc", SCHED_CLS, 0, SEC_NONE), SEC_DEF("classifier", SCHED_CLS, 0, SEC_NONE | SEC_SLOPPY_PFX | SEC_DEPRECATED), SEC_DEF("action", SCHED_ACT, 0, SEC_NONE | SEC_SLOPPY_PFX), @@ -10761,6 +10762,69 @@ struct bpf_link *bpf_program__attach_uprobe(const struct bpf_program *prog, return bpf_program__attach_uprobe_opts(prog, pid, binary_path, func_offset, &opts); } +/* Format of u[ret]probe section definition supporting auto-attach: + * u[ret]probe/prog:function[+offset] + * + * prog can be an absolute/relative path or a filename; the latter is resolved to a + * full path via bpf_program__attach_uprobe_opts. + * + * Many uprobe programs do not avail of auto-attach, so we need to handle the + * case where the format is uprobe/myfunc by returning 0 with *link set to NULL + * to identify the case where auto-attach is not supported. + */ +static int attach_uprobe(const struct bpf_program *prog, long cookie, struct bpf_link **link) +{ + DECLARE_LIBBPF_OPTS(bpf_uprobe_opts, opts); + char *func, *probe_name, *func_end; + char *func_name, binary_path[512]; + unsigned long long raw_offset; + size_t offset = 0; + int n; + + *link = NULL; + + opts.retprobe = str_has_pfx(prog->sec_name, "uretprobe/"); + if (opts.retprobe) + probe_name = prog->sec_name + sizeof("uretprobe/") - 1; + else + probe_name = prog->sec_name + sizeof("uprobe/") - 1; + + snprintf(binary_path, sizeof(binary_path), "%s", probe_name); + /* ':' should be prior to function+offset */ + func_name = strrchr(binary_path, ':'); + if (!func_name) { + pr_debug("section '%s' is old-style u[ret]probe/function, cannot auto-attach\n", + prog->sec_name); + return 0; + } + func_name[0] = '\0'; + func_name++; + n = sscanf(func_name, "%m[a-zA-Z0-9_.]+%li", &func, &offset); + if (n < 1) { + pr_warn("uprobe name '%s' is invalid\n", func_name); + return -EINVAL; + } + if (opts.retprobe && offset != 0) { + free(func); + pr_warn("uretprobes do not support offset specification\n"); + return -EINVAL; + } + + /* Is func a raw address? */ + errno = 0; + raw_offset = strtoull(func, &func_end, 0); + if (!errno && !*func_end) { + free(func); + func = NULL; + offset = (size_t)raw_offset; + } + opts.func_name = func; + + *link = bpf_program__attach_uprobe_opts(prog, -1, binary_path, offset, &opts); + free(func); + return 0; +} + static int determine_tracepoint_id(const char *tp_category, const char *tp_name) { -- 1.8.3.1