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libbpf: Add legacy uprobe attaching support
Similarly to recently added legacy kprobe attach interface support through tracefs, support attaching uprobes using the legacy interface if host kernel doesn't support newer FD-based interface. For uprobes event name consists of "libbpf_" prefix, PID, sanitized binary path and offset within that binary. Structuraly the code is aligned with kprobe logic refactoring in previous patch. struct bpf_link_perf is re-used and all the same legacy_probe_name and legacy_is_retprobe fields are used to ensure proper cleanup on bpf_link__destroy(). Users should be aware, though, that on old kernels which don't support FD-based interface for kprobe/uprobe attachment, if the application crashes before bpf_link__destroy() is called, uprobe legacy events will be left in tracefs. This is the same limitation as with legacy kprobe interfaces. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20210921210036.1545557-5-andrii@kernel.org
This commit is contained in:
parent
46ed5fc33d
commit
cc10623c68
1 changed files with 122 additions and 8 deletions
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@ -9021,6 +9021,7 @@ struct bpf_link_perf {
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};
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static int remove_kprobe_event_legacy(const char *probe_name, bool retprobe);
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static int remove_uprobe_event_legacy(const char *probe_name, bool retprobe);
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static int bpf_link_perf_detach(struct bpf_link *link)
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{
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@ -9034,11 +9035,14 @@ static int bpf_link_perf_detach(struct bpf_link *link)
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close(perf_link->perf_event_fd);
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close(link->fd);
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/* legacy kprobe needs to be removed after perf event fd closure */
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/* legacy uprobe/kprobe needs to be removed after perf event fd closure */
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if (perf_link->legacy_probe_name) {
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if (perf_link->legacy_is_kprobe) {
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err = remove_kprobe_event_legacy(perf_link->legacy_probe_name,
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perf_link->legacy_is_retprobe);
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} else {
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err = remove_uprobe_event_legacy(perf_link->legacy_probe_name,
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perf_link->legacy_is_retprobe);
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}
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}
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@ -9450,17 +9454,96 @@ static struct bpf_link *attach_kprobe(const struct bpf_program *prog)
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return link;
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}
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static void gen_uprobe_legacy_event_name(char *buf, size_t buf_sz,
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const char *binary_path, uint64_t offset)
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{
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int i;
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snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx", getpid(), binary_path, (size_t)offset);
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/* sanitize binary_path in the probe name */
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for (i = 0; buf[i]; i++) {
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if (!isalnum(buf[i]))
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buf[i] = '_';
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}
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}
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static inline int add_uprobe_event_legacy(const char *probe_name, bool retprobe,
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const char *binary_path, size_t offset)
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{
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const char *file = "/sys/kernel/debug/tracing/uprobe_events";
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return append_to_file(file, "%c:%s/%s %s:0x%zx",
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retprobe ? 'r' : 'p',
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retprobe ? "uretprobes" : "uprobes",
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probe_name, binary_path, offset);
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}
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static inline int remove_uprobe_event_legacy(const char *probe_name, bool retprobe)
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{
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const char *file = "/sys/kernel/debug/tracing/uprobe_events";
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return append_to_file(file, "-:%s/%s", retprobe ? "uretprobes" : "uprobes", probe_name);
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}
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static int determine_uprobe_perf_type_legacy(const char *probe_name, bool retprobe)
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{
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char file[512];
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snprintf(file, sizeof(file),
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"/sys/kernel/debug/tracing/events/%s/%s/id",
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retprobe ? "uretprobes" : "uprobes", probe_name);
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return parse_uint_from_file(file, "%d\n");
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}
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static int perf_event_uprobe_open_legacy(const char *probe_name, bool retprobe,
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const char *binary_path, size_t offset, int pid)
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{
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struct perf_event_attr attr;
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int type, pfd, err;
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err = add_uprobe_event_legacy(probe_name, retprobe, binary_path, offset);
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if (err < 0) {
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pr_warn("failed to add legacy uprobe event for %s:0x%zx: %d\n",
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binary_path, (size_t)offset, err);
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return err;
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}
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type = determine_uprobe_perf_type_legacy(probe_name, retprobe);
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if (type < 0) {
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pr_warn("failed to determine legacy uprobe event id for %s:0x%zx: %d\n",
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binary_path, offset, err);
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return type;
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}
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memset(&attr, 0, sizeof(attr));
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attr.size = sizeof(attr);
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attr.config = type;
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attr.type = PERF_TYPE_TRACEPOINT;
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pfd = syscall(__NR_perf_event_open, &attr,
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pid < 0 ? -1 : pid, /* pid */
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pid == -1 ? 0 : -1, /* cpu */
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-1 /* group_fd */, PERF_FLAG_FD_CLOEXEC);
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if (pfd < 0) {
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err = -errno;
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pr_warn("legacy uprobe perf_event_open() failed: %d\n", err);
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return err;
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}
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return pfd;
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}
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LIBBPF_API struct bpf_link *
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bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
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const char *binary_path, size_t func_offset,
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const struct bpf_uprobe_opts *opts)
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{
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DECLARE_LIBBPF_OPTS(bpf_perf_event_opts, pe_opts);
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char errmsg[STRERR_BUFSIZE];
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char errmsg[STRERR_BUFSIZE], *legacy_probe = NULL;
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struct bpf_link *link;
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size_t ref_ctr_off;
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int pfd, err;
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bool retprobe;
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bool retprobe, legacy;
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if (!OPTS_VALID(opts, bpf_uprobe_opts))
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return libbpf_err_ptr(-EINVAL);
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@ -9469,15 +9552,35 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
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ref_ctr_off = OPTS_GET(opts, ref_ctr_offset, 0);
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pe_opts.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0);
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pfd = perf_event_open_probe(true /* uprobe */, retprobe, binary_path,
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func_offset, pid, ref_ctr_off);
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legacy = determine_uprobe_perf_type() < 0;
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if (!legacy) {
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pfd = perf_event_open_probe(true /* uprobe */, retprobe, binary_path,
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func_offset, pid, ref_ctr_off);
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} else {
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char probe_name[512];
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if (ref_ctr_off)
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return libbpf_err_ptr(-EINVAL);
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gen_uprobe_legacy_event_name(probe_name, sizeof(probe_name),
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binary_path, func_offset);
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legacy_probe = strdup(probe_name);
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if (!legacy_probe)
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return libbpf_err_ptr(-ENOMEM);
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pfd = perf_event_uprobe_open_legacy(legacy_probe, retprobe,
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binary_path, func_offset, pid);
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}
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if (pfd < 0) {
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err = -errno;
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pr_warn("prog '%s': failed to create %s '%s:0x%zx' perf event: %s\n",
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prog->name, retprobe ? "uretprobe" : "uprobe",
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binary_path, func_offset,
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libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));
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return libbpf_err_ptr(pfd);
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libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
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goto err_out;
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}
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link = bpf_program__attach_perf_event_opts(prog, pfd, &pe_opts);
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err = libbpf_get_error(link);
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if (err) {
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@ -9486,9 +9589,20 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
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prog->name, retprobe ? "uretprobe" : "uprobe",
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binary_path, func_offset,
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libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
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return libbpf_err_ptr(err);
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goto err_out;
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}
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if (legacy) {
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struct bpf_link_perf *perf_link = container_of(link, struct bpf_link_perf, link);
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perf_link->legacy_probe_name = legacy_probe;
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perf_link->legacy_is_kprobe = false;
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perf_link->legacy_is_retprobe = retprobe;
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}
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return link;
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err_out:
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free(legacy_probe);
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return libbpf_err_ptr(err);
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}
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struct bpf_link *bpf_program__attach_uprobe(const struct bpf_program *prog,
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