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@xxxxxxxxxx>
---
tools/lib/bpf/libbpf.c | 130 ++++++++++++++++++++++++++++++++++++++---
1 file changed, 122 insertions(+), 8 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index aa842f0721cb..ef5db34bf913 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -9021,6 +9021,7 @@ struct bpf_link_perf {
};
static int remove_kprobe_event_legacy(const char *probe_name, bool retprobe);
+static int remove_uprobe_event_legacy(const char *probe_name, bool retprobe);
static int bpf_link_perf_detach(struct bpf_link *link)
{
@@ -9034,11 +9035,14 @@ static int bpf_link_perf_detach(struct bpf_link *link)
close(perf_link->perf_event_fd);
close(link->fd);
- /* legacy kprobe needs to be removed after perf event fd closure */
+ /* legacy uprobe/kprobe needs to be removed after perf event fd closure */
if (perf_link->legacy_probe_name) {
if (perf_link->legacy_is_kprobe) {
err = remove_kprobe_event_legacy(perf_link->legacy_probe_name,
perf_link->legacy_is_retprobe);
+ } else {
+ err = remove_uprobe_event_legacy(perf_link->legacy_probe_name,
+ perf_link->legacy_is_retprobe);
}
}
@@ -9450,17 +9454,96 @@ static struct bpf_link *attach_kprobe(const struct bpf_program *prog)
return link;
}
+static void gen_uprobe_legacy_event_name(char *buf, size_t buf_sz,
+ const char *binary_path, uint64_t offset)
+{
+ int i;
+
+ snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx", getpid(), binary_path, (size_t)offset);
+
+ /* sanitize binary_path in the probe name */
+ for (i = 0; buf[i]; i++) {
+ if (!isalnum(buf[i]))
+ buf[i] = '_';
+ }
+}
+
+static inline int add_uprobe_event_legacy(const char *probe_name, bool retprobe,
+ const char *binary_path, size_t offset)
+{
+ const char *file = "/sys/kernel/debug/tracing/uprobe_events";
+
+ return append_to_file(file, "%c:%s/%s %s:0x%zx",
+ retprobe ? 'r' : 'p',
+ retprobe ? "uretprobes" : "uprobes",
+ probe_name, binary_path, offset);
+}
+
+static inline int remove_uprobe_event_legacy(const char *probe_name, bool retprobe)
+{
+ const char *file = "/sys/kernel/debug/tracing/uprobe_events";
+
+ return append_to_file(file, "-:%s/%s", retprobe ? "uretprobes" : "uprobes", probe_name);
+}
+
+static int determine_uprobe_perf_type_legacy(const char *probe_name, bool retprobe)
+{
+ char file[512];
+
+ snprintf(file, sizeof(file),
+ "/sys/kernel/debug/tracing/events/%s/%s/id",
+ retprobe ? "uretprobes" : "uprobes", probe_name);
+
+ return parse_uint_from_file(file, "%d\n");
+}
+
+static int perf_event_uprobe_open_legacy(const char *probe_name, bool retprobe,
+ const char *binary_path, size_t offset, int pid)
+{
+ struct perf_event_attr attr;
+ int type, pfd, err;
+
+ err = add_uprobe_event_legacy(probe_name, retprobe, binary_path, offset);
+ if (err < 0) {
+ pr_warn("failed to add legacy uprobe event for %s:0x%zx: %d\n",
+ binary_path, (size_t)offset, err);
+ return err;
+ }
+ type = determine_uprobe_perf_type_legacy(probe_name, retprobe);
+ if (type < 0) {
+ pr_warn("failed to determine legacy uprobe event id for %s:0x%zx: %d\n",
+ binary_path, offset, err);
+ return type;
+ }
+
+ memset(&attr, 0, sizeof(attr));
+ attr.size = sizeof(attr);
+ attr.config = type;
+ attr.type = PERF_TYPE_TRACEPOINT;
+
+ pfd = syscall(__NR_perf_event_open, &attr,
+ pid < 0 ? -1 : pid, /* pid */
+ pid == -1 ? 0 : -1, /* cpu */
+ -1 /* group_fd */, PERF_FLAG_FD_CLOEXEC);
+ if (pfd < 0) {
+ err = -errno;
+ pr_warn("legacy uprobe perf_event_open() failed: %d\n", err);
+ return err;
+ }
+ return pfd;
+}
+
LIBBPF_API struct bpf_link *
bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
const char *binary_path, size_t func_offset,
const struct bpf_uprobe_opts *opts)
{
DECLARE_LIBBPF_OPTS(bpf_perf_event_opts, pe_opts);
- char errmsg[STRERR_BUFSIZE];
+ char errmsg[STRERR_BUFSIZE], *legacy_probe = NULL;
struct bpf_link *link;
size_t ref_ctr_off;
int pfd, err;
- bool retprobe;
+ bool retprobe, legacy;
if (!OPTS_VALID(opts, bpf_uprobe_opts))
return libbpf_err_ptr(-EINVAL);
@@ -9469,15 +9552,35 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
ref_ctr_off = OPTS_GET(opts, ref_ctr_offset, 0);
pe_opts.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0);
- pfd = perf_event_open_probe(true /* uprobe */, retprobe, binary_path,
- func_offset, pid, ref_ctr_off);
+ legacy = determine_uprobe_perf_type() < 0;
+ if (!legacy) {
+ pfd = perf_event_open_probe(true /* uprobe */, retprobe, binary_path,
+ func_offset, pid, ref_ctr_off);
+ } else {
+ char probe_name[512];
+
+ if (ref_ctr_off)
+ return libbpf_err_ptr(-EINVAL);
+
+ gen_uprobe_legacy_event_name(probe_name, sizeof(probe_name),
+ binary_path, func_offset);
+
+ legacy_probe = strdup(probe_name);
+ if (!legacy_probe)
+ return libbpf_err_ptr(-ENOMEM);
+
+ pfd = perf_event_uprobe_open_legacy(legacy_probe, retprobe,
+ binary_path, func_offset, pid);
+ }
if (pfd < 0) {
+ err = -errno;
pr_warn("prog '%s': failed to create %s '%s:0x%zx' perf event: %s\n",
prog->name, retprobe ? "uretprobe" : "uprobe",
binary_path, func_offset,
- libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));
- return libbpf_err_ptr(pfd);
+ libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
+ goto err_out;
}
+
link = bpf_program__attach_perf_event_opts(prog, pfd, &pe_opts);
err = libbpf_get_error(link);
if (err) {
@@ -9486,9 +9589,20 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
prog->name, retprobe ? "uretprobe" : "uprobe",
binary_path, func_offset,
libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
- return libbpf_err_ptr(err);
+ goto err_out;
+ }
+ if (legacy) {
+ struct bpf_link_perf *perf_link = container_of(link, struct bpf_link_perf, link);
+
+ perf_link->legacy_probe_name = legacy_probe;
+ perf_link->legacy_is_kprobe = false;
+ perf_link->legacy_is_retprobe = retprobe;
}
return link;
+err_out:
+ free(legacy_probe);
+ return libbpf_err_ptr(err);
+
}
struct bpf_link *bpf_program__attach_uprobe(const struct bpf_program *prog,
--
2.30.2
