Commit cc10623c authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov

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: default avatarAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210921210036.1545557-5-andrii@kernel.org
parent 46ed5fc3
...@@ -9021,6 +9021,7 @@ struct bpf_link_perf { ...@@ -9021,6 +9021,7 @@ struct bpf_link_perf {
}; };
static int remove_kprobe_event_legacy(const char *probe_name, bool retprobe); 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) static int bpf_link_perf_detach(struct bpf_link *link)
{ {
...@@ -9034,11 +9035,14 @@ 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(perf_link->perf_event_fd);
close(link->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_probe_name) {
if (perf_link->legacy_is_kprobe) { if (perf_link->legacy_is_kprobe) {
err = remove_kprobe_event_legacy(perf_link->legacy_probe_name, err = remove_kprobe_event_legacy(perf_link->legacy_probe_name,
perf_link->legacy_is_retprobe); 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) ...@@ -9450,17 +9454,96 @@ static struct bpf_link *attach_kprobe(const struct bpf_program *prog)
return link; 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 * LIBBPF_API struct bpf_link *
bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid, bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
const char *binary_path, size_t func_offset, const char *binary_path, size_t func_offset,
const struct bpf_uprobe_opts *opts) const struct bpf_uprobe_opts *opts)
{ {
DECLARE_LIBBPF_OPTS(bpf_perf_event_opts, pe_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; struct bpf_link *link;
size_t ref_ctr_off; size_t ref_ctr_off;
int pfd, err; int pfd, err;
bool retprobe; bool retprobe, legacy;
if (!OPTS_VALID(opts, bpf_uprobe_opts)) if (!OPTS_VALID(opts, bpf_uprobe_opts))
return libbpf_err_ptr(-EINVAL); return libbpf_err_ptr(-EINVAL);
...@@ -9469,15 +9552,35 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid, ...@@ -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); ref_ctr_off = OPTS_GET(opts, ref_ctr_offset, 0);
pe_opts.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0); pe_opts.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0);
pfd = perf_event_open_probe(true /* uprobe */, retprobe, binary_path, legacy = determine_uprobe_perf_type() < 0;
func_offset, pid, ref_ctr_off); 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) { if (pfd < 0) {
err = -errno;
pr_warn("prog '%s': failed to create %s '%s:0x%zx' perf event: %s\n", pr_warn("prog '%s': failed to create %s '%s:0x%zx' perf event: %s\n",
prog->name, retprobe ? "uretprobe" : "uprobe", prog->name, retprobe ? "uretprobe" : "uprobe",
binary_path, func_offset, binary_path, func_offset,
libbpf_strerror_r(pfd, errmsg, sizeof(errmsg))); libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
return libbpf_err_ptr(pfd); goto err_out;
} }
link = bpf_program__attach_perf_event_opts(prog, pfd, &pe_opts); link = bpf_program__attach_perf_event_opts(prog, pfd, &pe_opts);
err = libbpf_get_error(link); err = libbpf_get_error(link);
if (err) { if (err) {
...@@ -9486,9 +9589,20 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid, ...@@ -9486,9 +9589,20 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
prog->name, retprobe ? "uretprobe" : "uprobe", prog->name, retprobe ? "uretprobe" : "uprobe",
binary_path, func_offset, binary_path, func_offset,
libbpf_strerror_r(err, errmsg, sizeof(errmsg))); 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; return link;
err_out:
free(legacy_probe);
return libbpf_err_ptr(err);
} }
struct bpf_link *bpf_program__attach_uprobe(const struct bpf_program *prog, struct bpf_link *bpf_program__attach_uprobe(const struct bpf_program *prog,
......
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