Now that u[ret]probes can use name-based specification, it makes
sense to add support for auto-attach based on SEC() definition.
The format proposed is
SEC("u[ret]probe[/]/path/to/prog/function[+offset]")
For example, to trace malloc() in libc:
SEC("uprobe/usr/lib64/libc.so.6/malloc")
Auto-attach is done for all tasks (pid -1).
Future work will look at generalizing section specification to
substitute ':' for '/'.
Signed-off-by: Alan Maguire <alan.maguire@xxxxxxxxxx>
---
tools/lib/bpf/libbpf.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 58 insertions(+), 2 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 6479aae..1c8c8f0 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -8565,6 +8565,7 @@ int bpf_program__set_log_buf(struct bpf_program *prog, char *log_buf, size_t log
}
static struct bpf_link *attach_kprobe(const struct bpf_program *prog, long cookie);
+static struct bpf_link *attach_uprobe(const struct bpf_program *prog, long cookie);
static struct bpf_link *attach_tp(const struct bpf_program *prog, long cookie);
static struct bpf_link *attach_raw_tp(const struct bpf_program *prog, long cookie);
static struct bpf_link *attach_trace(const struct bpf_program *prog, long cookie);
@@ -8576,9 +8577,9 @@ 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_DEF("action", SCHED_ACT, 0, SEC_NONE | SEC_SLOPPY_PFX),
@@ -10454,6 +10455,61 @@ static ssize_t find_elf_func_offset(const char *binary_path, const char *name)
}
+/* Format of u[ret]probe section definition supporting auto-attach:
+ * u[ret]probe[/]/path/to/prog/function[+offset]
+ *
+ * Many uprobe programs do not avail of auto-attach, so we need to handle the
+ * case where the format is uprobe/myfunc by returning NULL rather than an
+ * error.
+ */
+static struct bpf_link *attach_uprobe(const struct bpf_program *prog, long cookie)
+{
+ DECLARE_LIBBPF_OPTS(bpf_uprobe_opts, opts);
+ char *func_name, binary_path[512];
+ char *func, *probe_name;
+ struct bpf_link *link;
+ size_t offset = 0;
+ int n, err;
+
+ 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;
+
+ /* First char in binary_path is a '/'; this allows us to support
+ * uprobe/path/2/prog and uprobe//path/2/prog, while also
+ * distinguishing between old-style uprobe/something definitions.
+ */
+ snprintf(binary_path, sizeof(binary_path) - 1, "/%s", probe_name);
+ /* last '/' should be prior to function+offset */
+ func_name = strrchr(binary_path + 1, '/');
+ if (!func_name) {
+ pr_debug("section '%s' is old-style u[ret]probe/function, cannot auto-attach\n",
+ prog->sec_name);
+ return NULL;
+ }
+ func_name[0] = '\0';
+ func_name++;
+ n = sscanf(func_name, "%m[a-zA-Z0-9_.]+%li", &func, &offset);
+ if (n < 1) {
+ err = -EINVAL;
+ pr_warn("uprobe name is invalid: %s\n", func_name);
+ return libbpf_err_ptr(err);
+ }
+ if (opts.retprobe && offset != 0) {
+ free(func);
+ err = -EINVAL;
+ pr_warn("uretprobes do not support offset specification\n");
+ return libbpf_err_ptr(err);
+ }
+ opts.func_name = func;
+
+ link = bpf_program__attach_uprobe_opts(prog, -1, binary_path, offset, &opts);
+ free(func);
+ return link;
+}
+
struct bpf_link *bpf_program__attach_uprobe(const struct bpf_program *prog,
bool retprobe, pid_t pid,
const char *binary_path,
--
1.8.3.1
