libbpf: Make perf_buffer__new() use OPTS-based interface

Add new variants of perf_buffer__new() and perf_buffer__new_raw() that
use OPTS-based options for future extensibility ([0]). Given all the
currently used API names are best fits, re-use them and use
___libbpf_override() approach and symbol versioning to preserve ABI and
source code compatibility. struct perf_buffer_opts and struct
perf_buffer_raw_opts are kept as well, but they are restructured such
that they are OPTS-based when used with new APIs. For struct
perf_buffer_raw_opts we keep few fields intact, so we have to also
preserve the memory location of them both when used as OPTS and for
legacy API variants. This is achieved with anonymous padding for OPTS
"incarnation" of the struct.  These pads can be eventually used for new
options.

  [0] Closes: https://github.com/libbpf/libbpf/issues/311

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211111053624.190580-6-andrii@kernel.org

1 files changed, 55 insertions, 15 deletions

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index a823b5ed705b..7db14859b27c 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -10578,11 +10578,18 @@ error:
 static struct perf_buffer *__perf_buffer__new(int map_fd, size_t page_cnt,
 					      struct perf_buffer_params *p);
 
-struct perf_buffer *perf_buffer__new(int map_fd, size_t page_cnt,
-				     const struct perf_buffer_opts *opts)
+DEFAULT_VERSION(perf_buffer__new_v0_6_0, perf_buffer__new, LIBBPF_0.6.0)
+struct perf_buffer *perf_buffer__new_v0_6_0(int map_fd, size_t page_cnt,
+					    perf_buffer_sample_fn sample_cb,
+					    perf_buffer_lost_fn lost_cb,
+					    void *ctx,
+					    const struct perf_buffer_opts *opts)
 {
 	struct perf_buffer_params p = {};
-	struct perf_event_attr attr = { 0, };
+	struct perf_event_attr attr = {};
+
+	if (!OPTS_VALID(opts, perf_buffer_opts))
+		return libbpf_err_ptr(-EINVAL);
 
 	attr.config = PERF_COUNT_SW_BPF_OUTPUT;
 	attr.type = PERF_TYPE_SOFTWARE;
@@ -10591,29 +10598,62 @@ struct perf_buffer *perf_buffer__new(int map_fd, size_t page_cnt,
 	attr.wakeup_events = 1;
 
 	p.attr = &attr;
-	p.sample_cb = opts ? opts->sample_cb : NULL;
-	p.lost_cb = opts ? opts->lost_cb : NULL;
-	p.ctx = opts ? opts->ctx : NULL;
+	p.sample_cb = sample_cb;
+	p.lost_cb = lost_cb;
+	p.ctx = ctx;
 
 	return libbpf_ptr(__perf_buffer__new(map_fd, page_cnt, &p));
 }
 
-struct perf_buffer *
-perf_buffer__new_raw(int map_fd, size_t page_cnt,
-		     const struct perf_buffer_raw_opts *opts)
+COMPAT_VERSION(perf_buffer__new_deprecated, perf_buffer__new, LIBBPF_0.0.4)
+struct perf_buffer *perf_buffer__new_deprecated(int map_fd, size_t page_cnt,
+						const struct perf_buffer_opts *opts)
+{
+	return perf_buffer__new_v0_6_0(map_fd, page_cnt,
+				       opts ? opts->sample_cb : NULL,
+				       opts ? opts->lost_cb : NULL,
+				       opts ? opts->ctx : NULL,
+				       NULL);
+}
+
+DEFAULT_VERSION(perf_buffer__new_raw_v0_6_0, perf_buffer__new_raw, LIBBPF_0.6.0)
+struct perf_buffer *perf_buffer__new_raw_v0_6_0(int map_fd, size_t page_cnt,
+						struct perf_event_attr *attr,
+						perf_buffer_event_fn event_cb, void *ctx,
+						const struct perf_buffer_raw_opts *opts)
 {
 	struct perf_buffer_params p = {};
 
-	p.attr = opts->attr;
-	p.event_cb = opts->event_cb;
-	p.ctx = opts->ctx;
-	p.cpu_cnt = opts->cpu_cnt;
-	p.cpus = opts->cpus;
-	p.map_keys = opts->map_keys;
+	if (page_cnt == 0 || !attr)
+		return libbpf_err_ptr(-EINVAL);
+
+	if (!OPTS_VALID(opts, perf_buffer_raw_opts))
+		return libbpf_err_ptr(-EINVAL);
+
+	p.attr = attr;
+	p.event_cb = event_cb;
+	p.ctx = ctx;
+	p.cpu_cnt = OPTS_GET(opts, cpu_cnt, 0);
+	p.cpus = OPTS_GET(opts, cpus, NULL);
+	p.map_keys = OPTS_GET(opts, map_keys, NULL);
 
 	return libbpf_ptr(__perf_buffer__new(map_fd, page_cnt, &p));
 }
 
+COMPAT_VERSION(perf_buffer__new_raw_deprecated, perf_buffer__new_raw, LIBBPF_0.0.4)
+struct perf_buffer *perf_buffer__new_raw_deprecated(int map_fd, size_t page_cnt,
+						    const struct perf_buffer_raw_opts *opts)
+{
+	LIBBPF_OPTS(perf_buffer_raw_opts, inner_opts,
+		.cpu_cnt = opts->cpu_cnt,
+		.cpus = opts->cpus,
+		.map_keys = opts->map_keys,
+	);
+
+	return perf_buffer__new_raw_v0_6_0(map_fd, page_cnt, opts->attr,
+					   opts->event_cb, opts->ctx, &inner_opts);
+}
+
 static struct perf_buffer *__perf_buffer__new(int map_fd, size_t page_cnt,
 					      struct perf_buffer_params *p)
 {