Merge branch 'libbpf: add bpf_program__insns() accessor'

Andrii Nakryiko says:

====================

Add libbpf APIs to access BPF program instructions. Both before and after
libbpf processing (before and after bpf_object__load()). This allows to
inspect what's going on with BPF program assembly instructions as libbpf
performs its processing magic.

But in more practical terms, this allows to do a no-brainer BPF program
cloning, which is something you need when working with fentry/fexit BPF
programs to be able to attach the same BPF program code to multiple kernel
functions. Currently, kernel needs multiple copies of BPF programs, each
loaded with its own target BTF ID. retsnoop is one such example that
previously had to rely on bpf_program__set_prep() API to hijack program
instructions ([0] for before and after).

Speaking of bpf_program__set_prep() API and the whole concept of
multiple-instance BPF programs in libbpf, all that is scheduled for
deprecation in v0.7. It doesn't work well, it's cumbersome, and it will become
more broken as libbpf adds more functionality. So deprecate and remove it in
libbpf 1.0. It doesn't seem to be used by anyone anyways (except for that
retsnoop hack, which is now much cleaner with new APIs as can be seen in [0]).

  [0] https://github.com/anakryiko/retsnoop/pull/1
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 24 insertions, 12 deletions

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 604abe00785f..4b2158657507 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -5405,7 +5405,7 @@ static int bpf_core_apply_relo(struct bpf_program *prog,
 	 * relocated, so it's enough to just subtract in-section offset
 	 */
 	insn_idx = insn_idx - prog->sec_insn_off;
-	if (insn_idx > prog->insns_cnt)
+	if (insn_idx >= prog->insns_cnt)
 		return -EINVAL;
 	insn = &prog->insns[insn_idx];
 
@@ -6653,8 +6653,6 @@ int bpf_program__load(struct bpf_program *prog, char *license, __u32 kern_ver)
 out:
 	if (err)
 		pr_warn("failed to load program '%s'\n", prog->name);
-	zfree(&prog->insns);
-	prog->insns_cnt = 0;
 	return libbpf_err(err);
 }
 
@@ -7360,8 +7358,7 @@ static int check_path(const char *path)
 	return err;
 }
 
-int bpf_program__pin_instance(struct bpf_program *prog, const char *path,
-			      int instance)
+static int bpf_program_pin_instance(struct bpf_program *prog, const char *path, int instance)
 {
 	char *cp, errmsg[STRERR_BUFSIZE];
 	int err;
@@ -7396,8 +7393,7 @@ int bpf_program__pin_instance(struct bpf_program *prog, const char *path,
 	return 0;
 }
 
-int bpf_program__unpin_instance(struct bpf_program *prog, const char *path,
-				int instance)
+static int bpf_program_unpin_instance(struct bpf_program *prog, const char *path, int instance)
 {
 	int err;
 
@@ -7425,6 +7421,12 @@ int bpf_program__unpin_instance(struct bpf_program *prog, const char *path,
 	return 0;
 }
 
+__attribute__((alias("bpf_program_pin_instance")))
+int bpf_object__pin_instance(struct bpf_program *prog, const char *path, int instance);
+
+__attribute__((alias("bpf_program_unpin_instance")))
+int bpf_program__unpin_instance(struct bpf_program *prog, const char *path, int instance);
+
 int bpf_program__pin(struct bpf_program *prog, const char *path)
 {
 	int i, err;
@@ -7449,7 +7451,7 @@ int bpf_program__pin(struct bpf_program *prog, const char *path)
 
 	if (prog->instances.nr == 1) {
 		/* don't create subdirs when pinning single instance */
-		return bpf_program__pin_instance(prog, path, 0);
+		return bpf_program_pin_instance(prog, path, 0);
 	}
 
 	for (i = 0; i < prog->instances.nr; i++) {
@@ -7465,7 +7467,7 @@ int bpf_program__pin(struct bpf_program *prog, const char *path)
 			goto err_unpin;
 		}
 
-		err = bpf_program__pin_instance(prog, buf, i);
+		err = bpf_program_pin_instance(prog, buf, i);
 		if (err)
 			goto err_unpin;
 	}
@@ -7483,7 +7485,7 @@ err_unpin:
 		else if (len >= PATH_MAX)
 			continue;
 
-		bpf_program__unpin_instance(prog, buf, i);
+		bpf_program_unpin_instance(prog, buf, i);
 	}
 
 	rmdir(path);
@@ -7511,7 +7513,7 @@ int bpf_program__unpin(struct bpf_program *prog, const char *path)
 
 	if (prog->instances.nr == 1) {
 		/* don't create subdirs when pinning single instance */
-		return bpf_program__unpin_instance(prog, path, 0);
+		return bpf_program_unpin_instance(prog, path, 0);
 	}
 
 	for (i = 0; i < prog->instances.nr; i++) {
@@ -7524,7 +7526,7 @@ int bpf_program__unpin(struct bpf_program *prog, const char *path)
 		else if (len >= PATH_MAX)
 			return libbpf_err(-ENAMETOOLONG);
 
-		err = bpf_program__unpin_instance(prog, buf, i);
+		err = bpf_program_unpin_instance(prog, buf, i);
 		if (err)
 			return err;
 	}
@@ -8143,6 +8145,16 @@ size_t bpf_program__size(const struct bpf_program *prog)
 	return prog->insns_cnt * BPF_INSN_SZ;
 }
 
+const struct bpf_insn *bpf_program__insns(const struct bpf_program *prog)
+{
+	return prog->insns;
+}
+
+size_t bpf_program__insn_cnt(const struct bpf_program *prog)
+{
+	return prog->insns_cnt;
+}
+
 int bpf_program__set_prep(struct bpf_program *prog, int nr_instances,
 			  bpf_program_prep_t prep)
 {