linux-kernel - [PATCH bpf-next] libbpf: Add ability to clear per-program load flags

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Date:   Thu, 18 Nov 2021 11:33:35 +0100
From:   Florent Revest <revest@...omium.org>
To:     bpf@...r.kernel.org
Cc:     andrii@...nel.org, kpsingh@...nel.org, jackmanb@...gle.com,
        linux-kernel@...r.kernel.org, Florent Revest <revest@...omium.org>
Subject: [PATCH bpf-next] libbpf: Add ability to clear per-program load flags

Recently, bpf_program__flags and bpf_program__set_extra_flags were
introduced to the libbpf API but they only allow adding load flags.

We have a use-case where we construct a skeleton with a sleepable
program and if it fails to load then we want to make it non-sleepable by
clearing BPF_F_SLEEPABLE.

Signed-off-by: Florent Revest <revest@...omium.org>
---
 tools/lib/bpf/libbpf.c   | 9 +++++++++
 tools/lib/bpf/libbpf.h   | 1 +
 tools/lib/bpf/libbpf.map | 1 +
 3 files changed, 11 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index de7e09a6b5ec..dcb7fced5fd2 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -8305,6 +8305,15 @@ int bpf_program__set_extra_flags(struct bpf_program *prog, __u32 extra_flags)
 	return 0;
 }
 
+int bpf_program__clear_flags(struct bpf_program *prog, __u32 flags)
+{
+	if (prog->obj->loaded)
+		return libbpf_err(-EBUSY);
+
+	prog->prog_flags &= ~flags;
+	return 0;
+}
+
 #define SEC_DEF(sec_pfx, ptype, atype, flags, ...) {			    \
 	.sec = sec_pfx,							    \
 	.prog_type = BPF_PROG_TYPE_##ptype,				    \
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 4ec69f224342..08f108e49841 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -495,6 +495,7 @@ bpf_program__set_expected_attach_type(struct bpf_program *prog,
 
 LIBBPF_API __u32 bpf_program__flags(const struct bpf_program *prog);
 LIBBPF_API int bpf_program__set_extra_flags(struct bpf_program *prog, __u32 extra_flags);
+LIBBPF_API int bpf_program__clear_flags(struct bpf_program *prog, __u32 flags);
 
 LIBBPF_API int
 bpf_program__set_attach_target(struct bpf_program *prog, int attach_prog_fd,
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 6a59514a48cf..eeff700240dc 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -401,6 +401,7 @@ LIBBPF_0.6.0 {
 		bpf_program__insn_cnt;
 		bpf_program__insns;
 		bpf_program__set_extra_flags;
+		bpf_program__clear_flags;
 		btf__add_btf;
 		btf__add_decl_tag;
 		btf__add_type_tag;
-- 
2.34.0.rc2.393.gf8c9666880-goog