From: Delyan Kratunov <delyank@fb.com>
Date: Wed, 16 Mar 2022 23:37:24 +0000
Subject: libbpf: .text routines are subprograms in strict mode
Patch-mainline: v5.18-rc1
Git-commit: bc380eb9d04812eda23fd1d2904389012b50d946
References: jsc#PED-1377

Currently, libbpf considers a single routine in .text to be a program. This
is particularly confusing when it comes to library objects - a single routine
meant to be used as an extern will instead be considered a bpf_program.

This patch hides this compatibility behavior behind the pre-existing
SEC_NAME strict mode flag.

Signed-off-by: Delyan Kratunov <delyank@fb.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/018de8d0d67c04bf436055270d35d394ba393505.1647473511.git.delyank@fb.com
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
 tools/lib/bpf/libbpf.c        |    7 +++++++
 tools/lib/bpf/libbpf_legacy.h |    4 ++++
 2 files changed, 11 insertions(+)

--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -3832,7 +3832,14 @@ static bool prog_is_subprog(const struct
 	 * .text programs are subprograms (even if they are not called from
 	 * other programs), because libbpf never explicitly supported mixing
 	 * SEC()-designated BPF programs and .text entry-point BPF programs.
+	 *
+	 * In libbpf 1.0 strict mode, we always consider .text
+	 * programs to be subprograms.
 	 */
+
+	if (libbpf_mode & LIBBPF_STRICT_SEC_NAME)
+		return prog->sec_idx == obj->efile.text_shndx;
+
 	return prog->sec_idx == obj->efile.text_shndx && obj->nr_programs > 1;
 }
 
--- a/tools/lib/bpf/libbpf_legacy.h
+++ b/tools/lib/bpf/libbpf_legacy.h
@@ -54,6 +54,10 @@ enum libbpf_strict_mode {
 	 *
 	 * Note, in this mode the program pin path will be based on the
 	 * function name instead of section name.
+	 *
+	 * Additionally, routines in the .text section are always considered
+	 * sub-programs. Legacy behavior allows for a single routine in .text
+	 * to be a program.
 	 */
 	LIBBPF_STRICT_SEC_NAME = 0x04,
 	/*