libbpf: .text routines are subprograms in strict mode

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

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index f3a3147..3b7eb6d 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -3832,7 +3832,14 @@ static bool prog_is_subprog(const struct bpf_object *obj,
         * .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;
 }
 

diff --git a/tools/lib/bpf/libbpf_legacy.h b/tools/lib/bpf/libbpf_legacy.h
index a283cf0..d7bcbd0 100644 (file)
--- 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,
        /*