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[bpf-next,v4,1/5] libbpf: .text routines are subprograms in strict mode

Message ID 018de8d0d67c04bf436055270d35d394ba393505.1647473511.git.delyank@fb.com (mailing list archive)
State Accepted
Commit bc380eb9d04812eda23fd1d2904389012b50d946
Delegated to: BPF
Headers show
Series Subskeleton support for BPF libraries | expand

Checks

Context Check Description
netdev/tree_selection success Clearly marked for bpf-next
netdev/fixes_present success Fixes tag not required for -next series
netdev/subject_prefix success Link
netdev/cover_letter success Series has a cover letter
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/cc_maintainers warning 6 maintainers not CCed: netdev@vger.kernel.org songliubraving@fb.com yhs@fb.com john.fastabend@gmail.com kafai@fb.com kpsingh@kernel.org
netdev/build_clang success Errors and warnings before: 0 this patch: 0
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 0 this patch: 0
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 24 lines checked
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
bpf/vmtest-bpf-next success VM_Test
bpf/vmtest-bpf-next-PR fail PR summary

Commit Message

Delyan Kratunov March 16, 2022, 11:37 p.m. UTC 
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>
---
 tools/lib/bpf/libbpf.c        | 7 +++++++
 tools/lib/bpf/libbpf_legacy.h | 4 ++++
 2 files changed, 11 insertions(+)
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Patch

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 43161fdd44bb..aa26163e4ca1 100644
--- 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 a283cf031665..d7bcbd01f66f 100644
--- 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,
 	/*