diff mbox series

[bpf-next,2/3] libbpf: support target-less SEC() definitions for BTF-backed programs

Message ID 20220408203433.2988727-3-andrii@kernel.org (mailing list archive)
State New, archived
Delegated to: BPF
Headers show
Series Add target-less tracing SEC() definitions | expand

Checks

Context Check Description
bpf/vmtest-bpf-next-PR pending PR summary
netdev/tree_selection success Clearly marked for bpf-next, async
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: songliubraving@fb.com netdev@vger.kernel.org kafai@fb.com yhs@fb.com john.fastabend@gmail.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 warning WARNING: line length of 102 exceeds 80 columns WARNING: line length of 110 exceeds 80 columns WARNING: line length of 112 exceeds 80 columns WARNING: line length of 113 exceeds 80 columns WARNING: line length of 114 exceeds 80 columns WARNING: line length of 86 exceeds 80 columns WARNING: line length of 94 exceeds 80 columns WARNING: line length of 96 exceeds 80 columns WARNING: line length of 97 exceeds 80 columns WARNING: line length of 98 exceeds 80 columns
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
bpf/vmtest-bpf-next-VM_Test-1 success Logs for Kernel LATEST on ubuntu-latest + selftests
bpf/vmtest-bpf-next-VM_Test-2 pending Logs for Kernel LATEST on z15 + selftests

Commit Message

Andrii Nakryiko April 8, 2022, 8:34 p.m. UTC 
Similar to previous patch, support target-less definitions like
SEC("fentry"), SEC("freplace"), etc. For such BTF-backed program types
it is expected that user will specify BTF target programmatically at
runtime using bpf_program__set_attach_target() *before* load phase. If
not, libbpf will report this as an error.

Aslo use SEC_ATTACH_BTF flag instead of explicitly listing a set of
types that are expected to require attach_btf_id. This was an accidental
omission during custom SEC() support refactoring.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 tools/lib/bpf/libbpf.c | 49 +++++++++++++++++++++++++++---------------
 1 file changed, 32 insertions(+), 17 deletions(-)

Comments

Song Liu April 8, 2022, 9:08 p.m. UTC | #1 
On Fri, Apr 8, 2022 at 1:34 PM Andrii Nakryiko <andrii@kernel.org> wrote:
>
> Similar to previous patch, support target-less definitions like
> SEC("fentry"), SEC("freplace"), etc. For such BTF-backed program types
> it is expected that user will specify BTF target programmatically at
> runtime using bpf_program__set_attach_target() *before* load phase. If
> not, libbpf will report this as an error.
>
> Aslo use SEC_ATTACH_BTF flag instead of explicitly listing a set of
> types that are expected to require attach_btf_id. This was an accidental
> omission during custom SEC() support refactoring.
>
> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

Acked-by: Song Liu <songliubraving@fb.com>
diff mbox series

Patch

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 81911a1e1f3e..76c0b3a5cde9 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -6628,17 +6628,32 @@  static int libbpf_prepare_prog_load(struct bpf_program *prog,
 	if (prog->type == BPF_PROG_TYPE_XDP && (def & SEC_XDP_FRAGS))
 		opts->prog_flags |= BPF_F_XDP_HAS_FRAGS;
 
-	if (def & SEC_DEPRECATED)
+	if (def & SEC_DEPRECATED) {
 		pr_warn("SEC(\"%s\") is deprecated, please see https://github.com/libbpf/libbpf/wiki/Libbpf-1.0-migration-guide#bpf-program-sec-annotation-deprecations for details\n",
 			prog->sec_name);
+	}
 
-	if ((prog->type == BPF_PROG_TYPE_TRACING ||
-	     prog->type == BPF_PROG_TYPE_LSM ||
-	     prog->type == BPF_PROG_TYPE_EXT) && !prog->attach_btf_id) {
+	if ((def & SEC_ATTACH_BTF) && !prog->attach_btf_id) {
 		int btf_obj_fd = 0, btf_type_id = 0, err;
 		const char *attach_name;
 
-		attach_name = strchr(prog->sec_name, '/') + 1;
+		attach_name = strchr(prog->sec_name, '/');
+		if (!attach_name) {
+			/* if BPF program is annotated with just SEC("fentry")
+			 * (or similar) without declaratively specifying
+			 * target, then it is expected that target will be
+			 * specified with bpf_program__set_attach_target() at
+			 * runtime before BPF object load step. If not, then
+			 * there is nothing to load into the kernel as BPF
+			 * verifier won't be able to validate BPF program
+			 * correctness anyways.
+			 */
+			pr_warn("prog '%s': no BTF-based attach target is specified, use bpf_program__set_attach_target()\n",
+				prog->name);
+			return -EINVAL;
+		}
+		attach_name++; /* skip over / */
+
 		err = libbpf_find_attach_btf_id(prog, attach_name, &btf_obj_fd, &btf_type_id);
 		if (err)
 			return err;
@@ -8684,18 +8699,18 @@  static const struct bpf_sec_def section_defs[] = {
 	SEC_DEF("raw_tp+",		RAW_TRACEPOINT, 0, SEC_NONE, attach_raw_tp),
 	SEC_DEF("raw_tracepoint.w+",	RAW_TRACEPOINT_WRITABLE, 0, SEC_NONE, attach_raw_tp),
 	SEC_DEF("raw_tp.w+",		RAW_TRACEPOINT_WRITABLE, 0, SEC_NONE, attach_raw_tp),
-	SEC_DEF("tp_btf/",		TRACING, BPF_TRACE_RAW_TP, SEC_ATTACH_BTF, attach_trace),
-	SEC_DEF("fentry/",		TRACING, BPF_TRACE_FENTRY, SEC_ATTACH_BTF, attach_trace),
-	SEC_DEF("fmod_ret/",		TRACING, BPF_MODIFY_RETURN, SEC_ATTACH_BTF, attach_trace),
-	SEC_DEF("fexit/",		TRACING, BPF_TRACE_FEXIT, SEC_ATTACH_BTF, attach_trace),
-	SEC_DEF("fentry.s/",		TRACING, BPF_TRACE_FENTRY, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),
-	SEC_DEF("fmod_ret.s/",		TRACING, BPF_MODIFY_RETURN, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),
-	SEC_DEF("fexit.s/",		TRACING, BPF_TRACE_FEXIT, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),
-	SEC_DEF("freplace/",		EXT, 0, SEC_ATTACH_BTF, attach_trace),
-	SEC_DEF("lsm/",			LSM, BPF_LSM_MAC, SEC_ATTACH_BTF, attach_lsm),
-	SEC_DEF("lsm.s/",		LSM, BPF_LSM_MAC, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_lsm),
-	SEC_DEF("iter/",		TRACING, BPF_TRACE_ITER, SEC_ATTACH_BTF, attach_iter),
-	SEC_DEF("iter.s/",		TRACING, BPF_TRACE_ITER, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_iter),
+	SEC_DEF("tp_btf+",		TRACING, BPF_TRACE_RAW_TP, SEC_ATTACH_BTF, attach_trace),
+	SEC_DEF("fentry+",		TRACING, BPF_TRACE_FENTRY, SEC_ATTACH_BTF, attach_trace),
+	SEC_DEF("fmod_ret+",		TRACING, BPF_MODIFY_RETURN, SEC_ATTACH_BTF, attach_trace),
+	SEC_DEF("fexit+",		TRACING, BPF_TRACE_FEXIT, SEC_ATTACH_BTF, attach_trace),
+	SEC_DEF("fentry.s+",		TRACING, BPF_TRACE_FENTRY, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),
+	SEC_DEF("fmod_ret.s+",		TRACING, BPF_MODIFY_RETURN, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),
+	SEC_DEF("fexit.s+",		TRACING, BPF_TRACE_FEXIT, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),
+	SEC_DEF("freplace+",		EXT, 0, SEC_ATTACH_BTF, attach_trace),
+	SEC_DEF("lsm+",			LSM, BPF_LSM_MAC, SEC_ATTACH_BTF, attach_lsm),
+	SEC_DEF("lsm.s+",		LSM, BPF_LSM_MAC, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_lsm),
+	SEC_DEF("iter+",		TRACING, BPF_TRACE_ITER, SEC_ATTACH_BTF, attach_iter),
+	SEC_DEF("iter.s+",		TRACING, BPF_TRACE_ITER, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_iter),
 	SEC_DEF("syscall",		SYSCALL, 0, SEC_SLEEPABLE),
 	SEC_DEF("xdp.frags/devmap",	XDP, BPF_XDP_DEVMAP, SEC_XDP_FRAGS),
 	SEC_DEF("xdp/devmap",		XDP, BPF_XDP_DEVMAP, SEC_ATTACHABLE),