netdev - [PATCH RFCv2 bpf-next 03/18] libbpf: patch module BTF obj+type ID into BPF insns

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Message-ID: <166256551578.1434226.1711667214489185920.stgit@firesoul>
Date:   Wed, 07 Sep 2022 17:45:15 +0200
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     bpf@...r.kernel.org
Cc:     Jesper Dangaard Brouer <brouer@...hat.com>, netdev@...r.kernel.org,
        xdp-hints@...-project.net, larysa.zaremba@...el.com,
        memxor@...il.com, Lorenzo Bianconi <lorenzo@...nel.org>,
        mtahhan@...hat.com,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Daniel Borkmann <borkmann@...earbox.net>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        dave@...cker.co.uk, Magnus Karlsson <magnus.karlsson@...el.com>,
        bjorn@...nel.org
Subject: [PATCH RFCv2 bpf-next 03/18] libbpf: patch module BTF obj+type ID
 into BPF insns

From: Larysa Zaremba <larysa.zaremba@...el.com>

Return both BTF type id and BTF object id from bpf_core_type_id_kernel().
Earlier only type id was returned despite the fact that llvm
has enabled the 64-bit return type for this instruction [1].
This was done as a preparation to the patch [2], which
also strongly served as a inspiration for this implementation.

[1] https://reviews.llvm.org/D91489
[2] https://lore.kernel.org/all/20201205025140.443115-1-andrii@kernel.org

Signed-off-by: Larysa Zaremba <larysa.zaremba@...el.com>
Signed-off-by: Alexander Lobakin <alexandr.lobakin@...el.com>
Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
---
 tools/lib/bpf/bpf_core_read.h |    3 ++-
 tools/lib/bpf/relo_core.c     |    8 +++++++-
 tools/lib/bpf/relo_core.h     |    1 +
 3 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/tools/lib/bpf/bpf_core_read.h b/tools/lib/bpf/bpf_core_read.h
index 496e6a8ee0dc..f033ec65fc01 100644
--- a/tools/lib/bpf/bpf_core_read.h
+++ b/tools/lib/bpf/bpf_core_read.h
@@ -168,7 +168,8 @@ enum bpf_enum_value_kind {
  * Convenience macro to get BTF type ID of a target kernel's type that matches
  * specified local type.
  * Returns:
- *    - valid 32-bit unsigned type ID in kernel BTF;
+ *    - valid 64-bit unsigned integer: the upper 32 bits is the BTF object ID
+ *      and the lower 32 bits is the BTF type ID within the BTF object.
  *    - 0, if no matching type was found in a target kernel BTF.
  */
 #define bpf_core_type_id_kernel(type)					    \
diff --git a/tools/lib/bpf/relo_core.c b/tools/lib/bpf/relo_core.c
index c4b0e81ae293..ca94f8e2c698 100644
--- a/tools/lib/bpf/relo_core.c
+++ b/tools/lib/bpf/relo_core.c
@@ -892,6 +892,7 @@ static int bpf_core_calc_relo(const char *prog_name,
 	res->fail_memsz_adjust = false;
 	res->orig_sz = res->new_sz = 0;
 	res->orig_type_id = res->new_type_id = 0;
+	res->btf_obj_id = 0;
 
 	if (core_relo_is_field_based(relo->kind)) {
 		err = bpf_core_calc_field_relo(prog_name, relo, local_spec,
@@ -942,6 +943,8 @@ static int bpf_core_calc_relo(const char *prog_name,
 	} else if (core_relo_is_type_based(relo->kind)) {
 		err = bpf_core_calc_type_relo(relo, local_spec, &res->orig_val, &res->validate);
 		err = err ?: bpf_core_calc_type_relo(relo, targ_spec, &res->new_val, NULL);
+		if (!err && relo->kind == BPF_CORE_TYPE_ID_TARGET)
+			res->btf_obj_id = btf_obj_id(targ_spec->btf);
 	} else if (core_relo_is_enumval_based(relo->kind)) {
 		err = bpf_core_calc_enumval_relo(relo, local_spec, &res->orig_val);
 		err = err ?: bpf_core_calc_enumval_relo(relo, targ_spec, &res->new_val);
@@ -1133,7 +1136,10 @@ int bpf_core_patch_insn(const char *prog_name, struct bpf_insn *insn,
 		}
 
 		insn[0].imm = new_val;
-		insn[1].imm = new_val >> 32;
+		/* For type IDs, upper 32 bits are used for BTF object ID */
+		insn[1].imm = relo->kind == BPF_CORE_TYPE_ID_TARGET ?
+					    res->btf_obj_id :
+					    (new_val >> 32);
 		pr_debug("prog '%s': relo #%d: patched insn #%d (LDIMM64) imm64 %llu -> %llu\n",
 			 prog_name, relo_idx, insn_idx,
 			 (unsigned long long)imm, (unsigned long long)new_val);
diff --git a/tools/lib/bpf/relo_core.h b/tools/lib/bpf/relo_core.h
index 1c0566daf8e8..52de7c018fb8 100644
--- a/tools/lib/bpf/relo_core.h
+++ b/tools/lib/bpf/relo_core.h
@@ -66,6 +66,7 @@ struct bpf_core_relo_res {
 	__u32 orig_type_id;
 	__u32 new_sz;
 	__u32 new_type_id;
+	__u32 btf_obj_id;
 };
 
 int __bpf_core_types_are_compat(const struct btf *local_btf, __u32 local_id,