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From: Andrii Nakryiko <andrii@kernel.org>
To: <bpf@vger.kernel.org>, <netdev@vger.kernel.org>, <ast@fb.com>,
	<daniel@iogearbox.net>
Cc: <andrii@kernel.org>, <kernel-team@fb.com>
Subject: [PATCH bpf-next 3/6] libbpf: support static map definitions
Date: Wed, 21 Apr 2021 18:45:53 -0700	[thread overview]
Message-ID: <20210422014556.3451936-4-andrii@kernel.org> (raw)
In-Reply-To: <20210422014556.3451936-1-andrii@kernel.org>

Change libbpf relocation logic to support references to static map
definitions. This allows to use static maps and, combined with static linking,
hide internal maps from other files, just like static variables. User-space
will still be able to look up and modify static maps.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 tools/lib/bpf/libbpf.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 82b1946a0802..a7c3bcb8e5ea 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -3632,6 +3632,8 @@ static int bpf_program__record_reloc(struct bpf_program *prog,
 
 	/* generic map reference relocation */
 	if (type == LIBBPF_MAP_UNSPEC) {
+		size_t map_offset = sym->st_value + insn->imm;
+
 		if (!bpf_object__shndx_is_maps(obj, shdr_idx)) {
 			pr_warn("prog '%s': bad map relo against '%s' in section '%s'\n",
 				prog->name, sym_name, sym_sec_name);
@@ -3641,7 +3643,7 @@ static int bpf_program__record_reloc(struct bpf_program *prog,
 			map = &obj->maps[map_idx];
 			if (map->libbpf_type != type ||
 			    map->sec_idx != sym->st_shndx ||
-			    map->sec_offset != sym->st_value)
+			    map->sec_offset != map_offset)
 				continue;
 			pr_debug("prog '%s': found map %zd (%s, sec %d, off %zu) for insn #%u\n",
 				 prog->name, map_idx, map->name, map->sec_idx,
@@ -3656,7 +3658,8 @@ static int bpf_program__record_reloc(struct bpf_program *prog,
 		reloc_desc->type = RELO_LD64;
 		reloc_desc->insn_idx = insn_idx;
 		reloc_desc->map_idx = map_idx;
-		reloc_desc->sym_off = 0; /* sym->st_value determines map_idx */
+		/* sym->st_value + insn->imm determines map_idx */
+		reloc_desc->sym_off = 0;
 		return 0;
 	}
 
-- 
2.30.2


  parent reply	other threads:[~2021-04-22  1:46 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-22  1:45 [PATCH bpf-next 0/6] BPF static linker: support static vars and maps Andrii Nakryiko
2021-04-22  1:45 ` [PATCH bpf-next 1/6] selftests/bpf: document latest Clang fix expectations for linking tests Andrii Nakryiko
2021-04-22  1:45 ` [PATCH bpf-next 2/6] libbpf: rename static variables during linking Andrii Nakryiko
2021-04-22  1:45 ` Andrii Nakryiko [this message]
2021-04-22  1:45 ` [PATCH bpf-next 4/6] bpftool: handle transformed static map names in BPF skeleton Andrii Nakryiko
2021-04-22  1:45 ` [PATCH bpf-next 5/6] selftests/bpf: extend linked_vars selftests with static variables Andrii Nakryiko
2021-04-22  1:45 ` [PATCH bpf-next 6/6] selftests/bpf: extend linked_maps selftests with static maps Andrii Nakryiko

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