linux-kernel - [RFC PATCH v5 08/30] bpf tools: Iterate over ELF sections to collect information

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Message-ID: <1433144296-74992-9-git-send-email-wangnan0@huawei.com>
Date:	Mon, 1 Jun 2015 07:37:54 +0000
From:	Wang Nan <wangnan0@...wei.com>
To:	<namhyung@...nel.org>, <alexei.starovoitov@...il.com>,
	<masami.hiramatsu.pt@...achi.com>, <acme@...nel.org>,
	<paulus@...ba.org>, <a.p.zijlstra@...llo.nl>, <mingo@...hat.com>,
	<jolsa@...nel.org>, <dsahern@...il.com>, <daniel@...earbox.net>,
	<brendan.d.gregg@...il.com>
CC:	<lizefan@...wei.com>, <hekuang@...wei.com>, <xiakaixu@...wei.com>,
	<linux-kernel@...r.kernel.org>, <pi3orama@....com>
Subject: [RFC PATCH v5 08/30] bpf tools: Iterate over ELF sections to collect information

bpf_obj_elf_collect() is introduced to iterate over each elf sections
to collection informations in eBPF object files. This function will
futher enhanced to collect license, kernel version, programs, configs
and map information.

Signed-off-by: Wang Nan <wangnan0@...wei.com>
Acked-by: Alexei Starovoitov <ast@...mgrid.com>
---
 tools/lib/bpf/libbpf.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 5d56c40..efc93dc 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -194,6 +194,57 @@ mismatch:
 	return -EINVAL;
 }
 
+static int bpf_object__elf_collect(struct bpf_object *obj)
+{
+	Elf *elf = obj->efile.elf;
+	GElf_Ehdr *ep = &obj->efile.ehdr;
+	Elf_Scn *scn = NULL;
+	int idx = 0, err = 0;
+
+	/* Elf is corrupted/truncated, avoid calling elf_strptr. */
+	if (!elf_rawdata(elf_getscn(elf, ep->e_shstrndx), NULL)) {
+		pr_warning("failed to get e_shstrndx from %s\n",
+			   obj->path);
+		return -EINVAL;
+	}
+
+	while ((scn = elf_nextscn(elf, scn)) != NULL) {
+		char *name;
+		GElf_Shdr sh;
+		Elf_Data *data;
+
+		idx++;
+		if (gelf_getshdr(scn, &sh) != &sh) {
+			pr_warning("failed to get section header from %s\n",
+				   obj->path);
+			err = -EINVAL;
+			goto out;
+		}
+
+		name = elf_strptr(elf, ep->e_shstrndx, sh.sh_name);
+		if (!name) {
+			pr_warning("failed to get section name from %s\n",
+				   obj->path);
+			err = -EINVAL;
+			goto out;
+		}
+
+		data = elf_getdata(scn, 0);
+		if (!data) {
+			pr_warning("failed to get section data from %s(%s)\n",
+				   name, obj->path);
+			err = -EINVAL;
+			goto out;
+		}
+		pr_debug("section %s, size %ld, link %d, flags %lx, type=%d\n",
+			 name, (unsigned long)data->d_size,
+			 (int)sh.sh_link, (unsigned long)sh.sh_flags,
+			 (int)sh.sh_type);
+	}
+out:
+	return err;
+}
+
 struct bpf_object *bpf_object__open(const char *path)
 {
 	struct bpf_object *obj;
@@ -217,6 +268,8 @@ struct bpf_object *bpf_object__open(const char *path)
 		goto out;
 	if (bpf_object__check_endianess(obj))
 		goto out;
+	if (bpf_object__elf_collect(obj))
+		goto out;
 
 	bpf_object__elf_finish(obj);
 	return obj;
-- 
1.8.3.4

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