linux-kernel - [RFC PATCH v3 11/37] bpf tools: Iterate over ELF sections to collect information

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Date:	Sun, 17 May 2015 10:56:36 +0000
From:	Wang Nan <wangnan0@...wei.com>
To:	<paulus@...ba.org>, <a.p.zijlstra@...llo.nl>, <mingo@...hat.com>,
	<acme@...nel.org>, <namhyung@...nel.org>, <jolsa@...nel.org>,
	<dsahern@...il.com>, <ast@...mgrid.com>, <daniel@...earbox.net>,
	<brendan.d.gregg@...il.com>, <masami.hiramatsu.pt@...achi.com>
CC:	<lizefan@...wei.com>, <linux-kernel@...r.kernel.org>,
	<pi3orama@....com>
Subject: [RFC PATCH v3 11/37] 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>
---
 tools/lib/bpf/libbpf.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index a4910a8..1af80c3 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -206,6 +206,58 @@ bpf_obj_swap_init(struct bpf_object *obj)
 	}
 }
 
+static int bpf_obj_elf_collect(struct bpf_object *obj)
+{
+	Elf *elf = obj->elf.elf;
+	GElf_Ehdr *ep = &obj->elf.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_open_object(const char *path)
 {
 	struct bpf_object *obj;
@@ -229,6 +281,8 @@ struct bpf_object *bpf_open_object(const char *path)
 		goto out;
 	if (bpf_obj_swap_init(obj))
 		goto out;
+	if (bpf_obj_elf_collect(obj))
+		goto out;
 
 	return obj;
 
-- 
1.8.3.4

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