linux-kernel - [RFC PATCH 07/22] perf bpf: iterater over elf sections to collect information.

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Date:	Thu, 30 Apr 2015 10:52:30 +0000
From:	Wang Nan <wangnan0@...wei.com>
To:	<ast@...mgrid.com>, <davem@...emloft.net>, <acme@...nel.org>,
	<mingo@...hat.com>, <a.p.zijlstra@...llo.nl>,
	<masami.hiramatsu.pt@...achi.com>, <jolsa@...nel.org>
CC:	<lizefan@...nel.org>, <linux-kernel@...r.kernel.org>,
	<pi3orama@....com>, <hekuang@...wei.com>
Subject: [RFC PATCH 07/22] perf bpf: iterater 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/perf/util/bpf-loader.c | 54 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index 14d76f6..9c077dd 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -157,6 +157,58 @@ bpf_obj_swap_init(struct bpf_obj *obj)
 	}
 }
 
+static int bpf_obj_elf_collect(struct bpf_obj *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_err("bpf: 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_err("bpf: 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_err("bpf: failed to get section name "
+				"from %s\n", obj->path);
+			err = -EINVAL;
+			goto out;
+		}
+
+		data = elf_getdata(scn, 0);
+		if (!data) {
+			pr_err("bpf: failed to get section data "
+				"from %s(%s)\n", name, obj->path);
+			err = -EINVAL;
+			goto out;
+		}
+		pr_debug("bpf: 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;
+}
+
 int bpf__load(const char *path)
 {
 	struct bpf_obj *obj;
@@ -179,6 +231,8 @@ int bpf__load(const char *path)
 		goto out;
 	if ((err = bpf_obj_swap_init(obj)))
 		goto out;
+	if ((err = bpf_obj_elf_collect(obj)))
+		goto out;
 
 	list_add(&obj->list, &bpf_obj_list);
 	return 0;
-- 
1.8.3.4

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