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authorWang Nan <wangnan0@huawei.com>2015-07-01 02:13:55 +0000
committerArnaldo Carvalho de Melo <acme@redhat.com>2015-08-07 10:16:56 -0300
commitcc4228d57c4c35ae0a29efa1e7687a817dc038d9 (patch)
tree0cef04e1c38b6d910a280b3f40f1b67b61fabdb1
parent6c956392b0486c170e382476ab9dd97a696fd169 (diff)
downloadop-kernel-dev-cc4228d57c4c35ae0a29efa1e7687a817dc038d9.zip
op-kernel-dev-cc4228d57c4c35ae0a29efa1e7687a817dc038d9.tar.gz
bpf tools: Check endianness and make libbpf fail early
Check endianness according to EHDR. Code is taken from tools/perf/util/symbol-elf.c. Libbpf doesn't magically convert missmatched endianness. Even if we swap eBPF instructions to correct byte order, we are unable to deal with endianness in code logical generated by LLVM. Therefore, libbpf should simply reject missmatched ELF object, and let LLVM to create good code. Signed-off-by: Wang Nan <wangnan0@huawei.com> Acked-by: Alexei Starovoitov <ast@plumgrid.com> Cc: Brendan Gregg <brendan.d.gregg@gmail.com> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: David Ahern <dsahern@gmail.com> Cc: He Kuang <hekuang@huawei.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Kaixu Xia <xiakaixu@huawei.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Zefan Li <lizefan@huawei.com> Cc: pi3orama@163.com Link: http://lkml.kernel.org/r/1435716878-189507-8-git-send-email-wangnan0@huawei.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
-rw-r--r--tools/lib/bpf/libbpf.c30
1 files changed, 30 insertions, 0 deletions
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 36dfbc1..15b3e82 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -192,6 +192,34 @@ errout:
return err;
}
+static int
+bpf_object__check_endianness(struct bpf_object *obj)
+{
+ static unsigned int const endian = 1;
+
+ switch (obj->efile.ehdr.e_ident[EI_DATA]) {
+ case ELFDATA2LSB:
+ /* We are big endian, BPF obj is little endian. */
+ if (*(unsigned char const *)&endian != 1)
+ goto mismatch;
+ break;
+
+ case ELFDATA2MSB:
+ /* We are little endian, BPF obj is big endian. */
+ if (*(unsigned char const *)&endian != 0)
+ goto mismatch;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ return 0;
+
+mismatch:
+ pr_warning("Error: endianness mismatch.\n");
+ return -EINVAL;
+}
+
static struct bpf_object *
__bpf_object__open(const char *path, void *obj_buf, size_t obj_buf_sz)
{
@@ -208,6 +236,8 @@ __bpf_object__open(const char *path, void *obj_buf, size_t obj_buf_sz)
if (bpf_object__elf_init(obj))
goto out;
+ if (bpf_object__check_endianness(obj))
+ goto out;
bpf_object__elf_finish(obj);
return obj;
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