openkylin
/
linux
mirror of https://gitee.com/openkylin/linux.git
9
0
Fork 0
Code Issues Projects Releases Wiki Activity

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>
This commit is contained in:
Wang Nan 2015-07-01 02:13:55 +00:00 committed by Arnaldo Carvalho de Melo
parent 6c956392b0
commit cc4228d57c
1 changed files with 30 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

30
tools/lib/bpf/libbpf.c
View File

@ -192,6 +192,34 @@ static int bpf_object__elf_init(struct bpf_object *obj)
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;