Commit 4d56a76e authored by Sandipan Das's avatar Sandipan Das Committed by Daniel Borkmann

bpf: fix multi-function JITed dump obtained via syscall

Currently, for multi-function programs, we cannot get the JITed
instructions using the bpf system call's BPF_OBJ_GET_INFO_BY_FD
command. Because of this, userspace tools such as bpftool fail
to identify a multi-function program as being JITed or not.

With the JIT enabled and the test program running, this can be
verified as follows:

  # cat /proc/sys/net/core/bpf_jit_enable
  1

Before applying this patch:

  # bpftool prog list
  1: kprobe  name foo  tag b811aab41a39ad3d  gpl
          loaded_at 2018-05-16T11:43:38+0530  uid 0
          xlated 216B  not jited  memlock 65536B
  ...

  # bpftool prog dump jited id 1
  no instructions returned

After applying this patch:

  # bpftool prog list
  1: kprobe  name foo  tag b811aab41a39ad3d  gpl
          loaded_at 2018-05-16T12:13:01+0530  uid 0
          xlated 216B  jited 308B  memlock 65536B
  ...

  # bpftool prog dump jited id 1
     0:   nop
     4:   nop
     8:   mflr    r0
     c:   std     r0,16(r1)
    10:   stdu    r1,-112(r1)
    14:   std     r31,104(r1)
    18:   addi    r31,r1,48
    1c:   li      r3,10
  ...
Signed-off-by: default avatarSandipan Das <sandipan@linux.vnet.ibm.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent f84192ee
...@@ -1970,13 +1970,44 @@ static int bpf_prog_get_info_by_fd(struct bpf_prog *prog, ...@@ -1970,13 +1970,44 @@ static int bpf_prog_get_info_by_fd(struct bpf_prog *prog,
* for offload. * for offload.
*/ */
ulen = info.jited_prog_len; ulen = info.jited_prog_len;
info.jited_prog_len = prog->jited_len; if (prog->aux->func_cnt) {
u32 i;
info.jited_prog_len = 0;
for (i = 0; i < prog->aux->func_cnt; i++)
info.jited_prog_len += prog->aux->func[i]->jited_len;
} else {
info.jited_prog_len = prog->jited_len;
}
if (info.jited_prog_len && ulen) { if (info.jited_prog_len && ulen) {
if (bpf_dump_raw_ok()) { if (bpf_dump_raw_ok()) {
uinsns = u64_to_user_ptr(info.jited_prog_insns); uinsns = u64_to_user_ptr(info.jited_prog_insns);
ulen = min_t(u32, info.jited_prog_len, ulen); ulen = min_t(u32, info.jited_prog_len, ulen);
if (copy_to_user(uinsns, prog->bpf_func, ulen))
return -EFAULT; /* for multi-function programs, copy the JITed
* instructions for all the functions
*/
if (prog->aux->func_cnt) {
u32 len, free, i;
u8 *img;
free = ulen;
for (i = 0; i < prog->aux->func_cnt; i++) {
len = prog->aux->func[i]->jited_len;
len = min_t(u32, len, free);
img = (u8 *) prog->aux->func[i]->bpf_func;
if (copy_to_user(uinsns, img, len))
return -EFAULT;
uinsns += len;
free -= len;
if (!free)
break;
}
} else {
if (copy_to_user(uinsns, prog->bpf_func, ulen))
return -EFAULT;
}
} else { } else {
info.jited_prog_insns = 0; info.jited_prog_insns = 0;
} }
......
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