On 6/23/20 5:40 PM, Alexei Starovoitov wrote:
On Sat, Jun 20, 2020 at 12:06 AM Yonghong Song <yhs@xxxxxx> wrote:
On 6/19/20 4:04 PM, Andrii Nakryiko wrote:
bpf_object__find_program_by_title(), used by CO-RE relocation code, doesn't
return .text "BPF program", if it is a function storage for sub-programs.
Because of that, any CO-RE relocation in helper non-inlined functions will
fail. Fix this by searching for .text-corresponding BPF program manually.
Adjust one of bpf_iter selftest to exhibit this pattern.
Reported-by: Yonghong Song <yhs@xxxxxx>
Fixes: ddc7c3042614 ("libbpf: implement BPF CO-RE offset relocation algorithm")
Signed-off-by: Andrii Nakryiko <andriin@xxxxxx>
Acked-by: Yonghong Song <yhs@xxxxxx>
But the fix here only fixed the issue for interpreter mode.
For jit only mode, we still have issues. The following patch can fix
the jit mode issue,
=============
From 4d66814513ec45b86a30a1231b8a000d4bfc6f1a Mon Sep 17 00:00:00 2001
From: Yonghong Song <yhs@xxxxxx>
Date: Fri, 19 Jun 2020 23:26:13 -0700
Subject: [PATCH bpf] bpf: set the number of exception entries properly for
subprograms
Currently, if a bpf program has more than one subprograms, each
program will be jitted separately. For tracing problem, the
prog->aux->num_exentries is not setup properly. For example,
with bpf_iter_netlink.c modified to force one function not inlined,
and with proper libbpf fix, with CONFIG_BPF_JIT_ALWAYS_ON,
we will have error like below:
$ ./test_progs -n 3/3
...
libbpf: failed to load program 'iter/netlink'
libbpf: failed to load object 'bpf_iter_netlink'
libbpf: failed to load BPF skeleton 'bpf_iter_netlink': -4007
test_netlink:FAIL:bpf_iter_netlink__open_and_load skeleton
open_and_load failed
#3/3 netlink:FAIL
The dmesg shows the following errors:
ex gen bug
which is triggered by the following code in arch/x86/net/bpf_jit_comp.c:
if (excnt >= bpf_prog->aux->num_exentries) {
pr_err("ex gen bug\n");
return -EFAULT;
}
If the program has more than one subprograms, num_exentries is actually
0 since it is not setup.
This patch fixed the issue by setuping proper num_exentries for
each subprogram before calling jit function.
Signed-off-by: Yonghong Song <yhs@xxxxxx>
Thanks for fixing. Applied both to bpf tree.
Yonghong, next time please submit the patch properly.
It was very awkward to copy-paste it manually from the thread.
I've edited the commit log a bit.
Thanks. I posted original commit as I am not sure how to proceed as
this and Andrii's patch belongs to the same patch set to fix
bpf_iter_netlink problem. I guess next time I will go ahead with
patch submit with proper description in the patch, which
sounds better for review and to get notice from other people.
