[PATCH bpf] tools/bpftool: move set_max_rlimit() before __bpf_object__open_xattr()

[PATCH bpf] tools/bpftool: move set_max_rlimit() before __bpf_object__open_xattr()

[Yonghong Song]

For a host which has a lower rlimit for max locked memory (e.g., 64KB),
the following error occurs in one of our production systems:
  # /usr/sbin/bpftool prog load /paragon/pods/52877437/home/mark.o \
    /sys/fs/bpf/paragon_mark_21 type cgroup/skb \
    map idx 0 pinned /sys/fs/bpf/paragon_map_21
  libbpf: Error in bpf_object__probe_name():Operation not permitted(1).
    Couldn't load basic 'r0 = 0' BPF program.
  Error: failed to open object file

The reason is due to low locked memory during bpf_object__probe_name()
which probes whether program name is supported in kernel or not
during __bpf_object__open_xattr().

bpftool program load already tries to relax mlock rlimit before
bpf_object__load(). Let us move set_max_rlimit() before
__bpf_object__open_xattr(), which fixed the issue here.

Fixes: 47eff61777c7 ("bpf, libbpf: introduce bpf_object__probe_caps to test BPF capabilities")
Signed-off-by: Yonghong Song <yhs@fb.com>
---
 tools/bpf/bpftool/prog.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
index fc495b27f0fc..26336bad0442 100644
--- a/tools/bpf/bpftool/prog.c
+++ b/tools/bpf/bpftool/prog.c
@@ -879,6 +879,8 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
 		}
 	}
 
+	set_max_rlimit();
+
 	obj = __bpf_object__open_xattr(&attr, bpf_flags);
 	if (IS_ERR_OR_NULL(obj)) {
 		p_err("failed to open object file");
@@ -958,8 +960,6 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
 		goto err_close_obj;
 	}
 
-	set_max_rlimit();
-
 	err = bpf_object__load(obj);
 	if (err) {
 		p_err("failed to load object file");
-- 
2.17.1

Re: [PATCH bpf] tools/bpftool: move set_max_rlimit() before __bpf_object__open_xattr()

[Alexei Starovoitov]

On Thu, May 16, 2019 at 11:31 AM Yonghong Song <yhs@fb.com> wrote:
>
> For a host which has a lower rlimit for max locked memory (e.g., 64KB),
> the following error occurs in one of our production systems:
>   # /usr/sbin/bpftool prog load /paragon/pods/52877437/home/mark.o \
>     /sys/fs/bpf/paragon_mark_21 type cgroup/skb \
>     map idx 0 pinned /sys/fs/bpf/paragon_map_21
>   libbpf: Error in bpf_object__probe_name():Operation not permitted(1).
>     Couldn't load basic 'r0 = 0' BPF program.
>   Error: failed to open object file
>
> The reason is due to low locked memory during bpf_object__probe_name()
> which probes whether program name is supported in kernel or not
> during __bpf_object__open_xattr().
>
> bpftool program load already tries to relax mlock rlimit before
> bpf_object__load(). Let us move set_max_rlimit() before
> __bpf_object__open_xattr(), which fixed the issue here.
>
> Fixes: 47eff61777c7 ("bpf, libbpf: introduce bpf_object__probe_caps to test BPF capabilities")
> Signed-off-by: Yonghong Song <yhs@fb.com>

Applied. Thanks