On Mon, Feb 07, 2022 at 06:57:20PM +0100, Jiri Olsa wrote:
> On Mon, Feb 07, 2022 at 09:42:25AM -0800, Andrii Nakryiko wrote:
> > On Mon, Feb 7, 2022 at 8:00 AM Yinjun Zhang <yinjun.zhang@xxxxxxxxxxxx> wrote:
> > >
> > > When reworking btf__get_from_id() in commit a19f93cfafdf the error
> > > handling when calling bpf_btf_get_fd_by_id() changed. Before the rework
> > > if bpf_btf_get_fd_by_id() failed the error would not be propagated to
> > > callers of btf__get_from_id(), after the rework it is. This lead to a
> > > change in behavior in print_key_value() that now prints an error when
> > > trying to lookup keys in maps with no btf available.
> > >
> > > Fix this by following the way used in dumping maps to allow to look up
> > > keys in no-btf maps, by which it decides whether and where to get the
> > > btf info according to the btf value type.
> > >
> > > Fixes: a19f93cfafdf ("libbpf: Add internal helper to load BTF data by FD")
> > > Signed-off-by: Yinjun Zhang <yinjun.zhang@xxxxxxxxxxxx>
> > > Reviewed-by: Niklas Söderlund <niklas.soderlund@xxxxxxxxxxxx>
> > > Signed-off-by: Simon Horman <simon.horman@xxxxxxxxxxxx>
> > > ---
> > > tools/bpf/bpftool/map.c | 6 ++----
> > > 1 file changed, 2 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
> > > index cc530a229812..4fc772d66e3a 100644
> > > --- a/tools/bpf/bpftool/map.c
> > > +++ b/tools/bpf/bpftool/map.c
> > > @@ -1054,11 +1054,9 @@ static void print_key_value(struct bpf_map_info *info, void *key,
> > > json_writer_t *btf_wtr;
> > > struct btf *btf;
> > >
> > > - btf = btf__load_from_kernel_by_id(info->btf_id);
> > > - if (libbpf_get_error(btf)) {
> > > - p_err("failed to get btf");
> > > + btf = get_map_kv_btf(info);
> > > + if (libbpf_get_error(btf))
> >
> > See discussion in [0], it seems relevant.
> >
> > [0] https://lore.kernel.org/bpf/20220204225823.339548-3-jolsa@xxxxxxxxxx/
>
> I checked and this patch does not fix the problem for me,
> but looks like similar issue, do you have test case for this?
>
> mine is to dump any no-btf map with -p option
anyway I think your change should go in separately,
I can send change below (v2 for [0] above) on top of yours
thanks,
jirka
---
tools/bpf/bpftool/map.c | 31 +++++++++++++------------------
1 file changed, 13 insertions(+), 18 deletions(-)
diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
index c66a3c979b7a..8562add7417d 100644
--- a/tools/bpf/bpftool/map.c
+++ b/tools/bpf/bpftool/map.c
@@ -805,29 +805,28 @@ static int maps_have_btf(int *fds, int nb_fds)
static struct btf *btf_vmlinux;
-static struct btf *get_map_kv_btf(const struct bpf_map_info *info)
+static int get_map_kv_btf(const struct bpf_map_info *info, struct btf **btf)
{
- struct btf *btf = NULL;
+ int err = 0;
if (info->btf_vmlinux_value_type_id) {
if (!btf_vmlinux) {
btf_vmlinux = libbpf_find_kernel_btf();
- if (libbpf_get_error(btf_vmlinux))
+ err = libbpf_get_error(btf_vmlinux);
+ if (err) {
p_err("failed to get kernel btf");
+ return err;
+ }
}
- return btf_vmlinux;
+ *btf = btf_vmlinux;
} else if (info->btf_value_type_id) {
- int err;
-
- btf = btf__load_from_kernel_by_id(info->btf_id);
- err = libbpf_get_error(btf);
- if (err) {
+ *btf = btf__load_from_kernel_by_id(info->btf_id);
+ err = libbpf_get_error(*btf);
+ if (err)
p_err("failed to get btf");
- btf = ERR_PTR(err);
- }
}
- return btf;
+ return err;
}
static void free_map_kv_btf(struct btf *btf)
@@ -862,8 +861,7 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
prev_key = NULL;
if (wtr) {
- btf = get_map_kv_btf(info);
- err = libbpf_get_error(btf);
+ err = get_map_kv_btf(info, &btf);
if (err) {
goto exit_free;
}
@@ -1054,11 +1052,8 @@ static void print_key_value(struct bpf_map_info *info, void *key,
json_writer_t *btf_wtr;
struct btf *btf;
- btf = btf__load_from_kernel_by_id(info->btf_id);
- if (libbpf_get_error(btf)) {
- p_err("failed to get btf");
+ if (get_map_kv_btf(info, &btf))
return;
- }
if (json_output) {
print_entry_json(info, key, value, btf);
--
2.34.1
