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bpftool: Support dumping a map with btf_vmlinux_value_type_id 

This patch makes bpftool support dumping a map's value properly
when the map's value type is a type of the running kernel's btf.
(i.e. map_info.btf_vmlinux_value_type_id is set instead of
map_info.btf_value_type_id).  The first usecase is for the
BPF_MAP_TYPE_STRUCT_OPS.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200115230044.1103008-1-kafai@fb.com
This commit is contained in:
Martin KaFai Lau 2020-01-15 15:00:44 -08:00 committed by Alexei Starovoitov
parent 84c72ceee9
commit 4e1ea33292
1 changed files with 50 additions and 11 deletions
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61
tools/bpf/bpftool/map.c
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@ -252,6 +252,7 @@ static int do_dump_btf(const struct btf_dumper *d,
struct bpf_map_info *map_info, void *key,
void *value)
{
__u32 value_id;
int ret;
/* start of key-value pair */
@ -265,9 +266,12 @@ static int do_dump_btf(const struct btf_dumper *d,
goto err_end_obj;
}
value_id = map_info->btf_vmlinux_value_type_id ?
: map_info->btf_value_type_id;
if (!map_is_per_cpu(map_info->type)) {
jsonw_name(d->jw, "value");
ret = btf_dumper_type(d, map_info->btf_value_type_id, value);
ret = btf_dumper_type(d, value_id, value);
} else {
unsigned int i, n, step;
@ -279,8 +283,7 @@ static int do_dump_btf(const struct btf_dumper *d,
jsonw_start_object(d->jw);
jsonw_int_field(d->jw, "cpu", i);
jsonw_name(d->jw, "value");
ret = btf_dumper_type(d, map_info->btf_value_type_id,
value + i * step);
ret = btf_dumper_type(d, value_id, value + i * step);
jsonw_end_object(d->jw);
if (ret)
break;
@ -932,6 +935,44 @@ static int maps_have_btf(int *fds, int nb_fds)
return 1;
}
static struct btf *btf_vmlinux;
static struct btf *get_map_kv_btf(const struct bpf_map_info *info)
{
struct btf *btf = NULL;
if (info->btf_vmlinux_value_type_id) {
if (!btf_vmlinux) {
btf_vmlinux = libbpf_find_kernel_btf();
if (IS_ERR(btf_vmlinux))
p_err("failed to get kernel btf");
}
return btf_vmlinux;
} else if (info->btf_value_type_id) {
int err;
err = btf__get_from_id(info->btf_id, &btf);
if (err || !btf) {
p_err("failed to get btf");
btf = err ? ERR_PTR(err) : ERR_PTR(-ESRCH);
}
}
return btf;
}
static void free_map_kv_btf(struct btf *btf)
{
if (!IS_ERR(btf) && btf != btf_vmlinux)
btf__free(btf);
}
static void free_btf_vmlinux(void)
{
if (!IS_ERR(btf_vmlinux))
btf__free(btf_vmlinux);
}
static int
map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
bool show_header)
@ -952,13 +993,10 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
prev_key = NULL;
if (wtr) {
if (info->btf_id) {
err = btf__get_from_id(info->btf_id, &btf);
if (err || !btf) {
err = err ? : -ESRCH;
p_err("failed to get btf");
goto exit_free;
}
btf = get_map_kv_btf(info);
if (IS_ERR(btf)) {
err = PTR_ERR(btf);
goto exit_free;
}
if (show_header) {
@ -999,7 +1037,7 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
free(key);
free(value);
close(fd);
btf__free(btf);
free_map_kv_btf(btf);
return err;
}
@ -1067,6 +1105,7 @@ static int do_dump(int argc, char **argv)
close(fds[i]);
exit_free:
free(fds);
free_btf_vmlinux();
return err;
}