From 4e1ea33292ff2ea0a82f52b2600abb4aba752094 Mon Sep 17 00:00:00 2001 From: Martin KaFai Lau Date: Wed, 15 Jan 2020 15:00:44 -0800 Subject: [PATCH] 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 Signed-off-by: Alexei Starovoitov Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20200115230044.1103008-1-kafai@fb.com --- tools/bpf/bpftool/map.c | 61 +++++++++++++++++++++++++++++++++-------- 1 file changed, 50 insertions(+), 11 deletions(-) diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c index 4c5b15d736b6..86f8ab0b7e63 100644 --- a/tools/bpf/bpftool/map.c +++ b/tools/bpf/bpftool/map.c @@ -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; }