From e3ecf048579afd7a673700d04893671627e85d57 Mon Sep 17 00:00:00 2001
From: Quentin Deslandes <qde@naccy.de>
Date: Wed, 21 Feb 2024 16:16:20 +0100
Subject: [PATCH] ss: pretty-print BPF socket-local storage
ss is able to print the map ID(s) for which a given socket has BPF
socket-local storage defined (using --bpf-maps or --bpf-map-id=). However,
the actual content of the map remains hidden.
This change aims to pretty-print the socket-local storage content following
the socket details, similar to what `bpftool map dump` would do. The exact
output format is inspired by drgn, while the BTF data processing is similar
to bpftool's.
ss will use libbpf's btf_dump__dump_type_data() to ease pretty-printing
of binary data. This requires out_bpf_sk_storage_print_fn() as a print
callback function used by btf_dump__dump_type_data(). vout() is also
introduced, which is similar to out() but accepts a va_list as
parameter.
ss' output remains unchanged unless --bpf-maps or --bpf-map-id= is used,
in which case each socket containing BPF local storage will be followed by
the content of the storage before the next socket's info is displayed.
Signed-off-by: Quentin Deslandes <qde@naccy.de>
Acked-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: David Ahern <dsahern@kernel.org>
---
misc/ss.c | 148 ++++++++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 137 insertions(+), 11 deletions(-)
diff --git a/misc/ss.c b/misc/ss.c
index 2c7e7c58..3ebac132 100644
--- a/misc/ss.c
+++ b/misc/ss.c
@@ -61,7 +61,9 @@
#define ENABLE_BPF_SKSTORAGE_SUPPORT
#include <bpf/bpf.h>
+#include <bpf/btf.h>
#include <bpf/libbpf.h>
+#include <linux/btf.h>
#if (LIBBPF_MAJOR_VERSION == 0) && (LIBBPF_MINOR_VERSION < 5)
#warning "libbpf version 0.5 or later is required, disabling BPF socket-local storage support"
@@ -1053,11 +1055,10 @@ static int buf_update(int len)
}
/* Append content to buffer as part of the current field */
-__attribute__((format(printf, 1, 2)))
-static void out(const char *fmt, ...)
+static void vout(const char *fmt, va_list args)
{
struct column *f = current_field;
- va_list args;
+ va_list _args;
char *pos;
int len;
@@ -1068,18 +1069,27 @@ static void out(const char *fmt, ...)
buffer.head = buf_chunk_new();
again: /* Append to buffer: if we have a new chunk, print again */
+ va_copy(_args, args);
pos = buffer.cur->data + buffer.cur->len;
- va_start(args, fmt);
/* Limit to tail room. If we hit the limit, buf_update() will tell us */
- len = vsnprintf(pos, buf_chunk_avail(buffer.tail), fmt, args);
- va_end(args);
+ len = vsnprintf(pos, buf_chunk_avail(buffer.tail), fmt, _args);
if (buf_update(len))
goto again;
}
+__attribute__((format(printf, 1, 2)))
+static void out(const char *fmt, ...)
+{
+ va_list args;
+
+ va_start(args, fmt);
+ vout(fmt, args);
+ va_end(args);
+}
+
static int print_left_spacing(struct column *f, int stored, int printed)
{
int s;
@@ -3413,6 +3423,9 @@ static struct bpf_map_opts {
struct bpf_sk_storage_map_info {
unsigned int id;
int fd;
+ struct bpf_map_info info;
+ struct btf *btf;
+ struct btf_dump *dump;
} maps[MAX_NR_BPF_MAP_ID_OPTS];
bool show_all;
} bpf_map_opts;
@@ -3423,10 +3436,36 @@ static void bpf_map_opts_mixed_error(void)
"ss: --bpf-maps and --bpf-map-id cannot be used together\n");
}
+static int bpf_maps_opts_load_btf(struct bpf_map_info *info, struct btf **btf)
+{
+ if (info->btf_value_type_id) {
+ *btf = btf__load_from_kernel_by_id(info->btf_id);
+ if (!*btf) {
+ fprintf(stderr, "ss: failed to load BTF for map ID %u\n",
+ info->id);
+ return -1;
+ }
+ } else {
+ *btf = NULL;
+ }
+
+ return 0;
+}
+
+static void out_bpf_sk_storage_print_fn(void *ctx, const char *fmt, va_list args)
+{
+ vout(fmt, args);
+}
+
static int bpf_map_opts_load_info(unsigned int map_id)
{
+ struct btf_dump_opts dopts = {
+ .sz = sizeof(struct btf_dump_opts)
+ };
struct bpf_map_info info = {};
uint32_t len = sizeof(info);
+ struct btf_dump *dump;
+ struct btf *btf;
int fd;
int r;
@@ -3464,8 +3503,25 @@ static int bpf_map_opts_load_info(unsigned int map_id)
return -1;
}
+ r = bpf_maps_opts_load_btf(&info, &btf);
+ if (r) {
+ close(fd);
+ return -1;
+ }
+
+ dump = btf_dump__new(btf, out_bpf_sk_storage_print_fn, NULL, &dopts);
+ if (!dump) {
+ btf__free(btf);
+ close(fd);
+ fprintf(stderr, "Failed to create btf_dump object\n");
+ return -1;
+ }
+
bpf_map_opts.maps[bpf_map_opts.nr_maps].id = map_id;
- bpf_map_opts.maps[bpf_map_opts.nr_maps++].fd = fd;
+ bpf_map_opts.maps[bpf_map_opts.nr_maps].fd = fd;
+ bpf_map_opts.maps[bpf_map_opts.nr_maps].info = info;
+ bpf_map_opts.maps[bpf_map_opts.nr_maps].btf = btf;
+ bpf_map_opts.maps[bpf_map_opts.nr_maps++].dump = dump;
return 0;
}
@@ -3517,8 +3573,11 @@ static void bpf_map_opts_destroy(void)
{
int i;
- for (i = 0; i < bpf_map_opts.nr_maps; ++i)
+ for (i = 0; i < bpf_map_opts.nr_maps; ++i) {
+ btf_dump__free(bpf_map_opts.maps[i].dump);
+ btf__free(bpf_map_opts.maps[i].btf);
close(bpf_map_opts.maps[i].fd);
+ }
}
static struct rtattr *bpf_map_opts_alloc_rta(void)
@@ -3571,10 +3630,74 @@ static struct rtattr *bpf_map_opts_alloc_rta(void)
return stgs_rta;
}
+static void out_bpf_sk_storage_oneline(struct bpf_sk_storage_map_info *info,
+ const void *data, size_t len)
+{
+ struct btf_dump_type_data_opts opts = {
+ .sz = sizeof(struct btf_dump_type_data_opts),
+ .emit_zeroes = 1,
+ .compact = 1
+ };
+ int r;
+
+ out(" map_id:%d", info->id);
+ r = btf_dump__dump_type_data(info->dump, info->info.btf_value_type_id,
+ data, len, &opts);
+ if (r < 0)
+ out("failed to dump data: %d", r);
+}
+
+static void out_bpf_sk_storage_multiline(struct bpf_sk_storage_map_info *info,
+ const void *data, size_t len)
+{
+ struct btf_dump_type_data_opts opts = {
+ .sz = sizeof(struct btf_dump_type_data_opts),
+ .indent_level = 2,
+ .emit_zeroes = 1
+ };
+ int r;
+
+ out("\n\tmap_id:%d [\n", info->id);
+
+ r = btf_dump__dump_type_data(info->dump, info->info.btf_value_type_id,
+ data, len, &opts);
+ if (r < 0)
+ out("\t\tfailed to dump data: %d", r);
+
+ out("\n\t]");
+}
+
+static void out_bpf_sk_storage(int map_id, const void *data, size_t len)
+{
+ struct bpf_sk_storage_map_info *map_info;
+
+ map_info = bpf_map_opts_get_info(map_id);
+ if (!map_info) {
+ /* The kernel might return a map we can't get info for, skip
+ * it but print the other ones.
+ */
+ out("\n\tmap_id: %d failed to fetch info, skipping\n", map_id);
+ return;
+ }
+
+ if (map_info->info.value_size != len) {
+ fprintf(stderr,
+ "map_id: %d: invalid value size, expecting %u, got %lu\n",
+ map_id, map_info->info.value_size, len);
+ return;
+ }
+
+ if (oneline)
+ out_bpf_sk_storage_oneline(map_info, data, len);
+ else
+ out_bpf_sk_storage_multiline(map_info, data, len);
+}
+
static void show_sk_bpf_storages(struct rtattr *bpf_stgs)
{
struct rtattr *tb[SK_DIAG_BPF_STORAGE_MAX + 1], *bpf_stg;
- unsigned int rem;
+ unsigned int rem, map_id;
+ struct rtattr *value;
for (bpf_stg = RTA_DATA(bpf_stgs), rem = RTA_PAYLOAD(bpf_stgs);
RTA_OK(bpf_stg, rem); bpf_stg = RTA_NEXT(bpf_stg, rem)) {
@@ -3586,8 +3709,11 @@ static void show_sk_bpf_storages(struct rtattr *bpf_stgs)
(struct rtattr *)bpf_stg);
if (tb[SK_DIAG_BPF_STORAGE_MAP_ID]) {
- out(" map_id:%u",
- rta_getattr_u32(tb[SK_DIAG_BPF_STORAGE_MAP_ID]));
+ map_id = rta_getattr_u32(tb[SK_DIAG_BPF_STORAGE_MAP_ID]);
+ value = tb[SK_DIAG_BPF_STORAGE_MAP_VALUE];
+
+ out_bpf_sk_storage(map_id, RTA_DATA(value),
+ RTA_PAYLOAD(value));
}
}
}
--
2.41.0