bpf: add bpffs pretty print for percpu arraymap/hash/lru_hash

Added bpffs pretty print for percpu arraymap, percpu hashmap
and percpu lru hashmap.

For each map <key, value> pair, the format is:
   <key_value>: {
	cpu0: <value_on_cpu0>
	cpu1: <value_on_cpu1>
	...
	cpun: <value_on_cpun>
   }

For example, on my VM, there are 4 cpus, and
for test_btf test in the next patch:
   cat /sys/fs/bpf/pprint_test_percpu_hash

You may get:
   ...
   43602: {
	cpu0: {43602,0,-43602,0x3,0xaa52,0x3,{43602|[82,170,0,0,0,0,0,0]},ENUM_TWO}
	cpu1: {43602,0,-43602,0x3,0xaa52,0x3,{43602|[82,170,0,0,0,0,0,0]},ENUM_TWO}
	cpu2: {43602,0,-43602,0x3,0xaa52,0x3,{43602|[82,170,0,0,0,0,0,0]},ENUM_TWO}
	cpu3: {43602,0,-43602,0x3,0xaa52,0x3,{43602|[82,170,0,0,0,0,0,0]},ENUM_TWO}
   }
   72847: {
	cpu0: {72847,0,-72847,0x3,0x11c8f,0x3,{72847|[143,28,1,0,0,0,0,0]},ENUM_THREE}
	cpu1: {72847,0,-72847,0x3,0x11c8f,0x3,{72847|[143,28,1,0,0,0,0,0]},ENUM_THREE}
	cpu2: {72847,0,-72847,0x3,0x11c8f,0x3,{72847|[143,28,1,0,0,0,0,0]},ENUM_THREE}
	cpu3: {72847,0,-72847,0x3,0x11c8f,0x3,{72847|[143,28,1,0,0,0,0,0]},ENUM_THREE}
   }
   ...

Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 24 insertions, 0 deletions

diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 0c17aab3ce5f..f9d24121be99 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -358,6 +358,29 @@ static void array_map_seq_show_elem(struct bpf_map *map, void *key,
         rcu_read_unlock();
 }
 
+static void percpu_array_map_seq_show_elem(struct bpf_map *map, void *key,
+                                           struct seq_file *m)
+{
+        struct bpf_array *array = container_of(map, struct bpf_array, map);
+        u32 index = *(u32 *)key;
+        void __percpu *pptr;
+        int cpu;
+
+        rcu_read_lock();
+
+        seq_printf(m, "%u: {\n", *(u32 *)key);
+        pptr = array->pptrs[index & array->index_mask];
+        for_each_possible_cpu(cpu) {
+                seq_printf(m, "\tcpu%d: ", cpu);
+                btf_type_seq_show(map->btf, map->btf_value_type_id,
+                                  per_cpu_ptr(pptr, cpu), m);
+                seq_puts(m, "\n");
+        }
+        seq_puts(m, "}\n");
+
+        rcu_read_unlock();
+}
+
 static int array_map_check_btf(const struct bpf_map *map,
                                const struct btf_type *key_type,
                                const struct btf_type *value_type)
@@ -398,6 +421,7 @@ const struct bpf_map_ops percpu_array_map_ops = {
         .map_lookup_elem = percpu_array_map_lookup_elem,
         .map_update_elem = array_map_update_elem,
         .map_delete_elem = array_map_delete_elem,
+        .map_seq_show_elem = percpu_array_map_seq_show_elem,
         .map_check_btf = array_map_check_btf,
 };