Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1// SPDX-License-Identifier: GPL-2.0
2/* Copyright (c) 2024 Google */
3#include <vmlinux.h>
4#include <bpf/bpf_helpers.h>
5#include <bpf/bpf_tracing.h>
6#include "bpf_experimental.h"
7
8char _license[] SEC("license") = "GPL";
9
10#define SLAB_NAME_MAX 32
11
12struct kmem_cache_result {
13 char name[SLAB_NAME_MAX];
14 long obj_size;
15};
16
17struct {
18 __uint(type, BPF_MAP_TYPE_HASH);
19 __uint(key_size, sizeof(void *));
20 __uint(value_size, SLAB_NAME_MAX);
21 __uint(max_entries, 1);
22} slab_hash SEC(".maps");
23
24struct {
25 __uint(type, BPF_MAP_TYPE_ARRAY);
26 __uint(key_size, sizeof(int));
27 __uint(value_size, sizeof(struct kmem_cache_result));
28 __uint(max_entries, 1024);
29} slab_result SEC(".maps");
30
31extern struct kmem_cache *bpf_get_kmem_cache(u64 addr) __ksym;
32
33/* Result, will be checked by userspace */
34int task_struct_found;
35int kmem_cache_seen;
36int open_coded_seen;
37
38SEC("iter/kmem_cache")
39int slab_info_collector(struct bpf_iter__kmem_cache *ctx)
40{
41 struct seq_file *seq = ctx->meta->seq;
42 struct kmem_cache *s = ctx->s;
43 struct kmem_cache_result *r;
44 int idx;
45
46 if (s) {
47 /* To make sure if the slab_iter implements the seq interface
48 * properly and it's also useful for debugging.
49 */
50 BPF_SEQ_PRINTF(seq, "%s: %u\n", s->name, s->size);
51
52 idx = kmem_cache_seen;
53 r = bpf_map_lookup_elem(&slab_result, &idx);
54 if (r == NULL)
55 return 0;
56
57 kmem_cache_seen++;
58
59 /* Save name and size to match /proc/slabinfo */
60 bpf_probe_read_kernel_str(r->name, sizeof(r->name), s->name);
61 r->obj_size = s->size;
62
63 if (!bpf_strncmp(r->name, 11, "task_struct"))
64 bpf_map_update_elem(&slab_hash, &s, r->name, BPF_NOEXIST);
65 }
66
67 return 0;
68}
69
70SEC("raw_tp/bpf_test_finish")
71int BPF_PROG(check_task_struct)
72{
73 u64 curr = bpf_get_current_task();
74 struct kmem_cache *s;
75 char *name;
76
77 s = bpf_get_kmem_cache(curr);
78 if (s == NULL) {
79 task_struct_found = -1;
80 return 0;
81 }
82 name = bpf_map_lookup_elem(&slab_hash, &s);
83 if (name && !bpf_strncmp(name, 11, "task_struct"))
84 task_struct_found = 1;
85 else
86 task_struct_found = -2;
87 return 0;
88}
89
90SEC("syscall")
91int open_coded_iter(const void *ctx)
92{
93 struct kmem_cache *s;
94
95 bpf_for_each(kmem_cache, s) {
96 struct kmem_cache_result *r;
97
98 r = bpf_map_lookup_elem(&slab_result, &open_coded_seen);
99 if (!r)
100 break;
101
102 if (r->obj_size != s->size)
103 break;
104
105 open_coded_seen++;
106 }
107 return 0;
108}