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The test traverses all slab caches using the kmem_cache_iter and save the data into slab_result array map. And check if current task's pointer is from "task_struct" slab cache using bpf_get_kmem_cache(). Also compare the result array with /proc/slabinfo if available (when CONFIG_SLUB_DEBUG is on). Note that many of the fields in the slabinfo are transient, so it only compares the name and objsize fields. Signed-off-by: Namhyung Kim <namhyung@kernel.org> Link: https://lore.kernel.org/r/20241010232505.1339892-4-namhyung@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org>
88 lines
1.9 KiB
C
88 lines
1.9 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/* Copyright (c) 2024 Google */
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#include "bpf_iter.h"
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#include <bpf/bpf_helpers.h>
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#include <bpf/bpf_tracing.h>
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char _license[] SEC("license") = "GPL";
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#define SLAB_NAME_MAX 32
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struct kmem_cache_result {
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char name[SLAB_NAME_MAX];
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long obj_size;
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};
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struct {
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__uint(type, BPF_MAP_TYPE_HASH);
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__uint(key_size, sizeof(void *));
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__uint(value_size, SLAB_NAME_MAX);
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__uint(max_entries, 1);
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} slab_hash SEC(".maps");
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struct {
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__uint(type, BPF_MAP_TYPE_ARRAY);
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__uint(key_size, sizeof(int));
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__uint(value_size, sizeof(struct kmem_cache_result));
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__uint(max_entries, 1024);
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} slab_result SEC(".maps");
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extern struct kmem_cache *bpf_get_kmem_cache(u64 addr) __ksym;
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/* Result, will be checked by userspace */
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int task_struct_found;
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int kmem_cache_seen;
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SEC("iter/kmem_cache")
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int slab_info_collector(struct bpf_iter__kmem_cache *ctx)
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{
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struct seq_file *seq = ctx->meta->seq;
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struct kmem_cache *s = ctx->s;
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struct kmem_cache_result *r;
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int idx;
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if (s) {
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/* To make sure if the slab_iter implements the seq interface
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* properly and it's also useful for debugging.
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*/
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BPF_SEQ_PRINTF(seq, "%s: %u\n", s->name, s->size);
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idx = kmem_cache_seen;
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r = bpf_map_lookup_elem(&slab_result, &idx);
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if (r == NULL)
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return 0;
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kmem_cache_seen++;
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/* Save name and size to match /proc/slabinfo */
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bpf_probe_read_kernel_str(r->name, sizeof(r->name), s->name);
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r->obj_size = s->size;
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if (!bpf_strncmp(r->name, 11, "task_struct"))
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bpf_map_update_elem(&slab_hash, &s, r->name, BPF_NOEXIST);
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}
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return 0;
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}
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SEC("raw_tp/bpf_test_finish")
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int BPF_PROG(check_task_struct)
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{
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u64 curr = bpf_get_current_task();
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struct kmem_cache *s;
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char *name;
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s = bpf_get_kmem_cache(curr);
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if (s == NULL) {
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task_struct_found = -1;
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return 0;
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}
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name = bpf_map_lookup_elem(&slab_hash, &s);
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if (name && !bpf_strncmp(name, 11, "task_struct"))
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task_struct_found = 1;
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else
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task_struct_found = -2;
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return 0;
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}
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