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https://gitee.com/bianbu-linux/linux-6.6
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67a43462ee
When building bpftool with !CONFIG_PERF_EVENTS:
skeleton/pid_iter.bpf.c:47:14: error: incomplete definition of type 'struct bpf_perf_link'
perf_link = container_of(link, struct bpf_perf_link, link);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
tools/bpf/bpftool/bootstrap/libbpf/include/bpf/bpf_helpers.h:74:22: note: expanded from macro 'container_of'
((type *)(__mptr - offsetof(type, member))); \
^~~~~~~~~~~~~~~~~~~~~~
tools/bpf/bpftool/bootstrap/libbpf/include/bpf/bpf_helpers.h:68:60: note: expanded from macro 'offsetof'
#define offsetof(TYPE, MEMBER) ((unsigned long)&((TYPE *)0)->MEMBER)
~~~~~~~~~~~^
skeleton/pid_iter.bpf.c:44:9: note: forward declaration of 'struct bpf_perf_link'
struct bpf_perf_link *perf_link;
^
&bpf_perf_link is being defined and used only under the ifdef.
Define struct bpf_perf_link___local with the `preserve_access_index`
attribute inside the pid_iter BPF prog to allow compiling on any
configs. CO-RE will substitute it with the real struct bpf_perf_link
accesses later on.
container_of() uses offsetof(), which does the necessary CO-RE
relocation if the field is specified with `preserve_access_index` - as
is the case for struct bpf_perf_link___local.
Fixes: cbdaf71f7e ("bpftool: Add bpf_cookie to link output")
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexander Lobakin <alobakin@pm.me>
Signed-off-by: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230707095425.168126-3-quentin@isovalent.com
112 lines
2.6 KiB
C
112 lines
2.6 KiB
C
// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
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/* Copyright (c) 2020 Facebook */
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#include <vmlinux.h>
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#include <bpf/bpf_helpers.h>
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#include <bpf/bpf_core_read.h>
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#include <bpf/bpf_tracing.h>
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#include "pid_iter.h"
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/* keep in sync with the definition in main.h */
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enum bpf_obj_type {
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BPF_OBJ_UNKNOWN,
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BPF_OBJ_PROG,
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BPF_OBJ_MAP,
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BPF_OBJ_LINK,
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BPF_OBJ_BTF,
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};
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struct bpf_perf_link___local {
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struct bpf_link link;
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struct file *perf_file;
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} __attribute__((preserve_access_index));
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struct perf_event___local {
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u64 bpf_cookie;
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} __attribute__((preserve_access_index));
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extern const void bpf_link_fops __ksym;
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extern const void bpf_map_fops __ksym;
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extern const void bpf_prog_fops __ksym;
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extern const void btf_fops __ksym;
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const volatile enum bpf_obj_type obj_type = BPF_OBJ_UNKNOWN;
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static __always_inline __u32 get_obj_id(void *ent, enum bpf_obj_type type)
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{
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switch (type) {
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case BPF_OBJ_PROG:
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return BPF_CORE_READ((struct bpf_prog *)ent, aux, id);
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case BPF_OBJ_MAP:
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return BPF_CORE_READ((struct bpf_map *)ent, id);
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case BPF_OBJ_BTF:
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return BPF_CORE_READ((struct btf *)ent, id);
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case BPF_OBJ_LINK:
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return BPF_CORE_READ((struct bpf_link *)ent, id);
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default:
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return 0;
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}
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}
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/* could be used only with BPF_LINK_TYPE_PERF_EVENT links */
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static __u64 get_bpf_cookie(struct bpf_link *link)
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{
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struct bpf_perf_link___local *perf_link;
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struct perf_event___local *event;
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perf_link = container_of(link, struct bpf_perf_link___local, link);
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event = BPF_CORE_READ(perf_link, perf_file, private_data);
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return BPF_CORE_READ(event, bpf_cookie);
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}
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SEC("iter/task_file")
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int iter(struct bpf_iter__task_file *ctx)
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{
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struct file *file = ctx->file;
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struct task_struct *task = ctx->task;
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struct pid_iter_entry e;
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const void *fops;
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if (!file || !task)
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return 0;
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switch (obj_type) {
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case BPF_OBJ_PROG:
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fops = &bpf_prog_fops;
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break;
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case BPF_OBJ_MAP:
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fops = &bpf_map_fops;
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break;
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case BPF_OBJ_BTF:
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fops = &btf_fops;
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break;
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case BPF_OBJ_LINK:
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fops = &bpf_link_fops;
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break;
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default:
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return 0;
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}
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if (file->f_op != fops)
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return 0;
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__builtin_memset(&e, 0, sizeof(e));
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e.pid = task->tgid;
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e.id = get_obj_id(file->private_data, obj_type);
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if (obj_type == BPF_OBJ_LINK) {
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struct bpf_link *link = (struct bpf_link *) file->private_data;
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if (BPF_CORE_READ(link, type) == BPF_LINK_TYPE_PERF_EVENT) {
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e.has_bpf_cookie = true;
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e.bpf_cookie = get_bpf_cookie(link);
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}
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}
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bpf_probe_read_kernel_str(&e.comm, sizeof(e.comm),
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task->group_leader->comm);
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bpf_seq_write(ctx->meta->seq, &e, sizeof(e));
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return 0;
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}
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char LICENSE[] SEC("license") = "Dual BSD/GPL";
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