95aa4299fc
[ Upstream commit fe879bb42f8a6513ed18e9d22efb99cb35590201 ]
Current 'bpftool link' command does not show pids, e.g.,
$ tools/build/bpftool/bpftool link
...
4: tracing prog 23
prog_type lsm attach_type lsm_mac
target_obj_id 1 target_btf_id 31320
Hack the following change to enable normal libbpf debug output,
# --- a/tools/bpf/bpftool/pids.c
# +++ b/tools/bpf/bpftool/pids.c
# @@ -121,9 +121,9 @@ int build_obj_refs_table(struct hashmap **map, enum bpf_obj_type type)
# /* we don't want output polluted with libbpf errors if bpf_iter is not
# * supported
# */
# - default_print = libbpf_set_print(libbpf_print_none);
# + /* default_print = libbpf_set_print(libbpf_print_none); */
# err = pid_iter_bpf__load(skel);
# - libbpf_set_print(default_print);
# + /* libbpf_set_print(default_print); */
Rerun the above bpftool command:
$ tools/build/bpftool/bpftool link
libbpf: prog 'iter': BPF program load failed: Permission denied
libbpf: prog 'iter': -- BEGIN PROG LOAD LOG --
0: R1=ctx() R10=fp0
; struct task_struct *task = ctx->task; @ pid_iter.bpf.c:69
0: (79) r6 = *(u64 *)(r1 +8) ; R1=ctx() R6_w=ptr_or_null_task_struct(id=1)
; struct file *file = ctx->file; @ pid_iter.bpf.c:68
...
; struct bpf_link *link = (struct bpf_link *) file->private_data; @ pid_iter.bpf.c:103
80: (79) r3 = *(u64 *)(r8 +432) ; R3_w=scalar() R8=ptr_file()
; if (link->type == bpf_core_enum_value(enum bpf_link_type___local, @ pid_iter.bpf.c:105
81: (61) r1 = *(u32 *)(r3 +12)
R3 invalid mem access 'scalar'
processed 39 insns (limit 1000000) max_states_per_insn 0 total_states 3 peak_states 3 mark_read 2
-- END PROG LOAD LOG --
libbpf: prog 'iter': failed to load: -13
...
The 'file->private_data' returns a 'void' type and this caused subsequent 'link->type'
(insn #81) failed in verification.
To fix the issue, restore the previous BPF_CORE_READ so old kernels can also work.
With this patch, the 'bpftool link' runs successfully with 'pids'.
$ tools/build/bpftool/bpftool link
...
4: tracing prog 23
prog_type lsm attach_type lsm_mac
target_obj_id 1 target_btf_id 31320
pids systemd(1)
Fixes: 44ba7b30e84f ("bpftool: Use a local copy of BPF_LINK_TYPE_PERF_EVENT in pid_iter.bpf.c")
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Tested-by: Quentin Monnet <quentin@isovalent.com>
Reviewed-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/bpf/20240312023249.3776718-1-yonghong.song@linux.dev
Signed-off-by: Sasha Levin <sashal@kernel.org>
120 lines
2.8 KiB
C
120 lines
2.8 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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enum bpf_link_type___local {
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BPF_LINK_TYPE_PERF_EVENT___local = 7,
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};
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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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bpf_core_enum_value_exists(enum bpf_link_type___local,
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BPF_LINK_TYPE_PERF_EVENT___local)) {
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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_core_enum_value(enum bpf_link_type___local,
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BPF_LINK_TYPE_PERF_EVENT___local)) {
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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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