This is a note to let you know that I've just added the patch titled
bpftool: Fix missing pids during link show
to the 6.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
bpftool-fix-missing-pids-during-link-show.patch
and it can be found in the queue-6.8 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 746b457a60fe264b40d0159057758f376947e969
Author: Yonghong Song <yonghong.song@xxxxxxxxx>
Date: Mon Mar 11 19:32:49 2024 -0700
bpftool: Fix missing pids during link show
[ 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@xxxxxxxxx>
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Tested-by: Quentin Monnet <quentin@xxxxxxxxxxxxx>
Reviewed-by: Quentin Monnet <quentin@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/bpf/20240312023249.3776718-1-yonghong.song@xxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/tools/bpf/bpftool/skeleton/pid_iter.bpf.c b/tools/bpf/bpftool/skeleton/pid_iter.bpf.c
index 26004f0c5a6ae..7bdbcac3cf628 100644
--- a/tools/bpf/bpftool/skeleton/pid_iter.bpf.c
+++ b/tools/bpf/bpftool/skeleton/pid_iter.bpf.c
@@ -102,8 +102,8 @@ int iter(struct bpf_iter__task_file *ctx)
BPF_LINK_TYPE_PERF_EVENT___local)) {
struct bpf_link *link = (struct bpf_link *) file->private_data;
- if (link->type == bpf_core_enum_value(enum bpf_link_type___local,
- BPF_LINK_TYPE_PERF_EVENT___local)) {
+ if (BPF_CORE_READ(link, type) == bpf_core_enum_value(enum bpf_link_type___local,
+ BPF_LINK_TYPE_PERF_EVENT___local)) {
e.has_bpf_cookie = true;
e.bpf_cookie = get_bpf_cookie(link);
}
