diff options
| author | Kui-Feng Lee <thinker.li@gmail.com> | 2024-03-13 22:41:37 +0100 |
|---|---|---|
| committer | Andrii Nakryiko <andrii@kernel.org> | 2024-03-14 21:47:05 +0100 |
| commit | c911fc61a7ce367f9ea48e457f31bb171e80ca4d (patch) | |
| tree | 80958ee01093375725f14731119423303eee93b0 /tools/lib | |
| parent | libbpf: Prevent null-pointer dereference when prog to load has no BTF (diff) | |
| download | linux-c911fc61a7ce367f9ea48e457f31bb171e80ca4d.tar.xz linux-c911fc61a7ce367f9ea48e457f31bb171e80ca4d.zip | |
libbpf: Skip zeroed or null fields if not found in the kernel type.
Accept additional fields of a struct_ops type with all zero values even if
these fields are not in the corresponding type in the kernel. This provides
a way to be backward compatible. User space programs can use the same map
on a machine running an old kernel by clearing fields that do not exist in
the kernel.
Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240313214139.685112-2-thinker.li@gmail.com
Diffstat (limited to 'tools/lib')
| -rw-r--r-- | tools/lib/bpf/libbpf.c | 24 |
1 files changed, 19 insertions, 5 deletions
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 124883eaa0cf..604368cfbf02 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -1132,8 +1132,26 @@ static int bpf_map__init_kern_struct_ops(struct bpf_map *map) const char *mname; mname = btf__name_by_offset(btf, member->name_off); + moff = member->offset / 8; + mdata = data + moff; + msize = btf__resolve_size(btf, member->type); + if (msize < 0) { + pr_warn("struct_ops init_kern %s: failed to resolve the size of member %s\n", + map->name, mname); + return msize; + } + kern_member = find_member_by_name(kern_btf, kern_type, mname); if (!kern_member) { + /* Skip all zeros or null fields if they are not + * presented in the kernel BTF. + */ + if (libbpf_is_mem_zeroed(mdata, msize)) { + pr_info("struct_ops %s: member %s not found in kernel, skipping it as it's set to zero\n", + map->name, mname); + continue; + } + pr_warn("struct_ops init_kern %s: Cannot find member %s in kernel BTF\n", map->name, mname); return -ENOTSUP; @@ -1147,10 +1165,7 @@ static int bpf_map__init_kern_struct_ops(struct bpf_map *map) return -ENOTSUP; } - moff = member->offset / 8; kern_moff = kern_member->offset / 8; - - mdata = data + moff; kern_mdata = kern_data + kern_moff; mtype = skip_mods_and_typedefs(btf, member->type, &mtype_id); @@ -1230,9 +1245,8 @@ static int bpf_map__init_kern_struct_ops(struct bpf_map *map) continue; } - msize = btf__resolve_size(btf, mtype_id); kern_msize = btf__resolve_size(kern_btf, kern_mtype_id); - if (msize < 0 || kern_msize < 0 || msize != kern_msize) { + if (kern_msize < 0 || msize != kern_msize) { pr_warn("struct_ops init_kern %s: Error in size of member %s: %zd != %zd(kernel)\n", map->name, mname, (ssize_t)msize, (ssize_t)kern_msize); |