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libbpf: support BPF token path setting through LIBBPF_BPF_TOKEN_PATH envvar

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To allow external admin authority to override default BPF FS location
(/sys/fs/bpf) for implicit BPF token creation, teach libbpf to recognize
LIBBPF_BPF_TOKEN_PATH envvar. If it is specified and user application
didn't explicitly specify neither bpf_token_path nor bpf_token_fd
option, it will be treated exactly like bpf_token_path option,
overriding default /sys/fs/bpf location and making BPF token mandatory.

Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20231213190842.3844987-10-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrii Nakryiko 2023-12-13 11:08:41 -08:00 committed by Alexei Starovoitov
parent 18678cf0ee
commit ed54124b88
2 changed files with 21 additions and 6 deletions
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14
tools/lib/bpf/libbpf.c
View file

@ -7171,11 +7171,17 @@ static struct bpf_object *bpf_object_open(const char *path, const void *obj_buf,
/* non-empty token path can't be combined with invalid token FD */
if (token_path && token_path[0] != '\0' && token_fd < 0)
return ERR_PTR(-EINVAL);
/* empty token path can't be combined with valid token FD */
if (token_path && token_path[0] == '\0' && token_fd > 0)
return ERR_PTR(-EINVAL);
/* if user didn't specify bpf_token_path/bpf_token_fd explicitly,
* check if LIBBPF_BPF_TOKEN_PATH envvar was set and treat it as
* bpf_token_path option
*/
if (token_fd == 0 && !token_path)
token_path = getenv("LIBBPF_BPF_TOKEN_PATH");
/* empty token_path is equivalent to invalid token_fd */
if (token_path && token_path[0] == '\0') {
/* empty token path can't be combined with valid token FD */
if (token_fd > 0)
return ERR_PTR(-EINVAL);
/* empty token_path is equivalent to invalid token_fd */
token_path = NULL;
token_fd = -1;
}

13
tools/lib/bpf/libbpf.h
View file

@ -185,8 +185,16 @@ struct bpf_object_open_opts {
* attempt to create BPF token from default BPF FS mount point
* (/sys/fs/bpf), in case this default behavior is undesirable.
*
* If bpf_token_path and bpf_token_fd are not specified, libbpf will
* consult LIBBPF_BPF_TOKEN_PATH environment variable. If set, it will
* be taken as a value of bpf_token_path option and will force libbpf
* to either create BPF token from provided custom BPF FS path, or
* will disable implicit BPF token creation, if envvar value is an
* empty string.
*
* bpf_token_path and bpf_token_fd are mutually exclusive and only one
* of those options should be set.
* of those options should be set. Either of them overrides
* LIBBPF_BPF_TOKEN_PATH envvar.
*/
int bpf_token_fd;
/* Path to BPF FS mount point to derive BPF token from.
@ -200,7 +208,8 @@ struct bpf_object_open_opts {
* point (/sys/fs/bpf), in case this default behavior is undesirable.
*
* bpf_token_path and bpf_token_fd are mutually exclusive and only one
* of those options should be set.
* of those options should be set. Either of them overrides
* LIBBPF_BPF_TOKEN_PATH envvar.
*/
const char *bpf_token_path;