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libbpf: Allow passing user log setting through bpf_object_open_opts

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Allow users to provide their own custom log_buf, log_size, and log_level
at bpf_object level through bpf_object_open_opts. This log_buf will be
used during BTF loading. Subsequent patch will use same log_buf during
BPF program loading, unless overriden at per-bpf_program level.

When such custom log_buf is provided, libbpf won't be attempting
retrying loading of BTF to try to provide its own log buffer to capture
kernel's error log output. User is responsible to provide big enough
buffer, otherwise they run a risk of getting -ENOSPC error from the
bpf() syscall.

See also comments in bpf_object_open_opts regarding log_level and
log_buf interactions.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211209193840.1248570-5-andrii@kernel.org
This commit is contained in:
Andrii Nakryiko
2021-12-09 11:38:32 -08:00
parent 1a190d1e8e
commit e0e3ea888c
3 changed files with 65 additions and 3 deletions
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24
tools/lib/bpf/libbpf.c
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@@ -573,6 +573,11 @@ struct bpf_object {
size_t btf_module_cnt;
size_t btf_module_cap;
/* optional log settings passed to BPF_BTF_LOAD and BPF_PROG_LOAD commands */
char *log_buf;
size_t log_size;
__u32 log_level;
void *priv;
bpf_object_clear_priv_t clear_priv;
@@ -3017,7 +3022,9 @@ static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj)
*/
btf__set_fd(kern_btf, 0);
} else {
err = btf__load_into_kernel(kern_btf);
/* currently BPF_BTF_LOAD only supports log_level 1 */
err = btf_load_into_kernel(kern_btf, obj->log_buf, obj->log_size,
obj->log_level ? 1 : 0);
}
if (sanitize) {
if (!err) {
@@ -6932,6 +6939,9 @@ __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,
struct bpf_object *obj;
char tmp_name[64];
int err;
char *log_buf;
size_t log_size;
__u32 log_level;
if (elf_version(EV_CURRENT) == EV_NONE) {
pr_warn("failed to init libelf for %s\n",
@@ -6954,10 +6964,22 @@ __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,
pr_debug("loading object '%s' from buffer\n", obj_name);
}
log_buf = OPTS_GET(opts, kernel_log_buf, NULL);
log_size = OPTS_GET(opts, kernel_log_size, 0);
log_level = OPTS_GET(opts, kernel_log_level, 0);
if (log_size > UINT_MAX)
return ERR_PTR(-EINVAL);
if (log_size && !log_buf)
return ERR_PTR(-EINVAL);
obj = bpf_object__new(path, obj_buf, obj_buf_sz, obj_name);
if (IS_ERR(obj))
return obj;
obj->log_buf = log_buf;
obj->log_size = log_size;
obj->log_level = log_level;
btf_tmp_path = OPTS_GET(opts, btf_custom_path, NULL);
if (btf_tmp_path) {
if (strlen(btf_tmp_path) >= PATH_MAX) {