/* SPDX-License-Identifier: LGPL-2.1+ */
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include "alloc-util.h"
#include "bpf-program.h"
#include "fd-util.h"
#include "log.h"
#include "missing.h"
#include "path-util.h"
#include "util.h"
int bpf_program_new(uint32_t prog_type, BPFProgram **ret) {
_cleanup_(bpf_program_unrefp) BPFProgram *p = NULL;
p = new0(BPFProgram, 1);
if (!p)
return log_oom();
p->n_ref = 1;
p->prog_type = prog_type;
p->kernel_fd = -1;
*ret = TAKE_PTR(p);
return 0;
}
BPFProgram *bpf_program_ref(BPFProgram *p) {
if (!p)
return NULL;
assert(p->n_ref > 0);
p->n_ref++;
return p;
}
BPFProgram *bpf_program_unref(BPFProgram *p) {
if (!p)
return NULL;
assert(p->n_ref > 0);
p->n_ref--;
if (p->n_ref > 0)
return NULL;
/* Unfortunately, the kernel currently doesn't implicitly detach BPF programs from their cgroups when the last
* fd to the BPF program is closed. This has nasty side-effects since this means that abnormally terminated
* programs that attached one of their BPF programs to a cgroup will leave this programs pinned for good with
* zero chance of recovery, until the cgroup is removed. This is particularly problematic if the cgroup in
* question is the root cgroup (or any other cgroup belonging to a service that cannot be restarted during
* operation, such as dbus), as the memory for the BPF program can only be reclaimed through a reboot. To
* counter this, we track closely to which cgroup a program was attached to and will detach it on our own
* whenever we close the BPF fd. */
(void) bpf_program_cgroup_detach(p);
safe_close(p->kernel_fd);
free(p->instructions);
free(p->attached_path);
return mfree(p);
}
int bpf_program_add_instructions(BPFProgram *p, const struct bpf_insn *instructions, size_t count) {
assert(p);
if (p->kernel_fd >= 0) /* don't allow modification after we uploaded things to the kernel */
return -EBUSY;
if (!GREEDY_REALLOC(p->instructions, p->allocated, p->n_instructions + count))
return -ENOMEM;
memcpy(p->instructions + p->n_instructions, instructions, sizeof(struct bpf_insn) * count);
p->n_instructions += count;
return 0;
}
int bpf_program_load_kernel(BPFProgram *p, char *log_buf, size_t log_size) {
union bpf_attr attr;
assert(p);
if (p->kernel_fd >= 0) { /* make this idempotent */
memzero(log_buf, log_size);
return 0;
}
attr = (union bpf_attr) {
.prog_type = p->prog_type,
.insns = PTR_TO_UINT64(p->instructions),
.insn_cnt = p->n_instructions,
.license = PTR_TO_UINT64("GPL"),
.log_buf = PTR_TO_UINT64(log_buf),
.log_level = !!log_buf,
.log_size = log_size,
};
p->kernel_fd = bpf(BPF_PROG_LOAD, &attr, sizeof(attr));
if (p->kernel_fd < 0)
return -errno;
return 0;
}
int bpf_program_cgroup_attach(BPFProgram *p, int type, const char *path, uint32_t flags) {
_cleanup_free_ char *copy = NULL;
_cleanup_close_ int fd = -1;
union bpf_attr attr;
int r;
assert(p);
assert(type >= 0);
assert(path);
if (!IN_SET(flags, 0, BPF_F_ALLOW_OVERRIDE, BPF_F_ALLOW_MULTI))
return -EINVAL;
/* We need to track which cgroup the program is attached to, and we can only track one attachment, hence let's
* refuse this early. */
if (p->attached_path) {
if (!path_equal(p->attached_path, path))
return -EBUSY;
if (p->attached_type != type)
return -EBUSY;
if (p->attached_flags != flags)
return -EBUSY;
/* Here's a shortcut: if we previously attached this program already, then we don't have to do so
* again. Well, with one exception: if we are in BPF_F_ALLOW_OVERRIDE mode then someone else might have
* replaced our program since the last time, hence let's reattach it again, just to be safe. In flags
* == 0 mode this is not an issue since nobody else can replace our program in that case, and in flags
* == BPF_F_ALLOW_MULTI mode any other's program would be installed in addition to ours hence ours
* would remain in effect. */
if (flags != BPF_F_ALLOW_OVERRIDE)
return 0;
}
/* Ensure we have a kernel object for this. */
r = bpf_program_load_kernel(p, NULL, 0);
if (r < 0)
return r;
copy = strdup(path);
if (!copy)
return -ENOMEM;
fd = open(path, O_DIRECTORY|O_RDONLY|O_CLOEXEC);
if (fd < 0)
return -errno;
attr = (union bpf_attr) {
.attach_type = type,
.target_fd = fd,
.attach_bpf_fd = p->kernel_fd,
.attach_flags = flags,
};
if (bpf(BPF_PROG_ATTACH, &attr, sizeof(attr)) < 0)
return -errno;
free_and_replace(p->attached_path, copy);
p->attached_type = type;
p->attached_flags = flags;
return 0;
}
int bpf_program_cgroup_detach(BPFProgram *p) {
_cleanup_close_ int fd = -1;
assert(p);
if (!p->attached_path)
return -EUNATCH;
fd = open(p->attached_path, O_DIRECTORY|O_RDONLY|O_CLOEXEC);
if (fd < 0) {
if (errno != ENOENT)
return -errno;
/* If the cgroup does not exist anymore, then we don't have to explicitly detach, it got detached
* implicitly by the removal, hence don't complain */
} else {
union bpf_attr attr;
attr = (union bpf_attr) {
.attach_type = p->attached_type,
.target_fd = fd,
.attach_bpf_fd = p->kernel_fd,
};
if (bpf(BPF_PROG_DETACH, &attr, sizeof(attr)) < 0)
return -errno;
}
p->attached_path = mfree(p->attached_path);
return 0;
}
int bpf_map_new(enum bpf_map_type type, size_t key_size, size_t value_size, size_t max_entries, uint32_t flags) {
union bpf_attr attr = {
.map_type = type,
.key_size = key_size,
.value_size = value_size,
.max_entries = max_entries,
.map_flags = flags,
};
int fd;
fd = bpf(BPF_MAP_CREATE, &attr, sizeof(attr));
if (fd < 0)
return -errno;
return fd;
}
int bpf_map_update_element(int fd, const void *key, void *value) {
union bpf_attr attr = {
.map_fd = fd,
.key = PTR_TO_UINT64(key),
.value = PTR_TO_UINT64(value),
};
if (bpf(BPF_MAP_UPDATE_ELEM, &attr, sizeof(attr)) < 0)
return -errno;
return 0;
}
int bpf_map_lookup_element(int fd, const void *key, void *value) {
union bpf_attr attr = {
.map_fd = fd,
.key = PTR_TO_UINT64(key),
.value = PTR_TO_UINT64(value),
};
if (bpf(BPF_MAP_LOOKUP_ELEM, &attr, sizeof(attr)) < 0)
return -errno;
return 0;
}