summaryrefslogtreecommitdiffstats
path: root/src/shared/bpf-program.c
diff options
context:
space:
mode:
Diffstat (limited to 'src/shared/bpf-program.c')
-rw-r--r--src/shared/bpf-program.c237
1 files changed, 237 insertions, 0 deletions
diff --git a/src/shared/bpf-program.c b/src/shared/bpf-program.c
new file mode 100644
index 0000000..2c61e04
--- /dev/null
+++ b/src/shared/bpf-program.c
@@ -0,0 +1,237 @@
+/* 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;
+}
+
+static BPFProgram *bpf_program_free(BPFProgram *p) {
+ assert(p);
+
+ /* 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);
+}
+
+DEFINE_TRIVIAL_REF_UNREF_FUNC(BPFProgram, bpf_program, bpf_program_free);
+
+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;
+}