From: Alexei Starovoitov <ast@xxxxxxxxxx>
The hash map is now fully converted to bpf_mem_alloc. Its implementation is not
allocating synchronously and not calling call_rcu() directly. It's now safe to
use non-preallocated hash maps in all types of tracing programs including
BPF_PROG_TYPE_PERF_EVENT that runs out of NMI context.
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
---
kernel/bpf/verifier.c | 42 ------------------------------------------
1 file changed, 42 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index d785f29047d7..a1ada707c57c 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -12599,48 +12599,6 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env,
{
enum bpf_prog_type prog_type = resolve_prog_type(prog);
- /*
- * Validate that trace type programs use preallocated hash maps.
- *
- * For programs attached to PERF events this is mandatory as the
- * perf NMI can hit any arbitrary code sequence.
- *
- * All other trace types using non-preallocated per-cpu hash maps are
- * unsafe as well because tracepoint or kprobes can be inside locked
- * regions of the per-cpu memory allocator or at a place where a
- * recursion into the per-cpu memory allocator would see inconsistent
- * state. Non per-cpu hash maps are using bpf_mem_alloc-tor which is
- * safe to use from kprobe/fentry and in RT.
- *
- * On RT enabled kernels run-time allocation of all trace type
- * programs is strictly prohibited due to lock type constraints. On
- * !RT kernels it is allowed for backwards compatibility reasons for
- * now, but warnings are emitted so developers are made aware of
- * the unsafety and can fix their programs before this is enforced.
- */
- if (is_tracing_prog_type(prog_type) && !is_preallocated_map(map)) {
- if (prog_type == BPF_PROG_TYPE_PERF_EVENT) {
- /* perf_event bpf progs have to use preallocated hash maps
- * because non-prealloc is still relying on call_rcu to free
- * elements.
- */
- verbose(env, "perf_event programs can only use preallocated hash map\n");
- return -EINVAL;
- }
- if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
- (map->inner_map_meta &&
- map->inner_map_meta->map_type == BPF_MAP_TYPE_PERCPU_HASH)) {
- if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
- verbose(env,
- "trace type programs can only use preallocated per-cpu hash map\n");
- return -EINVAL;
- }
- WARN_ONCE(1, "trace type BPF program uses run-time allocation\n");
- verbose(env,
- "trace type programs with run-time allocated per-cpu hash maps are unsafe."
- " Switch to preallocated hash maps.\n");
- }
- }
if (map_value_has_spin_lock(map)) {
if (prog_type == BPF_PROG_TYPE_SOCKET_FILTER) {
--
2.30.2
