Merge branch 'bpf-introduce-bpf-arena'

Alexei Starovoitov says:

====================
bpf: Introduce BPF arena.

From: Alexei Starovoitov <ast@kernel.org>

v2->v3:
- contains bpf bits only, but cc-ing past audience for continuity
- since prerequisite patches landed, this series focus on the main
  functionality of bpf_arena.
- adopted Andrii's approach to support arena in libbpf.
- simplified LLVM support. Instead of two instructions it's now only one.
- switched to cond_break (instead of open coded iters) in selftests
- implemented several follow-ups that will be sent after this set
  . remember first IP and bpf insn that faulted in arena.
    report to user space via bpftool
  . copy paste and tweak glob_match() aka mini-regex as a selftests/bpf
- see patch 1 for detailed description of bpf_arena

v1->v2:
- Improved commit log with reasons for using vmap_pages_range() in arena.
  Thanks to Johannes
- Added support for __arena global variables in bpf programs
- Fixed race conditions spotted by Barret
- Fixed wrap32 issue spotted by Barret
- Fixed bpf_map_mmap_sz() the way Andrii suggested

The work on bpf_arena was inspired by Barret's work:
https://github.com/google/ghost-userspace/blob/main/lib/queue.bpf.h
that implements queues, lists and AVL trees completely as bpf programs
using giant bpf array map and integer indices instead of pointers.
bpf_arena is a sparse array that allows to use normal C pointers to
build such data structures. Last few patches implement page_frag
allocator, link list and hash table as bpf programs.

v1:
bpf programs have multiple options to communicate with user space:
- Various ring buffers (perf, ftrace, bpf): The data is streamed
  unidirectionally from bpf to user space.
- Hash map: The bpf program populates elements, and user space consumes
  them via bpf syscall.
- mmap()-ed array map: Libbpf creates an array map that is directly
  accessed by the bpf program and mmap-ed to user space. It's the fastest
  way. Its disadvantage is that memory for the whole array is reserved at
  the start.
====================

Link: https://lore.kernel.org/r/20240308010812.89848-1-alexei.starovoitov@gmail.com
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

1 files changed, 42 insertions, 0 deletions

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index f63f4da4db5e..07f2a4db4511 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -164,6 +164,7 @@ static int bpf_map_update_value(struct bpf_map *map, struct file *map_file,
 	if (bpf_map_is_offloaded(map)) {
 		return bpf_map_offload_update_elem(map, key, value, flags);
 	} else if (map->map_type == BPF_MAP_TYPE_CPUMAP ||
+		   map->map_type == BPF_MAP_TYPE_ARENA ||
 		   map->map_type == BPF_MAP_TYPE_STRUCT_OPS) {
 		return map->ops->map_update_elem(map, key, value, flags);
 	} else if (map->map_type == BPF_MAP_TYPE_SOCKHASH ||
@@ -479,6 +480,39 @@ static void bpf_map_release_memcg(struct bpf_map *map)
 }
 #endif
 
+int bpf_map_alloc_pages(const struct bpf_map *map, gfp_t gfp, int nid,
+			unsigned long nr_pages, struct page **pages)
+{
+	unsigned long i, j;
+	struct page *pg;
+	int ret = 0;
+#ifdef CONFIG_MEMCG_KMEM
+	struct mem_cgroup *memcg, *old_memcg;
+
+	memcg = bpf_map_get_memcg(map);
+	old_memcg = set_active_memcg(memcg);
+#endif
+	for (i = 0; i < nr_pages; i++) {
+		pg = alloc_pages_node(nid, gfp | __GFP_ACCOUNT, 0);
+
+		if (pg) {
+			pages[i] = pg;
+			continue;
+		}
+		for (j = 0; j < i; j++)
+			__free_page(pages[j]);
+		ret = -ENOMEM;
+		break;
+	}
+
+#ifdef CONFIG_MEMCG_KMEM
+	set_active_memcg(old_memcg);
+	mem_cgroup_put(memcg);
+#endif
+	return ret;
+}
+
+
 static int btf_field_cmp(const void *a, const void *b)
 {
 	const struct btf_field *f1 = a, *f2 = b;
@@ -1176,6 +1210,7 @@ static int map_create(union bpf_attr *attr)
 	}
 
 	if (attr->map_type != BPF_MAP_TYPE_BLOOM_FILTER &&
+	    attr->map_type != BPF_MAP_TYPE_ARENA &&
 	    attr->map_extra != 0)
 		return -EINVAL;
 
@@ -1265,6 +1300,7 @@ static int map_create(union bpf_attr *attr)
 	case BPF_MAP_TYPE_LRU_PERCPU_HASH:
 	case BPF_MAP_TYPE_STRUCT_OPS:
 	case BPF_MAP_TYPE_CPUMAP:
+	case BPF_MAP_TYPE_ARENA:
 		if (!bpf_token_capable(token, CAP_BPF))
 			goto put_token;
 		break;
@@ -4417,6 +4453,12 @@ static struct bpf_insn *bpf_insn_prepare_dump(const struct bpf_prog *prog,
 			continue;
 		}
 
+		if ((BPF_CLASS(code) == BPF_LDX || BPF_CLASS(code) == BPF_STX ||
+		     BPF_CLASS(code) == BPF_ST) && BPF_MODE(code) == BPF_PROBE_MEM32) {
+			insns[i].code = BPF_CLASS(code) | BPF_SIZE(code) | BPF_MEM;
+			continue;
+		}
+
 		if (code != (BPF_LD | BPF_IMM | BPF_DW))
 			continue;