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, 16 insertions, 0 deletions

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 134b7979f537..bdbdc75cdcd5 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2932,6 +2932,11 @@ bool __weak bpf_jit_supports_far_kfunc_call(void)
 	return false;
 }
 
+bool __weak bpf_jit_supports_arena(void)
+{
+	return false;
+}
+
 /* Return TRUE if the JIT backend satisfies the following two conditions:
  * 1) JIT backend supports atomic_xchg() on pointer-sized words.
  * 2) Under the specific arch, the implementation of xchg() is the same
@@ -2976,6 +2981,17 @@ void __weak arch_bpf_stack_walk(bool (*consume_fn)(void *cookie, u64 ip, u64 sp,
 {
 }
 
+/* for configs without MMU or 32-bit */
+__weak const struct bpf_map_ops arena_map_ops;
+__weak u64 bpf_arena_get_user_vm_start(struct bpf_arena *arena)
+{
+	return 0;
+}
+__weak u64 bpf_arena_get_kern_vm_start(struct bpf_arena *arena)
+{
+	return 0;
+}
+
 #ifdef CONFIG_BPF_SYSCALL
 static int __init bpf_global_ma_init(void)
 {