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libbpf: Add support for bpf_arena.

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mmap() bpf_arena right after creation, since the kernel needs to
remember the address returned from mmap. This is user_vm_start.
LLVM will generate bpf_arena_cast_user() instructions where
necessary and JIT will add upper 32-bit of user_vm_start
to such pointers.

Fix up bpf_map_mmap_sz() to compute mmap size as
map->value_size * map->max_entries for arrays and
PAGE_SIZE * map->max_entries for arena.

Don't set BTF at arena creation time, since it doesn't support it.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240308010812.89848-9-alexei.starovoitov@gmail.com
This commit is contained in:
Alexei Starovoitov authored and Andrii Nakryiko committed 2024-03-25 21:58:26 -07:00
1 parent 086825355f
commit 4524a45a2a
2 files changed
+46 -8
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src/libbpf_probes.c
+7
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@@ -338,6 +338,13 @@ static int probe_map_create(enum bpf_map_type map_type)
key_size = 0;
max_entries = 1;
break;
case BPF_MAP_TYPE_ARENA:
key_size = 0;
value_size = 0;
max_entries = 1; /* one page */
opts.map_extra = 0; /* can mmap() at any address */
opts.map_flags = BPF_F_MMAPABLE;
break;
case BPF_MAP_TYPE_HASH:
case BPF_MAP_TYPE_ARRAY:
case BPF_MAP_TYPE_PROG_ARRAY: