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bpf: Add BPF_KPTR_PERCPU as a field type

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BPF_KPTR_PERCPU represents a percpu field type like below

  struct val_t {
    ... fields ...
  };
  struct t {
    ...
    struct val_t __percpu_kptr *percpu_data_ptr;
    ...
  };

where
  #define __percpu_kptr __attribute__((btf_type_tag("percpu_kptr")))

While BPF_KPTR_REF points to a trusted kernel object or a trusted
local object, BPF_KPTR_PERCPU points to a trusted local
percpu object.

This patch added basic support for BPF_KPTR_PERCPU
related to percpu_kptr field parsing, recording and free operations.
BPF_KPTR_PERCPU also supports the same map types
as BPF_KPTR_REF does.

Note that unlike a local kptr, it is possible that
a BPF_KTPR_PERCPU struct may not contain any
special fields like other kptr, bpf_spin_lock, bpf_list_head, etc.

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20230827152739.1996391-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Yonghong Song 2023-08-27 08:27:39 -07:00 committed by Alexei Starovoitov
parent 41a5db8d81
commit 55db92f42f
3 changed files with 21 additions and 6 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

18
include/linux/bpf.h
View file

@ -180,14 +180,15 @@ enum btf_field_type {
BPF_TIMER = (1 << 1),
BPF_KPTR_UNREF = (1 << 2),
BPF_KPTR_REF = (1 << 3),
BPF_KPTR = BPF_KPTR_UNREF | BPF_KPTR_REF,
BPF_LIST_HEAD = (1 << 4),
BPF_LIST_NODE = (1 << 5),
BPF_RB_ROOT = (1 << 6),
BPF_RB_NODE = (1 << 7),
BPF_KPTR_PERCPU = (1 << 4),
BPF_KPTR = BPF_KPTR_UNREF | BPF_KPTR_REF | BPF_KPTR_PERCPU,
BPF_LIST_HEAD = (1 << 5),
BPF_LIST_NODE = (1 << 6),
BPF_RB_ROOT = (1 << 7),
BPF_RB_NODE = (1 << 8),
BPF_GRAPH_NODE_OR_ROOT = BPF_LIST_NODE | BPF_LIST_HEAD |
BPF_RB_NODE | BPF_RB_ROOT,
BPF_REFCOUNT = (1 << 8),
BPF_REFCOUNT = (1 << 9),
};
typedef void (*btf_dtor_kfunc_t)(void *);
@ -300,6 +301,8 @@ static inline const char *btf_field_type_name(enum btf_field_type type)
case BPF_KPTR_UNREF:
case BPF_KPTR_REF:
return "kptr";
case BPF_KPTR_PERCPU:
return "percpu_kptr";
case BPF_LIST_HEAD:
return "bpf_list_head";
case BPF_LIST_NODE:
@ -325,6 +328,7 @@ static inline u32 btf_field_type_size(enum btf_field_type type)
return sizeof(struct bpf_timer);
case BPF_KPTR_UNREF:
case BPF_KPTR_REF:
case BPF_KPTR_PERCPU:
return sizeof(u64);
case BPF_LIST_HEAD:
return sizeof(struct bpf_list_head);
@ -351,6 +355,7 @@ static inline u32 btf_field_type_align(enum btf_field_type type)
return __alignof__(struct bpf_timer);
case BPF_KPTR_UNREF:
case BPF_KPTR_REF:
case BPF_KPTR_PERCPU:
return __alignof__(u64);
case BPF_LIST_HEAD:
return __alignof__(struct bpf_list_head);
@ -389,6 +394,7 @@ static inline void bpf_obj_init_field(const struct btf_field *field, void *addr)
case BPF_TIMER:
case BPF_KPTR_UNREF:
case BPF_KPTR_REF:
case BPF_KPTR_PERCPU:
break;
default:
WARN_ON_ONCE(1);

5
kernel/bpf/btf.c
View file

@ -3293,6 +3293,8 @@ static int btf_find_kptr(const struct btf *btf, const struct btf_type *t,
type = BPF_KPTR_UNREF;
else if (!strcmp("kptr", __btf_name_by_offset(btf, t->name_off)))
type = BPF_KPTR_REF;
else if (!strcmp("percpu_kptr", __btf_name_by_offset(btf, t->name_off)))
type = BPF_KPTR_PERCPU;
else
return -EINVAL;
@ -3457,6 +3459,7 @@ static int btf_find_struct_field(const struct btf *btf,
break;
case BPF_KPTR_UNREF:
case BPF_KPTR_REF:
case BPF_KPTR_PERCPU:
ret = btf_find_kptr(btf, member_type, off, sz,
idx < info_cnt ? &info[idx] : &tmp);
if (ret < 0)
@ -3523,6 +3526,7 @@ static int btf_find_datasec_var(const struct btf *btf, const struct btf_type *t,
break;
case BPF_KPTR_UNREF:
case BPF_KPTR_REF:
case BPF_KPTR_PERCPU:
ret = btf_find_kptr(btf, var_type, off, sz,
idx < info_cnt ? &info[idx] : &tmp);
if (ret < 0)
@ -3783,6 +3787,7 @@ struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type
break;
case BPF_KPTR_UNREF:
case BPF_KPTR_REF:
case BPF_KPTR_PERCPU:
ret = btf_parse_kptr(btf, &rec->fields[i], &info_arr[i]);
if (ret < 0)
goto end;

4
kernel/bpf/syscall.c
View file

@ -514,6 +514,7 @@ void btf_record_free(struct btf_record *rec)
switch (rec->fields[i].type) {
case BPF_KPTR_UNREF:
case BPF_KPTR_REF:
case BPF_KPTR_PERCPU:
if (rec->fields[i].kptr.module)
module_put(rec->fields[i].kptr.module);
btf_put(rec->fields[i].kptr.btf);
@ -560,6 +561,7 @@ struct btf_record *btf_record_dup(const struct btf_record *rec)
switch (fields[i].type) {
case BPF_KPTR_UNREF:
case BPF_KPTR_REF:
case BPF_KPTR_PERCPU:
btf_get(fields[i].kptr.btf);
if (fields[i].kptr.module && !try_module_get(fields[i].kptr.module)) {
ret = -ENXIO;
@ -650,6 +652,7 @@ void bpf_obj_free_fields(const struct btf_record *rec, void *obj)
WRITE_ONCE(*(u64 *)field_ptr, 0);
break;
case BPF_KPTR_REF:
case BPF_KPTR_PERCPU:
xchgd_field = (void *)xchg((unsigned long *)field_ptr, 0);
if (!xchgd_field)
break;
@ -1045,6 +1048,7 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf,
break;
case BPF_KPTR_UNREF:
case BPF_KPTR_REF:
case BPF_KPTR_PERCPU:
case BPF_REFCOUNT:
if (map->map_type != BPF_MAP_TYPE_HASH &&
map->map_type != BPF_MAP_TYPE_PERCPU_HASH &&