Since now there might be at most 10 offsets that need handling in
copy_map_value, the manual shuffling and special case is no longer going
to work. Hence, let's generalise the copy_map_value function by using
a sorted array of offsets to skip regions that must be avoided while
copying into and out of a map value.
When the map is created, we populate the offset array in struct map,
with one extra element for map->value_size, which is used as the final
offset to subtract previous offset from. Then, copy_map_value uses this
sorted offset array is used to memcpy while skipping timer, spin lock,
and kptr.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
---
include/linux/bpf.h | 55 +++++++++++++++++++++++---------------------
kernel/bpf/syscall.c | 52 +++++++++++++++++++++++++++++++++++++++++
2 files changed, 81 insertions(+), 26 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 9d424d567dd3..6474d2d44b78 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -158,6 +158,10 @@ struct bpf_map_ops {
enum {
/* Support at most 8 pointers in a BPF map value */
BPF_MAP_VALUE_OFF_MAX = 8,
+ BPF_MAP_OFF_ARR_MAX = BPF_MAP_VALUE_OFF_MAX +
+ 1 + /* for bpf_spin_lock */
+ 1 + /* for bpf_timer */
+ 1, /* for map->value_size sentinel */
};
enum {
@@ -206,9 +210,17 @@ struct bpf_map {
char name[BPF_OBJ_NAME_LEN];
bool bypass_spec_v1;
bool frozen; /* write-once; write-protected by freeze_mutex */
- /* 6 bytes hole */
-
- /* The 3rd and 4th cacheline with misc members to avoid false sharing
+ /* 2 bytes hole */
+ struct {
+ struct {
+ u32 off;
+ u8 sz;
+ } field[BPF_MAP_OFF_ARR_MAX];
+ u32 cnt;
+ } off_arr;
+ /* 40 bytes hole */
+
+ /* The 4th and 5th cacheline with misc members to avoid false sharing
* particularly with refcounting.
*/
atomic64_t refcnt ____cacheline_aligned;
@@ -250,36 +262,27 @@ static inline void check_and_init_map_value(struct bpf_map *map, void *dst)
memset(dst + map->spin_lock_off, 0, sizeof(struct bpf_spin_lock));
if (unlikely(map_value_has_timer(map)))
memset(dst + map->timer_off, 0, sizeof(struct bpf_timer));
+ if (unlikely(map_value_has_kptr(map))) {
+ struct bpf_map_value_off *tab = map->kptr_off_tab;
+ int i;
+
+ for (i = 0; i < tab->nr_off; i++)
+ *(u64 *)(dst + tab->off[i].offset) = 0;
+ }
}
/* copy everything but bpf_spin_lock and bpf_timer. There could be one of each. */
static inline void copy_map_value(struct bpf_map *map, void *dst, void *src)
{
- u32 s_off = 0, s_sz = 0, t_off = 0, t_sz = 0;
+ int i;
- if (unlikely(map_value_has_spin_lock(map))) {
- s_off = map->spin_lock_off;
- s_sz = sizeof(struct bpf_spin_lock);
- }
- if (unlikely(map_value_has_timer(map))) {
- t_off = map->timer_off;
- t_sz = sizeof(struct bpf_timer);
- }
+ memcpy(dst, src, map->off_arr.field[0].off);
+ for (i = 1; i < map->off_arr.cnt; i++) {
+ u32 curr_off = map->off_arr.field[i - 1].off;
+ u32 next_off = map->off_arr.field[i].off;
- if (unlikely(s_sz || t_sz)) {
- if (s_off < t_off || !s_sz) {
- swap(s_off, t_off);
- swap(s_sz, t_sz);
- }
- memcpy(dst, src, t_off);
- memcpy(dst + t_off + t_sz,
- src + t_off + t_sz,
- s_off - t_off - t_sz);
- memcpy(dst + s_off + s_sz,
- src + s_off + s_sz,
- map->value_size - s_off - s_sz);
- } else {
- memcpy(dst, src, map->value_size);
+ curr_off += map->off_arr.field[i - 1].sz;
+ memcpy(dst + curr_off, src + curr_off, next_off - curr_off);
}
}
void copy_map_value_locked(struct bpf_map *map, void *dst, void *src,
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 5990d6fa97ab..7b32537bd81f 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -30,6 +30,7 @@
#include <linux/pgtable.h>
#include <linux/bpf_lsm.h>
#include <linux/poll.h>
+#include <linux/sort.h>
#include <linux/bpf-netns.h>
#include <linux/rcupdate_trace.h>
#include <linux/memcontrol.h>
@@ -851,6 +852,55 @@ int map_check_no_btf(const struct bpf_map *map,
return -ENOTSUPP;
}
+static int map_off_arr_cmp(const void *_a, const void *_b)
+{
+ const u32 a = *(const u32 *)_a;
+ const u32 b = *(const u32 *)_b;
+
+ if (a < b)
+ return -1;
+ else if (a > b)
+ return 1;
+ return 0;
+}
+
+static void map_populate_off_arr(struct bpf_map *map)
+{
+ u32 i;
+
+ map->off_arr.cnt = 0;
+ if (map_value_has_spin_lock(map)) {
+ i = map->off_arr.cnt;
+
+ map->off_arr.field[i].off = map->spin_lock_off;
+ map->off_arr.field[i].sz = sizeof(struct bpf_spin_lock);
+ map->off_arr.cnt++;
+ }
+ if (map_value_has_timer(map)) {
+ i = map->off_arr.cnt;
+
+ map->off_arr.field[i].off = map->timer_off;
+ map->off_arr.field[i].sz = sizeof(struct bpf_timer);
+ map->off_arr.cnt++;
+ }
+ if (map_value_has_kptr(map)) {
+ struct bpf_map_value_off *tab = map->kptr_off_tab;
+ u32 j = map->off_arr.cnt;
+
+ for (i = 0; i < tab->nr_off; i++) {
+ map->off_arr.field[j + i].off = tab->off[i].offset;
+ map->off_arr.field[j + i].sz = sizeof(u64);
+ }
+ map->off_arr.cnt += tab->nr_off;
+ }
+
+ map->off_arr.field[map->off_arr.cnt++].off = map->value_size;
+ if (map->off_arr.cnt == 1)
+ return;
+ sort(map->off_arr.field, map->off_arr.cnt, sizeof(map->off_arr.field[0]),
+ map_off_arr_cmp, NULL);
+}
+
static int map_check_btf(struct bpf_map *map, const struct btf *btf,
u32 btf_key_id, u32 btf_value_id)
{
@@ -1018,6 +1068,8 @@ static int map_create(union bpf_attr *attr)
attr->btf_vmlinux_value_type_id;
}
+ map_populate_off_arr(map);
+
err = security_bpf_map_alloc(map);
if (err)
goto free_map;
--
2.35.1
