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bpf: Add bpf_dynptr_read and bpf_dynptr_write

This patch adds two helper functions, bpf_dynptr_read and bpf_dynptr_write: long bpf_dynptr_read(void *dst, u32 len, struct bpf_dynptr *src, u32 offset); long bpf_dynptr_write(struct bpf_dynptr *dst, u32 offset, void *src, u32 len); The dynptr passed into these functions must be valid dynptrs that have been initialized.

Joanne Koong committed 4 years ago

Commit 13bbbfb1 parent bc34dee3 files · +116 −0Browse files

Showing the changes to kernel (1 of 3 files). Show all

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kernel/bpf/helpers.c+78−0
@@ -1417,12 +1417,24 @@ const struct bpf_func_proto bpf_kptr_xchg_proto = { · 1416 unmodified lines
14171417 */
14181418 #define DYNPTR_MAX_SIZE ((1UL << 24) - 1)
14191419 #define DYNPTR_TYPE_SHIFT 28
1420+#define DYNPTR_SIZE_MASK 0xFFFFFF
1421+#define DYNPTR_RDONLY_BIT BIT(31)
1422+
1423+static bool bpf_dynptr_is_rdonly(struct bpf_dynptr_kern *ptr)
1424+{
1425+ return ptr->size & DYNPTR_RDONLY_BIT;
1426+}
14201427
14211428 static void bpf_dynptr_set_type(struct bpf_dynptr_kern *ptr, enum bpf_dynptr_type type)
14221429 {
14231430 ptr->size |= type << DYNPTR_TYPE_SHIFT;
14241431 }
14251432
1433+static u32 bpf_dynptr_get_size(struct bpf_dynptr_kern *ptr)
1434+{
1435+ return ptr->size & DYNPTR_SIZE_MASK;
1436+}
1437+
14261438 int bpf_dynptr_check_size(u32 size)
14271439 {
14281440 return size > DYNPTR_MAX_SIZE ? -E2BIG : 0;
@@ -1442,6 +1454,16 @@ void bpf_dynptr_set_null(struct bpf_dynptr_kern *ptr) · 13 unmodified lines
14421454 memset(ptr, 0, sizeof(*ptr));
14431455 }
14441456
1457+static int bpf_dynptr_check_off_len(struct bpf_dynptr_kern *ptr, u32 offset, u32 len)
1458+{
1459+ u32 size = bpf_dynptr_get_size(ptr);
1460+
1461+ if (len > size || offset > size - len)
1462+ return -E2BIG;
1463+
1464+ return 0;
1465+}
1466+
14451467 BPF_CALL_4(bpf_dynptr_from_mem, void *, data, u32, size, u64, flags, struct bpf_dynptr_kern *, ptr)
14461468 {
14471469 int err;
@@ -1475,6 +1497,58 @@ const struct bpf_func_proto bpf_dynptr_from_mem_proto = { · 27 unmodified lines
14751497 .arg4_type = ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_LOCAL | MEM_UNINIT,
14761498 };
14771499
1500+BPF_CALL_4(bpf_dynptr_read, void *, dst, u32, len, struct bpf_dynptr_kern *, src, u32, offset)
1501+{
1502+ int err;
1503+
1504+ if (!src->data)
1505+ return -EINVAL;
1506+
1507+ err = bpf_dynptr_check_off_len(src, offset, len);
1508+ if (err)
1509+ return err;
1510+
1511+ memcpy(dst, src->data + src->offset + offset, len);
1512+
1513+ return 0;
1514+}
1515+
1516+const struct bpf_func_proto bpf_dynptr_read_proto = {
1517+ .func = bpf_dynptr_read,
1518+ .gpl_only = false,
1519+ .ret_type = RET_INTEGER,
1520+ .arg1_type = ARG_PTR_TO_UNINIT_MEM,
1521+ .arg2_type = ARG_CONST_SIZE_OR_ZERO,
1522+ .arg3_type = ARG_PTR_TO_DYNPTR,
1523+ .arg4_type = ARG_ANYTHING,
1524+};
1525+
1526+BPF_CALL_4(bpf_dynptr_write, struct bpf_dynptr_kern *, dst, u32, offset, void *, src, u32, len)
1527+{
1528+ int err;
1529+
1530+ if (!dst->data || bpf_dynptr_is_rdonly(dst))
1531+ return -EINVAL;
1532+
1533+ err = bpf_dynptr_check_off_len(dst, offset, len);
1534+ if (err)
1535+ return err;
1536+
1537+ memcpy(dst->data + dst->offset + offset, src, len);
1538+
1539+ return 0;
1540+}
1541+
1542+const struct bpf_func_proto bpf_dynptr_write_proto = {
1543+ .func = bpf_dynptr_write,
1544+ .gpl_only = false,
1545+ .ret_type = RET_INTEGER,
1546+ .arg1_type = ARG_PTR_TO_DYNPTR,
1547+ .arg2_type = ARG_ANYTHING,
1548+ .arg3_type = ARG_PTR_TO_MEM | MEM_RDONLY,
1549+ .arg4_type = ARG_CONST_SIZE_OR_ZERO,
1550+};
1551+
14781552 const struct bpf_func_proto bpf_get_current_task_proto __weak;
14791553 const struct bpf_func_proto bpf_get_current_task_btf_proto __weak;
14801554 const struct bpf_func_proto bpf_probe_read_user_proto __weak;
@@ -1537,6 +1611,10 @@ bpf_base_func_proto(enum bpf_func_id func_id) · 56 unmodified lines
15371611 return &bpf_strncmp_proto;
15381612 case BPF_FUNC_dynptr_from_mem:
15391613 return &bpf_dynptr_from_mem_proto;
1614+ case BPF_FUNC_dynptr_read:
1615+ return &bpf_dynptr_read_proto;
1616+ case BPF_FUNC_dynptr_write:
1617+ return &bpf_dynptr_write_proto;
15401618 default:
15411619 break;
15421620 }