On 4/26/19 10:11 AM, Martin KaFai Lau wrote:
> This patch supports probing for the new BPF_MAP_TYPE_SK_STORAGE.
> BPF_MAP_TYPE_SK_STORAGE enforces BTF usage, so the new probe
> requires to create and load a BTF also.
>
> Signed-off-by: Martin KaFai Lau <ka...@fb.com>
> ---
> tools/bpf/bpftool/map.c | 1 +
> tools/lib/bpf/libbpf_probes.c | 74 ++++++++++++++++++++++++++++++++++-
> 2 files changed, 74 insertions(+), 1 deletion(-)
>
> diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
> index 10b6c9d3e525..693ab3da37de 100644
> --- a/tools/bpf/bpftool/map.c
> +++ b/tools/bpf/bpftool/map.c
> @@ -46,6 +46,7 @@ const char * const map_type_name[] = {
> [BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE] = "percpu_cgroup_storage",
> [BPF_MAP_TYPE_QUEUE] = "queue",
> [BPF_MAP_TYPE_STACK] = "stack",
> + [BPF_MAP_TYPE_SK_STORAGE] = "sk_storage",
> };
>
> const size_t map_type_name_size = ARRAY_SIZE(map_type_name);
> diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c
> index 0f25541632e3..2e26ddb005e4 100644
> --- a/tools/lib/bpf/libbpf_probes.c
> +++ b/tools/lib/bpf/libbpf_probes.c
> @@ -9,6 +9,7 @@
> #include <net/if.h>
> #include <sys/utsname.h>
>
> +#include <linux/btf.h>
> #include <linux/filter.h>
> #include <linux/kernel.h>
>
> @@ -130,11 +131,65 @@ bool bpf_probe_prog_type(enum bpf_prog_type prog_type,
> __u32 ifindex)
> return errno != EINVAL && errno != EOPNOTSUPP;
> }
>
> +static int load_btf(void)
> +{
> +#define BTF_INFO_ENC(kind, kind_flag, vlen) \
> + ((!!(kind_flag) << 31) | ((kind) << 24) | ((vlen) & BTF_MAX_VLEN))
> +#define BTF_TYPE_ENC(name, info, size_or_type) \
> + (name), (info), (size_or_type)
> +#define BTF_INT_ENC(encoding, bits_offset, nr_bits) \
> + ((encoding) << 24 | (bits_offset) << 16 | (nr_bits))
> +#define BTF_TYPE_INT_ENC(name, encoding, bits_offset, bits, sz) \
> + BTF_TYPE_ENC(name, BTF_INFO_ENC(BTF_KIND_INT, 0, 0), sz), \
> + BTF_INT_ENC(encoding, bits_offset, bits)
> +#define BTF_MEMBER_ENC(name, type, bits_offset) \
> + (name), (type), (bits_offset)
> +
> + const char btf_str_sec[] = "\0bpf_spin_lock\0val\0cnt\0l";
> + /* struct bpf_spin_lock {
> + * int val;
> + * };
> + * struct val {
> + * int cnt;
> + * struct bpf_spin_lock l;
> + * };
> + */
> + __u32 btf_raw_types[] = {
> + /* int */
> + BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4), /* [1] */
> + /* struct bpf_spin_lock */ /* [2] */
> + BTF_TYPE_ENC(1, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 1), 4),
> + BTF_MEMBER_ENC(15, 1, 0), /* int val; */
> + /* struct val */ /* [3] */
> + BTF_TYPE_ENC(15, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 2), 8),
> + BTF_MEMBER_ENC(19, 1, 0), /* int cnt; */
> + BTF_MEMBER_ENC(23, 2, 32),/* struct bpf_spin_lock l; */
> + };
> + struct btf_header btf_hdr = {
> + .magic = BTF_MAGIC,
> + .version = BTF_VERSION,
> + .hdr_len = sizeof(struct btf_header),
> + .type_len = sizeof(btf_raw_types),
> + .str_off = sizeof(btf_raw_types),
> + .str_len = sizeof(btf_str_sec),
> + };
> + __u8 raw_btf[sizeof(struct btf_header) + sizeof(btf_raw_types) +
> + sizeof(btf_str_sec)];
> +
> + memcpy(raw_btf, &btf_hdr, sizeof(btf_hdr));
> + memcpy(raw_btf + sizeof(btf_hdr), btf_raw_types, sizeof(btf_raw_types));
> + memcpy(raw_btf + sizeof(btf_hdr) + sizeof(btf_raw_types),
> + btf_str_sec, sizeof(btf_str_sec));
> +
> + return bpf_load_btf(raw_btf, sizeof(raw_btf), 0, 0, 0);
> +}
In the future, different map types could want to test different type
configurations. Maybe btf_raw_types and btf_str_sec could be provided
as a parameter for load_btf()?
> +
> bool bpf_probe_map_type(enum bpf_map_type map_type, __u32 ifindex)
> {
> int key_size, value_size, max_entries, map_flags;
> + __u32 btf_key_type_id = 0, btf_value_type_id = 0;
> struct bpf_create_map_attr attr = {};
> - int fd = -1, fd_inner;
> + int fd = -1, btf_fd = -1, fd_inner;
>
> key_size = sizeof(__u32);
> value_size = sizeof(__u32);
> @@ -160,6 +215,16 @@ bool bpf_probe_map_type(enum bpf_map_type map_type,
> __u32 ifindex)
> case BPF_MAP_TYPE_STACK:
> key_size = 0;
> break;
> + case BPF_MAP_TYPE_SK_STORAGE:
> + btf_key_type_id = 1;
> + btf_value_type_id = 3;
> + value_size = 8;
> + max_entries = 0;
> + map_flags = BPF_F_NO_PREALLOC;
> + btf_fd = load_btf();
> + if (btf_fd < 0)
> + return false;
> + break;
> case BPF_MAP_TYPE_UNSPEC:
> case BPF_MAP_TYPE_HASH:
> case BPF_MAP_TYPE_ARRAY:
> @@ -205,11 +270,18 @@ bool bpf_probe_map_type(enum bpf_map_type map_type,
> __u32 ifindex)
> attr.max_entries = max_entries;
> attr.map_flags = map_flags;
> attr.map_ifindex = ifindex;
> + if (btf_fd >= 0) {
> + attr.btf_fd = btf_fd;
> + attr.btf_key_type_id = btf_key_type_id;
> + attr.btf_value_type_id = btf_value_type_id;
> + }
>
> fd = bpf_create_map_xattr(&attr);
> }
> if (fd >= 0)
> close(fd);
> + if (btf_fd >= 0)
> + close(btf_fd);
>
> return fd >= 0;
> }
>
