bpf: add bpf_ktime_get_boot_ns()

On a device like a cellphone which is constantly suspending
and resuming CLOCK_MONOTONIC is not particularly useful for
keeping track of or reacting to external network events.
Instead you want to use CLOCK_BOOTTIME.

Hence add bpf_ktime_get_boot_ns() as a mirror of bpf_ktime_get_ns()
based around CLOCK_BOOTTIME instead of CLOCK_MONOTONIC.

Signed-off-by: Maciej Żenczykowski <maze@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/drivers/media/rc/bpf-lirc.c b/drivers/media/rc/bpf-lirc.c
index 0f3417d..069c42f 100644 (file)
--- a/drivers/media/rc/bpf-lirc.c
+++ b/drivers/media/rc/bpf-lirc.c
@@ -103,6 +103,8 @@ lirc_mode2_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
                return &bpf_map_peek_elem_proto;
        case BPF_FUNC_ktime_get_ns:
                return &bpf_ktime_get_ns_proto;
+       case BPF_FUNC_ktime_get_boot_ns:
+               return &bpf_ktime_get_boot_ns_proto;
        case BPF_FUNC_tail_call:
                return &bpf_tail_call_proto;
        case BPF_FUNC_get_prandom_u32:

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 5147e11..10960cf 100644 (file)
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1509,6 +1509,7 @@ extern const struct bpf_func_proto bpf_get_smp_processor_id_proto;
 extern const struct bpf_func_proto bpf_get_numa_node_id_proto;
 extern const struct bpf_func_proto bpf_tail_call_proto;
 extern const struct bpf_func_proto bpf_ktime_get_ns_proto;
+extern const struct bpf_func_proto bpf_ktime_get_boot_ns_proto;
 extern const struct bpf_func_proto bpf_get_current_pid_tgid_proto;
 extern const struct bpf_func_proto bpf_get_current_uid_gid_proto;
 extern const struct bpf_func_proto bpf_get_current_comm_proto;

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 7bbf1b6..4a6c47f 100644 (file)
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -652,6 +652,8 @@ union bpf_attr {
  * u64 bpf_ktime_get_ns(void)
  *     Description
  *             Return the time elapsed since system boot, in nanoseconds.
+ *             Does not include time the system was suspended.
+ *             See: clock_gettime(CLOCK_MONOTONIC)
  *     Return
  *             Current *ktime*.
  *
@@ -3025,6 +3027,14 @@ union bpf_attr {
  *             * **-EOPNOTSUPP**       Unsupported operation, for example a
  *                                     call from outside of TC ingress.
  *             * **-ESOCKTNOSUPPORT**  Socket type not supported (reuseport).
+ *
+ * u64 bpf_ktime_get_boot_ns(void)
+ *     Description
+ *             Return the time elapsed since system boot, in nanoseconds.
+ *             Does include the time the system was suspended.
+ *             See: clock_gettime(CLOCK_BOOTTIME)
+ *     Return
+ *             Current *ktime*.
  */
 #define __BPF_FUNC_MAPPER(FN)          \
        FN(unspec),                     \
@@ -3151,7 +3161,8 @@ union bpf_attr {
        FN(xdp_output),                 \
        FN(get_netns_cookie),           \
        FN(get_current_ancestor_cgroup_id),     \
-       FN(sk_assign),
+       FN(sk_assign),                  \
+       FN(ktime_get_boot_ns),
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 0cc9180..6aa11de 100644 (file)
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2156,6 +2156,7 @@ const struct bpf_func_proto bpf_get_prandom_u32_proto __weak;
 const struct bpf_func_proto bpf_get_smp_processor_id_proto __weak;
 const struct bpf_func_proto bpf_get_numa_node_id_proto __weak;
 const struct bpf_func_proto bpf_ktime_get_ns_proto __weak;
+const struct bpf_func_proto bpf_ktime_get_boot_ns_proto __weak;
 
 const struct bpf_func_proto bpf_get_current_pid_tgid_proto __weak;
 const struct bpf_func_proto bpf_get_current_uid_gid_proto __weak;

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 9a6b233..5c0290e 100644 (file)
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -155,6 +155,18 @@ const struct bpf_func_proto bpf_ktime_get_ns_proto = {
        .ret_type       = RET_INTEGER,
 };
 
+BPF_CALL_0(bpf_ktime_get_boot_ns)
+{
+       /* NMI safe access to clock boottime */
+       return ktime_get_boot_fast_ns();
+}
+
+const struct bpf_func_proto bpf_ktime_get_boot_ns_proto = {
+       .func           = bpf_ktime_get_boot_ns,
+       .gpl_only       = false,
+       .ret_type       = RET_INTEGER,
+};
+
 BPF_CALL_0(bpf_get_current_pid_tgid)
 {
        struct task_struct *task = current;
@@ -615,6 +627,8 @@ bpf_base_func_proto(enum bpf_func_id func_id)
                return &bpf_tail_call_proto;
        case BPF_FUNC_ktime_get_ns:
                return &bpf_ktime_get_ns_proto;
+       case BPF_FUNC_ktime_get_boot_ns:
+               return &bpf_ktime_get_boot_ns_proto;
        default:
                break;
        }

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index ca17967..e875c95 100644 (file)
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -797,6 +797,8 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
                return &bpf_map_peek_elem_proto;
        case BPF_FUNC_ktime_get_ns:
                return &bpf_ktime_get_ns_proto;
+       case BPF_FUNC_ktime_get_boot_ns:
+               return &bpf_ktime_get_boot_ns_proto;
        case BPF_FUNC_tail_call:
                return &bpf_tail_call_proto;
        case BPF_FUNC_get_current_pid_tgid:

diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 7bbf1b6..4a6c47f 100644 (file)
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -652,6 +652,8 @@ union bpf_attr {
  * u64 bpf_ktime_get_ns(void)
  *     Description
  *             Return the time elapsed since system boot, in nanoseconds.
+ *             Does not include time the system was suspended.
+ *             See: clock_gettime(CLOCK_MONOTONIC)
  *     Return
  *             Current *ktime*.
  *
@@ -3025,6 +3027,14 @@ union bpf_attr {
  *             * **-EOPNOTSUPP**       Unsupported operation, for example a
  *                                     call from outside of TC ingress.
  *             * **-ESOCKTNOSUPPORT**  Socket type not supported (reuseport).
+ *
+ * u64 bpf_ktime_get_boot_ns(void)
+ *     Description
+ *             Return the time elapsed since system boot, in nanoseconds.
+ *             Does include the time the system was suspended.
+ *             See: clock_gettime(CLOCK_BOOTTIME)
+ *     Return
+ *             Current *ktime*.
  */
 #define __BPF_FUNC_MAPPER(FN)          \
        FN(unspec),                     \
@@ -3151,7 +3161,8 @@ union bpf_attr {
        FN(xdp_output),                 \
        FN(get_netns_cookie),           \
        FN(get_current_ancestor_cgroup_id),     \
-       FN(sk_assign),
+       FN(sk_assign),                  \
+       FN(ktime_get_boot_ns),
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call