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[bpf-next,v5] bpf: Add bpf_ktime_get_real_ns

Message ID 20200924220736.23002-1-bimmy.pujari@intel.com
State Changes Requested
Delegated to: BPF Maintainers
Headers show
Series [bpf-next,v5] bpf: Add bpf_ktime_get_real_ns | expand

Commit Message

Pujari, Bimmy Sept. 24, 2020, 10:07 p.m. UTC 
From: Bimmy Pujari <bimmy.pujari@intel.com>

The existing bpf helper functions to get timestamp return the time
elapsed since system boot. This timestamp is not particularly useful
where epoch timestamp is required or more than one server is involved
and time sync is required. Instead, you want to use CLOCK_REALTIME,
which provides epoch timestamp. Hence adding a new helper function
bfp_ktime_get_real_ns() based around CLOCK_REALTIME.

Signed-off-by: Ashkan Nikravesh <ashkan.nikravesh@intel.com>
Signed-off-by: Bimmy Pujari <bimmy.pujari@intel.com>
---
 drivers/media/rc/bpf-lirc.c    |  2 ++
 include/linux/bpf.h            |  1 +
 include/uapi/linux/bpf.h       |  8 ++++++++
 kernel/bpf/core.c              |  1 +
 kernel/bpf/helpers.c           | 13 +++++++++++++
 kernel/trace/bpf_trace.c       |  2 ++
 tools/include/uapi/linux/bpf.h |  8 ++++++++
 7 files changed, 35 insertions(+)

Comments

David Ahern Sept. 24, 2020, 10:15 p.m. UTC | #1 
On 9/24/20 4:07 PM, bimmy.pujari@intel.com wrote:
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index a22812561064..198e69a6508d 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -3586,6 +3586,13 @@ union bpf_attr {
>   * 		the data in *dst*. This is a wrapper of **copy_from_user**\ ().
>   * 	Return
>   * 		0 on success, or a negative error in case of failure.
> + *
> + * u64 bpf_ktime_get_real_ns(void)
> + *	Description
> + *		Return the real time in nanoseconds.
> + *		See: **clock_gettime**\ (**CLOCK_REALTIME**)

This should be a little more explicit -- something like "See the caveats
regarding use of CLOCK_REALTIME in clock_gettime man page."


> + *	Return
> + *		Current *ktime*.
>   */
>  #define __BPF_FUNC_MAPPER(FN)		\
>  	FN(unspec),			\
> @@ -3737,6 +3744,7 @@ union bpf_attr {
>  	FN(inode_storage_delete),	\
>  	FN(d_path),			\
>  	FN(copy_from_user),		\
> +	FN(ktime_get_real_ns),		\
>  	/* */
>  
>  /* integer value in 'imm' field of BPF_CALL instruction selects which helper
Daniel Borkmann Sept. 24, 2020, 10:27 p.m. UTC | #2 
On 9/25/20 12:15 AM, David Ahern wrote:
> On 9/24/20 4:07 PM, bimmy.pujari@intel.com wrote:
>> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
>> index a22812561064..198e69a6508d 100644
>> --- a/include/uapi/linux/bpf.h
>> +++ b/include/uapi/linux/bpf.h
>> @@ -3586,6 +3586,13 @@ union bpf_attr {
>>    * 		the data in *dst*. This is a wrapper of **copy_from_user**\ ().
>>    * 	Return
>>    * 		0 on success, or a negative error in case of failure.
>> + *
>> + * u64 bpf_ktime_get_real_ns(void)
>> + *	Description
>> + *		Return the real time in nanoseconds.
>> + *		See: **clock_gettime**\ (**CLOCK_REALTIME**)
> 
> This should be a little more explicit -- something like "See the caveats
> regarding use of CLOCK_REALTIME in clock_gettime man page."

+1, and also other feedback got ignored along the way [0]; please don't just resend
several new revisions in the meantime when there were things that still need to be
addressed. Thanks!

   [0] https://lore.kernel.org/bpf/d232b77c-da79-da1c-e564-e2a5cb64acb6@iogearbox.net/T/#ma2997c90e80329c457eb92e9592e185f27ce222f
diff mbox series

Patch

diff --git a/drivers/media/rc/bpf-lirc.c b/drivers/media/rc/bpf-lirc.c
index 3fe3edd80876..fe0fd07a473f 100644
--- a/drivers/media/rc/bpf-lirc.c
+++ b/drivers/media/rc/bpf-lirc.c
@@ -105,6 +105,8 @@  lirc_mode2_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_ktime_get_ns_proto;
 	case BPF_FUNC_ktime_get_boot_ns:
 		return &bpf_ktime_get_boot_ns_proto;
+	case BPF_FUNC_ktime_get_real_ns:
+		return &bpf_ktime_get_real_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 fc5c901c7542..18c4fdce65c8 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1757,6 +1757,7 @@  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_ktime_get_real_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 a22812561064..198e69a6508d 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3586,6 +3586,13 @@  union bpf_attr {
  * 		the data in *dst*. This is a wrapper of **copy_from_user**\ ().
  * 	Return
  * 		0 on success, or a negative error in case of failure.
+ *
+ * u64 bpf_ktime_get_real_ns(void)
+ *	Description
+ *		Return the real time in nanoseconds.
+ *		See: **clock_gettime**\ (**CLOCK_REALTIME**)
+ *	Return
+ *		Current *ktime*.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -3737,6 +3744,7 @@  union bpf_attr {
 	FN(inode_storage_delete),	\
 	FN(d_path),			\
 	FN(copy_from_user),		\
+	FN(ktime_get_real_ns),		\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index c4811b139caa..0dbbda9b743b 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2208,6 +2208,7 @@  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_ktime_get_real_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 5cc7425ee476..300db9269996 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -166,6 +166,17 @@  const struct bpf_func_proto bpf_ktime_get_boot_ns_proto = {
 	.gpl_only	= false,
 	.ret_type	= RET_INTEGER,
 };
+BPF_CALL_0(bpf_ktime_get_real_ns)
+{
+	/* NMI safe access to clock realtime */
+	return ktime_get_real_fast_ns();
+}
+
+const struct bpf_func_proto bpf_ktime_get_real_ns_proto = {
+	.func		= bpf_ktime_get_real_ns,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+};
 
 BPF_CALL_0(bpf_get_current_pid_tgid)
 {
@@ -657,6 +668,8 @@  bpf_base_func_proto(enum bpf_func_id func_id)
 		return &bpf_ktime_get_ns_proto;
 	case BPF_FUNC_ktime_get_boot_ns:
 		return &bpf_ktime_get_boot_ns_proto;
+	case BPF_FUNC_ktime_get_real_ns:
+		return &bpf_ktime_get_real_ns_proto;
 	case BPF_FUNC_ringbuf_output:
 		return &bpf_ringbuf_output_proto;
 	case BPF_FUNC_ringbuf_reserve:
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 36508f46a8db..8ea2a0e50041 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1167,6 +1167,8 @@  bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_ktime_get_ns_proto;
 	case BPF_FUNC_ktime_get_boot_ns:
 		return &bpf_ktime_get_boot_ns_proto;
+	case BPF_FUNC_ktime_get_real_ns:
+		return &bpf_ktime_get_real_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 a22812561064..198e69a6508d 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -3586,6 +3586,13 @@  union bpf_attr {
  * 		the data in *dst*. This is a wrapper of **copy_from_user**\ ().
  * 	Return
  * 		0 on success, or a negative error in case of failure.
+ *
+ * u64 bpf_ktime_get_real_ns(void)
+ *	Description
+ *		Return the real time in nanoseconds.
+ *		See: **clock_gettime**\ (**CLOCK_REALTIME**)
+ *	Return
+ *		Current *ktime*.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -3737,6 +3744,7 @@  union bpf_attr {
 	FN(inode_storage_delete),	\
 	FN(d_path),			\
 	FN(copy_from_user),		\
+	FN(ktime_get_real_ns),		\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper