Approximate time helpers (#4013) (#4067)

* Approximate time helpers



* PR feedback



* Update expected c files



* Apply suggestions from code review



* Pickup latest usersim



---------

Signed-off-by: Alan Jowett <alan.jowett@microsoft.com>
Co-authored-by: Alan Jowett <alanjo@microsoft.com>
Co-authored-by: Alan Jowett <alan.jowett@microsoft.com>
Co-authored-by: Dave Thaler <dthaler1968@gmail.com>

Author: 4 people

include/bpf_helper_defs.h

@@ -473,3 +473,25 @@ EBPF_HELPER(size_t, bpf_strnlen_s, (const char* str, size_t str_size));
 #define memcpy_s bpf_memcpy
 #define memmove_s bpf_memmove
 #endif
+
+/**
+ * @brief Return time elapsed since boot in milliseconds including time while suspended.
+ * This function uses a lower resolution clock source than bpf_ktime_get_boot_ns, but is faster.
+ *
+ * @return Time elapsed since boot in milliseconds.
+ */
+EBPF_HELPER(uint64_t, bpf_ktime_get_boot_ms, ());
+#ifndef __doxygen
+#define bpf_ktime_get_boot_ms ((bpf_ktime_get_boot_ms_t)BPF_FUNC_ktime_get_boot_ms)
+#endif
+
+/**
+ * @brief Return time elapsed since boot in milliseconds excluding time while suspended.
+ * This function uses a lower resolution clock source than bpf_ktime_get_ns, but is faster.
+ *
+ * @return Time elapsed since boot in milliseconds.
+ */
+EBPF_HELPER(uint64_t, bpf_ktime_get_ms, ());
+#ifndef __doxygen
+#define bpf_ktime_get_ms ((bpf_ktime_get_ms_t)BPF_FUNC_ktime_get_ms)
+#endif

include/ebpf_structs.h

@@ -164,6 +164,8 @@ typedef enum
     BPF_FUNC_strncpy_s = 27,                 ///< \ref bpf_strncpy_s
     BPF_FUNC_strncat_s = 28,                 ///< \ref bpf_strncat_s
     BPF_FUNC_strnlen_s = 29,                 ///< \ref bpf_strnlen_s
+    BPF_FUNC_ktime_get_boot_ms = 30,         ///< \ref bpf_ktime_get_boot_ms
+    BPF_FUNC_ktime_get_ms = 31,              ///< \ref bpf_ktime_get_ms
 } ebpf_helper_id_t;
 
 // Cross-platform BPF program types.

libs/execution_context/ebpf_core.c

@@ -101,6 +101,12 @@ _ebpf_core_memmove(
     _In_reads_(source_length) const void* source,
     size_t source_length);
 
+static uint64_t
+_ebpf_core_get_time_since_boot_ms();
+
+static uint64_t
+_ebpf_core_get_time_ms();
+
 #define EBPF_CORE_GLOBAL_HELPER_EXTENSION_VERSION 0
 
 static ebpf_program_type_descriptor_t _ebpf_global_helper_program_descriptor = {
@@ -144,6 +150,8 @@ static const void* _ebpf_general_helpers[] = {
     (void*)&_ebpf_core_strncpy_s,
     (void*)&_ebpf_core_strncat_s,
     (void*)&_ebpf_core_strlen_s,
+    (void*)&_ebpf_core_get_time_since_boot_ms,
+    (void*)&_ebpf_core_get_time_ms,
 };
 
 static const ebpf_helper_function_addresses_t _ebpf_global_helper_function_dispatch_table = {
@@ -2257,17 +2265,33 @@ _ebpf_core_random_uint32()
 static uint64_t
 _ebpf_core_get_time_since_boot_ns()
 {
-    // ebpf_query_time_since_boot_precise returns time elapsed since
+    // cxplat_query_time_since_boot_precise returns time elapsed since
     // boot in units of 100 ns.
-    return ebpf_query_time_since_boot_precise(true) * EBPF_NS_PER_FILETIME;
+    return cxplat_query_time_since_boot_precise(true) * EBPF_NS_PER_FILETIME;
 }
 
 static uint64_t
 _ebpf_core_get_time_ns()
 {
-    // ebpf_query_time_since_boot_precise returns time elapsed since
+    // cxplat_query_time_since_boot_precise returns time elapsed since
+    // boot in units of 100 ns.
+    return cxplat_query_time_since_boot_precise(false) * EBPF_NS_PER_FILETIME;
+}
+
+static uint64_t
+_ebpf_core_get_time_since_boot_ms()
+{
+    // cxplat_query_time_since_boot_approximate returns time elapsed since
+    // boot in units of 100 ns.
+    return cxplat_query_time_since_boot_approximate(true) / EBPF_FILETIME_PER_MS;
+}
+
+static uint64_t
+_ebpf_core_get_time_ms()
+{
+    // cxplat_query_time_since_boot_approximate returns time elapsed since
     // boot in units of 100 ns.
-    return ebpf_query_time_since_boot_precise(false) * EBPF_NS_PER_FILETIME;
+    return cxplat_query_time_since_boot_approximate(false) / EBPF_FILETIME_PER_MS;
 }
 
 static uint64_t

libs/execution_context/ebpf_general_helpers.c

@@ -197,6 +197,12 @@ ebpf_helper_function_prototype_t ebpf_core_helper_function_prototype_array[] = {
          EBPF_ARGUMENT_TYPE_PTR_TO_READABLE_MEM,
          EBPF_ARGUMENT_TYPE_CONST_SIZE_OR_ZERO,
      }},
+    {EBPF_HELPER_FUNCTION_PROTOTYPE_HEADER,
+     BPF_FUNC_ktime_get_boot_ms,
+     "bpf_ktime_get_boot_ms",
+     EBPF_RETURN_TYPE_INTEGER,
+     {0}},
+    {EBPF_HELPER_FUNCTION_PROTOTYPE_HEADER, BPF_FUNC_ktime_get_ms, "bpf_ktime_get_ms", EBPF_RETURN_TYPE_INTEGER, {0}},
 };
 
 #ifdef __cplusplus

libs/execution_context/ebpf_maps.c

@@ -1224,15 +1224,15 @@ _insert_into_hot_list(_Inout_ ebpf_core_lru_map_t* map, size_t partition, _Inout
     switch (key_state) {
     case EBPF_LRU_KEY_UNINITIALIZED:
         EBPF_LRU_ENTRY_GENERATION_PTR(map, entry)[partition] = map->partitions[partition].current_generation;
-        EBPF_LRU_ENTRY_LAST_USED_TIME_PTR(map, entry)[partition] = ebpf_query_time_since_boot_approximate(false);
+        EBPF_LRU_ENTRY_LAST_USED_TIME_PTR(map, entry)[partition] = cxplat_query_time_since_boot_approximate(false);
         ebpf_list_insert_tail(
             &map->partitions[partition].hot_list, &EBPF_LRU_ENTRY_LIST_ENTRY_PTR(map, entry)[partition]);
         map->partitions[partition].hot_list_size++;
         break;
     case EBPF_LRU_KEY_COLD:
         // Remove from cold list.
         EBPF_LRU_ENTRY_GENERATION_PTR(map, entry)[partition] = map->partitions[partition].current_generation;
-        EBPF_LRU_ENTRY_LAST_USED_TIME_PTR(map, entry)[partition] = ebpf_query_time_since_boot_approximate(false);
+        EBPF_LRU_ENTRY_LAST_USED_TIME_PTR(map, entry)[partition] = cxplat_query_time_since_boot_approximate(false);
         ebpf_list_remove_entry(&EBPF_LRU_ENTRY_LIST_ENTRY_PTR(map, entry)[partition]);
         ebpf_list_insert_tail(
             &map->partitions[partition].hot_list, &EBPF_LRU_ENTRY_LIST_ENTRY_PTR(map, entry)[partition]);
@@ -1271,7 +1271,7 @@ _initialize_lru_entry(
     // Only insert into the current partition's hot list.
     ebpf_lock_state_t state = ebpf_lock_lock(&map->partitions[partition].lock);
     EBPF_LRU_ENTRY_GENERATION_PTR(map, entry)[partition] = map->partitions[partition].current_generation;
-    EBPF_LRU_ENTRY_LAST_USED_TIME_PTR(map, entry)[partition] = ebpf_query_time_since_boot_approximate(false);
+    EBPF_LRU_ENTRY_LAST_USED_TIME_PTR(map, entry)[partition] = cxplat_query_time_since_boot_approximate(false);
     ebpf_list_insert_tail(&map->partitions[partition].hot_list, &EBPF_LRU_ENTRY_LIST_ENTRY_PTR(map, entry)[partition]);
     map->partitions[partition].hot_list_size++;
 

libs/execution_context/ebpf_program.c

@@ -2454,7 +2454,7 @@ _ebpf_program_test_run_work_item(_In_ cxplat_preemptible_work_item_t* work_item,
         state_stored = true;
     }
 
-    uint64_t start_time = ebpf_query_time_since_boot_precise(false);
+    uint64_t start_time = cxplat_query_time_since_boot_precise(false);
     // Use a counter instead of performing a modulus operation to determine when to start a new epoch.
     // This is because the modulus operation is expensive and we want to minimize the overhead of
     // the test run.
@@ -2467,7 +2467,7 @@ _ebpf_program_test_run_work_item(_In_ cxplat_preemptible_work_item_t* work_item,
             ebpf_epoch_exit(&epoch_state);
             if (ebpf_should_yield_processor()) {
                 // Compute the elapsed time since the last yield.
-                end_time = ebpf_query_time_since_boot_precise(false);
+                end_time = cxplat_query_time_since_boot_precise(false);
 
                 // Add the elapsed time to the cumulative time.
                 cumulative_time += end_time - start_time;
@@ -2479,7 +2479,7 @@ _ebpf_program_test_run_work_item(_In_ cxplat_preemptible_work_item_t* work_item,
                 old_irql = ebpf_raise_irql(context->required_irql);
 
                 // Reset the start time.
-                start_time = ebpf_query_time_since_boot_precise(false);
+                start_time = cxplat_query_time_since_boot_precise(false);
             }
             ebpf_epoch_enter(&epoch_state);
         }
@@ -2489,7 +2489,7 @@ _ebpf_program_test_run_work_item(_In_ cxplat_preemptible_work_item_t* work_item,
             break;
         }
     }
-    end_time = ebpf_query_time_since_boot_precise(false);
+    end_time = cxplat_query_time_since_boot_precise(false);
 
     cumulative_time += end_time - start_time;
 

libs/runtime/ebpf_platform.c

@@ -222,34 +222,6 @@ ebpf_allocate_process_state()
     return state;
 }
 
-uint64_t
-ebpf_query_time_since_boot_precise(bool include_suspended_time)
-{
-    uint64_t qpc_time;
-    if (include_suspended_time) {
-        // KeQueryUnbiasedInterruptTimePrecise returns the current interrupt-time count in 100-nanosecond units.
-        // Unbiased Interrupt time is the total time since boot including time spent suspended.
-        // https://docs.microsoft.com/en-us/windows-hardware/drivers/ddi/wdm/nf-wdm-kequeryunbiasedinterrupttimeprecise
-        return KeQueryUnbiasedInterruptTimePrecise(&qpc_time);
-    } else {
-        // KeQueryInterruptTimePrecise returns the current interrupt-time count in 100-nanosecond units.
-        // (Biased) Interrupt time is the total time since boot excluding time spent suspended.        //
-        // https://docs.microsoft.com/en-us/windows-hardware/drivers/ddi/wdm/nf-wdm-kequeryinterrupttimeprecise
-        return KeQueryInterruptTimePrecise(&qpc_time);
-    }
-}
-
-uint64_t
-ebpf_query_time_since_boot_approximate(bool include_suspend_time)
-{
-    if (include_suspend_time) {
-        ebpf_assert(!"Include suspend time not supported on this platform.");
-        return 0;
-    } else {
-        return KeQueryInterruptTime();
-    }
-}
-
 MDL*
 ebpf_map_memory(size_t length)
 {

libs/runtime/ebpf_platform.h

@@ -39,6 +39,7 @@ extern "C"
     }
 
 #define EBPF_NS_PER_FILETIME 100
+#define EBPF_FILETIME_PER_MS 10000
 
     typedef enum _ebpf_code_integrity_state
     {
@@ -632,29 +633,6 @@ extern "C"
     ebpf_validate_security_descriptor(
         _In_ const ebpf_security_descriptor_t* security_descriptor, size_t security_descriptor_length);
 
-    /**
-     * @brief Return time elapsed since boot in units of 100 nanoseconds.
-     *
-     * @param[in] include_suspended_time Include time the system spent in a suspended state.
-     * @return Time elapsed since boot in 100 nanosecond units.
-     */
-    EBPF_INLINE_HINT
-    uint64_t
-    ebpf_query_time_since_boot_precise(bool include_suspended_time);
-
-    /**
-     * @brief Return time elapsed since boot in units of 100 nanoseconds.
-     * This function is faster than ebpf_query_time_since_boot_precise() but may not
-     * be as accurate.
-     *
-     * @param[in] include_suspended_time Include time the system spent in a suspended state.
-     *
-     * @return Time elapsed since boot in 100 nanosecond units.
-     */
-    EBPF_INLINE_HINT
-    uint64_t
-    ebpf_query_time_since_boot_approximate(bool include_suspended_time);
-
     /**
      * @brief Affinitize the current thread to a specific CPU by index and return the old affinity.
      *