Kernel: Start working on a syscall for logging performance events

This patch introduces sys$perf_event() with two event types:

- PERF_EVENT_MALLOC
- PERF_EVENT_FREE

After the first call to sys$perf_event(), a process will begin keeping
these events in a buffer. When the process dies, that buffer will be
written out to "perfcore" in the current directory unless that filename
is already taken.

This is probably not the best way to do this, but it's a start and will
make it possible to start doing memory allocation profiling. :^)

1 files changed, 126 insertions, 0 deletions

diff --git a/Kernel/PerformanceEventBuffer.cpp b/Kernel/PerformanceEventBuffer.cpp
new file mode 100644
index 0000000000..dc0618101e
--- /dev/null
+++ b/Kernel/PerformanceEventBuffer.cpp
@@ -0,0 +1,126 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/JsonArraySerializer.h>
+#include <AK/JsonObjectSerializer.h>
+#include <Kernel/KBufferBuilder.h>
+#include <Kernel/PerformanceEventBuffer.h>
+
+PerformanceEventBuffer::PerformanceEventBuffer()
+    : m_buffer(KBuffer::create_with_size(4 * MB))
+{
+}
+
+KResult PerformanceEventBuffer::append(int type, uintptr_t arg1, uintptr_t arg2)
+{
+    if (count() >= capacity())
+        return KResult(-ENOBUFS);
+
+    PerformanceEvent event;
+    event.type = type;
+
+    switch (type) {
+    case PERF_EVENT_MALLOC:
+        event.data.malloc.size = arg1;
+        event.data.malloc.ptr = arg2;
+#ifdef VERY_DEBUG
+        dbg() << "PERF_EVENT_MALLOC: " << (void*)event.data.malloc.ptr << " (" << event.data.malloc.size << ")";
+#endif
+        break;
+    case PERF_EVENT_FREE:
+        event.data.free.ptr = arg1;
+#ifdef VERY_DEBUG
+        dbg() << "PERF_EVENT_FREE: " << (void*)event.data.free.ptr;
+#endif
+        break;
+    default:
+        return KResult(-EINVAL);
+    }
+
+    uintptr_t ebp;
+    asm volatile("movl %%ebp, %%eax"
+                 : "=a"(ebp));
+    //copy_from_user(&ebp, (uintptr_t*)current->get_register_dump_from_stack().ebp);
+    Vector<uintptr_t> backtrace;
+    {
+        SmapDisabler disabler;
+        backtrace = current->raw_backtrace(ebp);
+    }
+    event.stack_size = min(sizeof(event.stack) / sizeof(uintptr_t), static_cast<size_t>(backtrace.size()));
+    memcpy(event.stack, backtrace.data(), event.stack_size * sizeof(uintptr_t));
+
+#ifdef VERY_DEBUG
+    for (size_t i = 0; i < event.stack_size; ++i)
+        dbg() << "    " << (void*)event.stack[i];
+#endif
+
+    event.timestamp = g_uptime;
+    at(m_count++) = event;
+    return KSuccess;
+}
+
+PerformanceEvent& PerformanceEventBuffer::at(size_t index)
+{
+    ASSERT(index < capacity());
+    auto* events = reinterpret_cast<PerformanceEvent*>(m_buffer.data());
+    return events[index];
+}
+
+KBuffer PerformanceEventBuffer::to_json(pid_t pid, const String& executable_path) const
+{
+    KBufferBuilder builder;
+
+    JsonObjectSerializer object(builder);
+    object.add("pid", pid);
+    object.add("executable", executable_path);
+
+    auto array = object.add_array("events");
+    for (size_t i = 0; i < m_count; ++i) {
+        auto& event = at(i);
+        auto object = array.add_object();
+        switch (event.type) {
+        case PERF_EVENT_MALLOC:
+            object.add("type", "malloc");
+            object.add("ptr", static_cast<u64>(event.data.malloc.ptr));
+            object.add("size", static_cast<u64>(event.data.malloc.size));
+            break;
+        case PERF_EVENT_FREE:
+            object.add("type", "free");
+            object.add("ptr", static_cast<u64>(event.data.free.ptr));
+            break;
+        }
+        object.add("timestamp", event.timestamp);
+        auto stack_array = object.add_array("stack");
+        for (size_t j = 0; j < event.stack_size; ++j) {
+            stack_array.add(event.stack[j]);
+        }
+        stack_array.finish();
+        object.finish();
+    }
+    array.finish();
+    object.finish();
+    return builder.build();
+}