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https://github.com/SerenityOS/serenity
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![Jean-Baptiste Boric](/assets/img/avatar_default.png)
This allows tracing the syscalls made by a thread through the kernel's performance event framework, which is similar in principle to strace. Currently, this merely logs a stack backtrace to the current thread's performance event buffer whenever a syscall is made, if profiling is enabled. Future improvements could include tracing the arguments and the return value, for example.
293 lines
11 KiB
C++
293 lines
11 KiB
C++
/*
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* Copyright (c) 2020-2021, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/JsonArraySerializer.h>
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#include <AK/JsonObjectSerializer.h>
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#include <AK/ScopeGuard.h>
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#include <Kernel/Arch/x86/SmapDisabler.h>
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#include <Kernel/FileSystem/Custody.h>
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#include <Kernel/KBufferBuilder.h>
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#include <Kernel/PerformanceEventBuffer.h>
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#include <Kernel/Process.h>
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namespace Kernel {
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PerformanceEventBuffer::PerformanceEventBuffer(NonnullOwnPtr<KBuffer> buffer)
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: m_buffer(move(buffer))
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{
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}
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NEVER_INLINE KResult PerformanceEventBuffer::append(int type, FlatPtr arg1, FlatPtr arg2, const StringView& arg3, Thread* current_thread)
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{
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FlatPtr ebp;
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asm volatile("movl %%ebp, %%eax"
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: "=a"(ebp));
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return append_with_ip_and_bp(current_thread->pid(), current_thread->tid(), 0, ebp, type, 0, arg1, arg2, arg3);
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}
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static Vector<FlatPtr, PerformanceEvent::max_stack_frame_count> raw_backtrace(FlatPtr bp, FlatPtr ip)
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{
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Vector<FlatPtr, PerformanceEvent::max_stack_frame_count> backtrace;
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if (ip != 0)
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backtrace.append(ip);
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FlatPtr stack_ptr_copy;
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FlatPtr stack_ptr = bp;
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// FIXME: Figure out how to remove this SmapDisabler without breaking profile stacks.
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SmapDisabler disabler;
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while (stack_ptr) {
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void* fault_at;
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if (!safe_memcpy(&stack_ptr_copy, (void*)stack_ptr, sizeof(FlatPtr), fault_at))
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break;
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FlatPtr retaddr;
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if (!safe_memcpy(&retaddr, (void*)(stack_ptr + sizeof(FlatPtr)), sizeof(FlatPtr), fault_at))
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break;
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if (retaddr == 0)
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break;
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backtrace.append(retaddr);
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if (backtrace.size() == PerformanceEvent::max_stack_frame_count)
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break;
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stack_ptr = stack_ptr_copy;
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}
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return backtrace;
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}
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KResult PerformanceEventBuffer::append_with_ip_and_bp(ProcessID pid, ThreadID tid,
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FlatPtr ip, FlatPtr bp, int type, u32 lost_samples, FlatPtr arg1, FlatPtr arg2, const StringView& arg3)
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{
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if (count() >= capacity())
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return ENOBUFS;
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if ((g_profiling_event_mask & type) == 0)
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return EINVAL;
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auto current_thread = Thread::current();
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u32 enter_count = 0;
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if (current_thread)
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enter_count = current_thread->enter_profiler();
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ScopeGuard leave_profiler([&] {
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if (current_thread)
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current_thread->leave_profiler();
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});
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if (enter_count > 0)
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return EINVAL;
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PerformanceEvent event;
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event.type = type;
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event.lost_samples = lost_samples;
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switch (type) {
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case PERF_EVENT_SAMPLE:
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break;
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case PERF_EVENT_MALLOC:
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event.data.malloc.size = arg1;
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event.data.malloc.ptr = arg2;
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break;
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case PERF_EVENT_FREE:
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event.data.free.ptr = arg1;
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break;
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case PERF_EVENT_MMAP:
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event.data.mmap.ptr = arg1;
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event.data.mmap.size = arg2;
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memset(event.data.mmap.name, 0, sizeof(event.data.mmap.name));
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if (!arg3.is_empty())
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memcpy(event.data.mmap.name, arg3.characters_without_null_termination(), min(arg3.length(), sizeof(event.data.mmap.name) - 1));
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break;
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case PERF_EVENT_MUNMAP:
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event.data.munmap.ptr = arg1;
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event.data.munmap.size = arg2;
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break;
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case PERF_EVENT_PROCESS_CREATE:
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event.data.process_create.parent_pid = arg1;
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memset(event.data.process_create.executable, 0, sizeof(event.data.process_create.executable));
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if (!arg3.is_empty()) {
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memcpy(event.data.process_create.executable, arg3.characters_without_null_termination(),
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min(arg3.length(), sizeof(event.data.process_create.executable) - 1));
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}
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break;
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case PERF_EVENT_PROCESS_EXEC:
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memset(event.data.process_exec.executable, 0, sizeof(event.data.process_exec.executable));
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if (!arg3.is_empty()) {
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memcpy(event.data.process_exec.executable, arg3.characters_without_null_termination(),
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min(arg3.length(), sizeof(event.data.process_exec.executable) - 1));
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}
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break;
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case PERF_EVENT_PROCESS_EXIT:
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break;
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case PERF_EVENT_THREAD_CREATE:
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event.data.thread_create.parent_tid = arg1;
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break;
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case PERF_EVENT_THREAD_EXIT:
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break;
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case PERF_EVENT_CONTEXT_SWITCH:
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event.data.context_switch.next_pid = arg1;
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event.data.context_switch.next_tid = arg2;
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break;
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case PERF_EVENT_KMALLOC:
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event.data.kmalloc.size = arg1;
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event.data.kmalloc.ptr = arg2;
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break;
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case PERF_EVENT_KFREE:
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event.data.kfree.size = arg1;
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event.data.kfree.ptr = arg2;
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break;
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case PERF_EVENT_PAGE_FAULT:
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break;
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case PERF_EVENT_SYSCALL:
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break;
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default:
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return EINVAL;
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}
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auto backtrace = raw_backtrace(bp, ip);
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event.stack_size = min(sizeof(event.stack) / sizeof(FlatPtr), static_cast<size_t>(backtrace.size()));
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memcpy(event.stack, backtrace.data(), event.stack_size * sizeof(FlatPtr));
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event.pid = pid.value();
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event.tid = tid.value();
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event.timestamp = TimeManagement::the().uptime_ms();
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at(m_count++) = event;
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return KSuccess;
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}
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PerformanceEvent& PerformanceEventBuffer::at(size_t index)
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{
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VERIFY(index < capacity());
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auto* events = reinterpret_cast<PerformanceEvent*>(m_buffer->data());
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return events[index];
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}
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template<typename Serializer>
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bool PerformanceEventBuffer::to_json_impl(Serializer& object) const
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{
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auto array = object.add_array("events");
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bool seen_first_sample = false;
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for (size_t i = 0; i < m_count; ++i) {
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auto& event = at(i);
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auto event_object = array.add_object();
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switch (event.type) {
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case PERF_EVENT_SAMPLE:
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event_object.add("type", "sample");
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break;
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case PERF_EVENT_MALLOC:
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event_object.add("type", "malloc");
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event_object.add("ptr", static_cast<u64>(event.data.malloc.ptr));
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event_object.add("size", static_cast<u64>(event.data.malloc.size));
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break;
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case PERF_EVENT_FREE:
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event_object.add("type", "free");
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event_object.add("ptr", static_cast<u64>(event.data.free.ptr));
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break;
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case PERF_EVENT_MMAP:
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event_object.add("type", "mmap");
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event_object.add("ptr", static_cast<u64>(event.data.mmap.ptr));
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event_object.add("size", static_cast<u64>(event.data.mmap.size));
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event_object.add("name", event.data.mmap.name);
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break;
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case PERF_EVENT_MUNMAP:
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event_object.add("type", "munmap");
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event_object.add("ptr", static_cast<u64>(event.data.munmap.ptr));
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event_object.add("size", static_cast<u64>(event.data.munmap.size));
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break;
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case PERF_EVENT_PROCESS_CREATE:
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event_object.add("type", "process_create");
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event_object.add("parent_pid", static_cast<u64>(event.data.process_create.parent_pid));
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event_object.add("executable", event.data.process_create.executable);
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break;
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case PERF_EVENT_PROCESS_EXEC:
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event_object.add("type", "process_exec");
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event_object.add("executable", event.data.process_exec.executable);
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break;
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case PERF_EVENT_PROCESS_EXIT:
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event_object.add("type", "process_exit");
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break;
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case PERF_EVENT_THREAD_CREATE:
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event_object.add("type", "thread_create");
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event_object.add("parent_tid", static_cast<u64>(event.data.thread_create.parent_tid));
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break;
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case PERF_EVENT_THREAD_EXIT:
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event_object.add("type", "thread_exit");
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break;
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case PERF_EVENT_CONTEXT_SWITCH:
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event_object.add("type", "context_switch");
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event_object.add("next_pid", static_cast<u64>(event.data.context_switch.next_pid));
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event_object.add("next_tid", static_cast<u64>(event.data.context_switch.next_tid));
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break;
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case PERF_EVENT_KMALLOC:
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event_object.add("type", "kmalloc");
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event_object.add("ptr", static_cast<u64>(event.data.kmalloc.ptr));
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event_object.add("size", static_cast<u64>(event.data.kmalloc.size));
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break;
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case PERF_EVENT_KFREE:
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event_object.add("type", "kfree");
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event_object.add("ptr", static_cast<u64>(event.data.kfree.ptr));
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event_object.add("size", static_cast<u64>(event.data.kfree.size));
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break;
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case PERF_EVENT_PAGE_FAULT:
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event_object.add("type", "page_fault");
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break;
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case PERF_EVENT_SYSCALL:
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event_object.add("type", "syscall");
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break;
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}
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event_object.add("pid", event.pid);
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event_object.add("tid", event.tid);
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event_object.add("timestamp", event.timestamp);
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event_object.add("lost_samples", seen_first_sample ? event.lost_samples : 0);
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if (event.type == PERF_EVENT_SAMPLE)
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seen_first_sample = true;
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auto stack_array = event_object.add_array("stack");
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for (size_t j = 0; j < event.stack_size; ++j) {
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stack_array.add(event.stack[j]);
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}
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stack_array.finish();
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event_object.finish();
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}
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array.finish();
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object.finish();
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return true;
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}
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bool PerformanceEventBuffer::to_json(KBufferBuilder& builder) const
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{
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JsonObjectSerializer object(builder);
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return to_json_impl(object);
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}
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OwnPtr<PerformanceEventBuffer> PerformanceEventBuffer::try_create_with_size(size_t buffer_size)
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{
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auto buffer = KBuffer::try_create_with_size(buffer_size, Memory::Region::Access::ReadWrite, "Performance events", AllocationStrategy::AllocateNow);
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if (!buffer)
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return {};
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return adopt_own_if_nonnull(new (nothrow) PerformanceEventBuffer(buffer.release_nonnull()));
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}
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void PerformanceEventBuffer::add_process(const Process& process, ProcessEventType event_type)
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{
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ScopedSpinLock locker(process.address_space().get_lock());
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String executable;
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if (process.executable())
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executable = process.executable()->absolute_path();
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else
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executable = String::formatted("<{}>", process.name());
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[[maybe_unused]] auto rc = append_with_ip_and_bp(process.pid(), 0, 0, 0,
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event_type == ProcessEventType::Create ? PERF_EVENT_PROCESS_CREATE : PERF_EVENT_PROCESS_EXEC,
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0, process.pid().value(), 0, executable);
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process.for_each_thread([&](auto& thread) {
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[[maybe_unused]] auto rc = append_with_ip_and_bp(process.pid(), thread.tid().value(),
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0, 0, PERF_EVENT_THREAD_CREATE, 0, 0, 0, nullptr);
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});
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for (auto& region : process.address_space().regions()) {
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[[maybe_unused]] auto rc = append_with_ip_and_bp(process.pid(), 0,
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0, 0, PERF_EVENT_MMAP, 0, region->range().base().get(), region->range().size(), region->name());
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}
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}
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}
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