From 0286160b62dd4871ddddd89276398739d7d737b0 Mon Sep 17 00:00:00 2001
From: Jean-Baptiste Boric <jblbeurope@gmail.com>
Date: Tue, 10 Aug 2021 21:02:59 +0200
Subject: Kernel: Add syscall performance event type

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.
---
 Kernel/PerformanceEventBuffer.cpp  |  5 +++++
 Kernel/PerformanceManager.h        | 11 +++++++++++
 Kernel/Syscall.cpp                 |  3 +++
 Kernel/UnixTypes.h                 |  1 +
 Userland/Libraries/LibC/serenity.h |  1 +
 Userland/Utilities/profile.cpp     |  4 +++-
 6 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/Kernel/PerformanceEventBuffer.cpp b/Kernel/PerformanceEventBuffer.cpp
index 0e5e3cb3a4..f461ad8db9 100644
--- a/Kernel/PerformanceEventBuffer.cpp
+++ b/Kernel/PerformanceEventBuffer.cpp
@@ -135,6 +135,8 @@ KResult PerformanceEventBuffer::append_with_ip_and_bp(ProcessID pid, ThreadID ti
         break;
     case PERF_EVENT_PAGE_FAULT:
         break;
+    case PERF_EVENT_SYSCALL:
+        break;
     default:
         return EINVAL;
     }
@@ -226,6 +228,9 @@ bool PerformanceEventBuffer::to_json_impl(Serializer& object) const
         case PERF_EVENT_PAGE_FAULT:
             event_object.add("type", "page_fault");
             break;
+        case PERF_EVENT_SYSCALL:
+            event_object.add("type", "syscall");
+            break;
         }
         event_object.add("pid", event.pid);
         event_object.add("tid", event.tid);
diff --git a/Kernel/PerformanceManager.h b/Kernel/PerformanceManager.h
index 7157d0e655..c05ad84d29 100644
--- a/Kernel/PerformanceManager.h
+++ b/Kernel/PerformanceManager.h
@@ -119,6 +119,17 @@ public:
         }
     }
 
+    inline static void add_syscall_event(Thread& thread, const RegisterState& regs)
+    {
+        if (thread.is_profiling_suppressed())
+            return;
+        if (auto* event_buffer = thread.process().current_perf_events_buffer()) {
+            [[maybe_unused]] auto rc = event_buffer->append_with_ip_and_bp(
+                thread.pid(), thread.tid(),
+                regs.ip(), regs.bp(), PERF_EVENT_SYSCALL, 0, 0, 0, nullptr);
+        }
+    }
+
     inline static void timer_tick(RegisterState const& regs)
     {
         static Time last_wakeup;
diff --git a/Kernel/Syscall.cpp b/Kernel/Syscall.cpp
index 58f6e80f1a..6c71c0b94e 100644
--- a/Kernel/Syscall.cpp
+++ b/Kernel/Syscall.cpp
@@ -9,6 +9,7 @@
 #include <Kernel/Arch/x86/TrapFrame.h>
 #include <Kernel/Memory/MemoryManager.h>
 #include <Kernel/Panic.h>
+#include <Kernel/PerformanceManager.h>
 #include <Kernel/Process.h>
 #include <Kernel/Sections.h>
 #include <Kernel/ThreadTracer.h>
@@ -108,6 +109,8 @@ KResultOr<FlatPtr> handle(RegisterState& regs, FlatPtr function, FlatPtr arg1, F
     auto& process = current_thread->process();
     current_thread->did_syscall();
 
+    PerformanceManager::add_syscall_event(*current_thread, regs);
+
     if (function >= Function::__Count) {
         dbgln("Unknown syscall {} requested ({:p}, {:p}, {:p}, {:p})", function, arg1, arg2, arg3, arg4);
         return ENOSYS;
diff --git a/Kernel/UnixTypes.h b/Kernel/UnixTypes.h
index 44a3351a8a..9ebc56bca8 100644
--- a/Kernel/UnixTypes.h
+++ b/Kernel/UnixTypes.h
@@ -62,6 +62,7 @@ enum {
     PERF_EVENT_KMALLOC = 2048,
     PERF_EVENT_KFREE = 4096,
     PERF_EVENT_PAGE_FAULT = 8192,
+    PERF_EVENT_SYSCALL = 16384,
 };
 
 #define WNOHANG 1
diff --git a/Userland/Libraries/LibC/serenity.h b/Userland/Libraries/LibC/serenity.h
index 649c0914eb..a2533479d6 100644
--- a/Userland/Libraries/LibC/serenity.h
+++ b/Userland/Libraries/LibC/serenity.h
@@ -112,6 +112,7 @@ enum {
     PERF_EVENT_KMALLOC = 2048,
     PERF_EVENT_KFREE = 4096,
     PERF_EVENT_PAGE_FAULT = 8192,
+    PERF_EVENT_SYSCALL = 16384,
 };
 
 #define PERF_EVENT_MASK_ALL (~0ull)
diff --git a/Userland/Utilities/profile.cpp b/Userland/Utilities/profile.cpp
index d1362ef8da..e11eac5d15 100644
--- a/Userland/Utilities/profile.cpp
+++ b/Userland/Utilities/profile.cpp
@@ -45,6 +45,8 @@ int main(int argc, char** argv)
                 event_mask |= PERF_EVENT_KFREE;
             else if (event_type == "page_fault")
                 event_mask |= PERF_EVENT_PAGE_FAULT;
+            else if (event_type == "syscall")
+                event_mask |= PERF_EVENT_SYSCALL;
             else {
                 warnln("Unknown event type '{}' specified.", event_type);
                 exit(1);
@@ -54,7 +56,7 @@ int main(int argc, char** argv)
 
     auto print_types = [] {
         outln();
-        outln("Event type can be one of: sample, context_switch, page_fault, kmalloc and kfree.");
+        outln("Event type can be one of: sample, context_switch, page_fault, syscall, kmalloc and kfree.");
     };
 
     if (!args_parser.parse(argc, argv, Core::ArgsParser::FailureBehavior::PrintUsage)) {
-- 
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