UserspaceEmulator: Handle PerfEvent syscalls

We only froward String setting and FlagPost creation for now, due to the
other performance events being nonsensical to forward.
We also record these signposts in the optionally generated profile.

Userland/DevTools/UserspaceEmulator/Emulator.h

@@ -33,11 +33,13 @@ public:
 
     Emulator(String const& executable_path, Vector<String> const& arguments, Vector<String> const& environment);
 
-    void set_profiling_details(bool should_dump_profile, size_t instruction_interval, OutputFileStream* profile_stream)
+    void set_profiling_details(bool should_dump_profile, size_t instruction_interval, OutputFileStream* profile_stream, NonnullOwnPtrVector<String>* profiler_strings, Vector<int>* profiler_string_id_map)
     {
         m_is_profiling = should_dump_profile;
         m_profile_instruction_interval = instruction_interval;
         m_profile_stream = profile_stream;
+        m_profiler_strings = profiler_strings;
+        m_profiler_string_id_map = profiler_string_id_map;
     }
 
     void set_in_region_of_interest(bool value)
@@ -46,6 +48,9 @@ public:
     }
 
     OutputFileStream& profile_stream() { return *m_profile_stream; }
+    NonnullOwnPtrVector<String>& profiler_strings() { return *m_profiler_strings; }
+    Vector<int>& profiler_string_id_map() { return *m_profiler_string_id_map; }
+
     bool is_profiling() const { return m_is_profiling; }
     bool is_in_region_of_interest() const { return m_is_in_region_of_interest; }
     size_t profile_instruction_interval() const { return m_profile_instruction_interval; }
@@ -137,6 +142,8 @@ private:
     int virt$gethostname(FlatPtr, ssize_t);
     int virt$profiling_enable(pid_t);
     int virt$profiling_disable(pid_t);
+    FlatPtr virt$perf_event(int type, FlatPtr arg1, FlatPtr arg2);
+    FlatPtr virt$perf_register_string(FlatPtr, size_t);
     int virt$disown(pid_t);
     int virt$purge(int mode);
     u32 virt$mmap(u32);
@@ -274,6 +281,9 @@ private:
     RangeAllocator m_range_allocator;
 
     OutputFileStream* m_profile_stream { nullptr };
+    Vector<int>* m_profiler_string_id_map { nullptr };
+    NonnullOwnPtrVector<String>* m_profiler_strings { nullptr };
+
     bool m_is_profiling { false };
     size_t m_profile_instruction_interval { 0 };
     bool m_is_in_region_of_interest { false };

Userland/DevTools/UserspaceEmulator/Emulator_syscalls.cpp

@@ -10,6 +10,7 @@
 #include <AK/Debug.h>
 #include <AK/FileStream.h>
 #include <AK/Format.h>
+#include <alloca.h>
 #include <fcntl.h>
 #include <sched.h>
 #include <serenity.h>
@@ -75,6 +76,10 @@ u32 Emulator::virt_syscall(u32 function, u32 arg1, u32 arg2, u32 arg3)
         return virt$profiling_enable(arg1);
     case SC_profiling_disable:
         return virt$profiling_disable(arg1);
+    case SC_perf_event:
+        return virt$perf_event((int)arg1, arg2, arg3);
+    case SC_perf_register_string:
+        return virt$perf_register_string(arg1, arg2);
     case SC_disown:
         return virt$disown(arg1);
     case SC_purge:
@@ -248,8 +253,6 @@ u32 Emulator::virt_syscall(u32 function, u32 arg1, u32 arg2, u32 arg3)
     case SC_futex:
         return virt$futex(arg1);
     case SC_map_time_page:
-    case SC_perf_register_string:
-    case SC_perf_event:
         return -ENOSYS;
     default:
         reportln("\n=={}==  \033[31;1mUnimplemented syscall: {}\033[0m, {:p}", getpid(), Syscall::to_string((Syscall::Function)function), function);
@@ -283,6 +286,37 @@ int Emulator::virt$profiling_disable(pid_t pid)
     return syscall(SC_profiling_disable, pid);
 }
 
+FlatPtr Emulator::virt$perf_event(int event, FlatPtr arg1, FlatPtr arg2)
+{
+    if (event == PERF_EVENT_SIGNPOST) {
+        if (is_profiling()) {
+            if (profiler_string_id_map().size() > arg1)
+                emit_profile_event(profile_stream(), "signpost", String::formatted("\"arg1\": {}, \"arg2\": {}", arg1, arg2));
+            syscall(SC_perf_event, PERF_EVENT_SIGNPOST, profiler_string_id_map().at(arg1), arg2);
+        } else {
+            syscall(SC_perf_event, PERF_EVENT_SIGNPOST, arg1, arg2);
+        }
+        return 0;
+    }
+    return -ENOSYS;
+}
+
+FlatPtr Emulator::virt$perf_register_string(FlatPtr string, size_t size)
+{
+    char* buffer = (char*)alloca(size + 4);
+    // FIXME: not nice, but works
+    __builtin_memcpy(buffer, "UE: ", 4);
+    mmu().copy_from_vm((buffer + 4), string, size);
+    auto ret = (int)syscall(SC_perf_register_string, buffer, size + 4);
+
+    if (ret >= 0 && is_profiling()) {
+        profiler_strings().append(make<String>(StringView { buffer + 4, size }));
+        profiler_string_id_map().append(ret);
+        ret = profiler_string_id_map().size() - 1;
+    }
+    return ret;
+}
+
 int Emulator::virt$disown(pid_t pid)
 {
     return syscall(SC_disown, pid);

Userland/DevTools/UserspaceEmulator/main.cpp

@@ -59,6 +59,9 @@ int main(int argc, char** argv, char** env)
         profile_dump_path = String::formatted("{}.{}.profile", LexicalPath(executable_path).basename(), getpid());
 
     OwnPtr<OutputFileStream> profile_stream;
+    OwnPtr<NonnullOwnPtrVector<String>> profile_strings;
+    OwnPtr<Vector<int>> profile_string_id_map;
+
     if (dump_profile) {
         profile_output_file = fopen(profile_dump_path.characters(), "w+");
         if (profile_output_file == nullptr) {
@@ -67,6 +70,8 @@ int main(int argc, char** argv, char** env)
             return 1;
         }
         profile_stream = make<OutputFileStream>(profile_output_file);
+        profile_strings = make<NonnullOwnPtrVector<String>>();
+        profile_string_id_map = make<Vector<int>>();
 
         profile_stream->write_or_error(R"({"events":[)"sv.bytes());
         timeval tv {};
@@ -85,7 +90,8 @@ int main(int argc, char** argv, char** env)
 
     // FIXME: It might be nice to tear down the emulator properly.
     auto& emulator = *new UserspaceEmulator::Emulator(executable_path, arguments, environment);
-    emulator.set_profiling_details(dump_profile, profile_instruction_interval, profile_stream);
+
+    emulator.set_profiling_details(dump_profile, profile_instruction_interval, profile_stream, profile_strings, profile_string_id_map);
     emulator.set_in_region_of_interest(!enable_roi_mode);
 
     if (!emulator.load_elf())
@@ -109,8 +115,14 @@ int main(int argc, char** argv, char** env)
 
     rc = emulator.exec();
 
-    if (dump_profile)
-        emulator.profile_stream().write_or_error(R"(], "strings": []})"sv.bytes());
-
+    if (dump_profile) {
+        emulator.profile_stream().write_or_error(", \"strings\": ["sv.bytes());
+        if (emulator.profiler_strings().size()) {
+            for (size_t i = 0; i < emulator.profiler_strings().size() - 1; ++i)
+                emulator.profile_stream().write_or_error(String::formatted("\"{}\", ", emulator.profiler_strings().at(i)).bytes());
+            emulator.profile_stream().write_or_error(String::formatted("\"{}\"", emulator.profiler_strings().last()).bytes());
+        }
+        emulator.profile_stream().write_or_error("]}"sv.bytes());
+    }
     return rc;
 }