Kernel+LibC: Add sys$perf_register_string()

This syscall allows userspace to register a keyed string that appears in a new "strings" JSON object in profile output. This will be used to add custom strings to profile signposts. :^)
Cnidarias · Aug 11, 2021 · 4657c79 · 4657c79
1 parent 00b11d7
commit 4657c79
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Showing 7 changed files with 43 additions and 0 deletions.
diff --git a/Kernel/API/Syscall.h b/Kernel/API/Syscall.h
@@ -131,6 +131,7 @@ enum class NeedsBigProcessLock {
  S(munmap, NeedsBigProcessLock::Yes) \
  S(open, NeedsBigProcessLock::Yes) \
  S(perf_event, NeedsBigProcessLock::Yes) \
+ S(perf_register_string, NeedsBigProcessLock::Yes) \
  S(pipe, NeedsBigProcessLock::Yes) \
  S(pledge, NeedsBigProcessLock::Yes) \
  S(poll, NeedsBigProcessLock::Yes) \

diff --git a/Kernel/PerformanceEventBuffer.cpp b/Kernel/PerformanceEventBuffer.cpp
@@ -166,6 +166,13 @@ PerformanceEvent& PerformanceEventBuffer::at(size_t index)
 template<typename Serializer>
 bool PerformanceEventBuffer::to_json_impl(Serializer& object) const
 {
+ {
+ auto strings = object.add_object("strings");
+ for (auto& it : m_strings) {
+ strings.add(String::number(it.key), it.value->view());
+ }
+ }
+
  auto array = object.add_array("events");
  bool seen_first_sample = false;
  for (size_t i = 0; i < m_count; ++i) {
@@ -298,4 +305,13 @@ void PerformanceEventBuffer::add_process(const Process& process, ProcessEventTyp
  }
 }
 
+KResult PerformanceEventBuffer::register_string(FlatPtr string_id, NonnullOwnPtr<KString> string)
+{
+ m_strings.set(string_id, move(string));
+
+ // FIXME: Switch m_strings to something that can signal allocation failure,
+ // and then propagate such failures here.
+ return KSuccess;
+}
+
 }
diff --git a/Kernel/PerformanceEventBuffer.h b/Kernel/PerformanceEventBuffer.h
@@ -120,6 +120,8 @@ class PerformanceEventBuffer {
 
  void add_process(const Process&, ProcessEventType event_type);
 
+ KResult register_string(FlatPtr string_id, NonnullOwnPtr<KString>);
+
 private:
  explicit PerformanceEventBuffer(NonnullOwnPtr<KBuffer>);
 
@@ -130,6 +132,8 @@ class PerformanceEventBuffer {
 
  size_t m_count { 0 };
  NonnullOwnPtr<KBuffer> m_buffer;
+
+ HashMap<FlatPtr, NonnullOwnPtr<KString>> m_strings;
 };
 
 extern bool g_profiling_all_threads;

diff --git a/Kernel/Process.h b/Kernel/Process.h
@@ -400,6 +400,7 @@ class Process
  KResultOr<FlatPtr> sys$pledge(Userspace<const Syscall::SC_pledge_params*>);
  KResultOr<FlatPtr> sys$unveil(Userspace<const Syscall::SC_unveil_params*>);
  KResultOr<FlatPtr> sys$perf_event(int type, FlatPtr arg1, FlatPtr arg2);
+ KResultOr<FlatPtr> sys$perf_register_string(FlatPtr string_id, Userspace<char const*>, size_t);
  KResultOr<FlatPtr> sys$get_stack_bounds(Userspace<FlatPtr*> stack_base, Userspace<size_t*> stack_size);
  KResultOr<FlatPtr> sys$ptrace(Userspace<const Syscall::SC_ptrace_params*>);
  KResultOr<FlatPtr> sys$sendfd(int sockfd, int fd);

diff --git a/Kernel/Syscalls/perf_event.cpp b/Kernel/Syscalls/perf_event.cpp
@@ -21,4 +21,18 @@ KResultOr<FlatPtr> Process::sys$perf_event(int type, FlatPtr arg1, FlatPtr arg2)
  return events_buffer->append(type, arg1, arg2, nullptr);
 }
 
+KResultOr<FlatPtr> Process::sys$perf_register_string(FlatPtr string_id, Userspace<char const*> user_string, size_t user_string_length)
+{
+ VERIFY_PROCESS_BIG_LOCK_ACQUIRED(this)
+ auto* events_buffer = current_perf_events_buffer();
+ if (!events_buffer)
+ return KSuccess;
+
+ auto string_or_error = try_copy_kstring_from_user(user_string, user_string_length);
+ if (string_or_error.is_error())
+ return string_or_error.error();
+
+ return events_buffer->register_string(string_id, string_or_error.release_value());
+}
+
 }
diff --git a/Userland/Libraries/LibC/serenity.cpp b/Userland/Libraries/LibC/serenity.cpp
@@ -95,6 +95,12 @@ int perf_event(int type, uintptr_t arg1, FlatPtr arg2)
  __RETURN_WITH_ERRNO(rc, rc, -1);
 }
 
+int perf_register_string(uintptr_t string_id, char const* string, size_t string_length)
+{
+ int rc = syscall(SC_perf_register_string, string_id, string, string_length);
+ __RETURN_WITH_ERRNO(rc, rc, -1);
+}
+
 int get_stack_bounds(uintptr_t* user_stack_base, size_t* user_stack_size)
 {
  int rc = syscall(SC_get_stack_bounds, user_stack_base, user_stack_size);

diff --git a/Userland/Libraries/LibC/serenity.h b/Userland/Libraries/LibC/serenity.h
@@ -119,6 +119,7 @@ enum {
 #define PERF_EVENT_MASK_ALL (~0ull)
 
 int perf_event(int type, uintptr_t arg1, uintptr_t arg2);
+int perf_register_string(uintptr_t string_id, char const* string, size_t string_length);
 
 int get_stack_bounds(uintptr_t* user_stack_base, size_t* user_stack_size);