IntelPTCollector.cpp

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//===-- IntelPTCollector.cpp ----------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
 
#include "IntelPTCollector.h"
 
#include "Plugins/Process/Linux/Procfs.h"
#include "Plugins/Process/POSIX/ProcessPOSIXLog.h"
#include "lldb/Utility/StreamString.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/MathExtras.h"
 
#include <fcntl.h>
#include <fstream>
#include <linux/perf_event.h>
#include <optional>
#include <sys/ioctl.h>
#include <sys/syscall.h>
 
using namespace lldb;
using namespace lldb_private;
using namespace process_linux;
using namespace llvm;
 
IntelPTCollector::IntelPTCollector(NativeProcessProtocol &process)
    : m_process(process) {}
 
llvm::Expected<LinuxPerfZeroTscConversion &>
IntelPTCollector::FetchPerfTscConversionParameters() {
  if (Expected<LinuxPerfZeroTscConversion> tsc_conversion =
          LoadPerfTscConversionParameters())
    return *tsc_conversion;
  else
    return createStringError(inconvertibleErrorCode(),
                             "Unable to load TSC to wall time conversion: %s",
                             toString(tsc_conversion.takeError()).c_str());
}
 
Error IntelPTCollector::TraceStop(lldb::tid_t tid) {
  if (m_process_trace_up && m_process_trace_up->TracesThread(tid))
    return m_process_trace_up->TraceStop(tid);
  return m_thread_traces.TraceStop(tid);
}
 
Error IntelPTCollector::TraceStop(const TraceStopRequest &request) {
  if (request.IsProcessTracing()) {
    Clear();
    return Error::success();
  } else {
    Error error = Error::success();
    for (int64_t tid : *request.tids)
      error = joinErrors(std::move(error),
                         TraceStop(static_cast<lldb::tid_t>(tid)));
    return error;
  }
}
 
/// \return
///   some file descriptor in /sys/fs/ associated with the cgroup of the given
///   pid, or \a std::nullopt if the pid is not part of a cgroup.
static std::optional<int> GetCGroupFileDescriptor(lldb::pid_t pid) {
  static std::optional<int> fd;
  if (fd)
    return fd;
 
  std::ifstream ifile;
  ifile.open(formatv("/proc/{0}/cgroup", pid));
  if (!ifile)
    return std::nullopt;
 
  std::string line;
  while (std::getline(ifile, line)) {
    if (line.find("0:") != 0)
      continue;
 
    std::string slice = line.substr(line.find_first_of('/'));
    if (slice.empty())
      return std::nullopt;
    std::string cgroup_file = formatv("/sys/fs/cgroup/{0}", slice);
    // This cgroup should for the duration of the target, so we don't need to
    // invoke close ourselves.
    int maybe_fd = open(cgroup_file.c_str(), O_RDONLY);
    if (maybe_fd != -1) {
      fd = maybe_fd;
      return fd;
    }
  }
  return std::nullopt;
}
 
Error IntelPTCollector::TraceStart(const TraceIntelPTStartRequest &request) {
  if (request.IsProcessTracing()) {
    if (m_process_trace_up) {
      return createStringError(
          inconvertibleErrorCode(),
          "Process currently traced. Stop process tracing first");
    }
    if (request.IsPerCpuTracing()) {
      if (m_thread_traces.GetTracedThreadsCount() > 0)
        return createStringError(
            inconvertibleErrorCode(),
            "Threads currently traced. Stop tracing them first.");
      // CPU tracing is useless if we can't convert tsc to nanos.
      Expected<LinuxPerfZeroTscConversion &> tsc_conversion =
          FetchPerfTscConversionParameters();
      if (!tsc_conversion)
        return tsc_conversion.takeError();
 
      // We force the enablement of TSCs, which is needed for correlating the
      // cpu traces.
      TraceIntelPTStartRequest effective_request = request;
      effective_request.enable_tsc = true;
 
      // We try to use cgroup filtering whenever possible
      std::optional<int> cgroup_fd;
      if (!request.disable_cgroup_filtering.value_or(false))
        cgroup_fd = GetCGroupFileDescriptor(m_process.GetID());
 
      if (Expected<IntelPTProcessTraceUP> trace =
              IntelPTMultiCoreTrace::StartOnAllCores(effective_request,
                                                     m_process, cgroup_fd)) {
        m_process_trace_up = std::move(*trace);
        return Error::success();
      } else {
        return trace.takeError();
      }
    } else {
      std::vector<lldb::tid_t> process_threads;
      for (NativeThreadProtocol &thread : m_process.Threads())
        process_threads.push_back(thread.GetID());
 
      // per-thread process tracing
      if (Expected<IntelPTProcessTraceUP> trace =
              IntelPTPerThreadProcessTrace::Start(request, process_threads)) {
        m_process_trace_up = std::move(trace.get());
        return Error::success();
      } else {
        return trace.takeError();
      }
    }
  } else {
    // individual thread tracing
    Error error = Error::success();
    for (int64_t tid : *request.tids) {
      if (m_process_trace_up && m_process_trace_up->TracesThread(tid))
        error = joinErrors(
            std::move(error),
            createStringError(inconvertibleErrorCode(),
                              formatv("Thread with tid {0} is currently "
                                      "traced. Stop tracing it first.",
                                      tid)
                                  .str()
                                  .c_str()));
      else
        error = joinErrors(std::move(error),
                           m_thread_traces.TraceStart(tid, request));
    }
    return error;
  }
}
 
void IntelPTCollector::ProcessWillResume() {
  if (m_process_trace_up)
    m_process_trace_up->ProcessWillResume();
}
 
void IntelPTCollector::ProcessDidStop() {
  if (m_process_trace_up)
    m_process_trace_up->ProcessDidStop();
}
 
Error IntelPTCollector::OnThreadCreated(lldb::tid_t tid) {
  if (m_process_trace_up)
    return m_process_trace_up->TraceStart(tid);
 
  return Error::success();
}
 
Error IntelPTCollector::OnThreadDestroyed(lldb::tid_t tid) {
  if (m_process_trace_up && m_process_trace_up->TracesThread(tid))
    return m_process_trace_up->TraceStop(tid);
  else if (m_thread_traces.TracesThread(tid))
    return m_thread_traces.TraceStop(tid);
  return Error::success();
}
 
Expected<json::Value> IntelPTCollector::GetState() {
  Expected<ArrayRef<uint8_t>> cpu_info = GetProcfsCpuInfo();
  if (!cpu_info)
    return cpu_info.takeError();
 
  TraceIntelPTGetStateResponse state;
  if (m_process_trace_up)
    state = m_process_trace_up->GetState();
 
  state.process_binary_data.push_back(
      {IntelPTDataKinds::kProcFsCpuInfo, cpu_info->size()});
 
  m_thread_traces.ForEachThread(
      [&](lldb::tid_t tid, const IntelPTSingleBufferTrace &thread_trace) {
        state.traced_threads.push_back(
            {tid,
             {{IntelPTDataKinds::kIptTrace, thread_trace.GetIptTraceSize()}}});
      });
 
  if (Expected<LinuxPerfZeroTscConversion &> tsc_conversion =
          FetchPerfTscConversionParameters())
    state.tsc_perf_zero_conversion = *tsc_conversion;
  else
    state.AddWarning(toString(tsc_conversion.takeError()));
  return toJSON(state);
}
 
Expected<std::vector<uint8_t>>
IntelPTCollector::GetBinaryData(const TraceGetBinaryDataRequest &request) {
  if (request.kind == IntelPTDataKinds::kProcFsCpuInfo)
    return GetProcfsCpuInfo();
 
  if (m_process_trace_up) {
    Expected<std::optional<std::vector<uint8_t>>> data =
        m_process_trace_up->TryGetBinaryData(request);
    if (!data)
      return data.takeError();
    if (*data)
      return **data;
  }
 
  {
    Expected<std::optional<std::vector<uint8_t>>> data =
        m_thread_traces.TryGetBinaryData(request);
    if (!data)
      return data.takeError();
    if (*data)
      return **data;
  }
 
  return createStringError(
      inconvertibleErrorCode(),
      formatv("Can't fetch data kind {0} for cpu_id {1}, tid {2} and "
              "\"process tracing\" mode {3}",
              request.kind, request.cpu_id, request.tid,
              m_process_trace_up ? "enabled" : "not enabled"));
}
 
bool IntelPTCollector::IsSupported() {
  if (Expected<uint32_t> intel_pt_type = GetIntelPTOSEventType()) {
    return true;
  } else {
    llvm::consumeError(intel_pt_type.takeError());
    return false;
  }
}
 
void IntelPTCollector::Clear() {
  m_process_trace_up.reset();
  m_thread_traces.Clear();
}