crashpad/util/fuchsia/koid_utilities.cc

// Copyright 2018 The Crashpad Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "util/fuchsia/koid_utilities.h"

#include <lib/zx/job.h>
#include <lib/zx/process.h>
#include <zircon/device/sysinfo.h>

#include <vector>

#include "base/files/file_path.h"
#include "base/fuchsia/fuchsia_logging.h"
#include "util/file/file_io.h"

namespace crashpad {

namespace {

// Casts |handle| into a container of type T, returning a null handle if the
// actual handle type does not match that of T.
template <typename T>
T CastHandle(zx::handle handle) {
  zx_info_handle_basic_t actual = {};
  zx_status_t status = handle.get_info(
      ZX_INFO_HANDLE_BASIC, &actual, sizeof(actual), nullptr, nullptr);
  if (status != ZX_OK) {
    ZX_LOG(ERROR, status) << "zx_object_get_info";
    return T();
  }
  if (actual.type != T::TYPE) {
    LOG(ERROR) << "Wrong type: " << actual.type << ", expected " << T::TYPE;
    return T();
  }
  return T(std::move(handle));
}

zx::job GetRootJob() {
  ScopedFileHandle sysinfo(
      LoggingOpenFileForRead(base::FilePath("/dev/misc/sysinfo")));
  if (!sysinfo.is_valid())
    return zx::job();

  zx::handle root_job;
  size_t n = ioctl_sysinfo_get_root_job(sysinfo.get(),
                                        root_job.reset_and_get_address());
  if (n != sizeof(zx_handle_t)) {
    LOG(ERROR) << "unexpected root job size";
    return zx::job();
  }
  return CastHandle<zx::job>(std::move(root_job));
}

// Returns null handle if |koid| is not found or an error occurs. If |was_found|
// is non-null then it will be set, to distinguish not-found from other errors.
template <typename T, typename U>
T GetChildHandleByKoid(const U& parent, zx_koid_t child_koid, bool* was_found) {
  zx::handle handle;
  zx_status_t status =
      parent.get_child(child_koid, ZX_RIGHT_SAME_RIGHTS, &handle);
  if (was_found)
    *was_found = (status != ZX_ERR_NOT_FOUND);
  if (status != ZX_OK) {
    ZX_LOG(ERROR, status) << "zx_object_get_child";
    return T();
  }

  return CastHandle<T>(std::move(handle));
}

// Returns an invalid handle if the |koid| was found, but was of the wrong
// type, or we could not open a handle to it.
zx::process FindProcess(const zx::job& job, zx_koid_t koid, bool* was_found) {
  DCHECK(!*was_found);

  // Look for |koid| as a direct descendent of |job|.
  auto process = GetChildHandleByKoid<zx::process>(job, koid, was_found);
  if (*was_found) {
    // |koid| was found. |process| may still be null, e.g. if a handle could not
    // be opened to it.
    return process;
  }

  // |koid| was not found under |job|, so search child jobs, if any.
  // Since we only hold a handle to the job we are currently enumerating, child
  // jobs may go away mid-enumeration.
  for (auto child_koid : GetChildKoids(job, ZX_INFO_JOB_CHILDREN)) {
    zx::job child_job = GetChildHandleByKoid<zx::job>(job, child_koid, nullptr);
    if (!child_job.is_valid())
      continue;
    zx::process process = FindProcess(child_job, koid, was_found);
    if (*was_found)
      return process;
  }

  DCHECK(!*was_found);
  return zx::process();
}

}  // namespace

std::vector<zx_koid_t> GetChildKoids(const zx::object_base& parent_object,
                                     zx_object_info_topic_t child_kind) {
  size_t actual = 0;
  size_t available = 0;
  std::vector<zx_koid_t> result(100);
  zx::unowned_handle parent(parent_object.get());

  // This is inherently racy. Better if the process is suspended, but there's
  // still no guarantee that a thread isn't externally created. As a result,
  // must be in a retry loop.
  for (;;) {
    zx_status_t status = parent->get_info(child_kind,
                                          result.data(),
                                          result.size() * sizeof(zx_koid_t),
                                          &actual,
                                          &available);
    // If the buffer is too small (even zero), the result is still ZX_OK, not
    // ZX_ERR_BUFFER_TOO_SMALL.
    if (status != ZX_OK) {
      ZX_LOG(ERROR, status) << "zx_object_get_info";
      break;
    }

    if (actual == available) {
      break;
    }

    // Resize to the expected number next time, with a bit of slop to handle the
    // race between here and the next request.
    result.resize(available + 10);
  }

  result.resize(actual);
  return result;
}

std::vector<zx::thread> GetThreadHandles(const zx::process& parent) {
  auto koids = GetChildKoids(parent, ZX_INFO_PROCESS_THREADS);
  return GetHandlesForThreadKoids(parent, koids);
}

std::vector<zx::thread> GetHandlesForThreadKoids(
    const zx::process& parent,
    const std::vector<zx_koid_t>& koids) {
  std::vector<zx::thread> result;
  result.reserve(koids.size());
  for (zx_koid_t koid : koids) {
    result.emplace_back(GetThreadHandleByKoid(parent, koid));
  }
  return result;
}

zx::thread GetThreadHandleByKoid(const zx::process& parent,
                                 zx_koid_t child_koid) {
  return GetChildHandleByKoid<zx::thread>(parent, child_koid, nullptr);
}

zx_koid_t GetKoidForHandle(const zx::object_base& object) {
  zx_info_handle_basic_t info;
  zx_status_t status = zx_object_get_info(object.get(),
                                          ZX_INFO_HANDLE_BASIC,
                                          &info,
                                          sizeof(info),
                                          nullptr,
                                          nullptr);
  if (status != ZX_OK) {
    ZX_LOG(ERROR, status) << "zx_object_get_info";
    return ZX_KOID_INVALID;
  }
  return info.koid;
}

// TODO(scottmg): This implementation uses some debug/temporary/hacky APIs and
// ioctls that are currently the only way to go from pid to handle. This should
// hopefully eventually be replaced by more or less a single
// zx_debug_something() syscall.
zx::process GetProcessFromKoid(zx_koid_t koid) {
  bool was_found = false;
  zx::process result = FindProcess(GetRootJob(), koid, &was_found);
  if (!result.is_valid())
    LOG(ERROR) << "process " << koid << " not found";
  return result;
}

}  // namespace crashpad