madvise.cc

// Copyright (c) 2010 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "debug.h"
#include "sandbox_impl.h"

namespace playground {

long Sandbox::sandbox_madvise(void* start, size_t length, int advice) {
  long long tm;
  Debug::syscall(&tm, __NR_madvise, "Executing handler");
  struct {
    struct RequestHeader header;
    MAdvise   madvise_req;
  } __attribute__((packed)) request;
  request.madvise_req.start  = start;
  request.madvise_req.len    = length;
  request.madvise_req.advice = advice;

  long rc = forwardSyscall(__NR_madvise, &request.header, sizeof(request));
  Debug::elapsed(tm, __NR_madvise);
  return rc;
}

bool Sandbox::process_madvise(const SecureMem::SyscallRequestInfo* info) {
  // Read request
  MAdvise madvise_req;
  SysCalls sys;
  if (read(sys, info->trustedProcessFd, &madvise_req, sizeof(madvise_req)) !=
      sizeof(madvise_req)) {
    die("Failed to read parameters for madvise() [process]");
  }
  switch (madvise_req.advice) {
    case MADV_NORMAL:
    case MADV_RANDOM:
    case MADV_SEQUENTIAL:
    case MADV_WILLNEED:
    ok:
      SecureMem::sendSystemCall(*info, SecureMem::SEND_UNLOCKED,
                                const_cast<void*>(madvise_req.start),
                                madvise_req.len, madvise_req.advice);
      return true;
    default:
      // All other flags to madvise() are potential dangerous (as opposed to
      // merely affecting overall performance). Do not allow them on memory
      // ranges that were part of the original mappings.
      if (isRegionProtected((void *) madvise_req.start, madvise_req.len)) {
        SecureMem::abandonSystemCall(*info, -EINVAL);
        return false;
      }

      // Changing attributes on memory regions that were newly mapped inside of
      // the sandbox is OK.
      goto ok;
  }
}

} // namespace