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// Copyright (c) 2012 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 "components/nacl/zygote/nacl_fork_delegate_linux.h"
#include <signal.h>
#include <stdlib.h>
#include <sys/resource.h>
#include <sys/socket.h>
#include <set>
#include "base/basictypes.h"
#include "base/command_line.h"
#include "base/cpu.h"
#include "base/files/file_path.h"
#include "base/logging.h"
#include "base/path_service.h"
#include "base/posix/eintr_wrapper.h"
#include "base/posix/unix_domain_socket_linux.h"
#include "base/process/launch.h"
#include "base/third_party/dynamic_annotations/dynamic_annotations.h"
#include "components/nacl/common/nacl_helper_linux.h"
#include "components/nacl/common/nacl_paths.h"
#include "components/nacl/common/nacl_switches.h"
namespace {
// Note these need to match up with their counterparts in nacl_helper_linux.c
// and nacl_helper_bootstrap_linux.c.
const char kNaClHelperReservedAtZero[] =
"--reserved_at_zero=0xXXXXXXXXXXXXXXXX";
const char kNaClHelperRDebug[] = "--r_debug=0xXXXXXXXXXXXXXXXX";
#if defined(ARCH_CPU_X86)
bool NonZeroSegmentBaseIsSlow() {
base::CPU cpuid;
// Using a non-zero segment base is known to be very slow on Intel
// Atom CPUs. See "Segmentation-based Memory Protection Mechanism
// on Intel Atom Microarchitecture: Coding Optimizations" (Leonardo
// Potenza, Intel).
//
// The following list of CPU model numbers is taken from:
// "Intel 64 and IA-32 Architectures Software Developer's Manual"
// (http://download.intel.com/products/processor/manual/325462.pdf),
// "Table 35-1. CPUID Signature Values of DisplayFamily_DisplayModel"
// (Volume 3C, 35-1), which contains:
// "06_36H - Intel Atom S Processor Family
// 06_1CH, 06_26H, 06_27H, 06_35, 06_36 - Intel Atom Processor Family"
if (cpuid.family() == 6) {
switch (cpuid.model()) {
case 0x1c:
case 0x26:
case 0x27:
case 0x35:
case 0x36:
return true;
}
}
return false;
}
#endif
}
NaClForkDelegate::NaClForkDelegate()
: status_(kNaClHelperUnused),
fd_(-1) {}
void NaClForkDelegate::Init(const int sandboxdesc) {
VLOG(1) << "NaClForkDelegate::Init()";
int fds[2];
// Confirm a hard-wired assumption.
// The NaCl constant is from chrome/nacl/nacl_linux_helper.h
DCHECK(kNaClSandboxDescriptor == sandboxdesc);
CHECK(socketpair(PF_UNIX, SOCK_SEQPACKET, 0, fds) == 0);
base::FileHandleMappingVector fds_to_map;
fds_to_map.push_back(std::make_pair(fds[1], kNaClZygoteDescriptor));
fds_to_map.push_back(std::make_pair(sandboxdesc, kNaClSandboxDescriptor));
// Using nacl_helper_bootstrap is not necessary on x86-64 because
// NaCl's x86-64 sandbox is not zero-address-based. Starting
// nacl_helper through nacl_helper_bootstrap works on x86-64, but it
// leaves nacl_helper_bootstrap mapped at a fixed address at the
// bottom of the address space, which is undesirable because it
// effectively defeats ASLR.
#if defined(ARCH_CPU_X86_64)
bool kUseNaClBootstrap = false;
#elif defined(ARCH_CPU_X86)
// Performance vs. security trade-off: We prefer using a
// non-zero-address-based sandbox on x86-32 because it provides some
// ASLR and so is more secure. However, on Atom CPUs, using a
// non-zero segment base is very slow, so we use a zero-based
// sandbox on those.
bool kUseNaClBootstrap = NonZeroSegmentBaseIsSlow();
#else
bool kUseNaClBootstrap = true;
#endif
status_ = kNaClHelperUnused;
base::FilePath helper_exe;
base::FilePath helper_bootstrap_exe;
if (!PathService::Get(nacl::FILE_NACL_HELPER, &helper_exe)) {
status_ = kNaClHelperMissing;
} else if (kUseNaClBootstrap &&
!PathService::Get(nacl::FILE_NACL_HELPER_BOOTSTRAP,
&helper_bootstrap_exe)) {
status_ = kNaClHelperBootstrapMissing;
} else if (RunningOnValgrind()) {
status_ = kNaClHelperValgrind;
} else {
CommandLine cmd_line(CommandLine::NO_PROGRAM);
if (kUseNaClBootstrap) {
cmd_line.SetProgram(helper_bootstrap_exe);
cmd_line.AppendArgPath(helper_exe);
cmd_line.AppendArgNative(kNaClHelperReservedAtZero);
cmd_line.AppendArgNative(kNaClHelperRDebug);
} else {
cmd_line.SetProgram(helper_exe);
}
base::LaunchOptions options;
options.fds_to_remap = &fds_to_map;
options.clone_flags = CLONE_FS | SIGCHLD;
// The NaCl processes spawned may need to exceed the ambient soft limit
// on RLIMIT_AS to allocate the untrusted address space and its guard
// regions. The nacl_helper itself cannot just raise its own limit,
// because the existing limit may prevent the initial exec of
// nacl_helper_bootstrap from succeeding, with its large address space
// reservation.
std::set<int> max_these_limits;
max_these_limits.insert(RLIMIT_AS);
options.maximize_rlimits = &max_these_limits;
if (!base::LaunchProcess(cmd_line.argv(), options, NULL))
status_ = kNaClHelperLaunchFailed;
// parent and error cases are handled below
}
if (HANDLE_EINTR(close(fds[1])) != 0)
LOG(ERROR) << "close(fds[1]) failed";
if (status_ == kNaClHelperUnused) {
const ssize_t kExpectedLength = strlen(kNaClHelperStartupAck);
char buf[kExpectedLength];
// Wait for ack from nacl_helper, indicating it is ready to help
const ssize_t nread = HANDLE_EINTR(read(fds[0], buf, sizeof(buf)));
if (nread == kExpectedLength &&
memcmp(buf, kNaClHelperStartupAck, nread) == 0) {
// all is well
status_ = kNaClHelperSuccess;
fd_ = fds[0];
return;
}
status_ = kNaClHelperAckFailed;
LOG(ERROR) << "Bad NaCl helper startup ack (" << nread << " bytes)";
}
// TODO(bradchen): Make this LOG(ERROR) when the NaCl helper
// becomes the default.
fd_ = -1;
if (HANDLE_EINTR(close(fds[0])) != 0)
LOG(ERROR) << "close(fds[0]) failed";
}
void NaClForkDelegate::InitialUMA(std::string* uma_name,
int* uma_sample,
int* uma_boundary_value) {
*uma_name = "NaCl.Client.Helper.InitState";
*uma_sample = status_;
*uma_boundary_value = kNaClHelperStatusBoundary;
}
NaClForkDelegate::~NaClForkDelegate() {
// side effect of close: delegate process will terminate
if (status_ == kNaClHelperSuccess) {
if (HANDLE_EINTR(close(fd_)) != 0)
LOG(ERROR) << "close(fd_) failed";
}
}
bool NaClForkDelegate::CanHelp(const std::string& process_type,
std::string* uma_name,
int* uma_sample,
int* uma_boundary_value) {
if (process_type != switches::kNaClLoaderProcess)
return false;
*uma_name = "NaCl.Client.Helper.StateOnFork";
*uma_sample = status_;
*uma_boundary_value = kNaClHelperStatusBoundary;
return status_ == kNaClHelperSuccess;
}
pid_t NaClForkDelegate::Fork(const std::vector<int>& fds) {
base::ProcessId naclchild;
VLOG(1) << "NaClForkDelegate::Fork";
DCHECK(fds.size() == kNaClParentFDIndex + 1);
if (!UnixDomainSocket::SendMsg(fd_, kNaClForkRequest,
strlen(kNaClForkRequest), fds)) {
LOG(ERROR) << "NaClForkDelegate::Fork: SendMsg failed";
return -1;
}
int nread = HANDLE_EINTR(read(fd_, &naclchild, sizeof(naclchild)));
if (nread != sizeof(naclchild)) {
LOG(ERROR) << "NaClForkDelegate::Fork: read failed";
return -1;
}
VLOG(1) << "nacl_child is " << naclchild << " (" << nread << " bytes)";
return naclchild;
}
bool NaClForkDelegate::AckChild(const int fd,
const std::string& channel_switch) {
int nwritten = HANDLE_EINTR(write(fd, channel_switch.c_str(),
channel_switch.length()));
if (nwritten != static_cast<int>(channel_switch.length())) {
return false;
}
return true;
}
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