blob: 155a1e0c6f45ad5c0644affa289efffa12ceeeb0 [file] [log] [blame]
// Copyright 2017 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/linux/ptrace_broker.h"
#include <fcntl.h>
#include <limits.h>
#include <string.h>
#include <syscall.h>
#include <unistd.h>
#include <algorithm>
#include "base/logging.h"
#include "base/posix/eintr_wrapper.h"
#include "util/misc/memory_sanitizer.h"
namespace crashpad {
namespace {
size_t FormatPID(char* buffer, pid_t pid) {
DCHECK_GE(pid, 0);
char pid_buf[16];
size_t length = 0;
do {
DCHECK_LT(length, sizeof(pid_buf));
pid_buf[length] = '0' + pid % 10;
pid /= 10;
++length;
} while (pid > 0);
for (size_t index = 0; index < length; ++index) {
buffer[index] = pid_buf[length - index - 1];
}
return length;
}
} // namespace
PtraceBroker::PtraceBroker(int sock, pid_t pid, bool is_64_bit)
: ptracer_(is_64_bit, /* can_log= */ false),
file_root_(file_root_buffer_),
attachments_(nullptr),
attach_count_(0),
attach_capacity_(0),
memory_file_(),
sock_(sock),
memory_pid_(pid),
tried_opening_mem_file_(false) {
AllocateAttachments();
static constexpr char kProc[] = "/proc/";
size_t root_length = strlen(kProc);
memcpy(file_root_buffer_, kProc, root_length);
if (pid >= 0) {
root_length += FormatPID(file_root_buffer_ + root_length, pid);
DCHECK_LT(root_length, sizeof(file_root_buffer_));
file_root_buffer_[root_length] = '/';
++root_length;
}
DCHECK_LT(root_length, sizeof(file_root_buffer_));
file_root_buffer_[root_length] = '\0';
}
PtraceBroker::~PtraceBroker() = default;
void PtraceBroker::SetFileRoot(const char* new_root) {
DCHECK_EQ(new_root[strlen(new_root) - 1], '/');
memory_pid_ = -1;
file_root_ = new_root;
}
int PtraceBroker::Run() {
int result = RunImpl();
ReleaseAttachments();
return result;
}
bool PtraceBroker::AllocateAttachments() {
constexpr size_t page_size = 4096;
constexpr size_t alloc_size =
(sizeof(ScopedPtraceAttach) + page_size - 1) & ~(page_size - 1);
void* alloc = sbrk(alloc_size);
if (reinterpret_cast<intptr_t>(alloc) == -1) {
return false;
}
if (attachments_ == nullptr) {
attachments_ = reinterpret_cast<ScopedPtraceAttach*>(alloc);
}
attach_capacity_ += alloc_size / sizeof(ScopedPtraceAttach);
return true;
}
void PtraceBroker::ReleaseAttachments() {
for (size_t index = 0; index < attach_count_; ++index) {
attachments_[index].Reset();
}
}
int PtraceBroker::RunImpl() {
while (true) {
Request request = {};
if (!ReadFileExactly(sock_, &request, sizeof(request))) {
return errno;
}
if (request.version != Request::kVersion) {
return EINVAL;
}
switch (request.type) {
case Request::kTypeAttach: {
ScopedPtraceAttach* attach;
ScopedPtraceAttach stack_attach;
bool attach_on_stack = false;
if (attach_capacity_ > attach_count_ || AllocateAttachments()) {
attach = new (&attachments_[attach_count_]) ScopedPtraceAttach;
} else {
attach = &stack_attach;
attach_on_stack = true;
}
ExceptionHandlerProtocol::Bool status =
ExceptionHandlerProtocol::kBoolFalse;
if (attach->ResetAttach(request.tid)) {
status = ExceptionHandlerProtocol::kBoolTrue;
if (!attach_on_stack) {
++attach_count_;
}
}
if (!WriteFile(sock_, &status, sizeof(status))) {
return errno;
}
if (status == ExceptionHandlerProtocol::kBoolFalse) {
ExceptionHandlerProtocol::Errno error = errno;
if (!WriteFile(sock_, &error, sizeof(error))) {
return errno;
}
}
if (attach_on_stack && status == ExceptionHandlerProtocol::kBoolTrue) {
return RunImpl();
}
continue;
}
case Request::kTypeIs64Bit: {
ExceptionHandlerProtocol::Bool is_64_bit =
ptracer_.Is64Bit() ? ExceptionHandlerProtocol::kBoolTrue
: ExceptionHandlerProtocol::kBoolFalse;
if (!WriteFile(sock_, &is_64_bit, sizeof(is_64_bit))) {
return errno;
}
continue;
}
case Request::kTypeGetThreadInfo: {
GetThreadInfoResponse response;
response.success = ptracer_.GetThreadInfo(request.tid, &response.info)
? ExceptionHandlerProtocol::kBoolTrue
: ExceptionHandlerProtocol::kBoolFalse;
if (!WriteFile(sock_, &response, sizeof(response))) {
return errno;
}
if (response.success == ExceptionHandlerProtocol::kBoolFalse) {
ExceptionHandlerProtocol::Errno error = errno;
if (!WriteFile(sock_, &error, sizeof(error))) {
return errno;
}
}
continue;
}
case Request::kTypeReadFile: {
ScopedFileHandle handle;
int result = ReceiveAndOpenFilePath(request.path.path_length,
/* is_directory= */ false,
&handle);
if (result != 0) {
return result;
}
if (!handle.is_valid()) {
continue;
}
result = SendFileContents(handle.get());
if (result != 0) {
return result;
}
continue;
}
case Request::kTypeReadMemory: {
int result =
SendMemory(request.tid, request.iov.base, request.iov.size);
if (result != 0) {
return result;
}
continue;
}
case Request::kTypeListDirectory: {
ScopedFileHandle handle;
int result = ReceiveAndOpenFilePath(request.path.path_length,
/* is_directory= */ true,
&handle);
if (result != 0) {
return result;
}
if (!handle.is_valid()) {
continue;
}
result = SendDirectory(handle.get());
if (result != 0) {
return result;
}
continue;
}
case Request::kTypeExit:
return 0;
}
DCHECK(false);
return EINVAL;
}
}
int PtraceBroker::SendError(ExceptionHandlerProtocol::Errno err) {
return WriteFile(sock_, &err, sizeof(err)) ? 0 : errno;
}
int PtraceBroker::SendReadError(ReadError error) {
int32_t rv = -1;
return WriteFile(sock_, &rv, sizeof(rv)) &&
WriteFile(sock_, &error, sizeof(error))
? 0
: errno;
}
int PtraceBroker::SendOpenResult(OpenResult result) {
return WriteFile(sock_, &result, sizeof(result)) ? 0 : errno;
}
int PtraceBroker::SendFileContents(FileHandle handle) {
char buffer[4096];
int32_t rv;
do {
rv = ReadFile(handle, buffer, sizeof(buffer));
if (rv < 0) {
return SendReadError(static_cast<ReadError>(errno));
}
if (!WriteFile(sock_, &rv, sizeof(rv))) {
return errno;
}
if (rv > 0) {
if (!WriteFile(sock_, buffer, static_cast<size_t>(rv))) {
return errno;
}
}
} while (rv > 0);
return 0;
}
void PtraceBroker::TryOpeningMemFile() {
if (tried_opening_mem_file_) {
return;
}
tried_opening_mem_file_ = true;
if (memory_pid_ < 0) {
return;
}
char mem_path[32];
size_t root_length = strlen(file_root_buffer_);
static constexpr char kMem[] = "mem";
DCHECK_LT(root_length + strlen(kMem) + 1, sizeof(mem_path));
memcpy(mem_path, file_root_buffer_, root_length);
// Include the trailing NUL.
memcpy(mem_path + root_length, kMem, strlen(kMem) + 1);
memory_file_.reset(
HANDLE_EINTR(open(mem_path, O_RDONLY | O_CLOEXEC | O_NOCTTY)));
}
int PtraceBroker::SendMemory(pid_t pid, VMAddress address, VMSize size) {
if (memory_pid_ >= 0 && pid != memory_pid_) {
return SendReadError(kReadErrorAccessDenied);
}
TryOpeningMemFile();
auto read_memory = [this, pid](VMAddress address, size_t size, char* buffer) {
return this->memory_file_.is_valid()
? HANDLE_EINTR(
pread64(this->memory_file_.get(), buffer, size, address))
: this->ptracer_.ReadUpTo(pid, address, size, buffer);
};
char buffer[4096];
while (size > 0) {
size_t to_read = std::min(size, VMSize{sizeof(buffer)});
int32_t bytes_read = read_memory(address, to_read, buffer);
if (bytes_read < 0) {
return SendReadError(static_cast<ReadError>(errno));
}
if (!WriteFile(sock_, &bytes_read, sizeof(bytes_read))) {
return errno;
}
if (bytes_read == 0) {
return 0;
}
if (!WriteFile(sock_, buffer, bytes_read)) {
return errno;
}
size -= bytes_read;
address += bytes_read;
}
return 0;
}
#if defined(MEMORY_SANITIZER)
// MSan doesn't intercept syscall() and doesn't see that buffer is initialized.
__attribute__((no_sanitize("memory")))
#endif // defined(MEMORY_SANITIZER)
int PtraceBroker::SendDirectory(FileHandle handle) {
char buffer[4096];
int rv;
do {
rv = syscall(SYS_getdents64, handle, buffer, sizeof(buffer));
if (rv < 0) {
return SendReadError(static_cast<ReadError>(errno));
}
if (!WriteFile(sock_, &rv, sizeof(rv))) {
return errno;
}
if (rv > 0) {
if (!WriteFile(sock_, buffer, static_cast<size_t>(rv))) {
return errno;
}
}
} while (rv > 0);
return 0;
}
int PtraceBroker::ReceiveAndOpenFilePath(VMSize path_length,
bool is_directory,
ScopedFileHandle* handle) {
char path[std::max(4096, PATH_MAX)];
if (path_length >= sizeof(path)) {
return SendOpenResult(kOpenResultTooLong);
}
if (!ReadFileExactly(sock_, path, path_length)) {
return errno;
}
path[path_length] = '\0';
if (strncmp(path, file_root_, strlen(file_root_)) != 0) {
return SendOpenResult(kOpenResultAccessDenied);
}
int flags = O_RDONLY | O_CLOEXEC | O_NOCTTY;
if (is_directory) {
flags |= O_DIRECTORY;
}
ScopedFileHandle local_handle(HANDLE_EINTR(open(path, flags)));
if (!local_handle.is_valid()) {
return SendOpenResult(static_cast<OpenResult>(errno));
}
handle->reset(local_handle.release());
return SendOpenResult(kOpenResultSuccess);
}
} // namespace crashpad