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This supports the “double handler” or “double handler with low probability” models from https://crashpad.chromium.org/bug/143. For crashpad_handler to be become its own client, it needs access to its own executable path to pass to CrashpadClient::StartHandler(). This was formerly available in the test-only test::Paths::Executable(). Bring that function’s implementation to the non-test Paths::Executable() in util/misc, and rename test::Paths to test::TestPaths to avoid future confusion. test::TestPaths must still be used to access TestDataRoot(), which does not make any sense to non-test code. test::TestPaths::Executable() is retained for use by tests, which most likely prefer the fatal semantics of that function. Paths::Executable() is not fatal because for the purposes of implementing the double handler, a failure to locate the executable path (which may happen on some systems in deeply-nested directory hierarchies) shouldn’t cause the initial crashpad_handler to abort, even if it does prevent a second crashpad_handler from being started. Bug: crashpad:143 Test: crashpad_util_test Paths.*, crashpad_test_test TestPaths.* Change-Id: I9f75bf61839ce51e33c9f7c0d7031cebead6a156 Reviewed-on: https://chromium-review.googlesource.com/466346 Reviewed-by: Scott Graham <scottmg@chromium.org> Commit-Queue: Mark Mentovai <mark@chromium.org>
62 lines
2.2 KiB
C++
62 lines
2.2 KiB
C++
// Copyright 2016 The Crashpad Authors. All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "util/misc/paths.h"
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#include <limits.h>
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#include <unistd.h>
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#include <algorithm>
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#include <string>
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#include "base/logging.h"
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namespace crashpad {
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// static
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bool Paths::Executable(base::FilePath* path) {
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// Linux does not provide a straightforward way to size the buffer before
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// calling readlink(). Normally, the st_size field returned by lstat() could
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// be used, but this is usually zero for things in /proc.
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//
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// The /proc filesystem does not provide any way to read “exe” links for
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// pathnames longer than a page. See linux-4.9.20/fs/proc/base.c
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// do_proc_readlink(), which allocates a single page to receive the path
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// string. Coincidentally, the page size and PATH_MAX are normally the same
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// value, although neither is strictly a limit on the length of a pathname.
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//
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// On Android, the smaller of the page size and PATH_MAX actually does serve
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// as an effective limit on the length of an executable’s pathname. See
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// Android 7.1.1 bionic/linker/linker.cpp get_executable_path(), which aborts
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// via __libc_fatal() if the “exe” link can’t be read into a PATH_MAX-sized
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// buffer.
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std::string exe_path(std::max(getpagesize(), PATH_MAX),
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std::string::value_type());
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ssize_t exe_path_len =
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readlink("/proc/self/exe", &exe_path[0], exe_path.size());
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if (exe_path_len < 0) {
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PLOG(ERROR) << "readlink";
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return false;
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} else if (static_cast<size_t>(exe_path_len) >= exe_path.size()) {
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LOG(ERROR) << "readlink";
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return false;
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}
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exe_path.resize(exe_path_len);
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*path = base::FilePath(exe_path);
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return true;
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}
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} // namespace crashpad
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