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/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#include "mongo/platform/basic.h"
#include <cstdio>
#include <cstdlib>
#include <cxxabi.h>
#include <functional>
#include <sstream>
#include <fmt/format.h>
#include <fmt/printf.h>
#define UNW_LOCAL_ONLY
#include <libunwind.h>
#include "mongo/logv2/log.h"
#include "mongo/unittest/unittest.h"
#include "mongo/util/stacktrace.h"
#include "mongo/util/stacktrace_libunwind_test_functions.h"
#define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kTest
namespace mongo {
// Must be a named namespace so the functions we want to unwind through have external linkage.
// Without that, the compiler optimizes them away.
namespace unwind_test_detail {
using namespace fmt::literals;
std::string trace() {
std::string out;
unw_cursor_t cursor;
unw_context_t context;
// Initialize cursor to current frame for local unwinding.
unw_getcontext(&context);
unw_init_local(&cursor, &context);
// Unwind frames one by one, going up the frame stack.
while (unw_step(&cursor) > 0) {
unw_word_t offset, pc;
unw_get_reg(&cursor, UNW_REG_IP, &pc);
if (pc == 0) {
break;
}
out += "0x{:x}:"_format(pc);
char sym[32 << 10];
char* name = sym;
int err;
if ((err = unw_get_proc_name(&cursor, sym, sizeof(sym), &offset)) != 0) {
out += " -- error: unable to obtain symbol name for this frame: {:d}\n"_format(err);
continue;
}
name = sym;
int status;
char* demangled_name;
if ((demangled_name = abi::__cxa_demangle(sym, nullptr, nullptr, &status))) {
name = demangled_name;
}
out += " ({:s}+0x{:x})\n"_format(name, offset);
if (name != sym) {
free(name); // allocated by abi::__cxa_demangle
}
}
return out;
}
struct Context {
std::vector<std::function<void(Context&)>> plan;
std::string s;
};
template <int N>
void callNext(Context& ctx) {
if constexpr (N == 0) {
ctx.s = trace();
} else {
ctx.plan[N - 1](ctx);
}
asm volatile(""); // NOLINT
}
void assertAndRemovePrefix(std::string_view& v, std::string_view prefix) {
auto pos = v.find(prefix);
ASSERT(pos != v.npos) << "expected to find '{}' in '{}'"_format(prefix, v);
v.remove_prefix(pos + prefix.size());
}
void assertAndRemoveSuffix(std::string_view& v, std::string_view suffix) {
auto pos = v.rfind(suffix);
ASSERT(pos != v.npos) << "expected to find '{}' in '{}'"_format(suffix, v);
v.remove_suffix(v.size() - pos);
}
TEST(Unwind, Demangled) {
// Trickery with std::vector<std::function> is to hide from the optimizer.
Context ctx{{
callNext<0>,
callNext<1>,
callNext<2>,
callNext<3>,
callNext<4>,
callNext<5>,
}};
ctx.plan.back()(ctx);
// Check that these function names appear in the trace, in order.
// There will of course be characters between them but ignore that.
const std::string frames[] = {
"void mongo::unwind_test_detail::callNext<0>(mongo::unwind_test_detail::Context&)",
"void mongo::unwind_test_detail::callNext<1>(mongo::unwind_test_detail::Context&)",
"void mongo::unwind_test_detail::callNext<2>(mongo::unwind_test_detail::Context&)",
"void mongo::unwind_test_detail::callNext<3>(mongo::unwind_test_detail::Context&)",
"void mongo::unwind_test_detail::callNext<4>(mongo::unwind_test_detail::Context&)",
"void mongo::unwind_test_detail::callNext<5>(mongo::unwind_test_detail::Context&)",
"main",
};
size_t pos = 0;
for (const auto& expected : frames) {
pos = ctx.s.find(expected, pos);
ASSERT_NE(pos, ctx.s.npos) << ctx.s;
}
}
TEST(Unwind, Linkage) {
// From backtrace_visibility_test.h. Calls a chain of functions and stores the backtrace at the
// bottom in the "stacktrace" argument.
std::ostringstream os;
normalFunction(os);
std::string stacktrace = os.str();
std::string_view view = stacktrace;
LOGV2_OPTIONS(31429, {logv2::LogTruncation::Disabled}, "Trace", "trace"_attr = view);
// Remove the backtrace JSON object, which is all one line.
assertAndRemovePrefix(view, R"(BACKTRACE: {"backtrace":)");
assertAndRemovePrefix(view, "}\n");
std::string_view remainder = stacktrace;
// Check that these function names appear in the trace, in order. The tracing code which
// preceded our libunwind integration could *not* symbolize hiddenFunction,
// anonymousNamespaceFunction, or staticFunction.
//
// When libunwind does cursor stepping, it picks up these procedure names with
// `unw_get_proc_name`. However, it doesn't provide a way to convert raw addrs to procedure
// names otherwise, so we can't do an `unw_backtrace` and then lookup the names in the usual
// way (i.e. `mergeDlInfo` calling `dladdr`).
std::string frames[] = {
"printStackTrace",
"staticFunction",
"anonymousNamespaceFunction",
"hiddenFunction",
"normalFunction",
};
for (const auto& name : frames) {
auto pos = remainder.find(name);
if (pos == remainder.npos) {
LOGV2_OPTIONS(
31378, {logv2::LogTruncation::Disabled}, "BACKTRACE", "trace"_attr = view);
FAIL("name '{}' is missing or out of order in sample backtrace"_format(name));
}
LOGV2(31379, "Removing prefix", "prefix"_attr = remainder.substr(0, pos));
remainder.remove_prefix(pos);
}
}
} // namespace unwind_test_detail
} // namespace mongo
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