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stack_trace_fuchsia.cc
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stack_trace_fuchsia.cc
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// Copyright 2017 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 "base/debug/stack_trace.h"
#include <link.h>
#include <stddef.h>
#include <string.h>
#include <threads.h>
#include <unwind.h>
#include <zircon/crashlogger.h>
#include <zircon/process.h>
#include <zircon/syscalls.h>
#include <zircon/syscalls/definitions.h>
#include <zircon/syscalls/port.h>
#include <zircon/types.h>
#include <algorithm>
#include <iomanip>
#include <iostream>
#include "base/logging.h"
namespace base {
namespace debug {
namespace {
const char kProcessNamePrefix[] = "app:";
const size_t kProcessNamePrefixLen = arraysize(kProcessNamePrefix) - 1;
struct BacktraceData {
void** trace_array;
size_t* count;
size_t max;
};
_Unwind_Reason_Code UnwindStore(struct _Unwind_Context* context,
void* user_data) {
BacktraceData* data = reinterpret_cast<BacktraceData*>(user_data);
uintptr_t pc = _Unwind_GetIP(context);
data->trace_array[*data->count] = reinterpret_cast<void*>(pc);
*data->count += 1;
if (*data->count == data->max)
return _URC_END_OF_STACK;
return _URC_NO_REASON;
}
// Stores and queries debugging symbol map info for the current process.
class SymbolMap {
public:
struct Entry {
void* addr;
char name[ZX_MAX_NAME_LEN + kProcessNamePrefixLen];
};
SymbolMap();
~SymbolMap() = default;
// Gets the symbol map entry for |address|. Returns null if no entry could be
// found for the address, or if the symbol map could not be queried.
Entry* GetForAddress(void* address);
private:
// Component builds of Chrome pull about 250 shared libraries (on Linux), so
// 512 entries should be enough in most cases.
static const size_t kMaxMapEntries = 512;
void Populate();
// Sorted in descending order by address, for lookup purposes.
Entry entries_[kMaxMapEntries];
size_t count_ = 0;
bool valid_ = false;
DISALLOW_COPY_AND_ASSIGN(SymbolMap);
};
SymbolMap::SymbolMap() {
Populate();
}
SymbolMap::Entry* SymbolMap::GetForAddress(void* address) {
if (!valid_) {
return nullptr;
}
// Working backwards in the address space, return the first map entry whose
// address comes before |address| (thereby enclosing it.)
for (size_t i = 0; i < count_; ++i) {
if (address >= entries_[i].addr) {
return &entries_[i];
}
}
return nullptr;
}
void SymbolMap::Populate() {
zx_handle_t process = zx_process_self();
// Try to fetch the name of the process' main executable, which was set as the
// name of the |process| kernel object.
// TODO(wez): Object names can only have up to ZX_MAX_NAME_LEN characters, so
// if we keep hitting problems with truncation, find a way to plumb argv[0]
// through to here instead, e.g. using CommandLine::GetProgramName().
char app_name[arraysize(SymbolMap::Entry::name)];
strcpy(app_name, kProcessNamePrefix);
zx_status_t status = zx_object_get_property(
process, ZX_PROP_NAME, app_name + kProcessNamePrefixLen,
sizeof(app_name) - kProcessNamePrefixLen);
if (status != ZX_OK) {
DPLOG(WARNING)
<< "Couldn't get name, falling back to 'app' for program name: "
<< status;
strlcat(app_name, "app", sizeof(app_name));
}
// Retrieve the debug info struct.
uintptr_t debug_addr;
status = zx_object_get_property(process, ZX_PROP_PROCESS_DEBUG_ADDR,
&debug_addr, sizeof(debug_addr));
if (status != ZX_OK) {
DPLOG(ERROR) << "Couldn't get symbol map for process: " << status;
return;
}
r_debug* debug_info = reinterpret_cast<r_debug*>(debug_addr);
// Get the link map from the debug info struct.
link_map* lmap = reinterpret_cast<link_map*>(debug_info->r_map);
if (!lmap) {
DPLOG(ERROR) << "Null link_map for process.";
return;
}
// Copy the contents of the link map linked list to |entries_|.
while (lmap != nullptr) {
if (count_ >= arraysize(entries_)) {
break;
}
SymbolMap::Entry* next_entry = &entries_[count_];
count_++;
next_entry->addr = reinterpret_cast<void*>(lmap->l_addr);
char* name_to_use = lmap->l_name[0] ? lmap->l_name : app_name;
strlcpy(next_entry->name, name_to_use, sizeof(next_entry->name));
lmap = lmap->l_next;
}
std::sort(
&entries_[0], &entries_[count_ - 1],
[](const Entry& a, const Entry& b) -> bool { return a.addr >= b.addr; });
valid_ = true;
}
} // namespace
// static
bool EnableInProcessStackDumping() {
// StackTrace works to capture the current stack (e.g. for diagnostics added
// to code), but for local capture and print of backtraces, we just let the
// system crashlogger take over. It handles printing out a nicely formatted
// backtrace with dso information, relative offsets, etc. that we can then
// filter with addr2line in the run script to get file/line info.
return true;
}
StackTrace::StackTrace(size_t count) : count_(0) {
BacktraceData data = {&trace_[0], &count_,
std::min(count, static_cast<size_t>(kMaxTraces))};
_Unwind_Backtrace(&UnwindStore, &data);
}
void StackTrace::Print() const {
OutputToStream(&std::cerr);
}
// Sample stack trace output is designed to be similar to Fuchsia's crashlogger:
// bt#00: pc 0x1527a058aa00 (app:/system/base_unittests,0x18bda00)
// bt#01: pc 0x1527a0254b5c (app:/system/base_unittests,0x1587b5c)
// bt#02: pc 0x15279f446ece (app:/system/base_unittests,0x779ece)
// ...
// bt#21: pc 0x1527a05b51b4 (app:/system/base_unittests,0x18e81b4)
// bt#22: pc 0x54fdbf3593de (libc.so,0x1c3de)
// bt#23: end
void StackTrace::OutputToStream(std::ostream* os) const {
SymbolMap map;
size_t i = 0;
for (; (i < count_) && os->good(); ++i) {
SymbolMap::Entry* entry = map.GetForAddress(trace_[i]);
if (entry) {
size_t offset = reinterpret_cast<uintptr_t>(trace_[i]) -
reinterpret_cast<uintptr_t>(entry->addr);
*os << "bt#" << std::setw(2) << std::setfill('0') << i << std::setw(0)
<< ": pc " << trace_[i] << " (" << entry->name << ",0x" << std::hex
<< offset << std::dec << std::setw(0) << ")\n";
} else {
// Fallback if the DSO map isn't available.
// Logged PC values are absolute memory addresses, and the shared object
// name is not emitted.
*os << "bt#" << std::setw(2) << std::setfill('0') << i << std::setw(0)
<< ": pc " << trace_[i] << "\n";
}
}
(*os) << "bt#" << std::setw(2) << i << ": end\n";
}
} // namespace debug
} // namespace base