133 lines
4.1 KiB
C++
133 lines
4.1 KiB
C++
/*
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* Copyright (C) 2014 The Android Open Source Project
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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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*/
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#include <cutils/trace.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "private/bionic_lock.h"
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#include "private/bionic_systrace.h"
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#include "private/libc_logging.h"
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#define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
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#include <sys/_system_properties.h>
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#define WRITE_OFFSET 32
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constexpr char SYSTRACE_PROPERTY_NAME[] = "debug.atrace.tags.enableflags";
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static Lock g_lock;
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static const prop_info* g_pinfo;
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static uint32_t g_property_serial = -1;
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static uint32_t g_property_area_serial = -1;
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static uint64_t g_tags;
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static int g_trace_marker_fd = -1;
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static bool should_trace() {
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bool result = false;
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g_lock.lock();
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// debug.atrace.tags.enableflags is set to a safe non-tracing value during property
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// space initialization, so it should only be null in two cases, if there are
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// insufficient permissions for this process to access the property, in which
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// case an audit will be logged, and during boot before the property server has
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// been started, in which case we store the global property_area serial to prevent
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// the costly find operation until we see a changed property_area.
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if (g_pinfo == nullptr && g_property_area_serial != __system_property_area_serial()) {
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g_property_area_serial = __system_property_area_serial();
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g_pinfo = __system_property_find(SYSTRACE_PROPERTY_NAME);
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}
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if (g_pinfo) {
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// Find out which tags have been enabled on the command line and set
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// the value of tags accordingly. If the value of the property changes,
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// the serial will also change, so the costly system_property_read function
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// can be avoided by calling the much cheaper system_property_serial
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// first. The values within pinfo may change, but its location is guaranteed
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// not to move.
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uint32_t cur_serial = __system_property_serial(g_pinfo);
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if (cur_serial != g_property_serial) {
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__system_property_read_callback(g_pinfo,
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[] (void*, const char*, const char* value, uint32_t serial) {
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g_property_serial = serial;
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g_tags = strtoull(value, nullptr, 0);
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}, nullptr);
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}
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result = ((g_tags & ATRACE_TAG_BIONIC) != 0);
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}
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g_lock.unlock();
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return result;
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}
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static int get_trace_marker_fd() {
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g_lock.lock();
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if (g_trace_marker_fd == -1) {
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g_trace_marker_fd = open("/sys/kernel/debug/tracing/trace_marker", O_CLOEXEC | O_WRONLY);
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}
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g_lock.unlock();
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return g_trace_marker_fd;
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}
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void bionic_trace_begin(const char* message) {
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if (!should_trace()) {
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return;
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}
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int trace_marker_fd = get_trace_marker_fd();
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if (trace_marker_fd == -1) {
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return;
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}
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// If bionic tracing has been enabled, then write the message to the
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// kernel trace_marker.
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int length = strlen(message);
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char buf[length + WRITE_OFFSET];
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size_t len = snprintf(buf, length + WRITE_OFFSET, "B|%d|%s", getpid(), message);
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// Tracing may stop just after checking property and before writing the message.
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// So the write is acceptable to fail. See b/20666100.
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TEMP_FAILURE_RETRY(write(trace_marker_fd, buf, len));
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}
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void bionic_trace_end() {
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if (!should_trace()) {
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return;
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}
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int trace_marker_fd = get_trace_marker_fd();
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if (trace_marker_fd == -1) {
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return;
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}
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TEMP_FAILURE_RETRY(write(trace_marker_fd, "E", 1));
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}
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ScopedTrace::ScopedTrace(const char* message) : called_end_(false) {
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bionic_trace_begin(message);
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}
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ScopedTrace::~ScopedTrace() {
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End();
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}
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void ScopedTrace::End() {
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if (!called_end_) {
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bionic_trace_end();
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called_end_ = true;
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}
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}
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