109 lines
3.7 KiB
C++
109 lines
3.7 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_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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static const prop_info* g_pinfo = NULL;
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static uint32_t g_serial = -1;
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static uint64_t g_tags = 0;
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static int g_trace_marker_fd = -1;
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static bool should_trace() {
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// If g_pinfo is null, this means that systrace hasn't been run and it's safe to
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// assume that no trace writing will need to take place. However, to avoid running
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// this costly find check each time, we set it to a non-tracing value so that next
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// time, it will just check the serial to see if the value has been changed.
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// this function also deals with the bootup case, during which the call to property
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// set will fail if the property server hasn't yet started.
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if (g_pinfo == NULL) {
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g_pinfo = __system_property_find("debug.atrace.tags.enableflags");
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if (g_pinfo == NULL) {
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__system_property_set("debug.atrace.tags.enableflags", "0");
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g_pinfo = __system_property_find("debug.atrace.tags.enableflags");
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if (g_pinfo == NULL) {
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return false;
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}
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}
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}
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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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const uint32_t cur_serial = __system_property_serial(g_pinfo);
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if (cur_serial != g_serial) {
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g_serial = cur_serial;
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char value[PROP_VALUE_MAX];
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__system_property_read(g_pinfo, 0, value);
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g_tags = strtoull(value, NULL, 0);
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}
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// Finally, verify that this tag value enables bionic tracing.
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return ((g_tags & ATRACE_TAG_BIONIC) != 0);
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}
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ScopedTrace::ScopedTrace(const char* message) {
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if (!should_trace()) {
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return;
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}
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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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if (g_trace_marker_fd == -1) {
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__libc_fatal("Could not open kernel trace file: %s\n", strerror(errno));
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}
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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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ssize_t wbytes = TEMP_FAILURE_RETRY(write(g_trace_marker_fd, buf, len));
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// Error while writing
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if (static_cast<size_t>(wbytes) != len) {
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__libc_fatal("Could not write to kernel trace file: %s\n", strerror(errno));
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}
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}
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ScopedTrace::~ScopedTrace() {
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if (!should_trace()) {
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return;
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}
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ssize_t wbytes = TEMP_FAILURE_RETRY(write(g_trace_marker_fd, "E", 1));
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// Error while writing
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if (static_cast<size_t>(wbytes) != 1) {
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__libc_fatal("Could not write to kernel trace file: %s\n", strerror(errno));
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}
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}
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