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platform_system_core/logd/LogKlog.cpp
Hao Wang f6e2296953 logd: enhance multiple blocking readers performance 
logd suffers performance degradation when multiple blocking
readers connect to it. Each time when the writer thread log
new entries, all of the readers are notified regardless of
which log id they are watching.

In this case, only give notification to the readers who are
actually watching new entries' log id. This decreases logd
CPU consumption by skipping unnecessary LogBuffer::flushTo
loops.

Test: liblog-unit-tests, logd-unit-tests & CtsLiblogTestCases
      logcat-unit-tests
Test: manual:
1.'logcat –b all' at constant heavy logging load level
2.simultaneously 'logcat –b crash' in another session,
   a healthy crash buffer usually keep empty
3.logd CPU consumption doesn't increase after step 2

Change-Id: I4ffc045c9feb7a0998f7e47ae2173f8f6aa28e8a
2017-12-05 18:46:24 +08:00

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/*
* Copyright (C) 2014 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <ctype.h>
#include <errno.h>
#include <inttypes.h>
#include <limits.h>
#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
#include <sys/prctl.h>
#include <sys/uio.h>
#include <syslog.h>
#include <private/android_filesystem_config.h>
#include <private/android_logger.h>
#include "LogBuffer.h"
#include "LogKlog.h"
#include "LogReader.h"
#define KMSG_PRIORITY(PRI) \
'<', '0' + (LOG_SYSLOG | (PRI)) / 10, '0' + (LOG_SYSLOG | (PRI)) % 10, '>'
static const char priority_message[] = { KMSG_PRIORITY(LOG_INFO), '\0' };
// List of the _only_ needles we supply here to android::strnstr
static const char suspendStr[] = "PM: suspend entry ";
static const char resumeStr[] = "PM: suspend exit ";
static const char suspendedStr[] = "Suspended for ";
static const char healthdStr[] = "healthd";
static const char batteryStr[] = ": battery ";
static const char auditStr[] = " audit(";
static const char klogdStr[] = "logd.klogd: ";
// Parsing is hard
// called if we see a '<', s is the next character, returns pointer after '>'
static char* is_prio(char* s, ssize_t len) {
if ((len <= 0) || !isdigit(*s++)) return nullptr;
--len;
static const size_t max_prio_len = (len < 4) ? len : 4;
size_t priolen = 0;
char c;
while (((c = *s++)) && (++priolen <= max_prio_len)) {
if (!isdigit(c)) return ((c == '>') && (*s == '[')) ? s : nullptr;
}
return nullptr;
}
// called if we see a '[', s is the next character, returns pointer after ']'
static char* is_timestamp(char* s, ssize_t len) {
while ((len > 0) && (*s == ' ')) {
++s;
--len;
}
if ((len <= 0) || !isdigit(*s++)) return nullptr;
--len;
bool first_period = true;
char c;
while ((len > 0) && ((c = *s++))) {
--len;
if ((c == '.') && first_period) {
first_period = false;
} else if (!isdigit(c)) {
return ((c == ']') && !first_period && (*s == ' ')) ? s : nullptr;
}
}
return nullptr;
}
// Like strtok_r with "\r\n" except that we look for log signatures (regex)
// \(\(<[0-9]\{1,4\}>\)\([[] *[0-9]+[.][0-9]+[]] \)\{0,1\}\|[[]
// *[0-9]+[.][0-9]+[]] \)
// and split if we see a second one without a newline.
// We allow nuls in content, monitoring the overall length and sub-length of
// the discovered tokens.
#define SIGNATURE_MASK 0xF0
// <digit> following ('0' to '9' masked with ~SIGNATURE_MASK) added to signature
#define LESS_THAN_SIG SIGNATURE_MASK
#define OPEN_BRACKET_SIG ((SIGNATURE_MASK << 1) & SIGNATURE_MASK)
// space is one more than <digit> of 9
#define OPEN_BRACKET_SPACE ((char)(OPEN_BRACKET_SIG | 10))
char* android::log_strntok_r(char* s, ssize_t& len, char*& last,
ssize_t& sublen) {
sublen = 0;
if (len <= 0) return nullptr;
if (!s) {
if (!(s = last)) return nullptr;
// fixup for log signature split <,
// LESS_THAN_SIG + <digit>
if ((*s & SIGNATURE_MASK) == LESS_THAN_SIG) {
*s = (*s & ~SIGNATURE_MASK) + '0';
*--s = '<';
++len;
}
// fixup for log signature split [,
// OPEN_BRACKET_SPACE is space, OPEN_BRACKET_SIG + <digit>
if ((*s & SIGNATURE_MASK) == OPEN_BRACKET_SIG) {
*s = (*s == OPEN_BRACKET_SPACE) ? ' ' : (*s & ~SIGNATURE_MASK) + '0';
*--s = '[';
++len;
}
}
while ((len > 0) && ((*s == '\r') || (*s == '\n'))) {
++s;
--len;
}
if (len <= 0) return last = nullptr;
char *peek, *tok = s;
for (;;) {
if (len <= 0) {
last = nullptr;
return tok;
}
char c = *s++;
--len;
ssize_t adjust;
switch (c) {
case '\r':
case '\n':
s[-1] = '\0';
last = s;
return tok;
case '<':
peek = is_prio(s, len);
if (!peek) break;
if (s != (tok + 1)) { // not first?
s[-1] = '\0';
*s &= ~SIGNATURE_MASK;
*s |= LESS_THAN_SIG; // signature for '<'
last = s;
return tok;
}
adjust = peek - s;
if (adjust > len) {
adjust = len;
}
sublen += adjust;
len -= adjust;
s = peek;
if ((*s == '[') && ((peek = is_timestamp(s + 1, len - 1)))) {
adjust = peek - s;
if (adjust > len) {
adjust = len;
}
sublen += adjust;
len -= adjust;
s = peek;
}
break;
case '[':
peek = is_timestamp(s, len);
if (!peek) break;
if (s != (tok + 1)) { // not first?
s[-1] = '\0';
if (*s == ' ') {
*s = OPEN_BRACKET_SPACE;
} else {
*s &= ~SIGNATURE_MASK;
*s |= OPEN_BRACKET_SIG; // signature for '['
}
last = s;
return tok;
}
adjust = peek - s;
if (adjust > len) {
adjust = len;
}
sublen += adjust;
len -= adjust;
s = peek;
break;
}
++sublen;
}
// NOTREACHED
}
log_time LogKlog::correction =
(log_time(CLOCK_REALTIME) < log_time(CLOCK_MONOTONIC))
? log_time::EPOCH
: (log_time(CLOCK_REALTIME) - log_time(CLOCK_MONOTONIC));
LogKlog::LogKlog(LogBuffer* buf, LogReader* reader, int fdWrite, int fdRead,
bool auditd)
: SocketListener(fdRead, false),
logbuf(buf),
reader(reader),
signature(CLOCK_MONOTONIC),
initialized(false),
enableLogging(true),
auditd(auditd) {
static const char klogd_message[] = "%s%s%" PRIu64 "\n";
char buffer[strlen(priority_message) + strlen(klogdStr) +
strlen(klogd_message) + 20];
snprintf(buffer, sizeof(buffer), klogd_message, priority_message, klogdStr,
signature.nsec());
write(fdWrite, buffer, strlen(buffer));
}
bool LogKlog::onDataAvailable(SocketClient* cli) {
if (!initialized) {
prctl(PR_SET_NAME, "logd.klogd");
initialized = true;
enableLogging = false;
}
char buffer[LOGGER_ENTRY_MAX_PAYLOAD];
ssize_t len = 0;
for (;;) {
ssize_t retval = 0;
if (len < (ssize_t)(sizeof(buffer) - 1)) {
retval =
read(cli->getSocket(), buffer + len, sizeof(buffer) - 1 - len);
}
if ((retval == 0) && (len <= 0)) {
break;
}
if (retval < 0) {
return false;
}
len += retval;
bool full = len == (sizeof(buffer) - 1);
char* ep = buffer + len;
*ep = '\0';
ssize_t sublen;
for (char *ptr = nullptr, *tok = buffer;
!!(tok = android::log_strntok_r(tok, len, ptr, sublen));
tok = nullptr) {
if (((tok + sublen) >= ep) && (retval != 0) && full) {
if (sublen > 0) memmove(buffer, tok, sublen);
len = sublen;
break;
}
if ((sublen > 0) && *tok) {
log(tok, sublen);
}
}
}
return true;
}
void LogKlog::calculateCorrection(const log_time& monotonic,
const char* real_string, ssize_t len) {
static const char real_format[] = "%Y-%m-%d %H:%M:%S.%09q UTC";
if (len < (ssize_t)(strlen(real_format) + 5)) return;
log_time real;
const char* ep = real.strptime(real_string, real_format);
if (!ep || (ep > &real_string[len]) || (real > log_time(CLOCK_REALTIME))) {
return;
}
// kernel report UTC, log_time::strptime is localtime from calendar.
// Bionic and liblog strptime does not support %z or %Z to pick up
// timezone so we are calculating our own correction.
time_t now = real.tv_sec;
struct tm tm;
memset(&tm, 0, sizeof(tm));
tm.tm_isdst = -1;
localtime_r(&now, &tm);
if ((tm.tm_gmtoff < 0) && ((-tm.tm_gmtoff) > (long)real.tv_sec)) {
real = log_time::EPOCH;
} else {
real.tv_sec += tm.tm_gmtoff;
}
if (monotonic > real) {
correction = log_time::EPOCH;
} else {
correction = real - monotonic;
}
}
void LogKlog::sniffTime(log_time& now, const char*& buf, ssize_t len,
bool reverse) {
if (len <= 0) return;
const char* cp = nullptr;
if ((len > 10) && (*buf == '[')) {
cp = now.strptime(buf, "[ %s.%q]"); // can index beyond buffer bounds
if (cp && (cp > &buf[len - 1])) cp = nullptr;
}
if (cp) {
len -= cp - buf;
if ((len > 0) && isspace(*cp)) {
++cp;
--len;
}
buf = cp;
if (isMonotonic()) return;
const char* b;
if (((b = android::strnstr(cp, len, suspendStr))) &&
(((b += strlen(suspendStr)) - cp) < len)) {
len -= b - cp;
calculateCorrection(now, b, len);
} else if (((b = android::strnstr(cp, len, resumeStr))) &&
(((b += strlen(resumeStr)) - cp) < len)) {
len -= b - cp;
calculateCorrection(now, b, len);
} else if (((b = android::strnstr(cp, len, healthdStr))) &&
(((b += strlen(healthdStr)) - cp) < len) &&
((b = android::strnstr(b, len -= b - cp, batteryStr))) &&
(((b += strlen(batteryStr)) - cp) < len)) {
// NB: healthd is roughly 150us late, so we use it instead to
// trigger a check for ntp-induced or hardware clock drift.
log_time real(CLOCK_REALTIME);
log_time mono(CLOCK_MONOTONIC);
correction = (real < mono) ? log_time::EPOCH : (real - mono);
} else if (((b = android::strnstr(cp, len, suspendedStr))) &&
(((b += strlen(suspendStr)) - cp) < len)) {
len -= b - cp;
log_time real;
char* endp;
real.tv_sec = strtol(b, &endp, 10);
if ((*endp == '.') && ((endp - b) < len)) {
unsigned long multiplier = NS_PER_SEC;
real.tv_nsec = 0;
len -= endp - b;
while (--len && isdigit(*++endp) && (multiplier /= 10)) {
real.tv_nsec += (*endp - '0') * multiplier;
}
if (reverse) {
if (real > correction) {
correction = log_time::EPOCH;
} else {
correction -= real;
}
} else {
correction += real;
}
}
}
convertMonotonicToReal(now);
} else {
if (isMonotonic()) {
now = log_time(CLOCK_MONOTONIC);
} else {
now = log_time(CLOCK_REALTIME);
}
}
}
pid_t LogKlog::sniffPid(const char*& buf, ssize_t len) {
if (len <= 0) return 0;
const char* cp = buf;
// sscanf does a strlen, let's check if the string is not nul terminated.
// pseudo out-of-bounds access since we always have an extra char on buffer.
if (((ssize_t)strnlen(cp, len) == len) && cp[len]) {
return 0;
}
// HTC kernels with modified printk "c0 1648 "
if ((len > 9) && (cp[0] == 'c') && isdigit(cp[1]) &&
(isdigit(cp[2]) || (cp[2] == ' ')) && (cp[3] == ' ')) {
bool gotDigit = false;
int i;
for (i = 4; i < 9; ++i) {
if (isdigit(cp[i])) {
gotDigit = true;
} else if (gotDigit || (cp[i] != ' ')) {
break;
}
}
if ((i == 9) && (cp[i] == ' ')) {
int pid = 0;
char dummy;
if (sscanf(cp + 4, "%d%c", &pid, &dummy) == 2) {
buf = cp + 10; // skip-it-all
return pid;
}
}
}
while (len) {
// Mediatek kernels with modified printk
if (*cp == '[') {
int pid = 0;
char dummy;
if (sscanf(cp, "[%d:%*[a-z_./0-9:A-Z]]%c", &pid, &dummy) == 2) {
return pid;
}
break; // Only the first one
}
++cp;
--len;
}
return 0;
}
// kernel log prefix, convert to a kernel log priority number
static int parseKernelPrio(const char*& buf, ssize_t len) {
int pri = LOG_USER | LOG_INFO;
const char* cp = buf;
if ((len > 0) && (*cp == '<')) {
pri = 0;
while (--len && isdigit(*++cp)) {
pri = (pri * 10) + *cp - '0';
}
if ((len > 0) && (*cp == '>')) {
++cp;
} else {
cp = buf;
pri = LOG_USER | LOG_INFO;
}
buf = cp;
}
return pri;
}
// Passed the entire SYSLOG_ACTION_READ_ALL buffer and interpret a
// compensated start time.
void LogKlog::synchronize(const char* buf, ssize_t len) {
const char* cp = android::strnstr(buf, len, suspendStr);
if (!cp) {
cp = android::strnstr(buf, len, resumeStr);
if (!cp) return;
} else {
const char* rp = android::strnstr(buf, len, resumeStr);
if (rp && (rp < cp)) cp = rp;
}
do {
--cp;
} while ((cp > buf) && (*cp != '\n'));
if (*cp == '\n') {
++cp;
}
parseKernelPrio(cp, len - (cp - buf));
log_time now;
sniffTime(now, cp, len - (cp - buf), true);
const char* suspended = android::strnstr(buf, len, suspendedStr);
if (!suspended || (suspended > cp)) {
return;
}
cp = suspended;
do {
--cp;
} while ((cp > buf) && (*cp != '\n'));
if (*cp == '\n') {
++cp;
}
parseKernelPrio(cp, len - (cp - buf));
sniffTime(now, cp, len - (cp - buf), true);
}
// Convert kernel log priority number into an Android Logger priority number
static int convertKernelPrioToAndroidPrio(int pri) {
switch (pri & LOG_PRIMASK) {
case LOG_EMERG:
// FALLTHRU
case LOG_ALERT:
// FALLTHRU
case LOG_CRIT:
return ANDROID_LOG_FATAL;
case LOG_ERR:
return ANDROID_LOG_ERROR;
case LOG_WARNING:
return ANDROID_LOG_WARN;
default:
// FALLTHRU
case LOG_NOTICE:
// FALLTHRU
case LOG_INFO:
break;
case LOG_DEBUG:
return ANDROID_LOG_DEBUG;
}
return ANDROID_LOG_INFO;
}
static const char* strnrchr(const char* s, ssize_t len, char c) {
const char* save = nullptr;
for (; len > 0; ++s, len--) {
if (*s == c) {
save = s;
}
}
return save;
}
//
// log a message into the kernel log buffer
//
// Filter rules to parse <PRI> <TIME> <tag> and <message> in order for
// them to appear correct in the logcat output:
//
// LOG_KERN (0):
// <PRI>[<TIME>] <tag> ":" <message>
// <PRI>[<TIME>] <tag> <tag> ":" <message>
// <PRI>[<TIME>] <tag> <tag>_work ":" <message>
// <PRI>[<TIME>] <tag> '<tag>.<num>' ":" <message>
// <PRI>[<TIME>] <tag> '<tag><num>' ":" <message>
// <PRI>[<TIME>] <tag>_host '<tag>.<num>' ":" <message>
// (unimplemented) <PRI>[<TIME>] <tag> '<num>.<tag>' ":" <message>
// <PRI>[<TIME>] "[INFO]"<tag> : <message>
// <PRI>[<TIME>] "------------[ cut here ]------------" (?)
// <PRI>[<TIME>] "---[ end trace 3225a3070ca3e4ac ]---" (?)
// LOG_USER, LOG_MAIL, LOG_DAEMON, LOG_AUTH, LOG_SYSLOG, LOG_LPR, LOG_NEWS
// LOG_UUCP, LOG_CRON, LOG_AUTHPRIV, LOG_FTP:
// <PRI+TAG>[<TIME>] (see sys/syslog.h)
// Observe:
// Minimum tag length = 3 NB: drops things like r5:c00bbadf, but allow PM:
// Maximum tag words = 2
// Maximum tag length = 16 NB: we are thinking of how ugly logcat can get.
// Not a Tag if there is no message content.
// leading additional spaces means no tag, inherit last tag.
// Not a Tag if <tag>: is "ERROR:", "WARNING:", "INFO:" or "CPU:"
// Drop:
// empty messages
// messages with ' audit(' in them if auditd is running
// logd.klogd:
// return -1 if message logd.klogd: <signature>
//
int LogKlog::log(const char* buf, ssize_t len) {
if (auditd && android::strnstr(buf, len, auditStr)) {
return 0;
}
const char* p = buf;
int pri = parseKernelPrio(p, len);
log_time now;
sniffTime(now, p, len - (p - buf), false);
// sniff for start marker
const char* start = android::strnstr(p, len - (p - buf), klogdStr);
if (start) {
uint64_t sig = strtoll(start + strlen(klogdStr), nullptr, 10);
if (sig == signature.nsec()) {
if (initialized) {
enableLogging = true;
} else {
enableLogging = false;
}
return -1;
}
return 0;
}
if (!enableLogging) {
return 0;
}
// Parse pid, tid and uid
const pid_t pid = sniffPid(p, len - (p - buf));
const pid_t tid = pid;
uid_t uid = AID_ROOT;
if (pid) {
logbuf->wrlock();
uid = logbuf->pidToUid(pid);
logbuf->unlock();
}
// Parse (rules at top) to pull out a tag from the incoming kernel message.
// Some may view the following as an ugly heuristic, the desire is to
// beautify the kernel logs into an Android Logging format; the goal is
// admirable but costly.
while ((p < &buf[len]) && (isspace(*p) || !*p)) {
++p;
}
if (p >= &buf[len]) { // timestamp, no content
return 0;
}
start = p;
const char* tag = "";
const char* etag = tag;
ssize_t taglen = len - (p - buf);
const char* bt = p;
static const char infoBrace[] = "[INFO]";
static const ssize_t infoBraceLen = strlen(infoBrace);
if ((taglen >= infoBraceLen) &&
!fastcmp<strncmp>(p, infoBrace, infoBraceLen)) {
// <PRI>[<TIME>] "[INFO]"<tag> ":" message
bt = p + infoBraceLen;
taglen -= infoBraceLen;
}
const char* et;
for (et = bt; (taglen > 0) && *et && (*et != ':') && !isspace(*et);
++et, --taglen) {
// skip ':' within [ ... ]
if (*et == '[') {
while ((taglen > 0) && *et && *et != ']') {
++et;
--taglen;
}
if (taglen <= 0) {
break;
}
}
}
const char* cp;
for (cp = et; (taglen > 0) && isspace(*cp); ++cp, --taglen) {
}
// Validate tag
ssize_t size = et - bt;
if ((taglen > 0) && (size > 0)) {
if (*cp == ':') {
// ToDo: handle case insensitive colon separated logging stutter:
// <tag> : <tag>: ...
// One Word
tag = bt;
etag = et;
p = cp + 1;
} else if ((taglen > size) && (tolower(*bt) == tolower(*cp))) {
// clean up any tag stutter
if (!fastcmp<strncasecmp>(bt + 1, cp + 1, size - 1)) { // no match
// <PRI>[<TIME>] <tag> <tag> : message
// <PRI>[<TIME>] <tag> <tag>: message
// <PRI>[<TIME>] <tag> '<tag>.<num>' : message
// <PRI>[<TIME>] <tag> '<tag><num>' : message
// <PRI>[<TIME>] <tag> '<tag><stuff>' : message
const char* b = cp;
cp += size;
taglen -= size;
while ((--taglen > 0) && !isspace(*++cp) && (*cp != ':')) {
}
const char* e;
for (e = cp; (taglen > 0) && isspace(*cp); ++cp, --taglen) {
}
if ((taglen > 0) && (*cp == ':')) {
tag = b;
etag = e;
p = cp + 1;
}
} else {
// what about <PRI>[<TIME>] <tag>_host '<tag><stuff>' : message
static const char host[] = "_host";
static const ssize_t hostlen = strlen(host);
if ((size > hostlen) &&
!fastcmp<strncmp>(bt + size - hostlen, host, hostlen) &&
!fastcmp<strncmp>(bt + 1, cp + 1, size - hostlen - 1)) {
const char* b = cp;
cp += size - hostlen;
taglen -= size - hostlen;
if (*cp == '.') {
while ((--taglen > 0) && !isspace(*++cp) &&
(*cp != ':')) {
}
const char* e;
for (e = cp; (taglen > 0) && isspace(*cp);
++cp, --taglen) {
}
if ((taglen > 0) && (*cp == ':')) {
tag = b;
etag = e;
p = cp + 1;
}
}
} else {
goto twoWord;
}
}
} else {
// <PRI>[<TIME>] <tag> <stuff>' : message
twoWord:
while ((--taglen > 0) && !isspace(*++cp) && (*cp != ':')) {
}
const char* e;
for (e = cp; (taglen > 0) && isspace(*cp); ++cp, --taglen) {
}
// Two words
if ((taglen > 0) && (*cp == ':')) {
tag = bt;
etag = e;
p = cp + 1;
}
}
} // else no tag
static const char cpu[] = "CPU";
static const ssize_t cpuLen = strlen(cpu);
static const char warning[] = "WARNING";
static const ssize_t warningLen = strlen(warning);
static const char error[] = "ERROR";
static const ssize_t errorLen = strlen(error);
static const char info[] = "INFO";
static const ssize_t infoLen = strlen(info);
size = etag - tag;
if ((size <= 1) ||
// register names like x9
((size == 2) && (isdigit(tag[0]) || isdigit(tag[1]))) ||
// register names like x18 but not driver names like en0
((size == 3) && (isdigit(tag[1]) && isdigit(tag[2]))) ||
// blacklist
((size == cpuLen) && !fastcmp<strncmp>(tag, cpu, cpuLen)) ||
((size == warningLen) &&
!fastcmp<strncasecmp>(tag, warning, warningLen)) ||
((size == errorLen) && !fastcmp<strncasecmp>(tag, error, errorLen)) ||
((size == infoLen) && !fastcmp<strncasecmp>(tag, info, infoLen))) {
p = start;
etag = tag = "";
}
// Suppress additional stutter in tag:
// eg: [143:healthd]healthd -> [143:healthd]
taglen = etag - tag;
// Mediatek-special printk induced stutter
const char* mp = strnrchr(tag, taglen, ']');
if (mp && (++mp < etag)) {
ssize_t s = etag - mp;
if (((s + s) < taglen) && !fastcmp<memcmp>(mp, mp - 1 - s, s)) {
taglen = mp - tag;
}
}
// Deal with sloppy and simplistic harmless p = cp + 1 etc above.
if (len < (p - buf)) {
p = &buf[len];
}
// skip leading space
while ((p < &buf[len]) && (isspace(*p) || !*p)) {
++p;
}
// truncate trailing space or nuls
ssize_t b = len - (p - buf);
while ((b > 0) && (isspace(p[b - 1]) || !p[b - 1])) {
--b;
}
// trick ... allow tag with empty content to be logged. log() drops empty
if ((b <= 0) && (taglen > 0)) {
p = " ";
b = 1;
}
// paranoid sanity check, can not happen ...
if (b > LOGGER_ENTRY_MAX_PAYLOAD) {
b = LOGGER_ENTRY_MAX_PAYLOAD;
}
if (taglen > LOGGER_ENTRY_MAX_PAYLOAD) {
taglen = LOGGER_ENTRY_MAX_PAYLOAD;
}
// calculate buffer copy requirements
ssize_t n = 1 + taglen + 1 + b + 1;
// paranoid sanity check, first two just can not happen ...
if ((taglen > n) || (b > n) || (n > (ssize_t)USHRT_MAX) || (n <= 0)) {
return -EINVAL;
}
// Careful.
// We are using the stack to house the log buffer for speed reasons.
// If we malloc'd this buffer, we could get away without n's USHRT_MAX
// test above, but we would then required a max(n, USHRT_MAX) as
// truncating length argument to logbuf->log() below. Gain is protection
// of stack sanity and speedup, loss is truncated long-line content.
char newstr[n];
char* np = newstr;
// Convert priority into single-byte Android logger priority
*np = convertKernelPrioToAndroidPrio(pri);
++np;
// Copy parsed tag following priority
memcpy(np, tag, taglen);
np += taglen;
*np = '\0';
++np;
// Copy main message to the remainder
memcpy(np, p, b);
np[b] = '\0';
if (!isMonotonic()) {
// Watch out for singular race conditions with timezone causing near
// integer quarter-hour jumps in the time and compensate accordingly.
// Entries will be temporal within near_seconds * 2. b/21868540
static uint32_t vote_time[3];
vote_time[2] = vote_time[1];
vote_time[1] = vote_time[0];
vote_time[0] = now.tv_sec;
if (vote_time[1] && vote_time[2]) {
static const unsigned near_seconds = 10;
static const unsigned timezones_seconds = 900;
int diff0 = (vote_time[0] - vote_time[1]) / near_seconds;
unsigned abs0 = (diff0 < 0) ? -diff0 : diff0;
int diff1 = (vote_time[1] - vote_time[2]) / near_seconds;
unsigned abs1 = (diff1 < 0) ? -diff1 : diff1;
if ((abs1 <= 1) && // last two were in agreement on timezone
((abs0 + 1) % (timezones_seconds / near_seconds)) <= 2) {
abs0 = (abs0 + 1) / (timezones_seconds / near_seconds) *
timezones_seconds;
now.tv_sec -= (diff0 < 0) ? -abs0 : abs0;
}
}
}
// Log message
int rc = logbuf->log(LOG_ID_KERNEL, now, uid, pid, tid, newstr,
(unsigned short)n);
// notify readers
if (!rc) {
reader->notifyNewLog(static_cast<log_mask_t>(1 << LOG_ID_KERNEL));
}
return rc;
}
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