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platform_system_core/logd/LogKlog.cpp
Tom Cherry cbfebdbadb logd: notify kernel log readers of new messages 
LogBuffer::log() returns either a negative number on error or a
positive number indicating the length of the message written.
Therefore, the check to notify kernel log readers of a new message
should be that this function's return value is > 0.

Bug: 78209416
Test: `adb logcat -b kernel` updates when new log messages are present
Change-Id: Icc18c0c22e62340994e5c26aedb72282d61c1541
2018-04-24 14:19:32 -07:00

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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 > 0) {
reader->notifyNewLog(static_cast<log_mask_t>(1 << LOG_ID_KERNEL));
}
return rc;
}
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