adb logcat 打印内核消息

在默认情况下，adb logcat只能显示应用程序的调试信息，我把logcat.cpp修改了一下，让它同时可以打印内核调试信息：

修改的文件：system/core/logcat/logcat.cpp

1、首先先加入头文件
#include <sys/klog.h> //add by Jay

2、定义所使用的TAG
#define KERNEL_TAG "Kernel"

3、替换readLogLines函数

staticvoidreadLogLines(log_device_t*devices)
{
log_device_t*dev;
intmax=0;
intret;
intqueued_lines=0;
boolsleep=true;
charbuffer[256]={0};//addby
 Jay Zhang


intresult;
fd_setreadset;


for(dev=devices;dev;dev=dev->next){
if(dev->fd>max){
max=dev->fd;
}
}


while(1){
do{
timevaltimeout={0,5000/*5ms*/};//Ifweoversleepit'sok,i.e.ignoreEINTR.
FD_ZERO(&readset);
for(dev=devices;dev;dev=dev->next){
FD_SET(dev->fd,&readset);
}
result=select(max+1,&readset,NULL,NULL,sleep?NULL:&timeout);
}while(result==-1&&errno==EINTR);


if(result>=0){
for(dev=devices;dev;dev=dev->next){
if(FD_ISSET(dev->fd,&readset)){
queued_entry_t*entry=newqueued_entry_t();
/*NOTE:driverguaranteeswereadexactlyonefullentry*/
ret=read(dev->fd,entry->buf,LOGGER_ENTRY_MAX_LEN);
if(ret<0){
if(errno==EINTR){
deleteentry;
gotonext;
}
if(errno==EAGAIN){
deleteentry;
break;
}
perror("logcatread");
exit(EXIT_FAILURE);
}
elseif(!ret){
fprintf(stderr,"read:UnexpectedEOF!\n");
exit(EXIT_FAILURE);
}


entry->entry.msg[entry->entry.len]='\0';


dev->enqueue(entry);
++queued_lines;


#if1//readkernellog
if((ret=klogctl(9,buffer,sizeof(buffer)))>0){
if((ret=klogctl(2,buffer,sizeof(buffer)))>0){
entry->entry.tid=0;
entry->entry.pid=getpid();
/*priority*/
entry->entry.msg[0]=Android_LOG_INFO;
/*tag*/
strcpy(entry->entry.msg+1,KERNEL_TAG);
/*message*/
strncpy(entry->entry.msg+1+sizeof(KERNEL_TAG),buffer,ret);
entry->entry.len=1+sizeof(KERNEL_TAG)+ret+1;
entry->entry.msg[entry->entry.len]='/0';
/*
if(g_printBinary){
printBinary(dev,entry->entry);
}else{
(void)processBuffer(dev,entry->entry);
}
*/
printNextEntry(dev);
}
}
#endif
}
}


if(result==0){
//wedidourshorttimeouttrickandthere'snothingnew
//printeverythingwehaveandwaitformoredata
sleep=true;
while(true){
chooseFirst(devices,&dev);
if(dev==NULL){
break;
}
if(g_tail_lines==0||queued_lines<=g_tail_lines){
printNextEntry(dev);
}else{
skipNextEntry(dev);
}
--queued_lines;
}


//thecallerrequestedtojustdumpthelogandexit
if(g_nonblock){
exit(0);
}
}else{
//printallthataren'tthelastintheirlist
sleep=false;
while(g_tail_lines==0||queued_lines>g_tail_lines){
chooseFirst(devices,&dev);
if(dev==NULL||dev->queue->next==NULL){
break;
}
if(g_tail_lines==0){
printNextEntry(dev);
}else{
skipNextEntry(dev);
}
--queued_lines;
}
}
}
next:
;
}
}

这里没有把内核调试信息的级别转换成Androind的LOG级别，entry->entry.msg[0] =Android_LOG_INFO;使用了ANDROID_LOG_INFO级别，进程ID用了当前的进程ID。

然后就可以使用logcat来抓取kernel的log了！

若只打印内核消息，使用：adb logcat -s Kernel:I
http://www.linuxidc.com/Linux/2011-09/43674.htm