Android(安卓)让adb logcat打印内核调试信息

Android让adb logcat打印内核调试信息

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

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

3、替换readLogLines函数

static void readLogLines(log_device_t* devices){    log_device_t* dev;    int max = 0;    int ret;    int queued_lines = 0;    bool sleep = true;char buffer[256] = {0}; //add by zhaofei    int result;    fd_set readset;    for (dev=devices; dev; dev = dev->next) {        if (dev->fd > max) {            max = dev->fd;        }    }    while (1) {        do {            timeval timeout = { 0, 5000 /* 5ms */ }; // If we oversleep it's ok, i.e. ignore EINTR.            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 = new queued_entry_t();                    /* NOTE: driver guarantees we read exactly one full entry */                    ret = read(dev->fd, entry->buf, LOGGER_ENTRY_MAX_LEN);                    if (ret < 0) {                        if (errno == EINTR) {                            delete entry;                            goto next;                        }                        if (errno == EAGAIN) {                            delete entry;                            break;                        }                        perror("logcat read");                        exit(EXIT_FAILURE);                    }                    else if (!ret) {                        fprintf(stderr, "read: Unexpected EOF!\n");                        exit(EXIT_FAILURE);                    }                    entry->entry.msg[entry->entry.len] = '\0';                    dev->enqueue(entry);                    ++queued_lines;#if 1 //read kernel log        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) {                // we did our short timeout trick and there's nothing new                // print everything we have and wait for more data                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;                }                // the caller requested to just dump the log and exit                if (g_nonblock) {                    exit(0);                }            } else {                // print all that aren't the last in their list                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！

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