X86 Kernel
搭建x86 Linux核心開發Debug環境
方案
- 我的測試系統在QEMU中運行, Host和Guest的架構都是x86_64,用Busybox生成的initrd做為根文件系統, KGDB做為調試器,
- Kernel : linux-3.15.7 + gcc-4.7 or linux-3.15.5 + gcc-4.8 都 ok Module 可以使用gdb
- Kernel linux-2.6.35.9 // gcc-4.4 才可以編譯 , Module 可以使用gdb
- Busybox : busybox-1.22.1
產生核心
- 核心中需要打開的選項是
CONFIG_EXPERIMENTAL=y
# 使得編譯的內核包含一些調試信息，使得調試更容易。
CONFIG_DEBUG_INFO=y
CONFIG_KGDB=y
# 使用串口進行通信
CONFIG_KGDB_SERIAL_CONSOLE=y
# 使能該選項可以kgdb 不依賴 notifier_call_chain() 機制來獲取斷點異常, 這樣就可以對 notifier_call_chain() 機制實現相關的函數進行單步調試。
CONFIG_KGDB_LOW_LEVEL_TRAP=y
# 使能該選項將使得內核使用幀指針寄存器來維護堆棧，從而就可以正確地執行堆棧回溯，即函數調用棧信息。
CONFIG_FRAME_POINTER=y
# ( 如果你選擇了KGDB_SERIAL_CONSOLE, 這個選項將自動被選上) 激活" 魔術 SysRq" 鍵. 該選項對kgdboc 調試非常有用，kgdb 向其註冊了'g' 魔術鍵來激活kgdb 。
CONFIG_MAGIC_SYSRQ=y
# 選擇這個選項來驅動qemu-kvm的網卡設備，以備以後使用。
CONFIG_8139CP=y
# 該選項是將內核的一些內存區域空間設置為只讀，這樣可能導致kgdb 的設置軟斷點功能失效
CONFIG_DEBUG_SET_MODULE_RONX=n
# 將內核的一些內存區域空間設置為只讀，這樣可能導致kgdb 的設置軟斷點功能失效
CONFIG_DEBUG_RODATA=n
CONFIG_MODULE_FORCE_LOAD=y
CONFIG_MODULE_UNLOAD=y
CONFIG_MODULE_FORCE_UNLOAD=y
# CONFIG_MODVERSIONS is not set
# CONFIG_MODULE_SRCVERSION_ALL is not set
修改編譯優化等級:
打開根目錄下Makefile 修改核心 Makefile 優化選項將KBUILD_CFLAGS += -O2, 修改為：KBUILD_CFLAGS += -O
make menuconfig
time make -j8 2>&1 | tee build.log
產生根文件系統
- 打開 Busybox 選項
CONFIG_STATIC=y
CONFIG_INSTALL_NO_USR=y
time make -j8 2>&1 | tee build.log
make install
創建initrd根文件系統
- 創建系統目錄 // 注意尾行的空白, 去除空白
mkdir temp && cd temp
mkdir -p dev etc/init.d mnt proc root sys tmp lib
mkdir -p modules/3.15.5 // 3.15.5 版本依實際情況而改 , rmmod 才可以正常使用
chmod a+rwxt tmp
cp -rf ../busybox/_install/* ./
#include <stdio.h>
int main(int argc, char *argv[])
{
printf("Hello world\n");
return 0;
}
ldd ./test
linux-vdso.so.1 => (0x00007fff4bd8f000)
libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007fbd55e5f000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fbd55a9f000)
/lib64/ld-linux-x86-64.so.2 (0x00007fbd5617b000)
test 執行檔用到 /lib64/ 跟 /lib/x86_64-linux-gnu/
cd lib
cp -a /lib/x86_64-linux-gnu/ .
cd ..
cp -a /lib64/ .
之後在可以在QEMU內執行支援動態函數庫的執行檔
- 掛載系統目錄
cat << EOF > etc/fstab
proc /proc proc defaults 0 0
sysfs /sys sysfs defaults 0 0
tmpfs /tmp tmpfs defaults 0 0
EOF
cat << EOF > etc/inittab
::sysinit:/etc/init.d/rcS
::respawn:-/bin/sh
tty2::askfirst:-/bin/sh
::ctrlaltdel:/bin/umount -a -r
EOF
- etc/init.d/rcS
#! /bin/sh
MAC=08:90:90:59:62:21
IP=192.168.100.2
Mask=255.255.255.0
Gateway=192.168.100.1
/sbin/ifconfig lo 127.0.0.1
ifconfig eth0 down
ifconfig eth0 hw ether $MAC
ifconfig eth0 $IP netmask $Mask up
route add default gw $Gateway
/bin/mount -a
/bin/mount -t sysfs sysfs /sys
/bin/mount -t tmpfs tmpfs /dev
/sbin/mdev -s
mount -o remount,rw,noatime -n /dev/root /
chmod 755 etc/init.d/rcS
產生 rootfs, 可在temp 下新增修改檔案
find ./ | cpio -o -H newc | gzip > ../rootfs.img
安裝 tftp
sudo apt-get install tftp-hpa tftpd-hpa
/etc/default/tftpd-hpa
# /etc/default/tftpd-hpa
TFTP_USERNAME="tftp"
TFTP_DIRECTORY="/tftpboot"
TFTP_ADDRESS="0.0.0.0:69"
TFTP_OPTIONS="-l -c -s"
- 建立 tftpboot
sudo mkdir /tftpboot
sudo chmod 777 /tftpboot
- restart service
sudo service tftpd-hpa restart
- test tftp
tftp host—ip // ex tftp localhost
get or put
啟動 tap
sudo ./nettap.sh // 必須加上 sudo
sudo apt-get install uml-utilities // tunctl
tunctl -u shihyu -t tap0
ifconfig tap0 192.168.100.1 up
echo 1 > /proc/sys/net/ipv4/ip_forward
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
iptables -I FORWARD 1 -i tap0 -j ACCEPT
iptables -I FORWARD 1 -o tap0 -m state --state RELATED,ESTABLISHED -j ACCEPT
- 如果成功下ifconfig 會出現下面 message
tap0 Link encap:Ethernet HWaddr 0a:18:ee:c4:f0:d0
inet addr:192.168.100.1 Bcast:192.168.100.255 Mask:255.255.255.0
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:500
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
啟動QEMU
qemu-system-x86_64 -kernel bzImage -serial stdio -append "root=/dev/ram rdinit=/sbin/init console=ttyS0" -initrd rootfs.img -k en-us -net nic,model=virtio -net tap,ifname=tap0,script=no -enable-kvm -m 2048 -smp 2
需要拿掉 -enable-kvm -m 2048 -smp 2 才能 break start_kernel
qemu-system-x86_64 -s -S -kernel bzImage -initrd rootfs.img -serial stdio -append "root=/dev/ram rdinit=/sbin/init console=ttyS0" -k en-us -net nic,model=virtio -net tap,ifname=tap0,script=no
使用 qemu-linaro 啟動要加上 sudo 目前原因不清楚
SIOCSIFADDR: 拒絕不符權限的操作
SIOCSIFFLAGS: 拒絕不符權限的操作
SIOCSIFFLAGS: 拒絕不符權限的操作
加上 sudo 不能 break start_kernel , 目前原因不確定
qemu-system-x86_64 -s -S -kernel bzImage -initrd rootfs.img -serial stdio -append "root=/dev/ram rdinit=/sbin/init console=ttyS0" -k en-us -net nic,model=virtio -net tap,ifname=tap0,script=no
啟動 GDB
cgdb ./vmlinux
target remote localhost:1234
比如在sched_clock函數處設置斷點 break sched_clock , continue 繼續運行, 到達斷點後打印jiffies_64變量 print jiffies_64 等等
另外, 運行過程中可以在測試系統裡執行 echo g > /proc/sysrqtrigger 讓gdb重新得到控制權
Hello world
- gcc -static test.c -o test //記得加上 -static , 因為沒動態函數庫支援
#include <stdio.h>
int main(int argc, char *argv[])
{
printf("\nHello world\n");
return 0;
}
載入 Linux Module
- globalmem.c
/*====================================================================
A globalmem driver as an example of char device drivers
The initial developer of the original code is Baohua Song
<author@linuxdriver.cn>. All Rights Reserved.
======================================================================*/
#include <linux/module.h>
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/cdev.h>
#include <asm/io.h>
//#include <asm/system.h>
#include <asm/uaccess.h>
#include <linux/slab.h>
#define GLOBALMEM_SIZE 0x1000 /*全局內存最大4K字節*/
#define MEM_CLEAR 0x1 /*清0全局內存*/
#define GLOBALMEM_MAJOR 245 /*預設的globalmem的主設備號*/
static int globalmem_major = GLOBALMEM_MAJOR;
/*globalmem設備結構體*/
struct globalmem_dev {
struct cdev cdev; /*cdev結構體*/
unsigned char mem[GLOBALMEM_SIZE]; /*全局內存*/
};
struct globalmem_dev* globalmem_devp; /*設備結構體指針*/
/*文件打開函數*/
int globalmem_open(struct inode* inode, struct file* filp) {
/*將設備結構體指針賦值給文件私有數據指針*/
filp->private_data = globalmem_devp;
return 0;
}
/*文件釋放函數*/
int globalmem_release(struct inode* inode, struct file* filp) {
return 0;
}
/* ioctl設備控制函數 */
static int globalmem_ioctl(struct inode* inodep, struct file* filp, unsigned
int cmd, unsigned long arg) {
struct globalmem_dev* dev = filp->private_data;/*獲得設備結構體指針*/
switch (cmd) {
case MEM_CLEAR:
memset(dev->mem, 0, GLOBALMEM_SIZE);
printk(KERN_INFO "globalmem is set to zero\n");
break;
default:
return - EINVAL;
}
return 0;
}
/*讀函數*/
static ssize_t globalmem_read(struct file* filp, char __user* buf, size_t size,
loff_t* ppos) {
unsigned long p = *ppos;
unsigned int count = size;
int ret = 0;
struct globalmem_dev* dev = filp->private_data; /*獲得設備結構體指針*/
/*分析和獲取有效的寫長度*/
if (p >= GLOBALMEM_SIZE) {
return count ? - ENXIO : 0;
}
if (count > GLOBALMEM_SIZE - p) {
count = GLOBALMEM_SIZE - p;
}
/*內核空間->用戶空間*/
if (copy_to_user(buf, (void*)(dev->mem + p), count)) {
ret = - EFAULT;
} else {
*ppos += count;
ret = count;
printk(KERN_INFO "read %d bytes(s) from %d\n", count, p);
}
return ret;
}
/*寫函數*/
static ssize_t globalmem_write(struct file* filp, const char __user* buf,
size_t size, loff_t* ppos) {
unsigned long p = *ppos;
unsigned int count = size;
int ret = 0;
struct globalmem_dev* dev = filp->private_data; /*獲得設備結構體指針*/
/*分析和獲取有效的寫長度*/
if (p >= GLOBALMEM_SIZE) {
return count ? - ENXIO : 0;
}
if (count > GLOBALMEM_SIZE - p) {
count = GLOBALMEM_SIZE - p;
}
/*用戶空間->內核空間*/
if (copy_from_user(dev->mem + p, buf, count)) {
ret = - EFAULT;
} else {
*ppos += count;
ret = count;
printk(KERN_INFO "written %d bytes(s) from %d\n", count, p);
}
return ret;
}
/* seek文件定位函數 */
static loff_t globalmem_llseek(struct file* filp, loff_t offset, int orig) {
loff_t ret = 0;
switch (orig) {
case 0: /*相對文件開始位置偏移*/
if (offset < 0) {
ret = - EINVAL;
break;
}
if ((unsigned int)offset > GLOBALMEM_SIZE) {
ret = - EINVAL;
break;
}
filp->f_pos = (unsigned int)offset;
ret = filp->f_pos;
break;
case 1: /*相對文件當前位置偏移*/
if ((filp->f_pos + offset) > GLOBALMEM_SIZE) {
ret = - EINVAL;
break;
}
if ((filp->f_pos + offset) < 0) {
ret = - EINVAL;
break;
}
filp->f_pos += offset;
ret = filp->f_pos;
break;
default:
ret = - EINVAL;
break;
}
return ret;
}
/*文件操作結構體*/
static const struct file_operations globalmem_fops = {
.owner = THIS_MODULE,
.llseek = globalmem_llseek,
.read = globalmem_read,
.write = globalmem_write,
.unlocked_ioctl = globalmem_ioctl,
.open = globalmem_open,
.release = globalmem_release,
};
/*初始化並註冊cdev*/
static void globalmem_setup_cdev(struct globalmem_dev* dev, int index) {
int err, devno = MKDEV(globalmem_major, index);
cdev_init(&dev->cdev, &globalmem_fops);
dev->cdev.owner = THIS_MODULE;
dev->cdev.ops = &globalmem_fops;
err = cdev_add(&dev->cdev, devno, 1);
if (err) {
printk(KERN_NOTICE "Error %d adding LED%d", err, index);
}
}
/*設備驅動模塊加載函數*/
int globalmem_init(void) {
int result;
dev_t devno = MKDEV(globalmem_major, 0);
/* 申請設備號*/
if (globalmem_major) {
result = register_chrdev_region(devno, 1, "globalmem");
} else { /* 動態申請設備號 */
result = alloc_chrdev_region(&devno, 0, 1, "globalmem");
globalmem_major = MAJOR(devno);
}
if (result < 0) {
return result;
}
/* 動態申請設備結構體的內存*/
globalmem_devp = kmalloc(sizeof(struct globalmem_dev), GFP_KERNEL);
if (!globalmem_devp) { /*申請失敗*/
result = - ENOMEM;
goto fail_malloc;
}
memset(globalmem_devp, 0, sizeof(struct globalmem_dev));
globalmem_setup_cdev(globalmem_devp, 0);
return 0;
fail_malloc:
unregister_chrdev_region(devno, 1);
return result;
}
/*模塊卸載函數*/
void globalmem_exit(void) {
cdev_del(&globalmem_devp->cdev); /*註銷cdev*/
kfree(globalmem_devp); /*釋放設備結構體內存*/
unregister_chrdev_region(MKDEV(globalmem_major, 0), 1); /*釋放設備號*/
}
MODULE_AUTHOR("Song Baohua");
MODULE_LICENSE("Dual BSD/GPL");
module_param(globalmem_major, int, S_IRUGO);
module_init(globalmem_init);
module_exit(globalmem_exit);
- Makefile 必須加上 -O0
obj-m += globalmem.o
KDIR = /home/shihyu/data/work/linux-3.15.5
EXTRA_CFLAGS=-g -O0
build:kernel_modules
kernel_modules:
make -C $(KDIR) M=$(CURDIR) modules
clean:
make -C $(KDIR) M=$(CURDIR) clean
insmod globalmem.ko
mknod /dev/globalmem c 245 0
# section.sh globalmem > gdb
# put.sh gdb
- gdb 加入 ./globalmem.ko ; 0xffffffffa0000000 是 .text address
add-symbol-file ./globalmem.ko 0xffffffffa0000000 \
-s .bss 0xffffffffa0000900 \
-s .data 0xffffffffa0000698 \
-s .gnu.linkonce.this_module 0xffffffffa00006a0 \
-s .note.gnu.build-id 0xffffffffa0000488 \
-s .rodata 0xffffffffa0000560 \
-s .rodata.str1.1 0xffffffffa00004ac \
-s .rodata.str1.8 0xffffffffa0000508 \
-s .strtab 0xffffffffa00025e8 \
-s .symtab 0xffffffffa0002000 \
-s __mcount_loc 0xffffffffa0000658 \
-s __param 0xffffffffa0000528
- (gdb) source MyGdbInit_first
# MyGdbInit_first
target remote localhost:1234
source /tftpboot/gdb
c
- (gdb) source MyGdbInit_second
# MyGdbInit_second
b globalmem_write
b globalmem_read
c
echo "Hello world" > /dev/globalmem