Linux内核:4.13-RC7 X86_64
为Linux内核调试配置了BuildRoot和Qemu。
使用以下命令启动QEMU:
qemu-system-x86_64 -kernel linux-4.13-rc7/arch/x86/boot/bzImage -initrd buildroot-2017.02.5/output/images/rootfs.cpio -append "root=/dev/ram0 console=tty0 kgdboc=ttyS0,9600 kgdbwait" -chardev pty,id=pty -device isa-serial,chardev=pty
现在,在下一个终端窗口中,启动GDB并按照GDB命令进行操作:
`
gdb-peda$ file vmlinux
Reading symbols from vmlinux...done.
warning: File "/root/drive/linux-4.13-rc7/scripts/gdb/vmlinux-gdb.py" auto-loading has been declined by your `auto-load safe-path' set to "$debugdir:$datadir/auto-load".
To enable execution of this file add
add-auto-load-safe-path /root/drive/linux-4.13-rc7/scripts/gdb/vmlinux-gdb.py
line to your configuration file "/root/.gdbinit".
To completely disable this security protection add
set auto-load safe-path /
line to your configuration file "/root/.gdbinit".
For more information about this security protection see the
"Auto-loading safe path" section in the GDB manual. E.g., run from the shell:
info "(gdb)Auto-loading safe path"
gdb-peda$ target remote /dev/pts/3
Remote debugging using /dev/pts/3
Warning: not running or target is remote
0xffffffffbd6f65af in ?? ()
gdb-peda$ b start_kernel
Breakpoint 1 at 0xffffffff81f79ad7: file init/main.c, line 510.
gdb-peda$ c
Continuing.
Warning:
Cannot insert breakpoint 1.
Cannot access memory at address 0xffffffff81f79ad7
Command aborted.
gdb-peda$ `
我还尝试了QEMU机器:
echo "g" > /proc/sysrq-trigger
。但是,什么都没有发生。
另外,尝试使用start_kernel
上的hbreak
设置硬件断点,但什么也没发生。
我自己弄清楚了解决方案,我做了以下操作以获取工作解决方案:
- 将补丁程序应用于GDB,然后用
<$GDB_FOLDER>/gdb/remote.c
文件中的补丁重新编译。
GDB补丁调整其内部缓冲区大小:
root# diff -u gdb-8 (1).0/gdb/remote.c gdb-8.0/gdb/remote.c
--- "gdb-8 (1).0/gdb/remote.c" 2017-06-04 21:24:54.000000000 +0530
+++ gdb-8.0/gdb/remote.c 2017-09-05 23:27:46.487820345 +0530
@@ -7583,7 +7583,27 @@
/* Further sanity checks, with knowledge of the architecture. */
if (buf_len > 2 * rsa->sizeof_g_packet)
- error (_("Remote 'g' packet reply is too long: %s"), rs->buf);
+ //error (_("Remote 'g' packet reply is too long: %s"), rs->buf); #patching
+ {
+ warning (_("Assuming long-mode change. [Remote 'g' packet reply is too long: %s]"), rs->buf);
+ rsa->sizeof_g_packet = buf_len ;
+
+ for (i = 0; i < gdbarch_num_regs (gdbarch); i++)
+ {
+ if (rsa->regs[i].pnum == -1)
+ continue;
+
+ if (rsa->regs[i].offset >= rsa->sizeof_g_packet)
+ rsa->regs[i].in_g_packet = 0;
+ else
+ rsa->regs[i].in_g_packet = 1;
+ }
+
+ // HACKFIX: Make sure at least the lower half of EIP is set correctly, so the proper
+ // breakpoint is recognized (and triggered).
+ rsa->regs[8].offset = 16*8;
+ }
+
/* Save the size of the packet sent to us by the target. It is used
as a heuristic when determining the max size of packets that the`
通过buildroot构建最小的rootf。
通过以下命令启动QEMU,然后启动新的GDB,然后加载VMlinux文件。
在一个终端中:
root# qemu-system-x86_64 -kernel /root/drive/linux-4.13-rc7/arch/x86/boot/bzImage -initrd /root/drive/buildroot-2017.02.5/output/images/rootfs.cpio -S -s
在另一个终端中:
gdb -q /root/drive/linux-4.13-rc7/vmlinux -ex "target remote localhost:1234"
现在将断点设置为
start_kernel
并继续,它将自动击中断点。