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我一直在尝试让QEMU在使用GDB远程调试它的情况下执行内核，但是我无法步进或设置断点。这里的GDB会话：无法使用QEMU/GDB调试内核
linux (master *) $ gdb vmlinux
GNU gdb (Debian 7.12-6) 7.12.0.20161007-git
Copyright (C) 2016 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
[LICENSE TEXT]
The target architecture is assumed to be i386:x86-64
Reading symbols from vmlinux...done.
(gdb) target remote localhost:1234
localhost:1234: Connection timed out.
(gdb) target remote localhost:1234
Remote debugging using localhost:1234
0xffffffffa13507ee in ??()
(gdb) c
Continuing.
^C
Thread 1 received signal SIGINT, Interrupt.
0xffffffffa13507ee in ??()
(gdb) b rcu_process_callbacks
Breakpoint 1 at 0xffffffff81101800: file kernel/rcu/tree.c, line 3037.
(gdb) c
Continuing.
Warning:
Cannot insert breakpoint 1.
Cannot access memory at address 0xffffffff81101800
Command aborted.
(gdb)
我编译与调试符号的内核内核文档中提到：
linux (master *) $ grep CONFIG_DEBUG .config | grep -v "^#"
CONFIG_DEBUG_DEVRES=y
CONFIG_DEBUG_INFO=y
CONFIG_DEBUG_FS=y
CONFIG_DEBUG_KERNEL=y
CONFIG_DEBUG_STACK_USAGE=y
CONFIG_DEBUG_MEMORY_INIT=y
CONFIG_DEBUG_STACKOVERFLOW=y
CONFIG_DEBUG_BUGVERBOSE=y
CONFIG_DEBUG_BOOT_PARAMS=y
如果构建内核调试符号我还检查。
linux (master *) $ nm --debug-syms vmlinux | grep "\.debug"
0000000000000000 N .debug_abbrev
0000000000000000 N .debug_aranges
0000000000000000 N .debug_frame
0000000000000000 N .debug_info
0000000000000000 N .debug_line
0000000000000000 N .debug_loc
0000000000000000 N .debug_ranges
0000000000000000 N .debug_str
我运行QEMU使用以下命令行：
linux (master *) $ qemu-system-x86_64 -smp 4 -cpu host \
-m 2048 -kernel arch/x86/boot/bzImage \
-initrd ../obj/initramfs-busybox-x86.cpio.gz -nographic \
-append "console=ttyS0" -enable-kvm \
-drive file=../disk.img,if=virtio,cache=none -s
我缺少的是这可能导致GDB失败也是这样吗？我也无法从内核GDB脚本执行GDB扩展命令，所以我猜这必须让GDB不知道它正在调试内核？我需要启用KGDB才能工作吗？
我正在使用Linux 4.12-rc5内核。