转自：https://blog.csdn.net/adaptiver/article/details/12778621
关于CONFIG_DEBUG_USER
把menuconfig中查到的 CONFIG_DEBUG_USER 信息copy在下面：
| CONFIG_DEBUG_USER:
|
| When a user program crashes due to an exception, the kernel can
| print a brief message explaining what the problem was. This is
| sometimes helpful for debugging but serves no purpose on a
| production system. Most people should say N here.
|
| In addition, you need to pass user_debug=N on the kernel command
| line to enable this feature. N consists of the sum of:
|
| 1 - undefined instruction events
| 2 - system calls
| 4 - invalid data aborts
| 8 - SIGSEGV faults
| 16 - SIGBUS faults
|
| Symbol: DEBUG_USER [=n]
| Type : boolean
| Prompt: Verbose user fault messages
| Defined at arch/arm/Kconfig.debug:49
| Location:
| -> Kernel hacking
要试用该功能：
首先在config文件中添加该选项，然后在 kernel 的cmdline中添加 user_debug=1 或者 user_debug=31
类似：
console=ttyS2 quiet user_debug=31
setenv bootargs console=ttySAC0,115200 user_debug=1 saveenv
user_debug的值可根据情况选定，下面这几个宏与上面的粗体部分可对照一下，可得知各个bit使能之后能得到的信息。
#define UDBG_UNDEFINED (1 << 0)
#define UDBG_SYSCALL (1 << 1)
#define UDBG_BADABORT (1 << 2)
#define UDBG_SEGV (1 << 3)
#define UDBG_BUS (1 << 4)
有一篇文章就这一点而言有参考意义：