static int __init sysrq_init(void)
{
sysrq_init_procfs(); //注册proc入口
if (sysrq_on()) //按键的话需要开关控制
sysrq_register_handler(); //注册按键处理入口
return 0;
}
module_init(sysrq_init);
sysrq proc的支持:
static void sysrq_init_procfs(void)
{
if (!proc_create("sysrq-trigger", S_IWUSR, NULL,
&proc_sysrq_trigger_operations))
pr_err("Failed to register proc interface\n");
}
static const struct file_operations proc_sysrq_trigger_operations = {
.write = write_sysrq_trigger,
.llseek = noop_llseek,
};
static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
if (count) {
char c;
if (get_user(c, buf))
return -EFAULT;
__handle_sysrq(c, false);
}
return count;
}
void __handle_sysrq(int key, bool check_mask)
{
struct sysrq_key_op *op_p;
...
op_p = __sysrq_get_key_op(key);
if (op_p) {
/*
* Should we check for enabled operations (/proc/sysrq-trigger
* should not) and is the invoked operation enabled?
*/
if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
printk("%s\n", op_p->action_msg);
console_loglevel = orig_log_level;
op_p->handler(key);
} else {
printk("This sysrq operation is disabled.\n");
}
}
...
}
struct sysrq_key_op *__sysrq_get_key_op(int key)
{
struct sysrq_key_op *op_p = NULL;
int i;
i = sysrq_key_table_key2index(key);
if (i != -1)
op_p = sysrq_key_table[i];
return op_p;
}
static struct sysrq_key_op *sysrq_key_table[36] = {
&sysrq_loglevel_op, /* 0 */
&sysrq_loglevel_op, /* 1 */
&sysrq_loglevel_op, /* 2 */
&sysrq_loglevel_op, /* 3 */
&sysrq_loglevel_op, /* 4 */
&sysrq_loglevel_op, /* 5 */
&sysrq_loglevel_op, /* 6 */
&sysrq_loglevel_op, /* 7 */
&sysrq_loglevel_op, /* 8 */
&sysrq_loglevel_op, /* 9 */
/*
* a: Don't use for system provided sysrqs, it is handled specially on
* sparc and will never arrive.
*/
NULL, /* a */
&sysrq_reboot_op, /* b */
&sysrq_crash_op, /* c & ibm_emac driver debug */
&sysrq_showlocks_op, /* d */
&sysrq_term_op, /* e */
&sysrq_moom_op, /* f */
/* g: May be registered for the kernel debugger */
NULL, /* g */
NULL, /* h - reserved for help */
&sysrq_kill_op, /* i */
#ifdef CONFIG_BLOCK
&sysrq_thaw_op, /* j */
#else
NULL, /* j */
#endif
&sysrq_SAK_op, /* k */
#ifdef CONFIG_SMP
&sysrq_showallcpus_op, /* l */
#else
NULL, /* l */
#endif
&sysrq_showmem_op, /* m */
&sysrq_unrt_op, /* n */
/* o: This will often be registered as 'Off' at init time */
NULL, /* o */
&sysrq_showregs_op, /* p */
&sysrq_show_timers_op, /* q */
&sysrq_unraw_op, /* r */
&sysrq_sync_op, /* s */
&sysrq_showstate_op, /* t */
&sysrq_mountro_op, /* u */
/* v: May be registered for frame buffer console restore */
NULL, /* v */
&sysrq_showstate_blocked_op, /* w */
/* x: May be registered on ppc/powerpc for xmon */
/* x: May be registered on sparc64 for global PMU dump */
NULL, /* x */
/* y: May be registered on sparc64 for global register dump */
NULL, /* y */
&sysrq_ftrace_dump_op, /* z */
}
sysrq按键的支持:
首先需要打开开关
打开这个功能,运行:
# echo 1 > /proc/sys/kernel/sysrq
关闭这个功能:
# echo 0 > /proc/sys/kernel/sysrq
#ifdef CONFIG_MAGIC_SYSRQ
{
.procname = "sysrq",
.data = &__sysrq_enabled,
.maxlen = sizeof (int),
.mode = 0644,
.proc_handler = sysrq_sysctl_handler,
},
#endif
int sysrq_toggle_support(int enable_mask)
{
bool was_enabled = sysrq_on();
sysrq_enabled = enable_mask;
if (was_enabled != sysrq_on()) {
if (sysrq_on())
sysrq_register_handler();
else
sysrq_unregister_handler();
}
return 0;
}
由实现可以看出支持动态打开和关闭
注册sysrq按键处理函数:
static inline void sysrq_register_handler(void)
{
int error;
error = input_register_handler(&sysrq_handler);
if (error)
pr_err("Failed to register input handler, error %d", error);
else
sysrq_handler_registered = true;
}
static struct input_handler sysrq_handler = {
.filter = sysrq_filter, //哪些消息给sysrq去处理
.connect = sysrq_connect,
.disconnect = sysrq_disconnect,
.name = "sysrq",
.id_table = sysrq_ids,
};
static bool sysrq_filter(struct input_handle *handle,
unsigned int type, unsigned int code, int value)
{
...
default:
if (sysrq->active && value && value != 2) {
sysrq->need_reinject = false;
__handle_sysrq(sysrq_xlate[code], true);
}
break;
}
....
}
可以看出sysrq按键最终和proc一样都是调用__handle_sysrq()来处理
sysrq: SysRq : HELP : loglevel(0-9) reboot(b) crash(c) terminate-all-tasks(e) memory-full-oom-kill(f) kill-all-tasks(i) thaw-filesystems(j) sak(k) show-backtrace-all-active-cpus(l) show-memory-usage(m) nice-all-R
查看内存信息:
# echo 'm' > /proc/sysrq-trigger
重启:
# echo 'b' > /proc/sysrq-trigger