proc: add pid mapping between host and container

create a pid mapping data to parent processes in file  /proc/$PID/status
create a proc file (/proc/$PID/hostinfo), mapping pid data to host pid

Signed-off-by: Lorin Liu <lorinliu@tencent.com>

fs/proc/array.c

@@ -91,11 +91,15 @@
 #include <linux/string_helpers.h>
 #include <linux/user_namespace.h>
 #include <linux/fs_struct.h>
+#include <linux/sched.h>
+#include <linux/sched/sysctl.h>
 
 #include <asm/pgtable.h>
 #include <asm/processor.h>
 #include "internal.h"
 
+unsigned int sysctl_watch_host_pid;
+
 static inline void task_name(struct seq_file *m, struct task_struct *p)
 {
 	char *buf;
@@ -165,6 +169,9 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
 	const struct cred *cred;
 	pid_t ppid, tpid = 0, tgid, ngid;
 	unsigned int max_fds = 0;
+#ifdef CONFIG_PID_NS
+	struct pid_namespace *current_pid_ns = task_active_pid_ns(current);
+#endif
 
 	rcu_read_lock();
 	ppid = pid_alive(p) ?
@@ -188,6 +195,21 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
 	task_unlock(p);
 	rcu_read_unlock();
 
+#ifdef CONFIG_PID_NS
+	seq_puts(m, "NStgid:");
+	for (g = current_pid_ns->level; g <= pid->level; g++)
+		seq_printf(m, "\t%d",
+			task_tgid_nr_ns(p, pid->numbers[g].ns));
+	seq_puts(m, "\nNSpid:");
+	for (g = current_pid_ns->level; g <= pid->level; g++)
+		seq_printf(m, "\t%d",
+			task_pid_nr_ns(p, pid->numbers[g].ns));
+	seq_puts(m, "\nNSsid:");
+	for (g = current_pid_ns->level; g <= pid->level; g++)
+		seq_printf(m, "\t%d",
+			task_session_nr_ns(p, pid->numbers[g].ns));
+	seq_putc(m, '\n');
+#endif
 	seq_printf(m, "State:\t%s", get_task_state(p));
 
 	seq_put_decimal_ull(m, "\nTgid:\t", tgid);
@@ -391,6 +413,35 @@ static void task_cpus_allowed(struct seq_file *m, struct task_struct *task)
 		   cpumask_pr_args(&task->cpus_allowed));
 }
 
+int host_pid_info(struct seq_file *m, struct pid_namespace *ns,
+			struct pid *pid, struct task_struct *task)
+{
+	if (sysctl_watch_host_pid) {
+		struct task_struct *p = task;
+		int g;
+		struct pid_namespace *current_pid_ns = task_active_pid_ns(current);
+
+		task_name(m, task);
+		rcu_read_lock();
+		seq_puts(m, "NStgid:");
+		for (g = current_pid_ns->level; g >= 0; g--)
+			seq_printf(m, "\t%d",
+				task_tgid_nr_ns(p, pid->numbers[g].ns));
+		seq_puts(m, "\nNSpid:");
+		for (g = current_pid_ns->level; g >= 0; g--)
+			seq_printf(m, "\t%d",
+				task_pid_nr_ns(p, pid->numbers[g].ns));
+		seq_puts(m, "\nNSsid:");
+		for (g = current_pid_ns->level; g >= 0; g--)
+			seq_printf(m, "\t%d",
+				task_session_nr_ns(p, pid->numbers[g].ns));
+		rcu_read_unlock();
+		seq_putc(m, '\n');
+		return 0;
+	}
+	return 0;
+}
+
 int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
 			struct pid *pid, struct task_struct *task)
 {

fs/proc/base.c

@@ -2946,6 +2946,7 @@ static const struct pid_entry tgid_base_stuff[] = {
 	REG("environ",    S_IRUSR, proc_environ_operations),
 	REG("auxv",       S_IRUSR, proc_auxv_operations),
 	ONE("status",     S_IRUGO, proc_pid_status),
+	ONE("hostinfo",   S_IRUGO, host_pid_info),
 	ONE("personality", S_IRUSR, proc_pid_personality),
 	ONE("limits",	  S_IRUGO, proc_pid_limits),
 #ifdef CONFIG_SCHED_DEBUG
@@ -3339,6 +3340,7 @@ static const struct pid_entry tid_base_stuff[] = {
 	REG("environ",   S_IRUSR, proc_environ_operations),
 	REG("auxv",      S_IRUSR, proc_auxv_operations),
 	ONE("status",    S_IRUGO, proc_pid_status),
+	ONE("hostinfo",  S_IRUGO, host_pid_info),
 	ONE("personality", S_IRUSR, proc_pid_personality),
 	ONE("limits",	 S_IRUGO, proc_pid_limits),
 #ifdef CONFIG_SCHED_DEBUG

fs/proc/internal.h

@@ -144,6 +144,8 @@ extern int proc_tgid_stat(struct seq_file *, struct pid_namespace *,
 			  struct pid *, struct task_struct *);
 extern int proc_pid_status(struct seq_file *, struct pid_namespace *,
 			   struct pid *, struct task_struct *);
+extern int host_pid_info(struct seq_file *, struct pid_namespace *,
+			  struct pid *, struct task_struct *);
 extern int proc_pid_statm(struct seq_file *, struct pid_namespace *,
 			  struct pid *, struct task_struct *);
 

include/linux/sched/sysctl.h

@@ -19,6 +19,7 @@ extern int proc_dohung_task_timeout_secs(struct ctl_table *table, int write,
 enum { sysctl_hung_task_timeout_secs = 0 };
 #endif
 
+extern unsigned int sysctl_watch_host_pid;
 extern unsigned int sysctl_sched_latency;
 extern unsigned int sysctl_sched_min_granularity;
 extern unsigned int sysctl_sched_wakeup_granularity;

kernel/sysctl.c

@@ -335,6 +335,15 @@ static struct ctl_table kern_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec,
 	},
+#ifdef CONFIG_PID_NS
+	{
+		.procname       = "watch_host_pid",
+		.data           = &sysctl_watch_host_pid,
+		.maxlen         = sizeof(unsigned int),
+		.mode           = 0644,
+		.proc_handler   = proc_dointvec,
+	},
+#endif
 #ifdef CONFIG_SCHED_DEBUG
 	{
 		.procname	= "sched_min_granularity_ns",