perf_counter: Use PID namespaces properly

Stop using task_struct::pid and start using PID namespaces.

PIDs will be reported in the PID namespace of the monitoring
task at the moment of counter creation.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/perf_counter.h

@@ -317,6 +317,7 @@ enum perf_event_type {
 #include <linux/spinlock.h>
 #include <linux/hrtimer.h>
 #include <linux/fs.h>
+#include <linux/pid_namespace.h>
 #include <asm/atomic.h>
 
 struct task_struct;
@@ -500,6 +501,8 @@ struct perf_counter {
 
 	void (*destroy)(struct perf_counter *);
 	struct rcu_head			rcu_head;
+
+	struct pid_namespace		*ns;
 #endif
 };
 

kernel/perf_counter.c

@@ -1432,6 +1432,8 @@ static void free_counter_rcu(struct rcu_head *head)
 	struct perf_counter *counter;
 
 	counter = container_of(head, struct perf_counter, rcu_head);
+	if (counter->ns)
+		put_pid_ns(counter->ns);
 	kfree(counter);
 }
 
@@ -2267,6 +2269,28 @@ static void perf_output_end(struct perf_output_handle *handle)
 	rcu_read_unlock();
 }
 
+static u32 perf_counter_pid(struct perf_counter *counter, struct task_struct *p)
+{
+	/*
+	 * only top level counters have the pid namespace they were created in
+	 */
+	if (counter->parent)
+		counter = counter->parent;
+
+	return task_tgid_nr_ns(p, counter->ns);
+}
+
+static u32 perf_counter_tid(struct perf_counter *counter, struct task_struct *p)
+{
+	/*
+	 * only top level counters have the pid namespace they were created in
+	 */
+	if (counter->parent)
+		counter = counter->parent;
+
+	return task_pid_nr_ns(p, counter->ns);
+}
+
 static void perf_counter_output(struct perf_counter *counter,
 				int nmi, struct pt_regs *regs, u64 addr)
 {
@@ -2303,8 +2327,8 @@ static void perf_counter_output(struct perf_counter *counter,
 
 	if (record_type & PERF_RECORD_TID) {
 		/* namespace issues */
-		tid_entry.pid = current->group_leader->pid;
-		tid_entry.tid = current->pid;
+		tid_entry.pid = perf_counter_pid(counter, current);
+		tid_entry.tid = perf_counter_tid(counter, current);
 
 		header.type |= PERF_RECORD_TID;
 		header.size += sizeof(tid_entry);
@@ -2432,6 +2456,9 @@ static void perf_counter_comm_output(struct perf_counter *counter,
 	if (ret)
 		return;
 
+	comm_event->event.pid = perf_counter_pid(counter, comm_event->task);
+	comm_event->event.tid = perf_counter_tid(counter, comm_event->task);
+
 	perf_output_put(&handle, comm_event->event);
 	perf_output_copy(&handle, comm_event->comm,
 				   comm_event->comm_size);
@@ -2504,8 +2531,6 @@ void perf_counter_comm(struct task_struct *task)
 		.task	= task,
 		.event  = {
 			.header = { .type = PERF_EVENT_COMM, },
-			.pid	= task->group_leader->pid,
-			.tid	= task->pid,
 		},
 	};
 
@@ -2542,6 +2567,9 @@ static void perf_counter_mmap_output(struct perf_counter *counter,
 	if (ret)
 		return;
 
+	mmap_event->event.pid = perf_counter_pid(counter, current);
+	mmap_event->event.tid = perf_counter_tid(counter, current);
+
 	perf_output_put(&handle, mmap_event->event);
 	perf_output_copy(&handle, mmap_event->file_name,
 				   mmap_event->file_size);
@@ -2641,8 +2669,6 @@ void perf_counter_mmap(unsigned long addr, unsigned long len,
 		.file   = file,
 		.event  = {
 			.header = { .type = PERF_EVENT_MMAP, },
-			.pid	= current->group_leader->pid,
-			.tid	= current->pid,
 			.start  = addr,
 			.len    = len,
 			.pgoff  = pgoff,
@@ -2664,8 +2690,6 @@ void perf_counter_munmap(unsigned long addr, unsigned long len,
 		.file   = file,
 		.event  = {
 			.header = { .type = PERF_EVENT_MUNMAP, },
-			.pid	= current->group_leader->pid,
-			.tid	= current->pid,
 			.start  = addr,
 			.len    = len,
 			.pgoff  = pgoff,
@@ -3445,6 +3469,8 @@ SYSCALL_DEFINE5(perf_counter_open,
 	list_add_tail(&counter->owner_entry, &current->perf_counter_list);
 	mutex_unlock(&current->perf_counter_mutex);
 
+	counter->ns = get_pid_ns(current->nsproxy->pid_ns);
+
 	fput_light(counter_file, fput_needed2);
 
 out_fput: