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Commit 38a81da2 authored by Matt Helsley's avatar Matt Helsley Committed by Ingo Molnar
Browse files

perf events: Clean up pid passing 

The kernel perf event creation path shouldn't use find_task_by_vpid()
because a vpid exists in a specific namespace. find_task_by_vpid() uses
current's pid namespace which isn't always the correct namespace to use
for the vpid in all the places perf_event_create_kernel_counter() (and
thus find_get_context()) is called.

The goal is to clean up pid namespace handling and prevent bugs like:

	https://bugzilla.kernel.org/show_bug.cgi?id=17281



Instead of using pids switch find_get_context() to use task struct
pointers directly. The syscall is responsible for resolving the pid to
a task struct. This moves the pid namespace resolution into the syscall
much like every other syscall that takes pid parameters.

Signed-off-by: default avatarMatt Helsley <matthltc@us.ibm.com>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Robin Green <greenrd@greenrd.org>
Cc: Prasad <prasad@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
LKML-Reference: <a134e5e392ab0204961fd1a62c84a222bf5874a9.1284407763.git.matthltc@us.ibm.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 2ebd4ffb

arch/arm/oprofile/common.c

+1 −1
Original line number Diff line number Diff line
@@ -96,7 +96,7 @@ static int op_create_counter(int cpu, int event) 
		return ret;



	pevent = perf_event_create_kernel_counter(&counter_config[event].attr,

						  cpu, -1,

						  cpu, NULL,

						  op_overflow_handler);



	if (IS_ERR(pevent)) {

include/linux/perf_event.h

+1 −1
Original line number Diff line number Diff line
@@ -902,7 +902,7 @@ extern int perf_event_release_kernel(struct perf_event *event); 
extern struct perf_event *

perf_event_create_kernel_counter(struct perf_event_attr *attr,

				int cpu,

				pid_t pid,

				struct task_struct *task,

				perf_overflow_handler_t callback);

extern u64 perf_event_read_value(struct perf_event *event,

				 u64 *enabled, u64 *running);

kernel/hw_breakpoint.c

+2 −3
Original line number Diff line number Diff line
@@ -433,8 +433,7 @@ register_user_hw_breakpoint(struct perf_event_attr *attr, 
			    perf_overflow_handler_t triggered,

			    struct task_struct *tsk)

{

	return perf_event_create_kernel_counter(attr, -1, task_pid_vnr(tsk),

						triggered);

	return perf_event_create_kernel_counter(attr, -1, tsk, triggered);

}

EXPORT_SYMBOL_GPL(register_user_hw_breakpoint);
@@ -516,7 +515,7 @@ register_wide_hw_breakpoint(struct perf_event_attr *attr, 
	get_online_cpus();

	for_each_online_cpu(cpu) {

		pevent = per_cpu_ptr(cpu_events, cpu);

		bp = perf_event_create_kernel_counter(attr, cpu, -1, triggered);

		bp = perf_event_create_kernel_counter(attr, cpu, NULL, triggered);



		*pevent = bp;

kernel/perf_event.c

+10 −11
Original line number Diff line number Diff line
@@ -2053,15 +2053,14 @@ find_lively_task_by_vpid(pid_t vpid) 
}



static struct perf_event_context *

find_get_context(struct pmu *pmu, pid_t pid, int cpu)

find_get_context(struct pmu *pmu, struct task_struct *task, int cpu)

{

	struct perf_event_context *ctx;

	struct perf_cpu_context *cpuctx;

	struct task_struct *task;

	unsigned long flags;

	int ctxn, err;



	if (pid == -1 && cpu != -1) {

	if (!task && cpu != -1) {

		/* Must be root to operate on a CPU event: */

		if (perf_paranoid_cpu() && !capable(CAP_SYS_ADMIN))

			return ERR_PTR(-EACCES);
@@ -2084,10 +2083,6 @@ find_get_context(struct pmu *pmu, pid_t pid, int cpu) 
		return ctx;

	}



	task = find_lively_task_by_vpid(pid);

	if (IS_ERR(task))

		return (void*)task;



	err = -EINVAL;

	ctxn = pmu->task_ctx_nr;

	if (ctxn < 0)
@@ -5527,6 +5522,7 @@ SYSCALL_DEFINE5(perf_event_open, 
	struct perf_event_context *ctx;

	struct file *event_file = NULL;

	struct file *group_file = NULL;

	struct task_struct *task = NULL;

	struct pmu *pmu;

	int event_fd;

	int fput_needed = 0;
@@ -5581,10 +5577,13 @@ SYSCALL_DEFINE5(perf_event_open, 
	if ((pmu->task_ctx_nr == perf_sw_context) && group_leader)

		pmu = group_leader->pmu;



	if (pid != -1)

		task = find_lively_task_by_vpid(pid);



	/*

	 * Get the target context (task or percpu):

	 */

	ctx = find_get_context(pmu, pid, cpu);

	ctx = find_get_context(pmu, task, cpu);

	if (IS_ERR(ctx)) {

		err = PTR_ERR(ctx);

		goto err_group_fd;
@@ -5666,11 +5665,11 @@ SYSCALL_DEFINE5(perf_event_open, 
 *

 * @attr: attributes of the counter to create

 * @cpu: cpu in which the counter is bound

 * @pid: task to profile

 * @task: task to profile (NULL for percpu)

 */

struct perf_event *

perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu,

				 pid_t pid,

				 struct task_struct *task,

				 perf_overflow_handler_t overflow_handler)

{

	struct perf_event_context *ctx;
@@ -5687,7 +5686,7 @@ perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu, 
		goto err;

	}



	ctx = find_get_context(event->pmu, pid, cpu);

	ctx = find_get_context(event->pmu, task, cpu);

	if (IS_ERR(ctx)) {

		err = PTR_ERR(ctx);

		goto err_free;

kernel/watchdog.c

+1 −1
Original line number Diff line number Diff line
@@ -358,7 +358,7 @@ static int watchdog_nmi_enable(int cpu) 
	/* Try to register using hardware perf events */

	wd_attr = &wd_hw_attr;

	wd_attr->sample_period = hw_nmi_get_sample_period();

	event = perf_event_create_kernel_counter(wd_attr, cpu, -1, watchdog_overflow_callback);

	event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback);

	if (!IS_ERR(event)) {

		printk(KERN_INFO "NMI watchdog enabled, takes one hw-pmu counter.\n");

		goto out_save;