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perf: Support only inheriting events if cloned with CLONE_THREAD 

Adds bit perf_event_attr::inherit_thread, to restricting inheriting
events only if the child was cloned with CLONE_THREAD.

This option supports the case where an event is supposed to be
process-wide only (including subthreads), but should not propagate
beyond the current process's shared environment.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/lkml/YBvj6eJR%2FDY2TsEB@hirez.programming.kicks-ass.net/
This commit is contained in:
Marco Elver 2021-04-08 12:35:58 +02:00 committed by Peter Zijlstra
parent 47f661eca0
commit 2b26f0aa00
4 changed files with 20 additions and 11 deletions
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5
include/linux/perf_event.h
View File

@ -958,7 +958,7 @@ extern void __perf_event_task_sched_in(struct task_struct *prev,
struct task_struct *task);
extern void __perf_event_task_sched_out(struct task_struct *prev,
struct task_struct *next);
extern int perf_event_init_task(struct task_struct *child);
extern int perf_event_init_task(struct task_struct *child, u64 clone_flags);
extern void perf_event_exit_task(struct task_struct *child);
extern void perf_event_free_task(struct task_struct *task);
extern void perf_event_delayed_put(struct task_struct *task);
@ -1449,7 +1449,8 @@ perf_event_task_sched_in(struct task_struct *prev,
static inline void
perf_event_task_sched_out(struct task_struct *prev,
struct task_struct *next) { }
static inline int perf_event_init_task(struct task_struct *child) { return 0; }
static inline int perf_event_init_task(struct task_struct *child,
u64 clone_flags) { return 0; }
static inline void perf_event_exit_task(struct task_struct *child) { }
static inline void perf_event_free_task(struct task_struct *task) { }
static inline void perf_event_delayed_put(struct task_struct *task) { }

3
include/uapi/linux/perf_event.h
View File

@ -389,7 +389,8 @@ struct perf_event_attr {
cgroup : 1, /* include cgroup events */
text_poke : 1, /* include text poke events */
build_id : 1, /* use build id in mmap2 events */
__reserved_1 : 29;
inherit_thread : 1, /* children only inherit if cloned with CLONE_THREAD */
__reserved_1 : 28;
union {
__u32 wakeup_events; /* wakeup every n events */

21
kernel/events/core.c
View File

@ -11653,6 +11653,9 @@ static int perf_copy_attr(struct perf_event_attr __user *uattr,
(attr->sample_type & PERF_SAMPLE_WEIGHT_STRUCT))
return -EINVAL;
if (!attr->inherit && attr->inherit_thread)
return -EINVAL;
out:
return ret;
@ -12873,12 +12876,13 @@ static int
inherit_task_group(struct perf_event *event, struct task_struct *parent,
struct perf_event_context *parent_ctx,
struct task_struct *child, int ctxn,
int *inherited_all)
u64 clone_flags, int *inherited_all)
{
int ret;
struct perf_event_context *child_ctx;
if (!event->attr.inherit) {
if (!event->attr.inherit ||
(event->attr.inherit_thread && !(clone_flags & CLONE_THREAD))) {
*inherited_all = 0;
return 0;
}
@ -12910,7 +12914,8 @@ inherit_task_group(struct perf_event *event, struct task_struct *parent,
/*
* Initialize the perf_event context in task_struct
*/
static int perf_event_init_context(struct task_struct *child, int ctxn)
static int perf_event_init_context(struct task_struct *child, int ctxn,
u64 clone_flags)
{
struct perf_event_context *child_ctx, *parent_ctx;
struct perf_event_context *cloned_ctx;
@ -12950,7 +12955,8 @@ static int perf_event_init_context(struct task_struct *child, int ctxn)
*/
perf_event_groups_for_each(event, &parent_ctx->pinned_groups) {
ret = inherit_task_group(event, parent, parent_ctx,
child, ctxn, &inherited_all);
child, ctxn, clone_flags,
&inherited_all);
if (ret)
goto out_unlock;
}
@ -12966,7 +12972,8 @@ static int perf_event_init_context(struct task_struct *child, int ctxn)
perf_event_groups_for_each(event, &parent_ctx->flexible_groups) {
ret = inherit_task_group(event, parent, parent_ctx,
child, ctxn, &inherited_all);
child, ctxn, clone_flags,
&inherited_all);
if (ret)
goto out_unlock;
}
@ -13008,7 +13015,7 @@ out_unlock:
/*
* Initialize the perf_event context in task_struct
*/
int perf_event_init_task(struct task_struct *child)
int perf_event_init_task(struct task_struct *child, u64 clone_flags)
{
int ctxn, ret;
@ -13017,7 +13024,7 @@ int perf_event_init_task(struct task_struct *child)
INIT_LIST_HEAD(&child->perf_event_list);
for_each_task_context_nr(ctxn) {
ret = perf_event_init_context(child, ctxn);
ret = perf_event_init_context(child, ctxn, clone_flags);
if (ret) {
perf_event_free_task(child);
return ret;

2
kernel/fork.c
View File

@ -2078,7 +2078,7 @@ static __latent_entropy struct task_struct *copy_process(
if (retval)
goto bad_fork_cleanup_policy;
retval = perf_event_init_task(p);
retval = perf_event_init_task(p, clone_flags);
if (retval)
goto bad_fork_cleanup_policy;
retval = audit_alloc(p);