9 files changed, 52 insertions, 24 deletions

diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index 0bebb5c348b8..d36f68b08acc 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -595,7 +595,7 @@ extern int  ftrace_profile_set_filter(struct perf_event *event, int event_id,
                                      char *filter_str);
 extern void ftrace_profile_free_filter(struct perf_event *event);
 extern void *perf_trace_buf_prepare(int size, unsigned short type,
-                                    struct pt_regs *regs, int *rctxp);
+                                    struct pt_regs **regs, int *rctxp);
 
 static inline void
 perf_trace_buf_submit(void *raw_data, int size, int rctx, u64 addr,
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 4f7a61ca4b39..3a7bd80b4db8 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -665,6 +665,7 @@ static inline int is_software_event(struct perf_event *event)
 
 extern struct static_key perf_swevent_enabled[PERF_COUNT_SW_MAX];
 
+extern void ___perf_sw_event(u32, u64, struct pt_regs *, u64);
 extern void __perf_sw_event(u32, u64, struct pt_regs *, u64);
 
 #ifndef perf_arch_fetch_caller_regs
@@ -689,14 +690,25 @@ static inline void perf_fetch_caller_regs(struct pt_regs *regs)
 static __always_inline void
 perf_sw_event(u32 event_id, u64 nr, struct pt_regs *regs, u64 addr)
 {
-        struct pt_regs hot_regs;
+        if (static_key_false(&perf_swevent_enabled[event_id]))
+                __perf_sw_event(event_id, nr, regs, addr);
+}
+
+DECLARE_PER_CPU(struct pt_regs, __perf_regs[4]);
 
+/*
+ * 'Special' version for the scheduler, it hard assumes no recursion,
+ * which is guaranteed by us not actually scheduling inside other swevents
+ * because those disable preemption.
+ */
+static __always_inline void
+perf_sw_event_sched(u32 event_id, u64 nr, u64 addr)
+{
         if (static_key_false(&perf_swevent_enabled[event_id])) {
-                if (!regs) {
-                        perf_fetch_caller_regs(&hot_regs);
-                        regs = &hot_regs;
-                }
-                __perf_sw_event(event_id, nr, regs, addr);
+                struct pt_regs *regs = this_cpu_ptr(&__perf_regs[0]);
+
+                perf_fetch_caller_regs(regs);
+                ___perf_sw_event(event_id, nr, regs, addr);
         }
 }
 
@@ -712,7 +724,7 @@ static inline void 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)
 {
-        perf_sw_event(PERF_COUNT_SW_CONTEXT_SWITCHES, 1, NULL, 0);
+        perf_sw_event_sched(PERF_COUNT_SW_CONTEXT_SWITCHES, 1, 0);
 
         if (static_key_false(&perf_sched_events.key))
                 __perf_event_task_sched_out(prev, next);
@@ -823,6 +835,8 @@ static inline int perf_event_refresh(struct perf_event *event, int refresh)
 static inline void
 perf_sw_event(u32 event_id, u64 nr, struct pt_regs *regs, u64 addr)     { }
 static inline void
+perf_sw_event_sched(u32 event_id, u64 nr, u64 addr)                     { }
+static inline void
 perf_bp_event(struct perf_event *event, void *data)                     { }
 
 static inline int perf_register_guest_info_callbacks
diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index 139b5067345b..27609dfcce25 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -763,7 +763,7 @@ perf_trace_##call(void *__data, proto)					\
         struct ftrace_event_call *event_call = __data;                  \
         struct ftrace_data_offsets_##call __maybe_unused __data_offsets;\
         struct ftrace_raw_##call *entry;                                \
-        struct pt_regs __regs;                                          \
+        struct pt_regs *__regs;                                         \
         u64 __addr = 0, __count = 1;                                    \
         struct task_struct *__task = NULL;                              \
         struct hlist_head *head;                                        \
@@ -782,18 +782,19 @@ perf_trace_##call(void *__data, proto)					\
                              sizeof(u64));                              \
         __entry_size -= sizeof(u32);                                    \
                                                                         \
-        perf_fetch_caller_regs(&__regs);                                \
         entry = perf_trace_buf_prepare(__entry_size,                    \
                         event_call->event.type, &__regs, &rctx);        \
         if (!entry)                                                     \
                 return;                                                 \
                                                                         \
+        perf_fetch_caller_regs(__regs);                                 \
+                                                                        \
         tstruct                                                         \
                                                                         \
         { assign; }                                                     \
                                                                         \
         perf_trace_buf_submit(entry, __entry_size, rctx, __addr,        \
-                __count, &__regs, head, __task);                        \
+                __count, __regs, head, __task);                         \
 }
 
 /*
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 882f835a0d85..c10124b772c4 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5889,6 +5889,8 @@ end:
         rcu_read_unlock();
 }
 
+DEFINE_PER_CPU(struct pt_regs, __perf_regs[4]);
+
 int perf_swevent_get_recursion_context(void)
 {
         struct swevent_htable *swhash = this_cpu_ptr(&swevent_htable);
@@ -5904,21 +5906,30 @@ inline void perf_swevent_put_recursion_context(int rctx)
         put_recursion_context(swhash->recursion, rctx);
 }
 
-void __perf_sw_event(u32 event_id, u64 nr, struct pt_regs *regs, u64 addr)
+void ___perf_sw_event(u32 event_id, u64 nr, struct pt_regs *regs, u64 addr)
 {
         struct perf_sample_data data;
-        int rctx;
 
-        preempt_disable_notrace();
-        rctx = perf_swevent_get_recursion_context();
-        if (rctx < 0)
+        if (WARN_ON_ONCE(!regs))
                 return;
 
         perf_sample_data_init(&data, addr, 0);
-
         do_perf_sw_event(PERF_TYPE_SOFTWARE, event_id, nr, &data, regs);
+}
+
+void __perf_sw_event(u32 event_id, u64 nr, struct pt_regs *regs, u64 addr)
+{
+        int rctx;
+
+        preempt_disable_notrace();
+        rctx = perf_swevent_get_recursion_context();
+        if (unlikely(rctx < 0))
+                goto fail;
+
+        ___perf_sw_event(event_id, nr, regs, addr);
 
         perf_swevent_put_recursion_context(rctx);
+fail:
         preempt_enable_notrace();
 }
 
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c0accc00566e..d22fb16a7153 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1082,7 +1082,7 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
                 if (p->sched_class->migrate_task_rq)
                         p->sched_class->migrate_task_rq(p, new_cpu);
                 p->se.nr_migrations++;
-                perf_sw_event(PERF_COUNT_SW_CPU_MIGRATIONS, 1, NULL, 0);
+                perf_sw_event_sched(PERF_COUNT_SW_CPU_MIGRATIONS, 1, 0);
         }
 
         __set_task_cpu(p, new_cpu);
diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
index 4b9c114ee9de..6fa484de2ba1 100644
--- a/kernel/trace/trace_event_perf.c
+++ b/kernel/trace/trace_event_perf.c
@@ -261,7 +261,7 @@ void perf_trace_del(struct perf_event *p_event, int flags)
 }
 
 void *perf_trace_buf_prepare(int size, unsigned short type,
-                             struct pt_regs *regs, int *rctxp)
+                             struct pt_regs **regs, int *rctxp)
 {
         struct trace_entry *entry;
         unsigned long flags;
@@ -280,6 +280,8 @@ void *perf_trace_buf_prepare(int size, unsigned short type,
         if (*rctxp < 0)
                 return NULL;
 
+        if (regs)
+                *regs = this_cpu_ptr(&__perf_regs[*rctxp]);
         raw_data = this_cpu_ptr(perf_trace_buf[*rctxp]);
 
         /* zero the dead bytes from align to not leak stack to user */
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 5edb518be345..296079ae6583 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -1148,7 +1148,7 @@ kprobe_perf_func(struct trace_kprobe *tk, struct pt_regs *regs)
         size = ALIGN(__size + sizeof(u32), sizeof(u64));
         size -= sizeof(u32);
 
-        entry = perf_trace_buf_prepare(size, call->event.type, regs, &rctx);
+        entry = perf_trace_buf_prepare(size, call->event.type, NULL, &rctx);
         if (!entry)
                 return;
 
@@ -1179,7 +1179,7 @@ kretprobe_perf_func(struct trace_kprobe *tk, struct kretprobe_instance *ri,
         size = ALIGN(__size + sizeof(u32), sizeof(u64));
         size -= sizeof(u32);
 
-        entry = perf_trace_buf_prepare(size, call->event.type, regs, &rctx);
+        entry = perf_trace_buf_prepare(size, call->event.type, NULL, &rctx);
         if (!entry)
                 return;
 
diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index c6ee36fcbf90..f97f6e3a676c 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -574,7 +574,7 @@ static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
         size -= sizeof(u32);
 
         rec = (struct syscall_trace_enter *)perf_trace_buf_prepare(size,
-                                sys_data->enter_event->event.type, regs, &rctx);
+                                sys_data->enter_event->event.type, NULL, &rctx);
         if (!rec)
                 return;
 
@@ -647,7 +647,7 @@ static void perf_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
         size -= sizeof(u32);
 
         rec = (struct syscall_trace_exit *)perf_trace_buf_prepare(size,
-                                sys_data->exit_event->event.type, regs, &rctx);
+                                sys_data->exit_event->event.type, NULL, &rctx);
         if (!rec)
                 return;
 
diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index 8520acc34b18..b11441321e7a 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -1111,7 +1111,7 @@ static void __uprobe_perf_func(struct trace_uprobe *tu,
         if (hlist_empty(head))
                 goto out;
 
-        entry = perf_trace_buf_prepare(size, call->event.type, regs, &rctx);
+        entry = perf_trace_buf_prepare(size, call->event.type, NULL, &rctx);
         if (!entry)
                 goto out;