2020-06-27 00:27:08

by Song Liu

Subject: [PATCH v3 bpf-next 1/4] perf: expose get/put_callchain_entry()

Sanitize and expose get/put_callchain_entry(). This would be used by bpf
stack map.

Suggested-by: Peter Zijlstra <[email protected]>
Signed-off-by: Song Liu <[email protected]>
---
include/linux/perf_event.h | 2 ++
kernel/events/callchain.c | 13 ++++++-------
2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index b4bb32082342c..00ab5efa38334 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1244,6 +1244,8 @@ get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
extern struct perf_callchain_entry *perf_callchain(struct perf_event *event, struct pt_regs *regs);
extern int get_callchain_buffers(int max_stack);
extern void put_callchain_buffers(void);
+extern struct perf_callchain_entry *get_callchain_entry(int *rctx);
+extern void put_callchain_entry(int rctx);

extern int sysctl_perf_event_max_stack;
extern int sysctl_perf_event_max_contexts_per_stack;
diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c
index 334d48b16c36d..c6ce894e4ce94 100644
--- a/kernel/events/callchain.c
+++ b/kernel/events/callchain.c
@@ -149,7 +149,7 @@ void put_callchain_buffers(void)
}
}

-static struct perf_callchain_entry *get_callchain_entry(int *rctx)
+struct perf_callchain_entry *get_callchain_entry(int *rctx)
{
int cpu;
struct callchain_cpus_entries *entries;
@@ -159,8 +159,10 @@ static struct perf_callchain_entry *get_callchain_entry(int *rctx)
return NULL;

entries = rcu_dereference(callchain_cpus_entries);
- if (!entries)
+ if (!entries) {
+ put_recursion_context(this_cpu_ptr(callchain_recursion), *rctx);
return NULL;
+ }

cpu = smp_processor_id();

@@ -168,7 +170,7 @@ static struct perf_callchain_entry *get_callchain_entry(int *rctx)
(*rctx * perf_callchain_entry__sizeof()));
}

-static void
+void
put_callchain_entry(int rctx)
{
put_recursion_context(this_cpu_ptr(callchain_recursion), rctx);
@@ -183,11 +185,8 @@ get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
int rctx;

entry = get_callchain_entry(&rctx);
- if (rctx == -1)
- return NULL;
-
if (!entry)
- goto exit_put;
+ return NULL;

ctx.entry = entry;
ctx.max_stack = max_stack;
--
2.24.1

2020-06-27 20:36:06

by Andrii Nakryiko

Subject: Re: [PATCH v3 bpf-next 1/4] perf: expose get/put_callchain_entry()

On Fri, Jun 26, 2020 at 5:26 PM Song Liu <[email protected]> wrote:
>
> Sanitize and expose get/put_callchain_entry(). This would be used by bpf
> stack map.
>
> Suggested-by: Peter Zijlstra <[email protected]>
> Signed-off-by: Song Liu <[email protected]>
> ---

Acked-by: Andrii Nakryiko <[email protected]>

> include/linux/perf_event.h | 2 ++
> kernel/events/callchain.c | 13 ++++++-------
> 2 files changed, 8 insertions(+), 7 deletions(-)
>

[...]