[PATCH bpf] bpf: preallocate a perf_sample

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* [PATCH bpf] bpf: preallocate a perf_sample_data per event fd
@ 2019-05-30 22:55 Matt Mullins
  2019-05-30 23:28 ` Song Liu
  0 siblings, 1 reply; 5+ messages in thread
From: Matt Mullins @ 2019-05-30 22:55 UTC (permalink / raw)
  To: hall, mmullins, ast, bpf, netdev
  Cc: linux-kernel, Daniel Borkmann, Martin KaFai Lau, Song Liu,
	Yonghong Song, Steven Rostedt, Ingo Molnar

It is possible that a BPF program can be called while another BPF
program is executing bpf_perf_event_output.  This has been observed with
I/O completion occurring as a result of an interrupt:

	bpf_prog_247fd1341cddaea4_trace_req_end+0x8d7/0x1000
	? trace_call_bpf+0x82/0x100
	? sch_direct_xmit+0xe2/0x230
	? blk_mq_end_request+0x1/0x100
	? blk_mq_end_request+0x5/0x100
	? kprobe_perf_func+0x19b/0x240
	? __qdisc_run+0x86/0x520
	? blk_mq_end_request+0x1/0x100
	? blk_mq_end_request+0x5/0x100
	? kprobe_ftrace_handler+0x90/0xf0
	? ftrace_ops_assist_func+0x6e/0xe0
	? ip6_input_finish+0xbf/0x460
	? 0xffffffffa01e80bf
	? nbd_dbg_flags_show+0xc0/0xc0 [nbd]
	? blkdev_issue_zeroout+0x200/0x200
	? blk_mq_end_request+0x1/0x100
	? blk_mq_end_request+0x5/0x100
	? flush_smp_call_function_queue+0x6c/0xe0
	? smp_call_function_single_interrupt+0x32/0xc0
	? call_function_single_interrupt+0xf/0x20
	? call_function_single_interrupt+0xa/0x20
	? swiotlb_map_page+0x140/0x140
	? refcount_sub_and_test+0x1a/0x50
	? tcp_wfree+0x20/0xf0
	? skb_release_head_state+0x62/0xc0
	? skb_release_all+0xe/0x30
	? napi_consume_skb+0xb5/0x100
	? mlx5e_poll_tx_cq+0x1df/0x4e0
	? mlx5e_poll_tx_cq+0x38c/0x4e0
	? mlx5e_napi_poll+0x58/0xc30
	? mlx5e_napi_poll+0x232/0xc30
	? net_rx_action+0x128/0x340
	? __do_softirq+0xd4/0x2ad
	? irq_exit+0xa5/0xb0
	? do_IRQ+0x7d/0xc0
	? common_interrupt+0xf/0xf
	</IRQ>
	? __rb_free_aux+0xf0/0xf0
	? perf_output_sample+0x28/0x7b0
	? perf_prepare_sample+0x54/0x4a0
	? perf_event_output+0x43/0x60
	? bpf_perf_event_output_raw_tp+0x15f/0x180
	? blk_mq_start_request+0x1/0x120
	? bpf_prog_411a64a706fc6044_should_trace+0xad4/0x1000
	? bpf_trace_run3+0x2c/0x80
	? nbd_send_cmd+0x4c2/0x690 [nbd]

This also cannot be alleviated by further splitting the per-cpu
perf_sample_data structs (as in commit 283ca526a9bd ("bpf: fix
corruption on concurrent perf_event_output calls")), as a raw_tp could
be attached to the block:block_rq_complete tracepoint and execute during
another raw_tp.  Instead, keep a pre-allocated perf_sample_data
structure per perf_event_array element and fail a bpf_perf_event_output
if that element is concurrently being used.

Fixes: 20b9d7ac4852 ("bpf: avoid excessive stack usage for perf_sample_data")
Signed-off-by: Matt Mullins <mmullins@fb.com>
---
It felt a bit overkill, but I had to split bpf_event_entry into its own
header file to break an include cycle from perf_event.h -> cgroup.h ->
cgroup-defs.h -> bpf-cgroup.h -> bpf.h -> (potentially) perf_event.h.

 include/linux/bpf.h       |  7 -------
 include/linux/bpf_event.h | 20 ++++++++++++++++++++
 kernel/bpf/arraymap.c     |  2 ++
 kernel/trace/bpf_trace.c  | 30 +++++++++++++++++-------------
 4 files changed, 39 insertions(+), 20 deletions(-)
 create mode 100644 include/linux/bpf_event.h

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 4fb3aa2dc975..13b253a36402 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -467,13 +467,6 @@ static inline bool bpf_map_flags_access_ok(u32 access_flags)
 	       (BPF_F_RDONLY_PROG | BPF_F_WRONLY_PROG);
 }
 
-struct bpf_event_entry {
-	struct perf_event *event;
-	struct file *perf_file;
-	struct file *map_file;
-	struct rcu_head rcu;
-};
-
 bool bpf_prog_array_compatible(struct bpf_array *array, const struct bpf_prog *fp);
 int bpf_prog_calc_tag(struct bpf_prog *fp);
 
diff --git a/include/linux/bpf_event.h b/include/linux/bpf_event.h
new file mode 100644
index 000000000000..9f415990f921
--- /dev/null
+++ b/include/linux/bpf_event.h
@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _LINUX_BPF_EVENT_H
+#define _LINUX_BPF_EVENT_H
+
+#include <linux/perf_event.h>
+#include <linux/types.h>
+
+struct file;
+
+struct bpf_event_entry {
+	struct perf_event *event;
+	struct file *perf_file;
+	struct file *map_file;
+	struct rcu_head rcu;
+	struct perf_sample_data sd;
+	atomic_t in_use;
+};
+
+#endif /* _LINUX_BPF_EVENT_H */
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 584636c9e2eb..08e5e486d563 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -11,6 +11,7 @@
  * General Public License for more details.
  */
 #include <linux/bpf.h>
+#include <linux/bpf_event.h>
 #include <linux/btf.h>
 #include <linux/err.h>
 #include <linux/slab.h>
@@ -659,6 +660,7 @@ static struct bpf_event_entry *bpf_event_entry_gen(struct file *perf_file,
 		ee->event = perf_file->private_data;
 		ee->perf_file = perf_file;
 		ee->map_file = map_file;
+		atomic_set(&ee->in_use, 0);
 	}
 
 	return ee;
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index f92d6ad5e080..a03e29957698 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -6,6 +6,7 @@
 #include <linux/types.h>
 #include <linux/slab.h>
 #include <linux/bpf.h>
+#include <linux/bpf_event.h>
 #include <linux/bpf_perf_event.h>
 #include <linux/filter.h>
 #include <linux/uaccess.h>
@@ -410,17 +411,17 @@ static const struct bpf_func_proto bpf_perf_event_read_value_proto = {
 	.arg4_type	= ARG_CONST_SIZE,
 };
 
-static DEFINE_PER_CPU(struct perf_sample_data, bpf_trace_sd);
-
 static __always_inline u64
 __bpf_perf_event_output(struct pt_regs *regs, struct bpf_map *map,
-			u64 flags, struct perf_sample_data *sd)
+			u64 flags, struct perf_raw_record *raw)
 {
 	struct bpf_array *array = container_of(map, struct bpf_array, map);
 	unsigned int cpu = smp_processor_id();
 	u64 index = flags & BPF_F_INDEX_MASK;
 	struct bpf_event_entry *ee;
 	struct perf_event *event;
+	struct perf_sample_data *sd;
+	u64 ret;
 
 	if (index == BPF_F_CURRENT_CPU)
 		index = cpu;
@@ -439,13 +440,22 @@ __bpf_perf_event_output(struct pt_regs *regs, struct bpf_map *map,
 	if (unlikely(event->oncpu != cpu))
 		return -EOPNOTSUPP;
 
-	return perf_event_output(event, sd, regs);
+	if (atomic_cmpxchg(&ee->in_use, 0, 1) != 0)
+		return -EBUSY;
+
+	sd = &ee->sd;
+	perf_sample_data_init(sd, 0, 0);
+	sd->raw = raw;
+
+	ret = perf_event_output(event, sd, regs);
+
+	atomic_set(&ee->in_use, 0);
+	return ret;
 }
 
 BPF_CALL_5(bpf_perf_event_output, struct pt_regs *, regs, struct bpf_map *, map,
 	   u64, flags, void *, data, u64, size)
 {
-	struct perf_sample_data *sd = this_cpu_ptr(&bpf_trace_sd);
 	struct perf_raw_record raw = {
 		.frag = {
 			.size = size,
@@ -456,10 +466,8 @@ BPF_CALL_5(bpf_perf_event_output, struct pt_regs *, regs, struct bpf_map *, map,
 	if (unlikely(flags & ~(BPF_F_INDEX_MASK)))
 		return -EINVAL;
 
-	perf_sample_data_init(sd, 0, 0);
-	sd->raw = &raw;
 
-	return __bpf_perf_event_output(regs, map, flags, sd);
+	return __bpf_perf_event_output(regs, map, flags, &raw);
 }
 
 static const struct bpf_func_proto bpf_perf_event_output_proto = {
@@ -474,12 +482,10 @@ static const struct bpf_func_proto bpf_perf_event_output_proto = {
 };
 
 static DEFINE_PER_CPU(struct pt_regs, bpf_pt_regs);
-static DEFINE_PER_CPU(struct perf_sample_data, bpf_misc_sd);
 
 u64 bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 meta_size,
 		     void *ctx, u64 ctx_size, bpf_ctx_copy_t ctx_copy)
 {
-	struct perf_sample_data *sd = this_cpu_ptr(&bpf_misc_sd);
 	struct pt_regs *regs = this_cpu_ptr(&bpf_pt_regs);
 	struct perf_raw_frag frag = {
 		.copy		= ctx_copy,
@@ -497,10 +503,8 @@ u64 bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 meta_size,
 	};
 
 	perf_fetch_caller_regs(regs);
-	perf_sample_data_init(sd, 0, 0);
-	sd->raw = &raw;
 
-	return __bpf_perf_event_output(regs, map, flags, sd);
+	return __bpf_perf_event_output(regs, map, flags, &raw);
 }
 
 BPF_CALL_0(bpf_get_current_task)
-- 
2.17.1


^ permalink raw reply related	[flat|nested] 5+ messages in thread

* Re: [PATCH bpf] bpf: preallocate a perf_sample_data per event fd
  2019-05-30 22:55 [PATCH bpf] bpf: preallocate a perf_sample_data per event fd Matt Mullins
@ 2019-05-30 23:28 ` Song Liu
  2019-05-31  0:01   ` Matt Mullins
  0 siblings, 1 reply; 5+ messages in thread
From: Song Liu @ 2019-05-30 23:28 UTC (permalink / raw)
  To: Matt Mullins
  Cc: Andrew Hall, Alexei Starovoitov, bpf@vger.kernel.org,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	Daniel Borkmann, Martin Lau, Yonghong Song, Steven Rostedt,
	Ingo Molnar



> On May 30, 2019, at 3:55 PM, Matt Mullins <mmullins@fb.com> wrote:
> 
> It is possible that a BPF program can be called while another BPF
> program is executing bpf_perf_event_output.  This has been observed with
> I/O completion occurring as a result of an interrupt:
> 
> 	bpf_prog_247fd1341cddaea4_trace_req_end+0x8d7/0x1000
> 	? trace_call_bpf+0x82/0x100
> 	? sch_direct_xmit+0xe2/0x230
> 	? blk_mq_end_request+0x1/0x100
> 	? blk_mq_end_request+0x5/0x100
> 	? kprobe_perf_func+0x19b/0x240
> 	? __qdisc_run+0x86/0x520
> 	? blk_mq_end_request+0x1/0x100
> 	? blk_mq_end_request+0x5/0x100
> 	? kprobe_ftrace_handler+0x90/0xf0
> 	? ftrace_ops_assist_func+0x6e/0xe0
> 	? ip6_input_finish+0xbf/0x460
> 	? 0xffffffffa01e80bf
> 	? nbd_dbg_flags_show+0xc0/0xc0 [nbd]
> 	? blkdev_issue_zeroout+0x200/0x200
> 	? blk_mq_end_request+0x1/0x100
> 	? blk_mq_end_request+0x5/0x100
> 	? flush_smp_call_function_queue+0x6c/0xe0
> 	? smp_call_function_single_interrupt+0x32/0xc0
> 	? call_function_single_interrupt+0xf/0x20
> 	? call_function_single_interrupt+0xa/0x20
> 	? swiotlb_map_page+0x140/0x140
> 	? refcount_sub_and_test+0x1a/0x50
> 	? tcp_wfree+0x20/0xf0
> 	? skb_release_head_state+0x62/0xc0
> 	? skb_release_all+0xe/0x30
> 	? napi_consume_skb+0xb5/0x100
> 	? mlx5e_poll_tx_cq+0x1df/0x4e0
> 	? mlx5e_poll_tx_cq+0x38c/0x4e0
> 	? mlx5e_napi_poll+0x58/0xc30
> 	? mlx5e_napi_poll+0x232/0xc30
> 	? net_rx_action+0x128/0x340
> 	? __do_softirq+0xd4/0x2ad
> 	? irq_exit+0xa5/0xb0
> 	? do_IRQ+0x7d/0xc0
> 	? common_interrupt+0xf/0xf
> 	</IRQ>
> 	? __rb_free_aux+0xf0/0xf0
> 	? perf_output_sample+0x28/0x7b0
> 	? perf_prepare_sample+0x54/0x4a0
> 	? perf_event_output+0x43/0x60
> 	? bpf_perf_event_output_raw_tp+0x15f/0x180
> 	? blk_mq_start_request+0x1/0x120
> 	? bpf_prog_411a64a706fc6044_should_trace+0xad4/0x1000
> 	? bpf_trace_run3+0x2c/0x80
> 	? nbd_send_cmd+0x4c2/0x690 [nbd]
> 
> This also cannot be alleviated by further splitting the per-cpu
> perf_sample_data structs (as in commit 283ca526a9bd ("bpf: fix
> corruption on concurrent perf_event_output calls")), as a raw_tp could
> be attached to the block:block_rq_complete tracepoint and execute during
> another raw_tp.  Instead, keep a pre-allocated perf_sample_data
> structure per perf_event_array element and fail a bpf_perf_event_output
> if that element is concurrently being used.
> 
> Fixes: 20b9d7ac4852 ("bpf: avoid excessive stack usage for perf_sample_data")
> Signed-off-by: Matt Mullins <mmullins@fb.com>
> ---
> It felt a bit overkill, but I had to split bpf_event_entry into its own
> header file to break an include cycle from perf_event.h -> cgroup.h ->
> cgroup-defs.h -> bpf-cgroup.h -> bpf.h -> (potentially) perf_event.h.
> 
> include/linux/bpf.h       |  7 -------
> include/linux/bpf_event.h | 20 ++++++++++++++++++++
> kernel/bpf/arraymap.c     |  2 ++
> kernel/trace/bpf_trace.c  | 30 +++++++++++++++++-------------
> 4 files changed, 39 insertions(+), 20 deletions(-)
> create mode 100644 include/linux/bpf_event.h
> 
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 4fb3aa2dc975..13b253a36402 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -467,13 +467,6 @@ static inline bool bpf_map_flags_access_ok(u32 access_flags)
> 	       (BPF_F_RDONLY_PROG | BPF_F_WRONLY_PROG);
> }
> 

I think we can avoid the include cycle as:

+struct perf_sample_data *sd;
struct bpf_event_entry {
	struct perf_event *event;
	struct file *perf_file;
	struct file *map_file;
	struct rcu_head rcu;
+	struct perf_sample_data *sd;
};

> -struct bpf_event_entry {
> -	struct perf_event *event;
> -	struct file *perf_file;
> -	struct file *map_file;
> -	struct rcu_head rcu;
> -};
> -
> bool bpf_prog_array_compatible(struct bpf_array *array, const struct bpf_prog *fp);
> int bpf_prog_calc_tag(struct bpf_prog *fp);
> 
> diff --git a/include/linux/bpf_event.h b/include/linux/bpf_event.h
> new file mode 100644
> index 000000000000..9f415990f921
> --- /dev/null
> +++ b/include/linux/bpf_event.h
> @@ -0,0 +1,20 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#ifndef _LINUX_BPF_EVENT_H
> +#define _LINUX_BPF_EVENT_H
> +
> +#include <linux/perf_event.h>
> +#include <linux/types.h>
> +
> +struct file;
> +
> +struct bpf_event_entry {
> +	struct perf_event *event;
> +	struct file *perf_file;
> +	struct file *map_file;
> +	struct rcu_head rcu;
> +	struct perf_sample_data sd;
> +	atomic_t in_use;
> +};
> +
> +#endif /* _LINUX_BPF_EVENT_H */
> diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
> index 584636c9e2eb..08e5e486d563 100644
> --- a/kernel/bpf/arraymap.c
> +++ b/kernel/bpf/arraymap.c
> @@ -11,6 +11,7 @@
>  * General Public License for more details.
>  */
> #include <linux/bpf.h>
> +#include <linux/bpf_event.h>
> #include <linux/btf.h>
> #include <linux/err.h>
> #include <linux/slab.h>
> @@ -659,6 +660,7 @@ static struct bpf_event_entry *bpf_event_entry_gen(struct file *perf_file,
> 		ee->event = perf_file->private_data;
> 		ee->perf_file = perf_file;
> 		ee->map_file = map_file;

And do the kzalloc() or some other trick here. 

> +		atomic_set(&ee->in_use, 0);
> 	}
> 
> 	return ee;
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index f92d6ad5e080..a03e29957698 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -6,6 +6,7 @@
> #include <linux/types.h>
> #include <linux/slab.h>
> #include <linux/bpf.h>
> +#include <linux/bpf_event.h>
> #include <linux/bpf_perf_event.h>
> #include <linux/filter.h>
> #include <linux/uaccess.h>
> @@ -410,17 +411,17 @@ static const struct bpf_func_proto bpf_perf_event_read_value_proto = {
> 	.arg4_type	= ARG_CONST_SIZE,
> };
> 
> -static DEFINE_PER_CPU(struct perf_sample_data, bpf_trace_sd);
> -
> static __always_inline u64
> __bpf_perf_event_output(struct pt_regs *regs, struct bpf_map *map,
> -			u64 flags, struct perf_sample_data *sd)
> +			u64 flags, struct perf_raw_record *raw)
> {
> 	struct bpf_array *array = container_of(map, struct bpf_array, map);
> 	unsigned int cpu = smp_processor_id();
> 	u64 index = flags & BPF_F_INDEX_MASK;
> 	struct bpf_event_entry *ee;
> 	struct perf_event *event;
> +	struct perf_sample_data *sd;
> +	u64 ret;
> 
> 	if (index == BPF_F_CURRENT_CPU)
> 		index = cpu;
> @@ -439,13 +440,22 @@ __bpf_perf_event_output(struct pt_regs *regs, struct bpf_map *map,
> 	if (unlikely(event->oncpu != cpu))
> 		return -EOPNOTSUPP;
> 
> -	return perf_event_output(event, sd, regs);
> +	if (atomic_cmpxchg(&ee->in_use, 0, 1) != 0)
> +		return -EBUSY;

And we only need xchg() here, so we can eliminate in_use. 

Does this make sense?

Thanks,
Song

> +
> +	sd = &ee->sd;
> +	perf_sample_data_init(sd, 0, 0);
> +	sd->raw = raw;
> +
> +	ret = perf_event_output(event, sd, regs);
> +
> +	atomic_set(&ee->in_use, 0);
> +	return ret;
> }
> 
> BPF_CALL_5(bpf_perf_event_output, struct pt_regs *, regs, struct bpf_map *, map,
> 	   u64, flags, void *, data, u64, size)
> {
> -	struct perf_sample_data *sd = this_cpu_ptr(&bpf_trace_sd);
> 	struct perf_raw_record raw = {
> 		.frag = {
> 			.size = size,
> @@ -456,10 +466,8 @@ BPF_CALL_5(bpf_perf_event_output, struct pt_regs *, regs, struct bpf_map *, map,
> 	if (unlikely(flags & ~(BPF_F_INDEX_MASK)))
> 		return -EINVAL;
> 
> -	perf_sample_data_init(sd, 0, 0);
> -	sd->raw = &raw;
> 
> -	return __bpf_perf_event_output(regs, map, flags, sd);
> +	return __bpf_perf_event_output(regs, map, flags, &raw);
> }
> 
> static const struct bpf_func_proto bpf_perf_event_output_proto = {
> @@ -474,12 +482,10 @@ static const struct bpf_func_proto bpf_perf_event_output_proto = {
> };
> 
> static DEFINE_PER_CPU(struct pt_regs, bpf_pt_regs);
> -static DEFINE_PER_CPU(struct perf_sample_data, bpf_misc_sd);
> 
> u64 bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 meta_size,
> 		     void *ctx, u64 ctx_size, bpf_ctx_copy_t ctx_copy)
> {
> -	struct perf_sample_data *sd = this_cpu_ptr(&bpf_misc_sd);
> 	struct pt_regs *regs = this_cpu_ptr(&bpf_pt_regs);
> 	struct perf_raw_frag frag = {
> 		.copy		= ctx_copy,
> @@ -497,10 +503,8 @@ u64 bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 meta_size,
> 	};
> 
> 	perf_fetch_caller_regs(regs);
> -	perf_sample_data_init(sd, 0, 0);
> -	sd->raw = &raw;
> 
> -	return __bpf_perf_event_output(regs, map, flags, sd);
> +	return __bpf_perf_event_output(regs, map, flags, &raw);
> }
> 
> BPF_CALL_0(bpf_get_current_task)
> -- 
> 2.17.1
> 


^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH bpf] bpf: preallocate a perf_sample_data per event fd
  2019-05-30 23:28 ` Song Liu
@ 2019-05-31  0:01   ` Matt Mullins
  2019-05-31  5:26     ` Song Liu
  0 siblings, 1 reply; 5+ messages in thread
From: Matt Mullins @ 2019-05-31  0:01 UTC (permalink / raw)
  To: Song Liu
  Cc: linux-kernel@vger.kernel.org, daniel@iogearbox.net,
	bpf@vger.kernel.org, ast@kernel.org, rostedt@goodmis.org,
	Andrew Hall, mingo@redhat.com, netdev@vger.kernel.org, Martin Lau,
	Yonghong Song

On Thu, 2019-05-30 at 23:28 +0000, Song Liu wrote:
> > On May 30, 2019, at 3:55 PM, Matt Mullins <mmullins@fb.com> wrote:
> > 
> > It is possible that a BPF program can be called while another BPF
> > program is executing bpf_perf_event_output.  This has been observed with
> > I/O completion occurring as a result of an interrupt:
> > 
> > 	bpf_prog_247fd1341cddaea4_trace_req_end+0x8d7/0x1000
> > 	? trace_call_bpf+0x82/0x100
> > 	? sch_direct_xmit+0xe2/0x230
> > 	? blk_mq_end_request+0x1/0x100
> > 	? blk_mq_end_request+0x5/0x100
> > 	? kprobe_perf_func+0x19b/0x240
> > 	? __qdisc_run+0x86/0x520
> > 	? blk_mq_end_request+0x1/0x100
> > 	? blk_mq_end_request+0x5/0x100
> > 	? kprobe_ftrace_handler+0x90/0xf0
> > 	? ftrace_ops_assist_func+0x6e/0xe0
> > 	? ip6_input_finish+0xbf/0x460
> > 	? 0xffffffffa01e80bf
> > 	? nbd_dbg_flags_show+0xc0/0xc0 [nbd]
> > 	? blkdev_issue_zeroout+0x200/0x200
> > 	? blk_mq_end_request+0x1/0x100
> > 	? blk_mq_end_request+0x5/0x100
> > 	? flush_smp_call_function_queue+0x6c/0xe0
> > 	? smp_call_function_single_interrupt+0x32/0xc0
> > 	? call_function_single_interrupt+0xf/0x20
> > 	? call_function_single_interrupt+0xa/0x20
> > 	? swiotlb_map_page+0x140/0x140
> > 	? refcount_sub_and_test+0x1a/0x50
> > 	? tcp_wfree+0x20/0xf0
> > 	? skb_release_head_state+0x62/0xc0
> > 	? skb_release_all+0xe/0x30
> > 	? napi_consume_skb+0xb5/0x100
> > 	? mlx5e_poll_tx_cq+0x1df/0x4e0
> > 	? mlx5e_poll_tx_cq+0x38c/0x4e0
> > 	? mlx5e_napi_poll+0x58/0xc30
> > 	? mlx5e_napi_poll+0x232/0xc30
> > 	? net_rx_action+0x128/0x340
> > 	? __do_softirq+0xd4/0x2ad
> > 	? irq_exit+0xa5/0xb0
> > 	? do_IRQ+0x7d/0xc0
> > 	? common_interrupt+0xf/0xf
> > 	</IRQ>
> > 	? __rb_free_aux+0xf0/0xf0
> > 	? perf_output_sample+0x28/0x7b0
> > 	? perf_prepare_sample+0x54/0x4a0
> > 	? perf_event_output+0x43/0x60
> > 	? bpf_perf_event_output_raw_tp+0x15f/0x180
> > 	? blk_mq_start_request+0x1/0x120
> > 	? bpf_prog_411a64a706fc6044_should_trace+0xad4/0x1000
> > 	? bpf_trace_run3+0x2c/0x80
> > 	? nbd_send_cmd+0x4c2/0x690 [nbd]
> > 
> > This also cannot be alleviated by further splitting the per-cpu
> > perf_sample_data structs (as in commit 283ca526a9bd ("bpf: fix
> > corruption on concurrent perf_event_output calls")), as a raw_tp could
> > be attached to the block:block_rq_complete tracepoint and execute during
> > another raw_tp.  Instead, keep a pre-allocated perf_sample_data
> > structure per perf_event_array element and fail a bpf_perf_event_output
> > if that element is concurrently being used.
> > 
> > Fixes: 20b9d7ac4852 ("bpf: avoid excessive stack usage for perf_sample_data")
> > Signed-off-by: Matt Mullins <mmullins@fb.com>
> > ---
> > It felt a bit overkill, but I had to split bpf_event_entry into its own
> > header file to break an include cycle from perf_event.h -> cgroup.h ->
> > cgroup-defs.h -> bpf-cgroup.h -> bpf.h -> (potentially) perf_event.h.
> > 
> > include/linux/bpf.h       |  7 -------
> > include/linux/bpf_event.h | 20 ++++++++++++++++++++
> > kernel/bpf/arraymap.c     |  2 ++
> > kernel/trace/bpf_trace.c  | 30 +++++++++++++++++-------------
> > 4 files changed, 39 insertions(+), 20 deletions(-)
> > create mode 100644 include/linux/bpf_event.h
> > 
> > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > index 4fb3aa2dc975..13b253a36402 100644
> > --- a/include/linux/bpf.h
> > +++ b/include/linux/bpf.h
> > @@ -467,13 +467,6 @@ static inline bool bpf_map_flags_access_ok(u32 access_flags)
> > 	       (BPF_F_RDONLY_PROG | BPF_F_WRONLY_PROG);
> > }
> > 
> 
> I think we can avoid the include cycle as:
> 
> +struct perf_sample_data *sd;
> struct bpf_event_entry {
> 	struct perf_event *event;
> 	struct file *perf_file;
> 	struct file *map_file;
> 	struct rcu_head rcu;
> +	struct perf_sample_data *sd;
> };

Yeah, that totally works.  I was mostly doing this so we had only one
kmalloc allocation, but I'm not too worried about having an extra
object in kmalloc-64 if it simplifies the code a lot.

> 
> > -struct bpf_event_entry {
> > -	struct perf_event *event;
> > -	struct file *perf_file;
> > -	struct file *map_file;
> > -	struct rcu_head rcu;
> > -};
> > -
> > bool bpf_prog_array_compatible(struct bpf_array *array, const struct bpf_prog *fp);
> > int bpf_prog_calc_tag(struct bpf_prog *fp);
> > 
> > diff --git a/include/linux/bpf_event.h b/include/linux/bpf_event.h
> > new file mode 100644
> > index 000000000000..9f415990f921
> > --- /dev/null
> > +++ b/include/linux/bpf_event.h
> > @@ -0,0 +1,20 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +
> > +#ifndef _LINUX_BPF_EVENT_H
> > +#define _LINUX_BPF_EVENT_H
> > +
> > +#include <linux/perf_event.h>
> > +#include <linux/types.h>
> > +
> > +struct file;
> > +
> > +struct bpf_event_entry {
> > +	struct perf_event *event;
> > +	struct file *perf_file;
> > +	struct file *map_file;
> > +	struct rcu_head rcu;
> > +	struct perf_sample_data sd;
> > +	atomic_t in_use;
> > +};
> > +
> > +#endif /* _LINUX_BPF_EVENT_H */
> > diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
> > index 584636c9e2eb..08e5e486d563 100644
> > --- a/kernel/bpf/arraymap.c
> > +++ b/kernel/bpf/arraymap.c
> > @@ -11,6 +11,7 @@
> >  * General Public License for more details.
> >  */
> > #include <linux/bpf.h>
> > +#include <linux/bpf_event.h>
> > #include <linux/btf.h>
> > #include <linux/err.h>
> > #include <linux/slab.h>
> > @@ -659,6 +660,7 @@ static struct bpf_event_entry *bpf_event_entry_gen(struct file *perf_file,
> > 		ee->event = perf_file->private_data;
> > 		ee->perf_file = perf_file;
> > 		ee->map_file = map_file;
> 
> And do the kzalloc() or some other trick here. 
> 
> > +		atomic_set(&ee->in_use, 0);
> > 	}
> > 
> > 	return ee;
> > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> > index f92d6ad5e080..a03e29957698 100644
> > --- a/kernel/trace/bpf_trace.c
> > +++ b/kernel/trace/bpf_trace.c
> > @@ -6,6 +6,7 @@
> > #include <linux/types.h>
> > #include <linux/slab.h>
> > #include <linux/bpf.h>
> > +#include <linux/bpf_event.h>
> > #include <linux/bpf_perf_event.h>
> > #include <linux/filter.h>
> > #include <linux/uaccess.h>
> > @@ -410,17 +411,17 @@ static const struct bpf_func_proto bpf_perf_event_read_value_proto = {
> > 	.arg4_type	= ARG_CONST_SIZE,
> > };
> > 
> > -static DEFINE_PER_CPU(struct perf_sample_data, bpf_trace_sd);
> > -
> > static __always_inline u64
> > __bpf_perf_event_output(struct pt_regs *regs, struct bpf_map *map,
> > -			u64 flags, struct perf_sample_data *sd)
> > +			u64 flags, struct perf_raw_record *raw)
> > {
> > 	struct bpf_array *array = container_of(map, struct bpf_array, map);
> > 	unsigned int cpu = smp_processor_id();
> > 	u64 index = flags & BPF_F_INDEX_MASK;
> > 	struct bpf_event_entry *ee;
> > 	struct perf_event *event;
> > +	struct perf_sample_data *sd;
> > +	u64 ret;
> > 
> > 	if (index == BPF_F_CURRENT_CPU)
> > 		index = cpu;
> > @@ -439,13 +440,22 @@ __bpf_perf_event_output(struct pt_regs *regs, struct bpf_map *map,
> > 	if (unlikely(event->oncpu != cpu))
> > 		return -EOPNOTSUPP;
> > 
> > -	return perf_event_output(event, sd, regs);
> > +	if (atomic_cmpxchg(&ee->in_use, 0, 1) != 0)
> > +		return -EBUSY;
> 
> And we only need xchg() here, so we can eliminate in_use. 
> 
> Does this make sense?

You mean xchg a null-pointer or something in there while it's in-use,
then xchg the slab back?  Makes sense to me.  I'll try that and see
where it gets me.

> 
> Thanks,
> Song
> 
> > +
> > +	sd = &ee->sd;
> > +	perf_sample_data_init(sd, 0, 0);
> > +	sd->raw = raw;
> > +
> > +	ret = perf_event_output(event, sd, regs);
> > +
> > +	atomic_set(&ee->in_use, 0);
> > +	return ret;
> > }
> > 
> > BPF_CALL_5(bpf_perf_event_output, struct pt_regs *, regs, struct bpf_map *, map,
> > 	   u64, flags, void *, data, u64, size)
> > {
> > -	struct perf_sample_data *sd = this_cpu_ptr(&bpf_trace_sd);
> > 	struct perf_raw_record raw = {
> > 		.frag = {
> > 			.size = size,
> > @@ -456,10 +466,8 @@ BPF_CALL_5(bpf_perf_event_output, struct pt_regs *, regs, struct bpf_map *, map,
> > 	if (unlikely(flags & ~(BPF_F_INDEX_MASK)))
> > 		return -EINVAL;
> > 
> > -	perf_sample_data_init(sd, 0, 0);
> > -	sd->raw = &raw;
> > 
> > -	return __bpf_perf_event_output(regs, map, flags, sd);
> > +	return __bpf_perf_event_output(regs, map, flags, &raw);
> > }
> > 
> > static const struct bpf_func_proto bpf_perf_event_output_proto = {
> > @@ -474,12 +482,10 @@ static const struct bpf_func_proto bpf_perf_event_output_proto = {
> > };
> > 
> > static DEFINE_PER_CPU(struct pt_regs, bpf_pt_regs);
> > -static DEFINE_PER_CPU(struct perf_sample_data, bpf_misc_sd);
> > 
> > u64 bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 meta_size,
> > 		     void *ctx, u64 ctx_size, bpf_ctx_copy_t ctx_copy)
> > {
> > -	struct perf_sample_data *sd = this_cpu_ptr(&bpf_misc_sd);
> > 	struct pt_regs *regs = this_cpu_ptr(&bpf_pt_regs);
> > 	struct perf_raw_frag frag = {
> > 		.copy		= ctx_copy,
> > @@ -497,10 +503,8 @@ u64 bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 meta_size,
> > 	};
> > 
> > 	perf_fetch_caller_regs(regs);
> > -	perf_sample_data_init(sd, 0, 0);
> > -	sd->raw = &raw;
> > 
> > -	return __bpf_perf_event_output(regs, map, flags, sd);
> > +	return __bpf_perf_event_output(regs, map, flags, &raw);
> > }
> > 
> > BPF_CALL_0(bpf_get_current_task)
> > -- 
> > 2.17.1
> > 
> 
> 

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH bpf] bpf: preallocate a perf_sample_data per event fd
  2019-05-31  0:01   ` Matt Mullins
@ 2019-05-31  5:26     ` Song Liu
  2019-06-08 20:39       ` Steven Rostedt
  0 siblings, 1 reply; 5+ messages in thread
From: Song Liu @ 2019-05-31  5:26 UTC (permalink / raw)
  To: Matt Mullins
  Cc: linux-kernel@vger.kernel.org, daniel@iogearbox.net,
	bpf@vger.kernel.org, ast@kernel.org, rostedt@goodmis.org,
	Andrew Hall, mingo@redhat.com, netdev@vger.kernel.org, Martin Lau,
	Yonghong Song



> On May 30, 2019, at 5:01 PM, Matt Mullins <mmullins@fb.com> wrote:
> 
> On Thu, 2019-05-30 at 23:28 +0000, Song Liu wrote:
>>> On May 30, 2019, at 3:55 PM, Matt Mullins <mmullins@fb.com> wrote:
>>> 
>>> It is possible that a BPF program can be called while another BPF
>>> program is executing bpf_perf_event_output.  This has been observed with
>>> I/O completion occurring as a result of an interrupt:
>>> 
>>> 	bpf_prog_247fd1341cddaea4_trace_req_end+0x8d7/0x1000
>>> 	? trace_call_bpf+0x82/0x100
>>> 	? sch_direct_xmit+0xe2/0x230
>>> 	? blk_mq_end_request+0x1/0x100
>>> 	? blk_mq_end_request+0x5/0x100
>>> 	? kprobe_perf_func+0x19b/0x240
>>> 	? __qdisc_run+0x86/0x520
>>> 	? blk_mq_end_request+0x1/0x100
>>> 	? blk_mq_end_request+0x5/0x100
>>> 	? kprobe_ftrace_handler+0x90/0xf0
>>> 	? ftrace_ops_assist_func+0x6e/0xe0
>>> 	? ip6_input_finish+0xbf/0x460
>>> 	? 0xffffffffa01e80bf
>>> 	? nbd_dbg_flags_show+0xc0/0xc0 [nbd]
>>> 	? blkdev_issue_zeroout+0x200/0x200
>>> 	? blk_mq_end_request+0x1/0x100
>>> 	? blk_mq_end_request+0x5/0x100
>>> 	? flush_smp_call_function_queue+0x6c/0xe0
>>> 	? smp_call_function_single_interrupt+0x32/0xc0
>>> 	? call_function_single_interrupt+0xf/0x20
>>> 	? call_function_single_interrupt+0xa/0x20
>>> 	? swiotlb_map_page+0x140/0x140
>>> 	? refcount_sub_and_test+0x1a/0x50
>>> 	? tcp_wfree+0x20/0xf0
>>> 	? skb_release_head_state+0x62/0xc0
>>> 	? skb_release_all+0xe/0x30
>>> 	? napi_consume_skb+0xb5/0x100
>>> 	? mlx5e_poll_tx_cq+0x1df/0x4e0
>>> 	? mlx5e_poll_tx_cq+0x38c/0x4e0
>>> 	? mlx5e_napi_poll+0x58/0xc30
>>> 	? mlx5e_napi_poll+0x232/0xc30
>>> 	? net_rx_action+0x128/0x340
>>> 	? __do_softirq+0xd4/0x2ad
>>> 	? irq_exit+0xa5/0xb0
>>> 	? do_IRQ+0x7d/0xc0
>>> 	? common_interrupt+0xf/0xf
>>> 	</IRQ>
>>> 	? __rb_free_aux+0xf0/0xf0
>>> 	? perf_output_sample+0x28/0x7b0
>>> 	? perf_prepare_sample+0x54/0x4a0
>>> 	? perf_event_output+0x43/0x60
>>> 	? bpf_perf_event_output_raw_tp+0x15f/0x180
>>> 	? blk_mq_start_request+0x1/0x120
>>> 	? bpf_prog_411a64a706fc6044_should_trace+0xad4/0x1000
>>> 	? bpf_trace_run3+0x2c/0x80
>>> 	? nbd_send_cmd+0x4c2/0x690 [nbd]
>>> 
>>> This also cannot be alleviated by further splitting the per-cpu
>>> perf_sample_data structs (as in commit 283ca526a9bd ("bpf: fix
>>> corruption on concurrent perf_event_output calls")), as a raw_tp could
>>> be attached to the block:block_rq_complete tracepoint and execute during
>>> another raw_tp.  Instead, keep a pre-allocated perf_sample_data
>>> structure per perf_event_array element and fail a bpf_perf_event_output
>>> if that element is concurrently being used.
>>> 
>>> Fixes: 20b9d7ac4852 ("bpf: avoid excessive stack usage for perf_sample_data")
>>> Signed-off-by: Matt Mullins <mmullins@fb.com>
>>> ---
>>> It felt a bit overkill, but I had to split bpf_event_entry into its own
>>> header file to break an include cycle from perf_event.h -> cgroup.h ->
>>> cgroup-defs.h -> bpf-cgroup.h -> bpf.h -> (potentially) perf_event.h.
>>> 
>>> include/linux/bpf.h       |  7 -------
>>> include/linux/bpf_event.h | 20 ++++++++++++++++++++
>>> kernel/bpf/arraymap.c     |  2 ++
>>> kernel/trace/bpf_trace.c  | 30 +++++++++++++++++-------------
>>> 4 files changed, 39 insertions(+), 20 deletions(-)
>>> create mode 100644 include/linux/bpf_event.h
>>> 
>>> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
>>> index 4fb3aa2dc975..13b253a36402 100644
>>> --- a/include/linux/bpf.h
>>> +++ b/include/linux/bpf.h
>>> @@ -467,13 +467,6 @@ static inline bool bpf_map_flags_access_ok(u32 access_flags)
>>> 	       (BPF_F_RDONLY_PROG | BPF_F_WRONLY_PROG);
>>> }
>>> 
>> 
>> I think we can avoid the include cycle as:
>> 
>> +struct perf_sample_data *sd;
>> struct bpf_event_entry {
>> 	struct perf_event *event;
>> 	struct file *perf_file;
>> 	struct file *map_file;
>> 	struct rcu_head rcu;
>> +	struct perf_sample_data *sd;
>> };
> 
> Yeah, that totally works.  I was mostly doing this so we had only one
> kmalloc allocation, but I'm not too worried about having an extra
> object in kmalloc-64 if it simplifies the code a lot.

We can also do something like

   ee = kzalloc(sizeof(struct bpf_event_entry) + sizeof(struct perf_sample_data));
   ee->sd = (void *)ee + sizeof(struct bpf_event_entry);

Thanks,
Song

> 
>> 
>>> -struct bpf_event_entry {
>>> -	struct perf_event *event;
>>> -	struct file *perf_file;
>>> -	struct file *map_file;
>>> -	struct rcu_head rcu;
>>> -};
>>> -
>>> bool bpf_prog_array_compatible(struct bpf_array *array, const struct bpf_prog *fp);
>>> int bpf_prog_calc_tag(struct bpf_prog *fp);
>>> 
>>> diff --git a/include/linux/bpf_event.h b/include/linux/bpf_event.h
>>> new file mode 100644
>>> index 000000000000..9f415990f921
>>> --- /dev/null
>>> +++ b/include/linux/bpf_event.h
>>> @@ -0,0 +1,20 @@
>>> +/* SPDX-License-Identifier: GPL-2.0 */
>>> +
>>> +#ifndef _LINUX_BPF_EVENT_H
>>> +#define _LINUX_BPF_EVENT_H
>>> +
>>> +#include <linux/perf_event.h>
>>> +#include <linux/types.h>
>>> +
>>> +struct file;
>>> +
>>> +struct bpf_event_entry {
>>> +	struct perf_event *event;
>>> +	struct file *perf_file;
>>> +	struct file *map_file;
>>> +	struct rcu_head rcu;
>>> +	struct perf_sample_data sd;
>>> +	atomic_t in_use;
>>> +};
>>> +
>>> +#endif /* _LINUX_BPF_EVENT_H */
>>> diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
>>> index 584636c9e2eb..08e5e486d563 100644
>>> --- a/kernel/bpf/arraymap.c
>>> +++ b/kernel/bpf/arraymap.c
>>> @@ -11,6 +11,7 @@
>>> * General Public License for more details.
>>> */
>>> #include <linux/bpf.h>
>>> +#include <linux/bpf_event.h>
>>> #include <linux/btf.h>
>>> #include <linux/err.h>
>>> #include <linux/slab.h>
>>> @@ -659,6 +660,7 @@ static struct bpf_event_entry *bpf_event_entry_gen(struct file *perf_file,
>>> 		ee->event = perf_file->private_data;
>>> 		ee->perf_file = perf_file;
>>> 		ee->map_file = map_file;
>> 
>> And do the kzalloc() or some other trick here. 
>> 
>>> +		atomic_set(&ee->in_use, 0);
>>> 	}
>>> 
>>> 	return ee;
>>> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
>>> index f92d6ad5e080..a03e29957698 100644
>>> --- a/kernel/trace/bpf_trace.c
>>> +++ b/kernel/trace/bpf_trace.c
>>> @@ -6,6 +6,7 @@
>>> #include <linux/types.h>
>>> #include <linux/slab.h>
>>> #include <linux/bpf.h>
>>> +#include <linux/bpf_event.h>
>>> #include <linux/bpf_perf_event.h>
>>> #include <linux/filter.h>
>>> #include <linux/uaccess.h>
>>> @@ -410,17 +411,17 @@ static const struct bpf_func_proto bpf_perf_event_read_value_proto = {
>>> 	.arg4_type	= ARG_CONST_SIZE,
>>> };
>>> 
>>> -static DEFINE_PER_CPU(struct perf_sample_data, bpf_trace_sd);
>>> -
>>> static __always_inline u64
>>> __bpf_perf_event_output(struct pt_regs *regs, struct bpf_map *map,
>>> -			u64 flags, struct perf_sample_data *sd)
>>> +			u64 flags, struct perf_raw_record *raw)
>>> {
>>> 	struct bpf_array *array = container_of(map, struct bpf_array, map);
>>> 	unsigned int cpu = smp_processor_id();
>>> 	u64 index = flags & BPF_F_INDEX_MASK;
>>> 	struct bpf_event_entry *ee;
>>> 	struct perf_event *event;
>>> +	struct perf_sample_data *sd;
>>> +	u64 ret;
>>> 
>>> 	if (index == BPF_F_CURRENT_CPU)
>>> 		index = cpu;
>>> @@ -439,13 +440,22 @@ __bpf_perf_event_output(struct pt_regs *regs, struct bpf_map *map,
>>> 	if (unlikely(event->oncpu != cpu))
>>> 		return -EOPNOTSUPP;
>>> 
>>> -	return perf_event_output(event, sd, regs);
>>> +	if (atomic_cmpxchg(&ee->in_use, 0, 1) != 0)
>>> +		return -EBUSY;
>> 
>> And we only need xchg() here, so we can eliminate in_use. 
>> 
>> Does this make sense?
> 
> You mean xchg a null-pointer or something in there while it's in-use,
> then xchg the slab back?  Makes sense to me.  I'll try that and see
> where it gets me.
> 
>> 
>> Thanks,
>> Song
>> 
>>> +
>>> +	sd = &ee->sd;
>>> +	perf_sample_data_init(sd, 0, 0);
>>> +	sd->raw = raw;
>>> +
>>> +	ret = perf_event_output(event, sd, regs);
>>> +
>>> +	atomic_set(&ee->in_use, 0);
>>> +	return ret;
>>> }
>>> 
>>> BPF_CALL_5(bpf_perf_event_output, struct pt_regs *, regs, struct bpf_map *, map,
>>> 	   u64, flags, void *, data, u64, size)
>>> {
>>> -	struct perf_sample_data *sd = this_cpu_ptr(&bpf_trace_sd);
>>> 	struct perf_raw_record raw = {
>>> 		.frag = {
>>> 			.size = size,
>>> @@ -456,10 +466,8 @@ BPF_CALL_5(bpf_perf_event_output, struct pt_regs *, regs, struct bpf_map *, map,
>>> 	if (unlikely(flags & ~(BPF_F_INDEX_MASK)))
>>> 		return -EINVAL;
>>> 
>>> -	perf_sample_data_init(sd, 0, 0);
>>> -	sd->raw = &raw;
>>> 
>>> -	return __bpf_perf_event_output(regs, map, flags, sd);
>>> +	return __bpf_perf_event_output(regs, map, flags, &raw);
>>> }
>>> 
>>> static const struct bpf_func_proto bpf_perf_event_output_proto = {
>>> @@ -474,12 +482,10 @@ static const struct bpf_func_proto bpf_perf_event_output_proto = {
>>> };
>>> 
>>> static DEFINE_PER_CPU(struct pt_regs, bpf_pt_regs);
>>> -static DEFINE_PER_CPU(struct perf_sample_data, bpf_misc_sd);
>>> 
>>> u64 bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 meta_size,
>>> 		     void *ctx, u64 ctx_size, bpf_ctx_copy_t ctx_copy)
>>> {
>>> -	struct perf_sample_data *sd = this_cpu_ptr(&bpf_misc_sd);
>>> 	struct pt_regs *regs = this_cpu_ptr(&bpf_pt_regs);
>>> 	struct perf_raw_frag frag = {
>>> 		.copy		= ctx_copy,
>>> @@ -497,10 +503,8 @@ u64 bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 meta_size,
>>> 	};
>>> 
>>> 	perf_fetch_caller_regs(regs);
>>> -	perf_sample_data_init(sd, 0, 0);
>>> -	sd->raw = &raw;
>>> 
>>> -	return __bpf_perf_event_output(regs, map, flags, sd);
>>> +	return __bpf_perf_event_output(regs, map, flags, &raw);
>>> }
>>> 
>>> BPF_CALL_0(bpf_get_current_task)
>>> -- 
>>> 2.17.1
>>> 
>> 
>> 


^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH bpf] bpf: preallocate a perf_sample_data per event fd
  2019-05-31  5:26     ` Song Liu
@ 2019-06-08 20:39       ` Steven Rostedt
  0 siblings, 0 replies; 5+ messages in thread
From: Steven Rostedt @ 2019-06-08 20:39 UTC (permalink / raw)
  To: Song Liu
  Cc: Matt Mullins, linux-kernel@vger.kernel.org, daniel@iogearbox.net,
	bpf@vger.kernel.org, ast@kernel.org, Andrew Hall,
	mingo@redhat.com, netdev@vger.kernel.org, Martin Lau,
	Yonghong Song

On Fri, 31 May 2019 05:26:30 +0000
Song Liu <songliubraving@fb.com> wrote:

> We can also do something like
> 
>    ee = kzalloc(sizeof(struct bpf_event_entry) + sizeof(struct perf_sample_data));
>    ee->sd = (void *)ee + sizeof(struct bpf_event_entry);

Or perhaps:

	ee->sd = (struct perf_sample_data *)(ee + 1);

-- Steve

^ permalink raw reply	[flat|nested] 5+ messages in thread

end of thread, other threads:[~2019-06-08 20:39 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2019-05-30 22:55 [PATCH bpf] bpf: preallocate a perf_sample_data per event fd Matt Mullins
2019-05-30 23:28 ` Song Liu
2019-05-31  0:01   ` Matt Mullins
2019-05-31  5:26     ` Song Liu
2019-06-08 20:39       ` Steven Rostedt

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