Make perf_event_open() propagate errors for use in bpf_perf_event_open()

PATCH/RFC Arnaldo Carvalho de Melo 4 participants 6 messages Jan 11, 2019 – Jan 22, 2019

Subsystems (7)

Networking Network drivers BPF perf events +3 more subsystems

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Arnaldo Carvalho de Melo

author maintainer

2019-01-11 15:55 UTC #0 lore raw

Hi Peter,

bpf_perf_event_open() already returns a value, but if
perf_event_output's output_begin (mostly perf_output_begin) fails, the only way to know about that is looking before/after the rb->lost, right?

For ring buffer users that is ok, we'll get a PERF_RECORD_LOST,
etc, but for BPF programs it would be convenient to get that -ENOSPC and do some fallback, whatever makes sense, like in my augmented_syscalls stuff for 'perf trace', i.e. don't augment it (i.e. push stuff at the end of the normal payload), just don't filter the raw_syscalls:sys_enter, 'perf trace' will get the enter syscall enter event without the pointer dereference at the end, etc, warn the user but don't lose a syscall in the strace-like output.

What do you think? Am I missing something? Probably ;-)

Ah, its just test built.

- Arnaldo

include/linux/perf_event.h +3 -3

index 1d5c551a5add..9ed2af2abd6d 100644
@@ -978,9 +978,9 @@ extern void perf_event_output_forward(struct perf_event *event,
 extern void perf_event_output_backward(struct perf_event *event,
 				       struct perf_sample_data *data,
 				       struct pt_regs *regs);
-extern void perf_event_output(struct perf_event *event,
-			      struct perf_sample_data *data,
-			      struct pt_regs *regs);
+extern int perf_event_output(struct perf_event *event,
+			     struct perf_sample_data *data,
+			     struct pt_regs *regs);
 
 static inline bool
 is_default_overflow_handler(struct perf_event *event)

kernel/events/core.c +7 -4

index 3cd13a30f732..dcbb2b508034 100644
@@ -6489,7 +6489,7 @@ void perf_prepare_sample(struct perf_event_header *header,
 		data->phys_addr = perf_virt_to_phys(data->addr);
 }
 
-static __always_inline void
+static __always_inline int
 __perf_event_output(struct perf_event *event,
 		    struct perf_sample_data *data,
 		    struct pt_regs *regs,

@@ -6499,13 +6499,15 @@ __perf_event_output(struct perf_event *event,
 {
 	struct perf_output_handle handle;
 	struct perf_event_header header;
+	int err;
 
 	/* protect the callchain buffers */
 	rcu_read_lock();
 
 	perf_prepare_sample(&header, data, event, regs);
 
-	if (output_begin(&handle, event, header.size))
+	err = output_begin(&handle, event, header.size);
+	if (err)
 		goto exit;
 
 	perf_output_sample(&handle, &header, data, event);

@@ -6514,6 +6516,7 @@ __perf_event_output(struct perf_event *event,
 
 exit:
 	rcu_read_unlock();
+	return err;
 }
 
 void

@@ -6532,12 +6535,12 @@ perf_event_output_backward(struct perf_event *event,
 	__perf_event_output(event, data, regs, perf_output_begin_backward);
 }
 
-void
+int
 perf_event_output(struct perf_event *event,
 		  struct perf_sample_data *data,
 		  struct pt_regs *regs)
 {
-	__perf_event_output(event, data, regs, perf_output_begin);
+	return __perf_event_output(event, data, regs, perf_output_begin);
 }
 
 /*

kernel/trace/bpf_trace.c +1 -2

index 8b068adb9da1..088c2032ceaf 100644
@@ -431,8 +431,7 @@ __bpf_perf_event_output(struct pt_regs *regs, struct bpf_map *map,
 	if (unlikely(event->oncpu != cpu))
 		return -EOPNOTSUPP;
 
-	perf_event_output(event, sd, regs);
-	return 0;
+	return perf_event_output(event, sd, regs);
 }
 
 BPF_CALL_5(bpf_perf_event_output, struct pt_regs *, regs, struct bpf_map *, map,

tools/perf/examples/bpf/augmented_raw_syscalls.c +2 -2

index 53c233370fae..9e9d4c66e53c 100644
@@ -141,8 +141,8 @@ int sys_enter(struct syscall_enter_args *args)
 		len = sizeof(augmented_args.args);
 	}
 
-	perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, &augmented_args, len);
-	return 0;
+	/* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */
+	return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, &augmented_args, len);
 }
 
 SEC("raw_syscalls:sys_exit")

tools/perf/examples/bpf/augmented_syscalls.c +7 -7

index 2ae44813ef2d..b7dba114e36c 100644
@@ -55,9 +55,9 @@ int syscall_enter(syscall)(struct syscall_enter_##syscall##_args *args)				\
 		len -= sizeof(augmented_args.filename.value) - augmented_args.filename.size;	\
 		len &= sizeof(augmented_args.filename.value) - 1;				\
 	}											\
-	perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, 			\
-			  &augmented_args, len);						\
-	return 0;										\
+	/* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */	\
+	return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, 		\
+				 &augmented_args, len);						\
 }												\
 int syscall_exit(syscall)(struct syscall_exit_args *args)					\
 {												\

@@ -125,10 +125,10 @@ int syscall_enter(syscall)(struct syscall_enter_##syscall##_args *args)				\
 /*		addrlen = augmented_args.args.addrlen;				     */		\
 /*										     */		\
 	probe_read(&augmented_args.addr, addrlen, args->addr_ptr); 				\
-	perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, 			\
-			  &augmented_args, 							\
-			  sizeof(augmented_args) - sizeof(augmented_args.addr) + addrlen);	\
-	return 0;										\
+	/* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */	\
+	return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, 		\
+				 &augmented_args, 						\
+				sizeof(augmented_args) - sizeof(augmented_args.addr) + addrlen);\
 }												\
 int syscall_exit(syscall)(struct syscall_exit_args *args)					\
 {												\

tools/perf/examples/bpf/etcsnoop.c +5 -5

index b59e8812ee8c..550e69c2e8d1 100644
@@ -49,11 +49,11 @@ int syscall_enter(syscall)(struct syscall_enter_##syscall##_args *args)				\
 						      args->filename_ptr); 			\
 	if (__builtin_memcmp(augmented_args.filename.value, etc, 4) != 0)			\
 		return 0;									\
-	perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, 			\
-			  &augmented_args, 							\
-			  (sizeof(augmented_args) - sizeof(augmented_args.filename.value) +	\
-			   augmented_args.filename.size));					\
-	return 0;										\
+	/* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */	\
+	return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, 		\
+				 &augmented_args,						\
+				 (sizeof(augmented_args) - sizeof(augmented_args.filename.value) + \
+				 augmented_args.filename.size));				\
 }
 
 struct syscall_enter_openat_args {

Jamal Hadi Salim

Tested-by

2019-01-12 13:59 UTC #1 lore raw

Quoted 16 lines · Arnaldo Carvalho de Melo

Hi Peter,
bpf_perf_event_open() already returns a value, but if
perf_event_output's output_begin (mostly perf_output_begin) fails, the only way to know about that is looking before/after the rb->lost, right?
For ring buffer users that is ok, we'll get a PERF_RECORD_LOST,
etc, but for BPF programs it would be convenient to get that -ENOSPC and do some fallback, whatever makes sense, like in my augmented_syscalls stuff for 'perf trace', i.e. don't augment it (i.e. push stuff at the end of the normal payload), just don't filter the raw_syscalls:sys_enter, 'perf trace' will get the enter syscall enter event without the pointer dereference at the end, etc, warn the user but don't lose a syscall in the strace-like output.

Quoted 3 lines

What do you think? Am I missing something? Probably ;-)
Ah, its just test built.

Works as advertised ;->

Tested-by Jamal Hadi Salim <[email protected]>

cheers,
jamal

Peter Zijlstra

maintainer

2019-01-18 14:52 UTC #2 lore raw

In reply to Arnaldo Carvalho de Melo

Quoted 16 lines · Arnaldo Carvalho de Melo

Hi Peter,
bpf_perf_event_open() already returns a value, but if
perf_event_output's output_begin (mostly perf_output_begin) fails, the only way to know about that is looking before/after the rb->lost, right?
For ring buffer users that is ok, we'll get a PERF_RECORD_LOST,
etc, but for BPF programs it would be convenient to get that -ENOSPC and do some fallback, whatever makes sense, like in my augmented_syscalls stuff for 'perf trace', i.e. don't augment it (i.e. push stuff at the end of the normal payload), just don't filter the raw_syscalls:sys_enter, 'perf trace' will get the enter syscall enter event without the pointer dereference at the end, etc, warn the user but don't lose a syscall in the strace-like output.

Quoted 1 line

What do you think? Am I missing something? Probably ;-)

Seems ok to do this.

Arnaldo Carvalho de Melo

author maintainer Tested-by Jamal Hadi Salim

2019-01-18 15:09 UTC #3 lore raw

Em Fri, Jan 18, 2019 at 03:52:37PM +0100, Peter Zijlstra escreveu:

Quoted 17 lines · Arnaldo Carvalho de Melo

Quoted 16 lines
Hi Peter,
bpf_perf_event_open() already returns a value, but if
perf_event_output's output_begin (mostly perf_output_begin) fails, the only way to know about that is looking before/after the rb->lost, right?
For ring buffer users that is ok, we'll get a PERF_RECORD_LOST,
etc, but for BPF programs it would be convenient to get that -ENOSPC and do some fallback, whatever makes sense, like in my augmented_syscalls stuff for 'perf trace', i.e. don't augment it (i.e. push stuff at the end of the normal payload), just don't filter the raw_syscalls:sys_enter, 'perf trace' will get the enter syscall enter event without the pointer dereference at the end, etc, warn the user but don't lose a syscall in the strace-like output.

Quoted 3 lines

Quoted 1 line
What do you think? Am I missing something? Probably ;-)
Seems ok to do this.

Can I take that as an Acked-by?

This is the patch with a cset comment, if you're ok, I'll put it together with Song's PERF_RECORD_{KSYMBOL,BPF_EVENT} into my perf/core branch and send to Ingo,

please advise,

- Arnaldo

commit 1b3b3dee572d0b77a316ab6715091201be6832de

Author: Arnaldo Carvalho de Melo <[email protected]>
Date:   Fri Jan 11 13:20:20 2019 -0300

perf: Make perf_event_output() propagate the output() return

For the original mode of operation it isn't needed, since we report back errors via PERF_RECORD_LOST records in the ring buffer, but for use in bpf_perf_event_output() it is convenient to return the errors, basically -ENOSPC.

Currently bpf_perf_event_output() returns an error indication, the last thing it does, which is to push it to the ring buffer is that can fail and if so, this failure won't be reported back to its users, fix it.

Reported-by Jamal Hadi Salim <[email protected]>

Tested-by Jamal Hadi Salim <[email protected]>

Cc Adrian Hunter <[email protected]>

Cc Alexei Starovoitov <[email protected]>

Cc Daniel Borkmann <[email protected]>

Cc Jiri Olsa <[email protected]>

Cc Namhyung Kim <[email protected]>

Cc Peter Zijlstra <[email protected]>

Link https://lkml.kernel.org/r/[email protected] open here

Signed-off-by Arnaldo Carvalho de Melo <[email protected]>

include/linux/perf_event.h +3 -3

index 1d5c551a5add..9ed2af2abd6d 100644
@@ -978,9 +978,9 @@ extern void perf_event_output_forward(struct perf_event *event,
 extern void perf_event_output_backward(struct perf_event *event,
 				       struct perf_sample_data *data,
 				       struct pt_regs *regs);
-extern void perf_event_output(struct perf_event *event,
-			      struct perf_sample_data *data,
-			      struct pt_regs *regs);
+extern int perf_event_output(struct perf_event *event,
+			     struct perf_sample_data *data,
+			     struct pt_regs *regs);
 
 static inline bool
 is_default_overflow_handler(struct perf_event *event)

kernel/events/core.c +7 -4

index 3cd13a30f732..dcbb2b508034 100644
@@ -6489,7 +6489,7 @@ void perf_prepare_sample(struct perf_event_header *header,
 		data->phys_addr = perf_virt_to_phys(data->addr);
 }
 
-static __always_inline void
+static __always_inline int
 __perf_event_output(struct perf_event *event,
 		    struct perf_sample_data *data,
 		    struct pt_regs *regs,

@@ -6499,13 +6499,15 @@ __perf_event_output(struct perf_event *event,
 {
 	struct perf_output_handle handle;
 	struct perf_event_header header;
+	int err;
 
 	/* protect the callchain buffers */
 	rcu_read_lock();
 
 	perf_prepare_sample(&header, data, event, regs);
 
-	if (output_begin(&handle, event, header.size))
+	err = output_begin(&handle, event, header.size);
+	if (err)
 		goto exit;
 
 	perf_output_sample(&handle, &header, data, event);

@@ -6514,6 +6516,7 @@ __perf_event_output(struct perf_event *event,
 
 exit:
 	rcu_read_unlock();
+	return err;
 }
 
 void

@@ -6532,12 +6535,12 @@ perf_event_output_backward(struct perf_event *event,
 	__perf_event_output(event, data, regs, perf_output_begin_backward);
 }
 
-void
+int
 perf_event_output(struct perf_event *event,
 		  struct perf_sample_data *data,
 		  struct pt_regs *regs)
 {
-	__perf_event_output(event, data, regs, perf_output_begin);
+	return __perf_event_output(event, data, regs, perf_output_begin);
 }
 
 /*

kernel/trace/bpf_trace.c +1 -2

index 8b068adb9da1..088c2032ceaf 100644
@@ -431,8 +431,7 @@ __bpf_perf_event_output(struct pt_regs *regs, struct bpf_map *map,
 	if (unlikely(event->oncpu != cpu))
 		return -EOPNOTSUPP;
 
-	perf_event_output(event, sd, regs);
-	return 0;
+	return perf_event_output(event, sd, regs);
 }
 
 BPF_CALL_5(bpf_perf_event_output, struct pt_regs *, regs, struct bpf_map *, map,

tools/perf/examples/bpf/augmented_raw_syscalls.c +2 -2

index 53c233370fae..9e9d4c66e53c 100644
@@ -141,8 +141,8 @@ int sys_enter(struct syscall_enter_args *args)
 		len = sizeof(augmented_args.args);
 	}
 
-	perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, &augmented_args, len);
-	return 0;
+	/* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */
+	return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, &augmented_args, len);
 }
 
 SEC("raw_syscalls:sys_exit")

tools/perf/examples/bpf/augmented_syscalls.c +7 -7

index 2ae44813ef2d..b7dba114e36c 100644
@@ -55,9 +55,9 @@ int syscall_enter(syscall)(struct syscall_enter_##syscall##_args *args)				\
 		len -= sizeof(augmented_args.filename.value) - augmented_args.filename.size;	\
 		len &= sizeof(augmented_args.filename.value) - 1;				\
 	}											\
-	perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, 			\
-			  &augmented_args, len);						\
-	return 0;										\
+	/* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */	\
+	return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, 		\
+				 &augmented_args, len);						\
 }												\
 int syscall_exit(syscall)(struct syscall_exit_args *args)					\
 {												\

@@ -125,10 +125,10 @@ int syscall_enter(syscall)(struct syscall_enter_##syscall##_args *args)				\
 /*		addrlen = augmented_args.args.addrlen;				     */		\
 /*										     */		\
 	probe_read(&augmented_args.addr, addrlen, args->addr_ptr); 				\
-	perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, 			\
-			  &augmented_args, 							\
-			  sizeof(augmented_args) - sizeof(augmented_args.addr) + addrlen);	\
-	return 0;										\
+	/* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */	\
+	return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, 		\
+				 &augmented_args, 						\
+				sizeof(augmented_args) - sizeof(augmented_args.addr) + addrlen);\
 }												\
 int syscall_exit(syscall)(struct syscall_exit_args *args)					\
 {												\

tools/perf/examples/bpf/etcsnoop.c +5 -5

index b59e8812ee8c..550e69c2e8d1 100644
@@ -49,11 +49,11 @@ int syscall_enter(syscall)(struct syscall_enter_##syscall##_args *args)				\
 						      args->filename_ptr); 			\
 	if (__builtin_memcmp(augmented_args.filename.value, etc, 4) != 0)			\
 		return 0;									\
-	perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, 			\
-			  &augmented_args, 							\
-			  (sizeof(augmented_args) - sizeof(augmented_args.filename.value) +	\
-			   augmented_args.filename.size));					\
-	return 0;										\
+	/* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */	\
+	return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, 		\
+				 &augmented_args,						\
+				 (sizeof(augmented_args) - sizeof(augmented_args.filename.value) + \
+				 augmented_args.filename.size));				\
 }
 
 struct syscall_enter_openat_args {

Peter Zijlstra

maintainer Acked-by

2019-01-18 16:20 UTC #4 lore raw

Quoted 15 lines · Arnaldo Carvalho de Melo

commit 1b3b3dee572d0b77a316ab6715091201be6832de
Author: Arnaldo Carvalho de Melo <[email protected]>
Date:   Fri Jan 11 13:20:20 2019 -0300
perf: Make perf_event_output() propagate the output() return
For the original mode of operation it isn't needed, since we report back errors via PERF_RECORD_LOST records in the ring buffer, but for use in bpf_perf_event_output() it is convenient to return the errors, basically -ENOSPC.
Currently bpf_perf_event_output() returns an error indication, the last thing it does, which is to push it to the ring buffer is that can fail and if so, this failure won't be reported back to its users, fix it.

Quoted 10 lines

Reported-by Jamal Hadi Salim <[email protected]>
Tested-by Jamal Hadi Salim <[email protected]>
Cc Adrian Hunter <[email protected]>
Cc Alexei Starovoitov <[email protected]>
Cc Daniel Borkmann <[email protected]>
Cc Jiri Olsa <[email protected]>
Cc Namhyung Kim <[email protected]>
Cc Peter Zijlstra <[email protected]>
Link https://lkml.kernel.org/r/[email protected] open here
Signed-off-by Arnaldo Carvalho de Melo <[email protected]>

/me hates on git-format :-)

Acked-by Peter Zijlstra (Intel) <[email protected]>

tip-bot for Arnaldo Carvalho de Melo

merge bot

2019-01-22 10:18 UTC #5 lore raw

[tip:perf/core] perf: Make perf_event_output() propagate the output() return

In reply to Arnaldo Carvalho de Melo

perf: Make perf_event_output() propagate the output() return

Commit-ID:  5620196951192f7cd2da0a04e7c0113f40bfc14e
Gitweb:     https://git.kernel.org/tip/5620196951192f7cd2da0a04e7c0113f40bfc14e
Author:     Arnaldo Carvalho de Melo <[email protected]>
AuthorDate: Fri, 11 Jan 2019 13:20:20 -0300
Committer:  Arnaldo Carvalho de Melo <[email protected]>
CommitDate: Mon, 21 Jan 2019 17:00:57 -0300

perf: Make perf_event_output() propagate the output() return

Reported-by Jamal Hadi Salim <[email protected]>

Tested-by Jamal Hadi Salim <[email protected]>

Acked-by Peter Zijlstra (Intel) <[email protected]>

Cc Adrian Hunter <[email protected]>

Cc Alexei Starovoitov <[email protected]>

Cc Daniel Borkmann <[email protected]>

Cc Jiri Olsa <[email protected]>

Cc Namhyung Kim <[email protected]>

Link https://lkml.kernel.org/r/[email protected] open here

Signed-off-by Arnaldo Carvalho de Melo <[email protected]>

---
 include/linux/perf_event.h                       |  6 +++---
 kernel/events/core.c                             | 11 +++++++----
 kernel/trace/bpf_trace.c                         |  3 +--
 tools/perf/examples/bpf/augmented_raw_syscalls.c |  4 ++--
 tools/perf/examples/bpf/augmented_syscalls.c     | 14 +++++++-------
 tools/perf/examples/bpf/etcsnoop.c               | 10 +++++-----
 6 files changed, 25 insertions(+), 23 deletions(-)

include/linux/perf_event.h +3 -3

index f8ec36197718..4eb88065a9b5 100644
@@ -978,9 +978,9 @@ extern void perf_event_output_forward(struct perf_event *event,
 extern void perf_event_output_backward(struct perf_event *event,
 				       struct perf_sample_data *data,
 				       struct pt_regs *regs);
-extern void perf_event_output(struct perf_event *event,
-			      struct perf_sample_data *data,
-			      struct pt_regs *regs);
+extern int perf_event_output(struct perf_event *event,
+			     struct perf_sample_data *data,
+			     struct pt_regs *regs);
 
 static inline bool
 is_default_overflow_handler(struct perf_event *event)

kernel/events/core.c +7 -4

index fbe59b793b36..bc525cd1615c 100644
@@ -6489,7 +6489,7 @@ void perf_prepare_sample(struct perf_event_header *header,
 		data->phys_addr = perf_virt_to_phys(data->addr);
 }
 
-static __always_inline void
+static __always_inline int
 __perf_event_output(struct perf_event *event,
 		    struct perf_sample_data *data,
 		    struct pt_regs *regs,

@@ -6499,13 +6499,15 @@ __perf_event_output(struct perf_event *event,
 {
 	struct perf_output_handle handle;
 	struct perf_event_header header;
+	int err;
 
 	/* protect the callchain buffers */
 	rcu_read_lock();
 
 	perf_prepare_sample(&header, data, event, regs);
 
-	if (output_begin(&handle, event, header.size))
+	err = output_begin(&handle, event, header.size);
+	if (err)
 		goto exit;
 
 	perf_output_sample(&handle, &header, data, event);

@@ -6514,6 +6516,7 @@ __perf_event_output(struct perf_event *event,
 
 exit:
 	rcu_read_unlock();
+	return err;
 }
 
 void

@@ -6532,12 +6535,12 @@ perf_event_output_backward(struct perf_event *event,
 	__perf_event_output(event, data, regs, perf_output_begin_backward);
 }
 
-void
+int
 perf_event_output(struct perf_event *event,
 		  struct perf_sample_data *data,
 		  struct pt_regs *regs)
 {
-	__perf_event_output(event, data, regs, perf_output_begin);
+	return __perf_event_output(event, data, regs, perf_output_begin);
 }
 
 /*

kernel/trace/bpf_trace.c +1 -2

index 8b068adb9da1..088c2032ceaf 100644
@@ -431,8 +431,7 @@ __bpf_perf_event_output(struct pt_regs *regs, struct bpf_map *map,
 	if (unlikely(event->oncpu != cpu))
 		return -EOPNOTSUPP;
 
-	perf_event_output(event, sd, regs);
-	return 0;
+	return perf_event_output(event, sd, regs);
 }
 
 BPF_CALL_5(bpf_perf_event_output, struct pt_regs *, regs, struct bpf_map *, map,

tools/perf/examples/bpf/augmented_raw_syscalls.c +2 -2

index 53c233370fae..9e9d4c66e53c 100644
@@ -141,8 +141,8 @@ int sys_enter(struct syscall_enter_args *args)
 		len = sizeof(augmented_args.args);
 	}
 
-	perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, &augmented_args, len);
-	return 0;
+	/* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */
+	return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, &augmented_args, len);
 }
 
 SEC("raw_syscalls:sys_exit")

tools/perf/examples/bpf/augmented_syscalls.c +7 -7

index 2ae44813ef2d..b7dba114e36c 100644
@@ -55,9 +55,9 @@ int syscall_enter(syscall)(struct syscall_enter_##syscall##_args *args)				\
 		len -= sizeof(augmented_args.filename.value) - augmented_args.filename.size;	\
 		len &= sizeof(augmented_args.filename.value) - 1;				\
 	}											\
-	perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, 			\
-			  &augmented_args, len);						\
-	return 0;										\
+	/* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */	\
+	return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, 		\
+				 &augmented_args, len);						\
 }												\
 int syscall_exit(syscall)(struct syscall_exit_args *args)					\
 {												\

@@ -125,10 +125,10 @@ int syscall_enter(syscall)(struct syscall_enter_##syscall##_args *args)				\
 /*		addrlen = augmented_args.args.addrlen;				     */		\
 /*										     */		\
 	probe_read(&augmented_args.addr, addrlen, args->addr_ptr); 				\
-	perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, 			\
-			  &augmented_args, 							\
-			  sizeof(augmented_args) - sizeof(augmented_args.addr) + addrlen);	\
-	return 0;										\
+	/* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */	\
+	return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, 		\
+				 &augmented_args, 						\
+				sizeof(augmented_args) - sizeof(augmented_args.addr) + addrlen);\
 }												\
 int syscall_exit(syscall)(struct syscall_exit_args *args)					\
 {												\

tools/perf/examples/bpf/etcsnoop.c +5 -5

index b59e8812ee8c..550e69c2e8d1 100644
@@ -49,11 +49,11 @@ int syscall_enter(syscall)(struct syscall_enter_##syscall##_args *args)				\
 						      args->filename_ptr); 			\
 	if (__builtin_memcmp(augmented_args.filename.value, etc, 4) != 0)			\
 		return 0;									\
-	perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, 			\
-			  &augmented_args, 							\
-			  (sizeof(augmented_args) - sizeof(augmented_args.filename.value) +	\
-			   augmented_args.filename.size));					\
-	return 0;										\
+	/* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */	\
+	return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, 		\
+				 &augmented_args,						\
+				 (sizeof(augmented_args) - sizeof(augmented_args.filename.value) + \
+				 augmented_args.filename.size));				\
 }
 
 struct syscall_enter_openat_args {