[PATCH v2] perf inject jit: Ignore memfd and anonymous mmap events if jitdump present

[PATCH v2] perf inject jit: Ignore memfd and anonymous mmap events if jitdump present

[Brian Robbins]

Some processes store jitted code in memfd mappings to avoid having rwx
mappings.  These processes map the code with a writeable mapping and a
read-execute mapping.  They write the code using the writeable mapping
and then unmap the writeable mapping.  All subsequent execution is
through the read-execute mapping.

perf inject --jit ignores //anon* mappings for each process where a
jitdump is present because it expects to inject mmap events for each
jitted code range, and said jitted code ranges will overlap with the
//anon* mappings.

Ignore /memfd: and [anon:* mappings so that jitted code contained in
/memfd: and [anon:* mappings is treated the same way as jitted code
contained in //anon* mappings.

Signed-off-by: Brian Robbins <brianrob@linux.microsoft.com>
---
 tools/perf/util/jitdump.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/jitdump.c b/tools/perf/util/jitdump.c
index a23255773c60..4e6632203704 100644
--- a/tools/perf/util/jitdump.c
+++ b/tools/perf/util/jitdump.c
@@ -845,8 +845,13 @@ jit_process(struct perf_session *session,
 	if (jit_detect(filename, pid, nsi)) {
 		nsinfo__put(nsi);
 
-		// Strip //anon* mmaps if we processed a jitdump for this pid
-		if (jit_has_pid(machine, pid) && (strncmp(filename, "//anon", 6) == 0))
+		/*
+		 * Strip //anon*, [anon:* and /memfd:* mmaps if we processed a jitdump for this pid
+		 */
+		if (jit_has_pid(machine, pid) &&
+			((strncmp(filename, "//anon", 6) == 0) ||
+			 (strncmp(filename, "[anon:", 6) == 0) ||
+			 (strncmp(filename, "/memfd:", 7) == 0)))
 			return 1;
 
 		return 0;
-- 
2.25.1

Re: [PATCH v2] perf inject jit: Ignore memfd and anonymous mmap events if jitdump present

[Ian Rogers]

On Fri, Aug 5, 2022 at 3:06 PM Brian Robbins
<brianrob@linux.microsoft.com> wrote:
>
> Some processes store jitted code in memfd mappings to avoid having rwx
> mappings.  These processes map the code with a writeable mapping and a
> read-execute mapping.  They write the code using the writeable mapping
> and then unmap the writeable mapping.  All subsequent execution is
> through the read-execute mapping.
>
> perf inject --jit ignores //anon* mappings for each process where a
> jitdump is present because it expects to inject mmap events for each
> jitted code range, and said jitted code ranges will overlap with the
> //anon* mappings.
>
> Ignore /memfd: and [anon:* mappings so that jitted code contained in
> /memfd: and [anon:* mappings is treated the same way as jitted code
> contained in //anon* mappings.
>
> Signed-off-by: Brian Robbins <brianrob@linux.microsoft.com>

Acked-by: Ian Rogers <irogers@google.com>

Thanks,
Ian

> ---
>  tools/perf/util/jitdump.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/util/jitdump.c b/tools/perf/util/jitdump.c
> index a23255773c60..4e6632203704 100644
> --- a/tools/perf/util/jitdump.c
> +++ b/tools/perf/util/jitdump.c
> @@ -845,8 +845,13 @@ jit_process(struct perf_session *session,
>         if (jit_detect(filename, pid, nsi)) {
>                 nsinfo__put(nsi);
>
> -               // Strip //anon* mmaps if we processed a jitdump for this pid
> -               if (jit_has_pid(machine, pid) && (strncmp(filename, "//anon", 6) == 0))
> +               /*
> +                * Strip //anon*, [anon:* and /memfd:* mmaps if we processed a jitdump for this pid
> +                */
> +               if (jit_has_pid(machine, pid) &&
> +                       ((strncmp(filename, "//anon", 6) == 0) ||
> +                        (strncmp(filename, "[anon:", 6) == 0) ||
> +                        (strncmp(filename, "/memfd:", 7) == 0)))
>                         return 1;
>
>                 return 0;
> --
> 2.25.1
>

Re: [PATCH v2] perf inject jit: Ignore memfd and anonymous mmap events if jitdump present

[Arnaldo Carvalho de Melo]

Em Fri, Aug 05, 2022 at 03:06:45PM -0700, Brian Robbins escreveu:
> Some processes store jitted code in memfd mappings to avoid having rwx
> mappings.  These processes map the code with a writeable mapping and a
> read-execute mapping.  They write the code using the writeable mapping
> and then unmap the writeable mapping.  All subsequent execution is
> through the read-execute mapping.
> 
> perf inject --jit ignores //anon* mappings for each process where a
> jitdump is present because it expects to inject mmap events for each
> jitted code range, and said jitted code ranges will overlap with the
> //anon* mappings.
> 
> Ignore /memfd: and [anon:* mappings so that jitted code contained in
> /memfd: and [anon:* mappings is treated the same way as jitted code
> contained in //anon* mappings.

Removed v1, applied this one.

- Arnaldo
 
> Signed-off-by: Brian Robbins <brianrob@linux.microsoft.com>
> ---
>  tools/perf/util/jitdump.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/util/jitdump.c b/tools/perf/util/jitdump.c
> index a23255773c60..4e6632203704 100644
> --- a/tools/perf/util/jitdump.c
> +++ b/tools/perf/util/jitdump.c
> @@ -845,8 +845,13 @@ jit_process(struct perf_session *session,
>  	if (jit_detect(filename, pid, nsi)) {
>  		nsinfo__put(nsi);
>  
> -		// Strip //anon* mmaps if we processed a jitdump for this pid
> -		if (jit_has_pid(machine, pid) && (strncmp(filename, "//anon", 6) == 0))
> +		/*
> +		 * Strip //anon*, [anon:* and /memfd:* mmaps if we processed a jitdump for this pid
> +		 */
> +		if (jit_has_pid(machine, pid) &&
> +			((strncmp(filename, "//anon", 6) == 0) ||
> +			 (strncmp(filename, "[anon:", 6) == 0) ||
> +			 (strncmp(filename, "/memfd:", 7) == 0)))
>  			return 1;
>  
>  		return 0;
> -- 
> 2.25.1

-- 

- Arnaldo