[PATCH v3] perf sched: fix wrong conversion of task state

[PATCH v3] perf sched: fix wrong conversion of task state

[Tomoki Sekiyama]

sched_out_state() converts the prev_state u64 bitmask to a char in
a wrong way, which may cause invalid memory access.
TASK_STATE_TO_CHAR_STR should also be fixed to adapt current
kernel's sched.h.

Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama.qu@hitachi.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
---
 tools/perf/builtin-sched.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
index 0dfe8df..5776263 100644
--- a/tools/perf/builtin-sched.c
+++ b/tools/perf/builtin-sched.c
@@ -70,7 +70,7 @@ struct sched_atom {
 	struct task_desc	*wakee;
 };
 
-#define TASK_STATE_TO_CHAR_STR "RSDTtZXxKWP"
+#define TASK_STATE_TO_CHAR_STR "RSDTtXZxKWPNn"
 
 enum thread_state {
 	THREAD_SLEEPING = 0,
@@ -897,9 +897,10 @@ static int thread_atoms_insert(struct perf_sched *sched, struct thread *thread)
 
 static char sched_out_state(u64 prev_state)
 {
-	const char *str = TASK_STATE_TO_CHAR_STR;
+	const char str[] = TASK_STATE_TO_CHAR_STR;
+	unsigned int bit = prev_state ? __ffs(prev_state) + 1 : 0;
 
-	return str[prev_state];
+	return bit < ARRAY_SIZE(str) - 1 ? str[bit] : '?';
 }
 
 static int
-- 
2.7.4

Re: [PATCH v3] perf sched: fix wrong conversion of task state

[David Ahern]

On 7/28/16 10:00 PM, Tomoki Sekiyama wrote:
> sched_out_state() converts the prev_state u64 bitmask to a char in
> a wrong way, which may cause invalid memory access.
> TASK_STATE_TO_CHAR_STR should also be fixed to adapt current
> kernel's sched.h.

Masami's point is that this should be 2 separate patches -- as suggested 
by the 'also' in the description.

>
> Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama.qu@hitachi.com>
> Cc: Jiri Olsa <jolsa@kernel.org>
> Cc: David Ahern <dsahern@gmail.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Cc: Masami Hiramatsu <mhiramat@kernel.org>
> ---
>  tools/perf/builtin-sched.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
> index 0dfe8df..5776263 100644
> --- a/tools/perf/builtin-sched.c
> +++ b/tools/perf/builtin-sched.c
> @@ -70,7 +70,7 @@ struct sched_atom {
>  	struct task_desc	*wakee;
>  };
>
> -#define TASK_STATE_TO_CHAR_STR "RSDTtZXxKWP"
> +#define TASK_STATE_TO_CHAR_STR "RSDTtXZxKWPNn"

Patch 1 updates this macro to latest kernel version.

>
>  enum thread_state {
>  	THREAD_SLEEPING = 0,
> @@ -897,9 +897,10 @@ static int thread_atoms_insert(struct perf_sched *sched, struct thread *thread)
>
>  static char sched_out_state(u64 prev_state)
>  {
> -	const char *str = TASK_STATE_TO_CHAR_STR;
> +	const char str[] = TASK_STATE_TO_CHAR_STR;
> +	unsigned int bit = prev_state ? __ffs(prev_state) + 1 : 0;
>
> -	return str[prev_state];
> +	return bit < ARRAY_SIZE(str) - 1 ? str[bit] : '?';
>  }
>
>  static int
>

Patch 2 fixes access to str by treating prev_state as a bitmask and 
adding the Fixes:

Fixes: cdce9d738b91e ("perf sched: Add sched latency profiling")

Re: [PATCH v3] perf sched: fix wrong conversion of task state

[Masami Hiramatsu]

On Fri, 29 Jul 2016 13:00:08 +0900
Tomoki Sekiyama <tomoki.sekiyama.qu@hitachi.com> wrote:

> sched_out_state() converts the prev_state u64 bitmask to a char in
> a wrong way, which may cause invalid memory access.
> TASK_STATE_TO_CHAR_STR should also be fixed to adapt current
> kernel's sched.h.

This still have 2 things...

> 
> Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama.qu@hitachi.com>
> Cc: Jiri Olsa <jolsa@kernel.org>
> Cc: David Ahern <dsahern@gmail.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Cc: Masami Hiramatsu <mhiramat@kernel.org>
> ---
>  tools/perf/builtin-sched.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
> index 0dfe8df..5776263 100644
> --- a/tools/perf/builtin-sched.c
> +++ b/tools/perf/builtin-sched.c
> @@ -70,7 +70,7 @@ struct sched_atom {
>  	struct task_desc	*wakee;
>  };
>  
> -#define TASK_STATE_TO_CHAR_STR "RSDTtZXxKWP"
> +#define TASK_STATE_TO_CHAR_STR "RSDTtXZxKWPNn"
>  
>  enum thread_state {
>  	THREAD_SLEEPING = 0,
> @@ -897,9 +897,10 @@ static int thread_atoms_insert(struct perf_sched *sched, struct thread *thread)
>  
>  static char sched_out_state(u64 prev_state)
>  {
> -	const char *str = TASK_STATE_TO_CHAR_STR;
> +	const char str[] = TASK_STATE_TO_CHAR_STR;
> +	unsigned int bit = prev_state ? __ffs(prev_state) + 1 : 0;
>  
> -	return str[prev_state];
> +	return bit < ARRAY_SIZE(str) - 1 ? str[bit] : '?';
>  }
>  
>  static int
> -- 
> 2.7.4
> 


-- 
Masami Hiramatsu <mhiramat@kernel.org>