[PATCH] perf stat: Fix NULL vs IS_ERR() checking in check_per_pkg

[PATCH] perf stat: Fix NULL vs IS_ERR() checking in check_per_pkg

[Miaoqian Lin]

The hashmap__new() function does not return NULL on errors. It returns
ERR_PTR(-ENOMEM). Using IS_ERR() to check the return value
to fix this.

Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
---
 tools/perf/util/stat.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/stat.c b/tools/perf/util/stat.c
index 09ea334586f2..a77052680087 100644
--- a/tools/perf/util/stat.c
+++ b/tools/perf/util/stat.c
@@ -311,8 +311,8 @@ static int check_per_pkg(struct evsel *counter,
 
 	if (!mask) {
 		mask = hashmap__new(pkg_id_hash, pkg_id_equal, NULL);
-		if (!mask)
-			return -ENOMEM;
+		if (IS_ERR(mask))
+			return PTR_ERR(mask);
 
 		counter->per_pkg_mask = mask;
 	}
-- 
2.17.1

Re: [PATCH] perf stat: Fix NULL vs IS_ERR() checking in check_per_pkg

[German Gomez]

Hi Miaoqian,

On 12/12/2021 04:23, Miaoqian Lin wrote:
> The hashmap__new() function does not return NULL on errors. It returns
> ERR_PTR(-ENOMEM). Using IS_ERR() to check the return value
> to fix this.
>
> Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
> ---
>  tools/perf/util/stat.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/util/stat.c b/tools/perf/util/stat.c
> index 09ea334586f2..a77052680087 100644
> --- a/tools/perf/util/stat.c
> +++ b/tools/perf/util/stat.c
> @@ -311,8 +311,8 @@ static int check_per_pkg(struct evsel *counter,
>  
>  	if (!mask) {
>  		mask = hashmap__new(pkg_id_hash, pkg_id_equal, NULL);
> -		if (!mask)
> -			return -ENOMEM;
> +		if (IS_ERR(mask))
> +			return PTR_ERR(mask);

I see that callers to "ids__new" are also missing these checks. Did you
consider patching those also?

Thanks,
German

>  
>  		counter->per_pkg_mask = mask;
>  	}

Re: [PATCH] perf stat: Fix NULL vs IS_ERR() checking in check_per_pkg

[German Gomez]

On 12/12/2021 14:55, German Gomez wrote:
> Hi Miaoqian,
>
> On 12/12/2021 04:23, Miaoqian Lin wrote:
>> The hashmap__new() function does not return NULL on errors. It returns
>> ERR_PTR(-ENOMEM). Using IS_ERR() to check the return value
>> to fix this.
>>
>> Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
>> ---
>>  tools/perf/util/stat.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/tools/perf/util/stat.c b/tools/perf/util/stat.c
>> index 09ea334586f2..a77052680087 100644
>> --- a/tools/perf/util/stat.c
>> +++ b/tools/perf/util/stat.c
>> @@ -311,8 +311,8 @@ static int check_per_pkg(struct evsel *counter,
>>  
>>  	if (!mask) {
>>  		mask = hashmap__new(pkg_id_hash, pkg_id_equal, NULL);
>> -		if (!mask)
>> -			return -ENOMEM;
>> +		if (IS_ERR(mask))
>> +			return PTR_ERR(mask);

Also (sorry, I haven't tried/tested the patch yet) is this return
necessary? To me it seems it's still ok to keep the "return -ENOMEM".

> I see that callers to "ids__new" are also missing these checks. Did you
> consider patching those also?
>
> Thanks,
> German
>
>>  
>>  		counter->per_pkg_mask = mask;
>>  	}

[PATCH] perf expr: Fix return value of ids__new

[Miaoqian Lin]

callers of ids__new() function only do NULL checking for the return
value. ids__new() calles hashmap__new(), which may return
ERR_PTR(-ENOMEM). Instead of changing the checking one-by-one.
return NULL instead of ERR_PTR(-ENOMEM) to keep
consistent.

Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
---
 tools/perf/util/expr.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/expr.c b/tools/perf/util/expr.c
index 1d532b9fed29..aabdc112300c 100644
--- a/tools/perf/util/expr.c
+++ b/tools/perf/util/expr.c
@@ -65,7 +65,13 @@ static bool key_equal(const void *key1, const void *key2,
 
 struct hashmap *ids__new(void)
 {
-	return hashmap__new(key_hash, key_equal, NULL);
+	struct hashmap *hash;
+
+	hash = hashmap__new(key_hash, key_equal, NULL);
+	if (IS_ERR(hash))
+		return NULL;
+	else
+		return hash;
 }
 
 void ids__free(struct hashmap *ids)
-- 
2.17.1

Re: [PATCH] perf expr: Fix return value of ids__new

[German Gomez]

Hi Miaoqian,

Fails to build due to missing import: "#import <linux/err.h>".

Could you please verify?

Other than that, it looks good to me. I shared the testing below:

On 13/12/2021 07:09, Miaoqian Lin wrote:
> callers of ids__new() function only do NULL checking for the return
> value. ids__new() calles hashmap__new(), which may return
> ERR_PTR(-ENOMEM). Instead of changing the checking one-by-one.
> return NULL instead of ERR_PTR(-ENOMEM) to keep
> consistent.
>
> Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
> ---
>  tools/perf/util/expr.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/expr.c b/tools/perf/util/expr.c
> index 1d532b9fed29..aabdc112300c 100644
> --- a/tools/perf/util/expr.c
> +++ b/tools/perf/util/expr.c
> @@ -65,7 +65,13 @@ static bool key_equal(const void *key1, const void *key2,
>  
>  struct hashmap *ids__new(void)
>  {
> -	return hashmap__new(key_hash, key_equal, NULL);
> +	struct hashmap *hash;
> +
> +	hash = hashmap__new(key_hash, key_equal, NULL);
> +	if (IS_ERR(hash))
> +		return NULL;
> +	else
> +		return hash;
>  }
>  
>  void ids__free(struct hashmap *ids)
Before this patch, perf-test was segfaulting instead of a graceful fail.
I think this could have been an issue in the perf tool as well.

(I forced hashmap__new in "tools/perf/util/hashmap.c" to always return
the error for the purposes of the test).

  $ make DEBUG=1 NO_LIBBPF=1 # builds with tools/perf/util/hashmap.c
  $ ./perf test 7 -v
  Couldn't bump rlimit(MEMLOCK), failures may take place when creating BPF maps, etc
   7: Simple expression parser                                        :
  --- start ---
  test child forked, pid 1953536
  perf: Segmentation fault
  Obtained 16 stack frames.
  ./perf(dump_stack+0x31) [0x559222b3ae48]
  ./perf(sighandler_dump_stack+0x33) [0x559222b3af30]
  /lib/x86_64-linux-gnu/libc.so.6(+0x4620f) [0x7ff81df6220f]
  ./perf(hashmap__size+0x23) [0x559222bf9f47]
  ./perf(ids__union+0x5f) [0x559222be1f0e]
  ./perf(+0x2d9ba8) [0x559222ac7ba8]
  ./perf(+0x2da223) [0x559222ac8223]
  ./perf(+0x2a5fe9) [0x559222a93fe9]
  ./perf(+0x2a6119) [0x559222a94119]
  ./perf(+0x2a6de7) [0x559222a94de7]
  ./perf(cmd_test+0x25f) [0x559222a95686]
  ./perf(+0x2e4d25) [0x559222ad2d25]
  ./perf(+0x2e4faa) [0x559222ad2faa]
  ./perf(+0x2e50fd) [0x559222ad30fd]
  ./perf(main+0x29d) [0x559222ad3500]
  /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf2) [0x7ff81df430b2]
  test child interrupted
  ---- end ----
  Simple expression parser: FAILED!

After the patch:

  $ make DEBUG=1 NO_LIBBPF=1
  $ ./perf test 7 -v
  Couldn't bump rlimit(MEMLOCK), failures may take place when creating BPF maps, etc
   7: Simple expression parser                                        :
  --- start ---
  test child forked, pid 1960026
  FAILED tests/expr.c:16 ids__new
  FAILED tests/expr.c:16 ids__new
  FAILED tests/expr.c:73 ids_union (-1 != 0)
  test child finished with -1
  ---- end ----

  Simple expression parser: FAILED!

so with the missing import fixex:

Tested-by: German Gomez <german.gomez@arm.com>
Reviewed-by: German Gomez <german.gomez@arm.com>

Re: [PATCH] perf expr: Fix return value of ids__new

[German Gomez]

This message appeared in my client as a separate thread, but it seems to
be a reply to a message from a different thread:

"In-Reply-To: <864ad02d-6afe-791c-f742-56582b633482@arm.com>"

On 13/12/2021 07:09, Miaoqian Lin wrote:
> callers of ids__new() function only do NULL checking for the return
> value. ids__new() calles hashmap__new(), which may return
> ERR_PTR(-ENOMEM). Instead of changing the checking one-by-one.
> return NULL instead of ERR_PTR(-ENOMEM) to keep
> consistent.
>
> Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
> ---
>  tools/perf/util/expr.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/expr.c b/tools/perf/util/expr.c
> index 1d532b9fed29..aabdc112300c 100644
> --- a/tools/perf/util/expr.c
> +++ b/tools/perf/util/expr.c
> @@ -65,7 +65,13 @@ static bool key_equal(const void *key1, const void *key2,
>  
>  struct hashmap *ids__new(void)
>  {
> -	return hashmap__new(key_hash, key_equal, NULL);
> +	struct hashmap *hash;
> +
> +	hash = hashmap__new(key_hash, key_equal, NULL);
> +	if (IS_ERR(hash))
> +		return NULL;
> +	else
> +		return hash;
>  }
>  
>  void ids__free(struct hashmap *ids)

Re: [PATCH] perf expr: Fix return value of ids__new

[German Gomez]

On 13/12/2021 13:13, German Gomez wrote:
> [...]
>
> On 13/12/2021 07:09, Miaoqian Lin wrote:
>> callers of ids__new() function only do NULL checking for the return
>> value. ids__new() calles hashmap__new(), which may return
>> ERR_PTR(-ENOMEM). Instead of changing the checking one-by-one.
>> return NULL instead of ERR_PTR(-ENOMEM) to keep
>> consistent.
>>
>> Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
>> ---
>>  tools/perf/util/expr.c | 8 +++++++-
>>  1 file changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/perf/util/expr.c b/tools/perf/util/expr.c
>> index 1d532b9fed29..aabdc112300c 100644
>> --- a/tools/perf/util/expr.c
>> +++ b/tools/perf/util/expr.c
>> @@ -65,7 +65,13 @@ static bool key_equal(const void *key1, const void *key2,
>>  
>>  struct hashmap *ids__new(void)
>>  {
>> -	return hashmap__new(key_hash, key_equal, NULL);
>> +	struct hashmap *hash;
>> +
>> +	hash = hashmap__new(key_hash, key_equal, NULL);
>> +	if (IS_ERR(hash))
>> +		return NULL;
>> +	else
>> +		return hash;

Small nitpick but can remove the else branch and simply return at the
end? Your patch still compiles for me but I think most other functions
do that.

>> [...]