Re: [greybus-dev] [PATCH] staging: greybus: fix stack size warning with UBSAN

On 1/3/21 4:35 PM, Arnd Bergmann wrote:

From: Arnd Bergmann arnd@arndb.de

clang warns about excessive stack usage in this driver when UBSAN is enabled:

drivers/staging/greybus/audio_topology.c:977:12: error: stack frame size of 1836 bytes in function 'gbaudio_tplg_create_widget' [-Werror,-Wframe-larger-than=]

Rework this code to no longer use compound literals for initializing the structure in each case, but instead keep the common bits in a preallocated constant array and copy them as needed.

This is good, but I have a few comments.

You took out the default case, and it seems you are using a w->type value bigger than the initialization array to determine validity. But there are more values defined in the snd_soc_dapm_type enumerated type than are explicitly listed as cases in the switch statement. So the switch statement no longer treats some types as invalid (such as snd_soc_dapm_demux). Am I missing something?

You are setting explicit names, such as "spk", "hp", "mic", etc. in the initialization array. But you update the name after (struct) assigning from the array. I have no real objection I guess, but why bother? Why not just use null pointers in the initialization array?

You change a semicolon to a comma in one spot, and you should not have. I'll point that out below.

I like that you got rid of the type casts, which were apparently unnecessary.

You dropped the break in the final case in the switch statement, but in an earlier discussion I think we concluded that wasn't a problem.

I guess the main thing is the first thing mentioned.

Thanks.

-Alex

Signed-off-by: Arnd Bergmann arnd@arndb.de

drivers/staging/greybus/audio_topology.c | 106 ++++++++++------------- 1 file changed, 47 insertions(+), 59 deletions(-)

diff --git a/drivers/staging/greybus/audio_topology.c b/drivers/staging/greybus/audio_topology.c index 96b8b29fe899..c03873915c20 100644 --- a/drivers/staging/greybus/audio_topology.c +++ b/drivers/staging/greybus/audio_topology.c @@ -974,6 +974,44 @@ static int gbaudio_widget_event(struct snd_soc_dapm_widget *w, return ret; } +static const struct snd_soc_dapm_widget gbaudio_widgets[] = {

• [snd_soc_dapm_spk] = SND_SOC_DAPM_SPK("spk", gbcodec_event_spk),
• [snd_soc_dapm_hp] = SND_SOC_DAPM_HP("hp", gbcodec_event_hp),
• [snd_soc_dapm_mic] = SND_SOC_DAPM_MIC("mic", gbcodec_event_int_mic),

. . .

@@ -1050,78 +1088,28 @@ static int gbaudio_tplg_create_widget(struct gbaudio_module_info *module, strlcpy(temp_name, w->name, NAME_SIZE); snprintf(w->name, NAME_SIZE, "GB %d %s", module->dev_id, temp_name);

• if (w->type > ARRAY_SIZE(gbaudio_widgets)) {

• ret = -EINVAL;
  

• goto error;
  

• }
• *dw = gbaudio_widgets[w->type];
• dw->name = w->name;
• switch (w->type) { case snd_soc_dapm_spk:

• *dw = (struct snd_soc_dapm_widget)
  

• 	SND_SOC_DAPM_SPK(w->name, gbcodec_event_spk);
  

  module->op_devices |= GBAUDIO_DEVICE_OUT_SPEAKER; break; case snd_soc_dapm_hp:

• *dw = (struct snd_soc_dapm_widget)
  

• 	SND_SOC_DAPM_HP(w->name, gbcodec_event_hp);
  

  module->op_devices |= (GBAUDIO_DEVICE_OUT_WIRED_HEADSET

• 			| GBAUDIO_DEVICE_OUT_WIRED_HEADPHONE);
  

• 			| GBAUDIO_DEVICE_OUT_WIRED_HEADPHONE),
  

Please fix this (above) to preserve the original semicolon.

module->ip_devices |= GBAUDIO_DEVICE_IN_WIRED_HEADSET;
break;

case snd_soc_dapm_mic:

• *dw = (struct snd_soc_dapm_widget)
  

• 	SND_SOC_DAPM_MIC(w->name, gbcodec_event_int_mic);
  

  module->ip_devices |= GBAUDIO_DEVICE_IN_BUILTIN_MIC; break;

. . .