Re: [Intel-gfx] [PATCH 1/9] drm/i915/sdvo: Reduce the size of the on stack buffers

[Jani Nikula <jani.nikula@linux.intel.com>]

On Wed, 08 Jan 2020, Ville Syrjala <ville.syrjala@linux.intel.com> wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> The strings we want to print to the on stack buffers should
> be no more than
> 8 * 3 + strlen("(GET_SCALED_HDTV_RESOLUTION_SUPPORT)") + 1 = 61
> bytes. So let's shrink the buffers down to 64 bytes.
>
> Also switch the BUG_ON()s to WARN_ON()s if I made a mistake in
> my arithmentic.
>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

Reviewed-by: Jani Nikula <jani.nikula@intel.com>

> ---
>  drivers/gpu/drm/i915/display/intel_sdvo.c | 19 ++++++++-----------
>  1 file changed, 8 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_sdvo.c b/drivers/gpu/drm/i915/display/intel_sdvo.c
> index 8758ee2a4442..02119c827c80 100644
> --- a/drivers/gpu/drm/i915/display/intel_sdvo.c
> +++ b/drivers/gpu/drm/i915/display/intel_sdvo.c
> @@ -414,12 +414,10 @@ static void intel_sdvo_debug_write(struct intel_sdvo *intel_sdvo, u8 cmd,
>  {
>  	const char *cmd_name;
>  	int i, pos = 0;
> -#define BUF_LEN 256
> -	char buffer[BUF_LEN];
> +	char buffer[64];
>  
>  #define BUF_PRINT(args...) \
> -	pos += snprintf(buffer + pos, max_t(int, BUF_LEN - pos, 0), args)
> -
> +	pos += snprintf(buffer + pos, max_t(int, sizeof(buffer) - pos, 0), args)
>  
>  	for (i = 0; i < args_len; i++) {
>  		BUF_PRINT("%02X ", ((u8 *)args)[i]);
> @@ -433,9 +431,9 @@ static void intel_sdvo_debug_write(struct intel_sdvo *intel_sdvo, u8 cmd,
>  		BUF_PRINT("(%s)", cmd_name);
>  	else
>  		BUF_PRINT("(%02X)", cmd);
> -	BUG_ON(pos >= BUF_LEN - 1);
> +
> +	WARN_ON(pos >= sizeof(buffer) - 1);
>  #undef BUF_PRINT
> -#undef BUF_LEN
>  
>  	DRM_DEBUG_KMS("%s: W: %02X %s\n", SDVO_NAME(intel_sdvo), cmd, buffer);
>  }
> @@ -540,8 +538,7 @@ static bool intel_sdvo_read_response(struct intel_sdvo *intel_sdvo,
>  	u8 retry = 15; /* 5 quick checks, followed by 10 long checks */
>  	u8 status;
>  	int i, pos = 0;
> -#define BUF_LEN 256
> -	char buffer[BUF_LEN];
> +	char buffer[64];
>  
>  	buffer[0] = '\0';
>  
> @@ -581,7 +578,7 @@ static bool intel_sdvo_read_response(struct intel_sdvo *intel_sdvo,
>  	}
>  
>  #define BUF_PRINT(args...) \
> -	pos += snprintf(buffer + pos, max_t(int, BUF_LEN - pos, 0), args)
> +	pos += snprintf(buffer + pos, max_t(int, sizeof(buffer) - pos, 0), args)
>  
>  	cmd_status = sdvo_cmd_status(status);
>  	if (cmd_status)
> @@ -600,9 +597,9 @@ static bool intel_sdvo_read_response(struct intel_sdvo *intel_sdvo,
>  			goto log_fail;
>  		BUF_PRINT(" %02X", ((u8 *)response)[i]);
>  	}
> -	BUG_ON(pos >= BUF_LEN - 1);
> +
> +	WARN_ON(pos >= sizeof(buffer) - 1);
>  #undef BUF_PRINT
> -#undef BUF_LEN
>  
>  	DRM_DEBUG_KMS("%s: R: %s\n", SDVO_NAME(intel_sdvo), buffer);
>  	return true;

-- 
Jani Nikula, Intel Open Source Graphics Center
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