linux-kernel - Re: [PATCH] firmware: cs_dsp: avoid large local variables

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Message-ID: <ec6881c2-10a9-4b4d-a53b-f882d6aa89d3@opensource.cirrus.com>
Date: Mon, 16 Dec 2024 11:18:55 +0000
From: Richard Fitzgerald <rf@...nsource.cirrus.com>
To: Arnd Bergmann <arnd@...nel.org>,
        Simon Trimmer
	<simont@...nsource.cirrus.com>,
        Charles Keepax
	<ckeepax@...nsource.cirrus.com>,
        Mark Brown <broonie@...nel.org>
CC: Arnd Bergmann <arnd@...db.de>, <patches@...nsource.cirrus.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] firmware: cs_dsp: avoid large local variables

On 16/12/2024 10:38 am, Richard Fitzgerald wrote:
> On 16/12/2024 8:33 am, Arnd Bergmann wrote:
>> From: Arnd Bergmann <arnd@...db.de>
>>
>> Having 1280 bytes of local variables on the stack exceeds the limit
>> on 32-bit architectures:
>>
>> drivers/firmware/cirrus/test/cs_dsp_test_bin.c: In function 
>> 'bin_patch_mixed_packed_unpacked_random':
>> drivers/firmware/cirrus/test/cs_dsp_test_bin.c:2097:1: error: the 
>> frame size of 1784 bytes is larger than 1024 bytes [-Werror=frame- 
>> larger-than=]
>>
>> Use dynamic allocation for the largest two here.
>>
>> Fixes: dd0b6b1f29b9 ("firmware: cs_dsp: Add KUnit testing of bin file 
>> download")
>> Signed-off-by: Arnd Bergmann <arnd@...db.de>
>> ---
>>   .../firmware/cirrus/test/cs_dsp_test_bin.c    | 36 +++++++++++--------
>>   1 file changed, 22 insertions(+), 14 deletions(-)
>>
>> diff --git a/drivers/firmware/cirrus/test/cs_dsp_test_bin.c b/drivers/ 
>> firmware/cirrus/test/cs_dsp_test_bin.c
>> index 689190453307..f1955813919c 100644
>> --- a/drivers/firmware/cirrus/test/cs_dsp_test_bin.c
>> +++ b/drivers/firmware/cirrus/test/cs_dsp_test_bin.c
>> @@ -1978,8 +1978,10 @@ static void 
>> bin_patch_mixed_packed_unpacked_random(struct kunit *test)
>>            4, 51, 76, 72, 16,  6, 39, 62, 15, 41, 28, 73, 53, 40, 45, 54,
>>           14, 55, 46, 66, 64, 59, 23,  9, 67, 47, 19, 71, 35, 18, 42,  1,
>>       };
>> -    u32 packed_payload[80][3];
>> -    u32 unpacked_payload[80];
>> +    struct {
>> +        u32 packed[80][3];
>> +        u32 unpacked[80];
>> +    } *payload;
>>       u32 readback[3];
>>       unsigned int alg_base_words, patch_pos_words;
>>       unsigned int alg_base_in_packed_regs, patch_pos_in_packed_regs;
>> @@ -1988,8 +1990,12 @@ static void 
>> bin_patch_mixed_packed_unpacked_random(struct kunit *test)
>>       struct firmware *fw;
>>       int i;
>> -    get_random_bytes(packed_payload, sizeof(packed_payload));
>> -    get_random_bytes(unpacked_payload, sizeof(unpacked_payload));
>> +    payload = kmalloc(sizeof(*payload), GFP_KERNEL);
> 
> Should be kunit_kmalloc() so the kunit framework frees it automatically
> if any test case fails and the test terminates early.
> 
> Apart from that it looks ok to me.

Also the check for NULL should use KUNIT_ASSERT_NOT_NULL() so the test
case will error-out.