linux-kernel - Re: [PATCH] drm/imagination: fix ARRAY

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Date: Thu, 18 Jan 2024 09:00:13 -0800
From: Randy Dunlap <rdunlap@...radead.org>
To: Matt Coster <Matt.Coster@...tec.com>
Cc: Maxime Ripard <mripard@...nel.org>, Frank Binns <Frank.Binns@...tec.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>,
 Daniel Vetter <daniel@...ll.ch>,
 "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/imagination: fix ARRAY_SIZE build error

Hi Matt,

On 1/18/24 01:38, Matt Coster wrote:
> On 10/01/2024 00:23, Randy Dunlap wrote:
>> Fix a build error when using GCC 13.2.0 from kernel.org crosstools
>> by changing ARRAY_SIZE() to the macro PVR_MIPS_PT_PAGE_COUNT:
> 
> I assume you're referring to the x86_64 => aarch64 toolchain here?

Yes.

> 
>> drivers/gpu/drm/imagination/pvr_vm_mips.c: In function 'pvr_vm_mips_fini':
>> ../include/linux/array_size.h:11:25: warning: overflow in conversion from 'long unsigned int' to 'int' changes value from '18446744073709551615' to '-1' [-Woverflow]
>>     11 | #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) + __must_be_array(arr))
>>        |                         ^
>> drivers/gpu/drm/imagination/pvr_vm_mips.c:105:24: note: in expansion of macro 'ARRAY_SIZE'
>>    105 |         for (page_nr = ARRAY_SIZE(mips_data->pt_pages) - 1; page_nr >= 0; page_nr--) {
>>        |                        ^~~~~~~~~~
> 
> I can't seem to reproduce this using the above toolchain (or any other),
> even with -Woverflow explicitly specified.
> 
> The use of ARRAY_SIZE() in loop bounds is a pretty common construction –
> even within the pvr driver. Do you see similar warnings anywhere else?

No, this is the only place that I have seen this issue.

Thanks.

> -- 
> Matt Coster
> Imagination Technologies
> 
>> Fixes: 927f3e0253c1 ("drm/imagination: Implement MIPS firmware processor and MMU support")
>> Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
>> Cc: Donald Robson <donald.robson@...tec.com>
>> Cc: Maxime Ripard <mripard@...nel.org>
>> Cc: Frank Binns <frank.binns@...tec.com>
>> Cc: Matt Coster <matt.coster@...tec.com>
>> Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
>> Cc: Thomas Zimmermann <tzimmermann@...e.de>
>> Cc: David Airlie <airlied@...il.com>
>> Cc: Daniel Vetter <daniel@...ll.ch>
>> Cc: dri-devel@...ts.freedesktop.org
>> ---
>>   drivers/gpu/drm/imagination/pvr_vm_mips.c |    4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff -- a/drivers/gpu/drm/imagination/pvr_vm_mips.c b/drivers/gpu/drm/imagination/pvr_vm_mips.c
>> --- a/drivers/gpu/drm/imagination/pvr_vm_mips.c
>> +++ b/drivers/gpu/drm/imagination/pvr_vm_mips.c
>> @@ -46,7 +46,7 @@ pvr_vm_mips_init(struct pvr_device *pvr_
>>       if (!mips_data)
>>           return -ENOMEM;
>>   -    for (page_nr = 0; page_nr < ARRAY_SIZE(mips_data->pt_pages); page_nr++) {
>> +    for (page_nr = 0; page_nr < PVR_MIPS_PT_PAGE_COUNT; page_nr++) {
>>           mips_data->pt_pages[page_nr] = alloc_page(GFP_KERNEL | __GFP_ZERO);
>>           if (!mips_data->pt_pages[page_nr]) {
>>               err = -ENOMEM;
>> @@ -102,7 +102,7 @@ pvr_vm_mips_fini(struct pvr_device *pvr_
>>       int page_nr;
>>         vunmap(mips_data->pt);
>> -    for (page_nr = ARRAY_SIZE(mips_data->pt_pages) - 1; page_nr >= 0; page_nr--) {
>> +    for (page_nr = PVR_MIPS_PT_PAGE_COUNT - 1; page_nr >= 0; page_nr--) {
>>           dma_unmap_page(from_pvr_device(pvr_dev)->dev,
>>                      mips_data->pt_dma_addr[page_nr], PAGE_SIZE, DMA_TO_DEVICE);
>>   

-- 
#Randy