linux-kernel - Re: [v11 2/2] misc: pci_endpoint_test: Fix overflow of bar

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Message-ID: <87FA054A-053E-4E73-94D7-CB9F4F655053@kernel.org>
Date: Tue, 21 Jan 2025 21:31:14 +0100
From: Niklas Cassel <cassel@...nel.org>
To: Jon Hunter <jonathanh@...dia.com>, Hans Zhang <18255117159@....com>,
 manivannan.sadhasivam@...aro.org
CC: kw@...ux.com, kishon@...nel.org, arnd@...db.de, gregkh@...uxfoundation.org,
 linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
 rockswang7@...il.com,
 "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [v11 2/2] misc: pci_endpoint_test: Fix overflow of bar_size



On 21 January 2025 18:46:43 CET, Jon Hunter <jonathanh@...dia.com> wrote:
>Hi Hans,
>
>On 09/01/2025 09:45, Hans Zhang wrote:
>> With 8GB BAR2, running pcitest -b 2 fails with "TEST FAILED".
>> 
>> The return value of the `pci_resource_len` interface is not an integer.
>> Using `pcitest` with an 8GB BAR2, the bar_size of integer type will
>> overflow.
>> 
>> Change the data type of bar_size from integer to resource_size_t, to fix
>> the above issue.
>> 
>> Signed-off-by: Hans Zhang <18255117159@....com>
>> Suggested-by: Niklas Cassel <cassel@...nel.org>
>> Reviewed-by: Niklas Cassel <cassel@...nel.org>
>> ---
>> Changes since v10:
>> https://lore.kernel.org/linux-pci/20250108080951.1700230-3-18255117159@163.com/
>> 
>> - Replace do_div with the div_u64 API.
>> 
>> Changes since v8-v9:
>> https://lore.kernel.org/linux-pci/20250104151652.1652181-1-18255117159@163.com/
>> 
>> - Split the patch.
>> 
>> Changes since v4-v7:
>> https://lore.kernel.org/linux-pci/20250102120222.1403906-1-18255117159@163.com/
>> 
>> - Fix 32-bit OS warnings and errors.
>> - Fix undefined reference to `__udivmoddi4`
>> 
>> Changes since v3:
>> https://lore.kernel.org/linux-pci/20241221141009.27317-1-18255117159@163.com/
>> 
>> - The patch subject were modified.
>> 
>> Changes since v2:
>> https://lore.kernel.org/linux-pci/20241220075253.16791-1-18255117159@163.com/
>> 
>> - Fix "changes" part goes below the --- line
>> - The patch commit message were modified.
>> 
>> Changes since v1:
>> https://lore.kernel.org/linux-pci/20241217121220.19676-1-18255117159@163.com/
>> 
>> - The patch subject and commit message were modified.
>> ---
>>   drivers/misc/pci_endpoint_test.c | 5 +++--
>>   1 file changed, 3 insertions(+), 2 deletions(-)
>> 
>> diff --git a/drivers/misc/pci_endpoint_test.c b/drivers/misc/pci_endpoint_test.c
>> index f78c7540c52c..0f6291801078 100644
>> --- a/drivers/misc/pci_endpoint_test.c
>> +++ b/drivers/misc/pci_endpoint_test.c
>> @@ -280,10 +280,11 @@ static int pci_endpoint_test_bar_memcmp(struct pci_endpoint_test *test,
>>   static bool pci_endpoint_test_bar(struct pci_endpoint_test *test,
>>   				  enum pci_barno barno)
>>   {
>> -	int j, bar_size, buf_size, iters;
>> +	int j, buf_size, iters;
>>   	void *write_buf __free(kfree) = NULL;
>>   	void *read_buf __free(kfree) = NULL;
>>   	struct pci_dev *pdev = test->pdev;
>> +	resource_size_t bar_size;
>>     	if (!test->bar[barno])
>>   		return false;
>> @@ -307,7 +308,7 @@ static bool pci_endpoint_test_bar(struct pci_endpoint_test *test,
>>   	if (!read_buf)
>>   		return false;
>>   -	iters = bar_size / buf_size;
>> +	iters = div_u64(bar_size, buf_size);
>>   	for (j = 0; j < iters; j++)
>>   		if (pci_endpoint_test_bar_memcmp(test, barno, buf_size * j,
>>   						 write_buf, read_buf, buf_size))
>
>
>This change breaks building the kernel with GCC v7 and I see ...
>
>ERROR: modpost: "__aeabi_uldivmod" [drivers/misc/pci_endpoint_test.ko] undefined!
>ERROR: modpost: "__aeabi_ldivmod" [drivers/misc/pci_endpoint_test.ko] undefined!
>
>I know that this is an old GCC version, but this is a farm builder and the kernel still indicates that GCC v5.1 is still supported [0].
>

Hmm.. div_u64() should work on gcc 5.1.

Out of curiosity, is there any difference if you add:

#include <linux/math64.h>
to
drivers/misc/pci_endpoint_test.c ?


Kind regards,
Niklas