re: PCI: Add TLP Prefix reading to pcie_read_tlp_log()

re: PCI: Add TLP Prefix reading to pcie_read_tlp_log()

[Colin King (gmail)]

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Hi,

Static analysis shows there is a potential issue in the following commit:

commit 00048c2d5f113bb4e82a0a30dfc4ee12590b81f5
Author: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Date:   Tue Jan 14 19:08:39 2025 +0200

     PCI: Add TLP Prefix reading to pcie_read_tlp_log()


The issue is described as follows:

unsigned int aer_tlp_log_len(struct pci_dev *dev, u32 aercc)
{
         return PCIE_STD_NUM_TLP_HEADERLOG +
                (aercc & PCI_ERR_CAP_PREFIX_LOG_PRESENT) ?
                dev->eetlp_prefix_max : 0;
}


static analysis is warning that the left hand size of the ? operator is 
always true and so dev->eetlp_prefix_max is always being returned and 
the 0 is never returned (dead code).

I suspect the expected behaviour is as follows:

         return PCIE_STD_NUM_TLP_HEADERLOG +
                ((aercc & PCI_ERR_CAP_PREFIX_LOG_PRESENT) ?
                dev->eetlp_prefix_max : 0);

..I'm reluctant to send a fix in case this is not the original intention.

Colin

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re: PCI: Add TLP Prefix reading to pcie_read_tlp_log()

[Ilpo Järvinen]

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On Thu, 16 Jan 2025, Colin King (gmail) wrote:

> Hi,
> 
> Static analysis shows there is a potential issue in the following commit:
> 
> commit 00048c2d5f113bb4e82a0a30dfc4ee12590b81f5
> Author: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
> Date:   Tue Jan 14 19:08:39 2025 +0200
> 
>     PCI: Add TLP Prefix reading to pcie_read_tlp_log()
> 
> 
> The issue is described as follows:
> 
> unsigned int aer_tlp_log_len(struct pci_dev *dev, u32 aercc)
> {
>         return PCIE_STD_NUM_TLP_HEADERLOG +
>                (aercc & PCI_ERR_CAP_PREFIX_LOG_PRESENT) ?
>                dev->eetlp_prefix_max : 0;
> }
> 
> 
> static analysis is warning that the left hand size of the ? operator is always
> true and so dev->eetlp_prefix_max is always being returned and the 0 is never
> returned (dead code).
> 
> I suspect the expected behaviour is as follows:
> 
>         return PCIE_STD_NUM_TLP_HEADERLOG +
>                ((aercc & PCI_ERR_CAP_PREFIX_LOG_PRESENT) ?
>                dev->eetlp_prefix_max : 0);
> 
> ..I'm reluctant to send a fix in case this is not the original intention.

Your fix looks correct, it should have the parenthesis due to operator 
precedence rules. The intention is to calculate 4 DWs + optionally n E-E 
TLP prefixes.

-- 
 i.

Re: PCI: Add TLP Prefix reading to pcie_read_tlp_log()

[Colin King (gmail)]

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On 16/01/2025 16:18, Ilpo Järvinen wrote:
> On Thu, 16 Jan 2025, Colin King (gmail) wrote:
> 
>> Hi,
>>
>> Static analysis shows there is a potential issue in the following commit:
>>
>> commit 00048c2d5f113bb4e82a0a30dfc4ee12590b81f5
>> Author: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
>> Date:   Tue Jan 14 19:08:39 2025 +0200
>>
>>      PCI: Add TLP Prefix reading to pcie_read_tlp_log()
>>
>>
>> The issue is described as follows:
>>
>> unsigned int aer_tlp_log_len(struct pci_dev *dev, u32 aercc)
>> {
>>          return PCIE_STD_NUM_TLP_HEADERLOG +
>>                 (aercc & PCI_ERR_CAP_PREFIX_LOG_PRESENT) ?
>>                 dev->eetlp_prefix_max : 0;
>> }
>>
>>
>> static analysis is warning that the left hand size of the ? operator is always
>> true and so dev->eetlp_prefix_max is always being returned and the 0 is never
>> returned (dead code).
>>
>> I suspect the expected behaviour is as follows:
>>
>>          return PCIE_STD_NUM_TLP_HEADERLOG +
>>                 ((aercc & PCI_ERR_CAP_PREFIX_LOG_PRESENT) ?
>>                 dev->eetlp_prefix_max : 0);
>>
>> ..I'm reluctant to send a fix in case this is not the original intention.
> 
> Your fix looks correct, it should have the parenthesis due to operator
> precedence rules. The intention is to calculate 4 DWs + optionally n E-E
> TLP prefixes.
> 

OK, I'll send a patch later today.

Colin

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