Re: [RFC] Coverity 1128445 - Reliance on integer endianness

["Måns Rullgård" <mans@mansr.com>]

Geyslan Gregório Bem <geyslan@gmail.com> writes:

> Hi,
>
> Coverity detected in 'arch/x86/kernel/cpu/perf_event_intel_uncore.c' a
> possible reliance on integer endianness. Is that a positive one?

No, x86 is always little endian.

> static u64 ivt_uncore_irp_read_counter(struct intel_uncore_box *box,
> struct perf_event *event)
> 1369{
> 1370        struct pci_dev *pdev = box->pci_dev;
> 1371        struct hw_perf_event *hwc = &event->hw;
> 1372        u64 count = 0;
> 1373
>
> CID 1128445 (#1 of 1): Reliance on integer endianness
> (INCOMPATIBLE_CAST)incompatible_cast: Pointer "&count" points to an
> object whose effective type is "unsigned long long" (64 bits,
> unsigned) but is dereferenced as a narrower "unsigned int" (32 bits,
> unsigned). This may lead to unexpected results depending on machine
> endianness.[show details]
>
> 1374        pci_read_config_dword(pdev, ivt_uncore_irp_ctrs[hwc->idx],
> (u32 *)&count);
> 1375        pci_read_config_dword(pdev, ivt_uncore_irp_ctrs[hwc->idx]
> + 4, (u32 *)&count + 1);
> 1376
> 1377        return count;
> 1378}

This looks intentional and correct apart from possible strict aliasing
issues.

-- 
Måns Rullgård
mans@mansr.com