Re: [PATCH v2] perf tool: fix endianness handling of u32 data in samples

[Arnaldo Carvalho de Melo <acme@ghostprotocols.net>]

Em Fri, Sep 02, 2011 at 10:03:46AM -0600, David Ahern escreveu:
>  	if (type & PERF_SAMPLE_RAW) {
> -		u32 *p = (u32 *)array;
> +		u.val64 = *array;
> +		if (swapped) {
> +			static bool show_warn = true;
> +
> +			/* undo swap of u64, then swap on individual u32s */
> +			u.val64 = bswap_64(u.val64);
> +			u.val32[0] = bswap_32(u.val32[0]);
> +			u.val32[1] = bswap_32(u.val32[1]);
> +
> +			if (show_warn) {
> +				pr_warning("Endianness of raw data not corrected!\n");
> +				show_warn = false;
> +			}
> +		}

Can you use WARN_ONCE? Would become:
	
		if (WARN_ONCE(swapped, "Endianness of raw data not corrected!\n")) {
			/* undo swap of u64, then swap on individual u32s */
			u.val64 = bswap_64(u.val64);
			u.val32[0] = bswap_32(u.val32[0]);
			u.val32[1] = bswap_32(u.val32[1]);
		}

We have that and its the usual idiom in the kernel proper :-)

See tools/perf/util/include/asm/bug.h and net/can/af_can.c can_rcv for
an example.

Thanks,

- Arnaldo