linux-kernel - Re: [PATCH] perf tools: Fix a problem when opening old perf.data with different byte order

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Date:	Wed, 17 Jun 2015 10:46:16 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Wang Nan <wangnan0@...wei.com>
Cc:	acme@...nel.org, namhyung@...nel.org,
	masami.hiramatsu.pt@...achi.com, a.p.zijlstra@...llo.nl,
	mingo@...hat.com, jolsa@...nel.org, linux-kernel@...r.kernel.org,
	pi3orama@....com, lizefan@...wei.com
Subject: Re: [PATCH] perf tools: Fix a problem when opening old perf.data
 with different byte order

On Wed, Jun 17, 2015 at 03:40:42AM +0000, Wang Nan wrote:
> Following error occurs when trying to use 'perf report' on x86_64 to
> cross analysis a perf.data generated by an old perf on a big-endian
> machine:
> 

SNIP

> -	attr->branch_sample_type = bswap_64(attr->branch_sample_type);
> -	attr->sample_regs_user	 = bswap_64(attr->sample_regs_user);
> -	attr->sample_stack_user  = bswap_32(attr->sample_stack_user);
> -	attr->aux_watermark	 = bswap_32(attr->aux_watermark);
> -
> -	swap_bitfield((u8 *) (&attr->read_format + 1), sizeof(u64));
> +#define bswap_safe(f) \
> +	(attr->size > offsetof(struct perf_event_attr, f))
> +#define bswap_field(f, sz) 			\
> +do { 						\
> +	if (bswap_safe(f))			\
> +		attr->f = bswap_##sz(attr->f);	\
> +} while(0)
> +#define bswap_field_32(f) bswap_field(f, 32)
> +#define bswap_field_64(f) bswap_field(f, 64)

all macros are function specific, please undef them
at the bottom

> +
> +	bswap_field_64(config);
> +	bswap_field_64(sample_period);
> +	bswap_field_64(sample_type);
> +	bswap_field_64(read_format);
> +	bswap_field_32(wakeup_events);
> +	bswap_field_32(bp_type);
> +	bswap_field_64(bp_addr);
> +	bswap_field_64(bp_len);
> +	bswap_field_64(branch_sample_type);
> +	bswap_field_64(sample_regs_user);
> +	bswap_field_32(sample_stack_user);
> +	bswap_field_32(aux_watermark);
> +
> +	if (bswap_safe(read_format))

should this check for 'read_format + 1' ?

jirka

> +		swap_bitfield((u8 *) (&attr->read_format + 1),
> +			      sizeof(u64));


>  }
>  
>  static void perf_event__hdr_attr_swap(union perf_event *event,
> -- 
> 1.8.3.4
> 
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