linux-kernel - Re: [PATCH] gcov: support GCC 12.1 and newer compilers

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Date:   Fri, 14 Oct 2022 11:30:51 +0200
From:   Peter Oberparleiter <oberpar@...ux.ibm.com>
To:     Martin Liška <mliska@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] gcov: support GCC 12.1 and newer compilers

On 13.10.2022 09:40, Martin Liška wrote:
> Starting with GCC 12.1, there are 2 significant changes to the .gcda
> file format that needs to be supported:
> 
> a) [gcov: Use system IO buffering] (23eb66d1d46a34cb28c4acbdf8a1deb80a7c5a05) changed
>    that all sizes in the format are in bytes and not in words (4B)
> b) [gcov: make profile merging smarter] (72e0c742bd01f8e7e6dcca64042b9ad7e75979de)
>    add a new checksum to the file header.
> 
> Tested with GCC 7.5, 10.4, 12.2 and the current master.
> 
> Signed-off-by: Martin Liska <mliska@...e.cz>

Looks good, thanks! I successfully tested this patch on s390 using GCC
12.2 and 11.2.

Tested-by: Peter Oberparleiter <oberpar@...ux.ibm.com>
Reviewed-by: Peter Oberparleiter <oberpar@...ux.ibm.com>

Andrew, could you add this patch via your tree?


> ---
>  kernel/gcov/gcc_4_7.c | 18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/gcov/gcc_4_7.c b/kernel/gcov/gcc_4_7.c
> index 460c12b7dfea..7971e989e425 100644
> --- a/kernel/gcov/gcc_4_7.c
> +++ b/kernel/gcov/gcc_4_7.c
> @@ -30,6 +30,13 @@
>  
>  #define GCOV_TAG_FUNCTION_LENGTH	3
>  
> +/* Since GCC 12.1 sizes are in BYTES and not in WORDS (4B). */
> +#if (__GNUC__ >= 12)
> +#define GCOV_UNIT_SIZE				4
> +#else
> +#define GCOV_UNIT_SIZE				1
> +#endif
> +
>  static struct gcov_info *gcov_info_head;
>  
>  /**
> @@ -383,12 +390,18 @@ size_t convert_to_gcda(char *buffer, struct gcov_info *info)
>  	pos += store_gcov_u32(buffer, pos, info->version);
>  	pos += store_gcov_u32(buffer, pos, info->stamp);
>  
> +#if (__GNUC__ >= 12)
> +	/* Use zero as checksum of the compilation unit. */
> +	pos += store_gcov_u32(buffer, pos, 0);
> +#endif
> +
>  	for (fi_idx = 0; fi_idx < info->n_functions; fi_idx++) {
>  		fi_ptr = info->functions[fi_idx];
>  
>  		/* Function record. */
>  		pos += store_gcov_u32(buffer, pos, GCOV_TAG_FUNCTION);
> -		pos += store_gcov_u32(buffer, pos, GCOV_TAG_FUNCTION_LENGTH);
> +		pos += store_gcov_u32(buffer, pos,
> +			GCOV_TAG_FUNCTION_LENGTH * GCOV_UNIT_SIZE);
>  		pos += store_gcov_u32(buffer, pos, fi_ptr->ident);
>  		pos += store_gcov_u32(buffer, pos, fi_ptr->lineno_checksum);
>  		pos += store_gcov_u32(buffer, pos, fi_ptr->cfg_checksum);
> @@ -402,7 +415,8 @@ size_t convert_to_gcda(char *buffer, struct gcov_info *info)
>  			/* Counter record. */
>  			pos += store_gcov_u32(buffer, pos,
>  					      GCOV_TAG_FOR_COUNTER(ct_idx));
> -			pos += store_gcov_u32(buffer, pos, ci_ptr->num * 2);
> +			pos += store_gcov_u32(buffer, pos,
> +				ci_ptr->num * 2 * GCOV_UNIT_SIZE);
>  
>  			for (cv_idx = 0; cv_idx < ci_ptr->num; cv_idx++) {
>  				pos += store_gcov_u64(buffer, pos,

-- 
Peter Oberparleiter
Linux on IBM Z Development - IBM Germany R&D