Re: [PATCH v5 14/16] modules: Support extended MODVERSIONS info

[Christophe Leroy <christophe.leroy@csgroup.eu>]

Le 26/09/2024 à 01:38, Matthew Maurer a écrit :
> Adds a new format for MODVERSIONS which stores each field in a separate
> ELF section. This initially adds support for variable length names, but
> could later be used to add additional fields to MODVERSIONS in a
> backwards compatible way if needed. Any new fields will be ignored by
> old user tooling, unlike the current format where user tooling cannot
> tolerate adjustments to the format (for example making the name field
> longer).
> 
> Since PPC munges its version records to strip leading dots, we reproduce
> the munging for the new format. Other architectures do not appear to
> have architecture-specific usage of this information.
> 
> Signed-off-by: Matthew Maurer <mmaurer@google.com>
> ---
>   arch/powerpc/kernel/module_64.c | 23 ++++++++-
>   kernel/module/internal.h        | 11 ++++
>   kernel/module/main.c            | 92 ++++++++++++++++++++++++++++++---
>   kernel/module/version.c         | 45 ++++++++++++++++
>   4 files changed, 161 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
> index e9bab599d0c2..4e7b156dd8b2 100644
> --- a/arch/powerpc/kernel/module_64.c
> +++ b/arch/powerpc/kernel/module_64.c
> @@ -355,6 +355,23 @@ static void dedotify_versions(struct modversion_info *vers,
>   		}
>   }
>   
> +static void dedotify_ext_version_names(char *str_seq, unsigned long size)
> +{
> +	unsigned long out = 0;
> +	unsigned long in;
> +	char last = '\0';
> +
> +	for (in = 0; in < size; in++) {
> +		/* Skip one leading dot */
> +		if (last == '\0' && str_seq[in] == '.')
> +			in++;
> +		last = str_seq[in];
> +		str_seq[out++] = last;
> +	}

Why do you need a loop here ?

Can't you just do something like:

	if (str_seq[0] == '.')
		memmove(str_seq, str_seq + 1, size);


> +	/* Zero the trailing portion of the names table for robustness */
> +	memset(&str_seq[out], 0, size - out);

This seems unneeded.

> +}
> +
>   /*
>    * Undefined symbols which refer to .funcname, hack to funcname. Make .TOC.
>    * seem to be defined (value set later).



Christophe