Re: [PATCH 3/3] s390: add support for --reuse-cmdline

[Philipp Rudo <prudo@redhat.com>]

Hi Sven,

makes absolutely sense to have this option. One problem though...

On Mon, 22 Nov 2021 08:14:01 +0100
Sven Schnelle <svens@linux.ibm.com> wrote:

> --reuse-cmdline reads the command line of the currently
> running kernel from /proc/cmdline and uses that for the
> kernel that should be kexec'd.
> 
> Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
> Reviewed-by: Alexander Egorenkov <egorenar@linux.ibm.com>
> ---
>  kexec/arch/s390/include/arch/options.h | 10 ++++++----
>  kexec/arch/s390/kexec-image.c          |  9 +++++++++
>  2 files changed, 15 insertions(+), 4 deletions(-)
> 
> diff --git a/kexec/arch/s390/include/arch/options.h b/kexec/arch/s390/include/arch/options.h
> index 76044a301ceb..b030b61d61be 100644
[...]
> diff --git a/kexec/arch/s390/kexec-image.c b/kexec/arch/s390/kexec-image.c
> index dbeb689b830a..310d967ea331 100644
> --- a/kexec/arch/s390/kexec-image.c
> +++ b/kexec/arch/s390/kexec-image.c
> @@ -72,6 +72,10 @@ int image_s390_load_file(int argc, char **argv, struct kexec_info *info)
>  		case OPT_RAMDISK:
>  			ramdisk = optarg;
>  			break;
> +		case OPT_REUSE_CMDLINE:
> +			free(command_line);
> +			command_line = get_command_line();

get_command_line reads a maximum of 2048 bytes from /prc/cmdline. With
the configurable size on s390 defaulting to 4096 bytes this will
ultimately cause problems. So you need to make get_command_line more
flexible first.

Thanks
Philipp

> +			break;
>  		}
>  	}
>  
> @@ -123,6 +127,10 @@ image_s390_load(int argc, char **argv, const char *kernel_buf,
>  			if (command_line_add(optarg))
>  				return -1;
>  			break;
> +		case OPT_REUSE_CMDLINE:
> +			free(command_line);
> +			command_line = get_command_line();
> +			break;
>  		case OPT_RAMDISK:
>  			ramdisk = optarg;
>  			break;
> @@ -223,5 +231,6 @@ image_s390_usage(void)
>  	printf("--command-line=STRING Set the kernel command line to STRING.\n"
>  	       "--append=STRING       Set the kernel command line to STRING.\n"
>  	       "--initrd=FILENAME     Use the file FILENAME as a ramdisk.\n"
> +	       "--reuse-cmdline       Use kernel command line from running system.\n"
>  		);
>  }


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