[Skiboot] [PATCH] pflash: Add --skip option for reading

[Samuel Mendoza-Jonas]

On Tue, 2018-10-23 at 13:47 -0500, Adriana Kobylak wrote:
> Add a --skip=N option to pflash to skip N number of bytes when reading.
> This would allow users to print the VERSION partition without the STB
> header by specifying the --skip=4096 argument, and it's a more generic
> solution rather than making pflash depend on secure/trusted boot code.
> 
> Signed-off-by: Adriana Kobylak <anoo at linux.ibm.com>

Reviewed-by: Samuel Mendoza-Jonas <sam at mendozajonas.com>

> ---
>  external/pflash/pflash.c | 26 +++++++++++++++++++++++---
>  1 file changed, 23 insertions(+), 3 deletions(-)
> 
> diff --git a/external/pflash/pflash.c b/external/pflash/pflash.c
> index 72b90fc8..c81520cb 100644
> --- a/external/pflash/pflash.c
> +++ b/external/pflash/pflash.c
> @@ -471,7 +471,7 @@ out:
>  }
>  
>  static int do_read_file(struct blocklevel_device *bl, const char *file,
> -		uint32_t start, uint32_t size)
> +		uint32_t start, uint32_t size, uint32_t skip_size)
>  {
>  	int fd, rc = 0;
>  	uint32_t done = 0;
> @@ -481,6 +481,9 @@ static int do_read_file(struct blocklevel_device *bl, const char *file,
>  		perror("Failed to open file");
>  		return 1;
>  	}
> +	start += skip_size;
> +	size -= skip_size;
> +
>  	printf("Reading to \"%s\" from 0x%08x..0x%08x !\n",
>  	       file, start, start + size);
>  
> @@ -644,6 +647,8 @@ static void print_help(const char *pname)
>  	printf("\t\tTarget filename instead of actual flash.\n\n");
>  	printf("\t-S, --side\n");
>  	printf("\t\tSide of the flash on which to operate, 0 (default) or 1\n\n");
> +	printf("\t--skip=N\n");
> +	printf("\t\tSkip N number of bytes from the start when reading\n\n");
>  	printf("\t-T, --toc\n");
>  	printf("\t\tlibffs TOC on which to operate, defaults to 0.\n");
>  	printf("\t\tleading 0x is required for interpretation of a hex value\n\n");
> @@ -709,7 +714,7 @@ int main(int argc, char *argv[])
>  	bool no_action = false, tune = false;
>  	char *write_file = NULL, *read_file = NULL, *part_name = NULL;
>  	bool ffs_toc_seen = false, direct = false, print_detail = false;
> -	int flash_side = 0;
> +	int flash_side = 0, skip_size = 0;
>  	int rc = 0;
>  
>  	while(1) {
> @@ -735,6 +740,7 @@ int main(int argc, char *argv[])
>  			{"version",	no_argument,		NULL,	'v'},
>  			{"debug",	no_argument,		NULL,	'g'},
>  			{"side",	required_argument,	NULL,	'S'},
> +			{"skip",	required_argument,	NULL,	'k'},
>  			{"toc",		required_argument,	NULL,	'T'},
>  			{"clear",   no_argument,        NULL,   'c'},
>  			{NULL,	    0,                  NULL,    0 }
> @@ -826,6 +832,13 @@ int main(int argc, char *argv[])
>  		case 'S':
>  			flash_side = atoi(optarg);
>  			break;
> +		case 'k':
> +			skip_size = strtoul(optarg, &endptr, 0);
> +			if (*endptr != '\0') {
> +				rc = 1;
> +				no_action = true;
> +			}
> +			break;
>  		case 'T':
>  			if (!optarg)
>  				break;
> @@ -935,6 +948,13 @@ int main(int argc, char *argv[])
>  		goto out;
>  	}
>  
> +	/* Skip only supported on read */
> +	if (skip_size && !do_read) {
> +		fprintf(stderr, "--skip requires a --read command !\n");
> +		rc = 1;
> +		goto out;
> +	}
> +
>  	/* Program command should always come with a file */
>  	if (program && !write_file) {
>  		fprintf(stderr, "Program with no file specified !\n");
> @@ -1142,7 +1162,7 @@ int main(int argc, char *argv[])
>  	}
>  	rc = 0;
>  	if (do_read)
> -		rc = do_read_file(flash.bl, read_file, address, read_size);
> +		rc = do_read_file(flash.bl, read_file, address, read_size, skip_size);
>  	if (!rc && erase_all)
>  		rc = erase_chip(&flash);
>  	else if (!rc && erase)