Re: [PATCH 04/17] MIPS: qemu-malta: generate swapped image as part of multi-image build

[Jules Maselbas <jmaselbas@kalray.eu>]

Hi Ahmad,

Just in case you didn't know, the byte swap can be done
without a writting C program but with a simple shell script.

You can use objcopy to create a byte swapped image:
objcopy -I binary --reverse-bytes=4 barebox barebox.swapped

You can use truncate to make sure the file size is multiple of 4 bytes:
truncate -s %4 file

bswap32 script could be implemented like this:
cp $in $out
truncate -s %4 $out
objcopy -I binary --reverse-byte=4 $out

Best,
Jules

On Mon, Apr 12, 2021 at 09:16:38AM +0200, Ahmad Fatoum wrote:
> Having to manually swap the words in the MIPS Malta image for QEMU
> little endian emulation is annoying.
> 
> Have the multi-image build for Malta generate a second .swapped
> image that can be readily used if needed.
> 
> Cc: Antony Pavlov <antonynpavlov@gmail.com>
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> ---
>  Documentation/boards/mips/qemu-malta.rst | 16 ++---
>  images/.gitignore                        |  1 +
>  images/Makefile                          |  2 +-
>  images/Makefile.malta                    |  8 ++-
>  scripts/Makefile                         |  1 +
>  scripts/bswap.c                          | 83 ++++++++++++++++++++++++
>  6 files changed, 97 insertions(+), 14 deletions(-)
>  create mode 100644 scripts/bswap.c
> 
> diff --git a/Documentation/boards/mips/qemu-malta.rst b/Documentation/boards/mips/qemu-malta.rst
> index e188ae8c642a..fd37d5edb229 100644
> --- a/Documentation/boards/mips/qemu-malta.rst
> +++ b/Documentation/boards/mips/qemu-malta.rst
> @@ -10,31 +10,23 @@ QEMU run string:
>  
>    qemu-system-mips -nodefaults -M malta -m 256 \
>        -device VGA -serial stdio -monitor null \
> -      -bios barebox-flash-image
> +      -bios ./images/barebox-qemu-malta.img
>  
>  
>  Little-endian mode
>  ------------------
>  
> -Running little-endian Malta is a bit tricky.
>  In little-endian mode the 32bit words in the boot flash image are swapped,
>  a neat trick which allows bi-endian firmware.
>  
> -You have to swap words of ``zbarebox.bin`` image, e.g.:
> -
> -.. code-block:: sh
> -
> -  echo arch/mips/pbl/zbarebox.bin \
> -      | cpio --create \
> -      | cpio --extract --swap --unconditional
> -
> -QEMU run string:
> +The barebox build generates a second ``./images/barebox-qemu-malta.img.swapped``
> +image that can be used in this case, e.g.:
>  
>  .. code-block:: sh
>  
>    qemu-system-mipsel -nodefaults -M malta -m 256 \
>        -device VGA -serial stdio -monitor null \
> -      -bios barebox-flash-image
> +      -bios ./images/barebox-qemu-malta.img.swapped
>  
>  
>  Using GXemul
> diff --git a/images/.gitignore b/images/.gitignore
> index eafdb44b5bdd..3a9a77dad16e 100644
> --- a/images/.gitignore
> +++ b/images/.gitignore
> @@ -32,3 +32,4 @@ barebox.sum
>  *.mvebu1img
>  *.stm32
>  *.nmon
> +*.swapped
> diff --git a/images/Makefile b/images/Makefile
> index c185982c17ed..cc330d957597 100644
> --- a/images/Makefile
> +++ b/images/Makefile
> @@ -218,5 +218,5 @@ $(flash-list): $(image-y-path)
>  clean-files := *.pbl *.pblb *.map start_*.imximg *.img barebox.z start_*.kwbimg \
>  	start_*.kwbuartimg *.socfpgaimg *.mlo *.t20img *.t20img.cfg *.t30img \
>  	*.t30img.cfg *.t124img *.t124img.cfg *.mlospi *.mlo *.mxsbs *.mxssd \
> -	start_*.simximg start_*.usimximg *.zynqimg *.image
> +	start_*.simximg start_*.usimximg *.zynqimg *.image *.swapped
>  clean-files += pbl.lds
> diff --git a/images/Makefile.malta b/images/Makefile.malta
> index 5739ec464092..ce7b4424b63b 100644
> --- a/images/Makefile.malta
> +++ b/images/Makefile.malta
> @@ -1,3 +1,9 @@
> +quiet_cmd_bswap32_image = BSWAP4  $@
> +      cmd_bswap32_image = scripts/bswap -B 4 $< > $@
> +
> +$(obj)/%.img.swapped: $(obj)/%.img FORCE
> +	$(call if_changed,bswap32_image)
> +
>  pblb-$(CONFIG_BOARD_QEMU_MALTA) += start_qemu_malta
>  FILE_barebox-qemu-malta.img = start_qemu_malta.pblb
> -image-$(CONFIG_BOARD_QEMU_MALTA) += barebox-qemu-malta.img
> +image-$(CONFIG_BOARD_QEMU_MALTA) += barebox-qemu-malta.img barebox-qemu-malta.img.swapped
> diff --git a/scripts/Makefile b/scripts/Makefile
> index 2d322fd1c923..57861fa9b2f8 100644
> --- a/scripts/Makefile
> +++ b/scripts/Makefile
> @@ -16,6 +16,7 @@ hostprogs-always-$(CONFIG_KALLSYMS)			+= kallsyms
>  hostprogs-always-$(CONFIG_MIPS)				+= mips-relocs
>  hostprogs-always-$(CONFIG_MVEBU_HOSTTOOLS)		+= kwbimage kwboot mvebuimg
>  hostprogs-always-$(CONFIG_ARCH_OMAP)			+= omap_signGP mk-omap-image
> +hostprogs-always-$(CONFIG_BOARD_QEMU_MALTA)		+= bswap
>  hostprogs-always-$(CONFIG_ARCH_S5PCxx)			+= s5p_cksum
>  hostprogs-always-$(CONFIG_ARCH_DAVINCI)			+= mkublheader
>  HOSTCFLAGS_zynq_mkimage.o = -I$(srctree) -I$(srctree)/arch/arm/mach-zynq/include
> diff --git a/scripts/bswap.c b/scripts/bswap.c
> new file mode 100644
> index 000000000000..e87d30cfe51e
> --- /dev/null
> +++ b/scripts/bswap.c
> @@ -0,0 +1,83 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +// SPDX-FileCopyrightText: 2012 Jan Luebbe <j.luebbe@pengutronix.de>
> +
> +#define _BSD_SOURCE
> +#define _DEFAULT_SOURCE
> +
> +#include <stdio.h>
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +#include <fcntl.h>
> +#include <unistd.h>
> +#include <stdint.h>
> +#include <limits.h>
> +#include <errno.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <getopt.h>
> +#include <endian.h>
> +
> +static void usage(char *prgname)
> +{
> +	printf("usage: %s [OPTION] FILE > IMAGE\n"
> +	       "\n"
> +	       "options:\n"
> +	       "  -B           number of bytes to swap each time\n",
> +	       prgname);
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +	FILE *input;
> +	int opt;
> +	size_t size;
> +	unsigned long bytes = 0;
> +	uint32_t temp_u32;
> +
> +	while((opt = getopt(argc, argv, "B:")) != -1) {
> +		switch (opt) {
> +		case 'B':
> +			bytes = strtoul(optarg, NULL, 0);
> +			break;
> +		}
> +	}
> +
> +	if (optind >= argc) {
> +		usage(argv[0]);
> +		return 1;
> +	}
> +
> +	if (bytes != 4) {
> +		fprintf(stderr, "-B %s unsupported\n", optarg);
> +		return 1;
> +	}
> +
> +	input = fopen(argv[optind], "r");
> +	if (input == NULL) {
> +		perror("fopen");
> +		return 1;
> +	}
> +
> +	for (;;) {
> +		size = fread(&temp_u32, 1, sizeof(uint32_t), input);
> +		if (!size)
> +			break;
> +		if (size < 4 && !feof(input)) {
> +			perror("fread");
> +			return 1;
> +		}
> +
> +		temp_u32 = htobe32(le32toh(temp_u32));
> +		if (fwrite(&temp_u32, 1, sizeof(uint32_t), stdout) != 4) {
> +			perror("fwrite");
> +			return 1;
> +		}
> +	}
> +
> +	if (fclose(input) != 0) {
> +		perror("fclose");
> +		return 1;
> +	}
> +
> +	return 0;
> +}
> -- 
> 2.29.2
> 
> 
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