Re: [PATCH 6] ARM: support big/little endian switching in "bootz".

[Sascha Hauer <s.hauer@pengutronix.de>]

Hi Krzysztof,

On Mon, Dec 20, 2010 at 11:58:11PM +0100, Krzysztof Halasa wrote:
> ARM: support big/little endian switching in "bootz".
> Perhaps one should make this conditional? Mostly for big-endian
> Barebox loading little-endian (e.g. armel Debian) Linux.

Making it conditional could require a lot of ifdefs, maybe you could
just do...

> 
> Signed-off-by: Krzysztof Hałasa <khc@pm.waw.pl>
> 
> diff --git a/arch/arm/lib/armlinux.c b/arch/arm/lib/armlinux.c
> index f826da6..4d1c757 100644
> --- a/arch/arm/lib/armlinux.c
> +++ b/arch/arm/lib/armlinux.c
> @@ -41,6 +41,7 @@
>  #include <asm/setup.h>
>  #include <asm/barebox-arm.h>
>  #include <asm/armlinux.h>
> +#include <asm/system.h>
>  
>  static struct tag *params;
>  static int armlinux_architecture = 0;
> @@ -85,9 +86,10 @@ static void setup_memory_tags(void)
>  	}
>  }
>  
> -static void setup_commandline_tag(const char *commandline)
> +static void setup_commandline_tag(const char *commandline, int swap)
>  {
>  	const char *p;
> +	size_t words;
>  
>  	if (!commandline)
>  		return;
> @@ -102,12 +104,18 @@ static void setup_commandline_tag(const char *commandline)
>  	if (*p == '\0')
>  		return;
>  
> +	words = (strlen(p) + 1 /* NUL */ + 3 /* round up */) >> 2;
>  	params->hdr.tag = ATAG_CMDLINE;
> -	params->hdr.size =
> -	    (sizeof (struct tag_header) + strlen(p) + 1 + 4) >> 2;
> +	params->hdr.size = (sizeof(struct tag_header) >> 2) + words;
>  
>  	strcpy(params->u.cmdline.cmdline, p);
>  
> +	if (swap) {
> +		u32 *cmd = (u32 *)params->u.cmdline.cmdline;
> +		while (words--)
> +			cmd[words] = swab32(cmd[words]);
> +	}
> +
>  	params = tag_next(params);
>  }
>  
> @@ -156,13 +164,13 @@ static void setup_end_tag (void)
>  	params->hdr.size = 0;
>  }
>  
> -static void setup_tags(struct image_data *data)
> +static void setup_tags(struct image_data *data, int swap)
>  {
>  	const char *commandline = getenv("bootargs");
>  
>  	setup_start_tag();
>  	setup_memory_tags();
> -	setup_commandline_tag(commandline);
> +	setup_commandline_tag(commandline, swap);
>  
>  	if (data && data->initrd)
>  		setup_initrd_tag (&data->initrd->header);
> @@ -231,7 +239,7 @@ static int do_bootm_linux(struct image_data *data)
>  	debug("## Transferring control to Linux (at address 0x%p) ...\n",
>  	       theKernel);
>  
> -	setup_tags(data);
> +	setup_tags(data, 0);
>  
>  	if (relocate_image(data->os, (void *)image_get_load(os_header)))
>  		return -1;
> @@ -290,18 +298,21 @@ late_initcall(armlinux_register_image_handler);
>  
>  #ifdef CONFIG_CMD_BOOTZ
>  struct zimage_header {
> -	u32	unsused[9];
> +	u32	unused[9];
>  	u32	magic;
>  	u32	start;
>  	u32	end;
>  };
>  
> +#define ZIMAGE_MAGIC 0x016F2818
> +
>  static int do_bootz(struct command *cmdtp, int argc, char *argv[])
>  {
>  	void (*theKernel)(int zero, int arch, void *params);
> -	int fd, ret;
> +	int fd, ret, swap = 0;
>  	struct zimage_header header;
>  	void *zimage;
> +	u32 end;

#ifdef CONFIG_BOOTZ_ENDIANESS_SWAP
	int enable_swap = 1;
#else
	int enable_swap = 0;
#endif

>  
>  	if (argc != 2) {
>  		barebox_cmd_usage(cmdtp);
> @@ -320,27 +331,51 @@ static int do_bootz(struct command *cmdtp, int argc, char *argv[])
>  		goto err_out;
>  	}
>  
> -	if (header.magic != 0x016f2818) {
> +	switch (header.magic) {
> +	case swab32(ZIMAGE_MAGIC):
> +		swap = 1;

		swap = enable_swap;

This should be enough for the compiler to throw away most overhead.

> +		/* fall through */
> +	case ZIMAGE_MAGIC:
> +		break;
> +	default:
>  		printf("invalid magic 0x%08x\n", header.magic);
>  		goto err_out;
>  	}
>  
> -	zimage = xmalloc(header.end);
> +	end = header.end;
> +
> +	if (swap)
> +		end = swab32(end);
> +
> +	zimage = xmalloc(end);
>  	memcpy(zimage, &header, sizeof(header));
>  
> -	ret = read(fd, zimage + sizeof(header), header.end - sizeof(header));
> -	if (ret < header.end - sizeof(header)) {
> +	ret = read(fd, zimage + sizeof(header), end - sizeof(header));
> +	if (ret < end - sizeof(header)) {
>  		printf("could not read %s\n", argv[1]);
>  		goto err_out1;
>  	}
>  
> +	if (swap) {
> +		void *ptr;
> +		for (ptr = zimage; ptr < zimage + end; ptr += 4)
> +			*(u32 *)ptr = swab32(*(u32 *)ptr);
> +	}
> +
>  	theKernel = zimage;
>  
> -	printf("loaded zImage from %s with size %d\n", argv[1], header.end);
> +	printf("loaded zImage from %s with size %d\n", argv[1], end);
>  
> -	setup_tags(NULL);
> +	setup_tags(NULL, swap);
>  
>  	shutdown_barebox();
> +	if (swap) {
> +		u32 reg;
> +		__asm__ __volatile__("mrc p15, 0, %0, c1, c0" : "=r" (reg));
> +		reg ^= CR_B; /* swap big-endian flag */
> +		__asm__ __volatile__("mcr p15, 0, %0, c1, c0" :: "r" (reg));
> +	}
> +
>  	theKernel(0, armlinux_architecture, armlinux_bootparams);
>  
>  	return 0;
> 
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