Re: [RFC 08/10] bootm: add kexec ELF support

From: Sascha Hauer <s.hauer@pengutronix.de>
To: Antony Pavlov <antonynpavlov@gmail.com>
Cc: barebox@lists.infradead.org
Subject: Re: [RFC 08/10] bootm: add kexec ELF support
Date: Wed, 23 Apr 2014 11:15:51 +0200	[thread overview]
Message-ID: <20140423091551.GG5858@pengutronix.de> (raw)
In-Reply-To: <1397547514-19925-9-git-send-email-antonynpavlov@gmail.com>

On Tue, Apr 15, 2014 at 11:38:32AM +0400, Antony Pavlov wrote:
> Also introduce reboot() for starting already loaded
> via kexec ELF segments.
> 
> Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
> ---
>  include/linux/reboot.h      | 14 ++++++++++++++
>  lib/kexec/Makefile          |  1 +
>  lib/kexec/kexec-bootm-elf.c | 36 ++++++++++++++++++++++++++++++++++++
>  3 files changed, 51 insertions(+)
>  create mode 100644 include/linux/reboot.h
>  create mode 100644 lib/kexec/kexec-bootm-elf.c
> 
> diff --git a/include/linux/reboot.h b/include/linux/reboot.h
> new file mode 100644
> index 0000000..454ed33
> --- /dev/null
> +++ b/include/linux/reboot.h
> @@ -0,0 +1,14 @@
> +#ifndef _LINUX_REBOOT_H
> +#define _LINUX_REBOOT_H
> +
> +/*
> + * Commands accepted by the _reboot() system call.
> + *
> + * KEXEC       Restart system using a previously loaded Linux kernel
> + */
> +
> +#define	LINUX_REBOOT_CMD_KEXEC		0x45584543
> +
> +extern int reboot(int cmd);
> +
> +#endif /* _LINUX_REBOOT_H */
> diff --git a/lib/kexec/Makefile b/lib/kexec/Makefile
> index 8febef1..2f3dc1d 100644
> --- a/lib/kexec/Makefile
> +++ b/lib/kexec/Makefile
> @@ -1,3 +1,4 @@
>  obj-y	+= kexec.o
>  obj-y	+= kexec-elf.o
>  obj-y	+= kexec-elf-exec.o
> +obj-y	+= kexec-bootm-elf.o
> diff --git a/lib/kexec/kexec-bootm-elf.c b/lib/kexec/kexec-bootm-elf.c
> new file mode 100644
> index 0000000..6c8071a
> --- /dev/null
> +++ b/lib/kexec/kexec-bootm-elf.c
> @@ -0,0 +1,36 @@
> +#include <boot.h>
> +#include <init.h>
> +#include <binfmt.h>
> +#include <errno.h>
> +#include <linux/reboot.h>
> +
> +#include "kexec.h"
> +
> +static int do_bootm_elf(struct image_data *data)
> +{
> +	kexec_load_file(data->os_file, 0);
> +	setenv("global.bootm.image", data->os_file);
> +	reboot(LINUX_REBOOT_CMD_KEXEC);
> +
> +	return -ERESTARTSYS;
> +}
> +
> +static struct image_handler elf_handler = {
> +	.name = "ELF",
> +	.bootm = do_bootm_elf,
> +	.filetype = filetype_elf,
> +};
> +
> +static struct binfmt_hook binfmt_elf_hook = {
> +	.type = filetype_elf,
> +	.exec = "bootm",
> +};
> +
> +static int elf_register_image_handler(void)
> +{
> +	register_image_handler(&elf_handler);
> +	binfmt_register(&binfmt_elf_hook);
> +
> +	return 0;
> +}
> +late_initcall(elf_register_image_handler);

Instead of making this an initcall I suggest that you call this function
from Malta specific code along with a pointer to a kexec_execute_file
function. This makes sure the generic code does not have to call into
global architecture specific functions. Also the dataflow can be done
clearer. kexec_load_file() currently loads the image *somewhere* and
reboot() is expected to know where it is loaded. I imagine kexec_load_file
should return information about the loaded image which is then passed to
reboot().

Sascha

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