Re: [RFC v2 6/8] bootm: add kexec ELF support

[Antony Pavlov <antonynpavlov@gmail.com>]

On Wed, 7 Dec 2016 20:59:04 +0100
Sascha Hauer <s.hauer@pengutronix.de> wrote:

> On Mon, Dec 05, 2016 at 12:40:31PM +0300, 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 | 37 +++++++++++++++++++++++++++++++++++++
> >  3 files changed, 52 insertions(+)
> > 
> > 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..ceef6c7
> > --- /dev/null
> > +++ b/lib/kexec/kexec-bootm-elf.c
> > @@ -0,0 +1,37 @@
> > +#include <bootm.h>
> > +#include <init.h>
> > +#include <binfmt.h>
> > +#include <errno.h>
> > +#include <linux/reboot.h>
> > +#include <environment.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);
> 
> The code needed to actually start a kexec kernel is architecture
> specific, so the registration of the ELF handler should be done by this
> architecture specific code. Then you also don't need this awkward reboot()
> stuff. I'm thinking of a
> 
> int bootm_register_kexec_handler(int (*do_bootm)(struct image_data *data));
> 
> to be called by MIPS or malta specific code.
> 

Moreover current RFC v2 kexec patchseries contains too many redundant code
(e.g. kexec uses it's own filetype-like infrastructure).

I agree. Current barebox kexec infrastructure is used only for MIPS so I can move
some code from lib/ to arch/mips. 

-- 
Best regards,
  Antony Pavlov

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