Why prot_size subtract GRUB_DISK_SECTOR_SIZE in the file grub-1.98/loader/i386/linux.c ?

Why prot_size subtract GRUB_DISK_SECTOR_SIZE in the file grub-1.98/loader/i386/linux.c ?

[Baisheng Wang]

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Dear all:

In the file grub-1.98/loader/i386/linux.c, for the variable prot_size, why
subtract GRUB_DISK_SECTOR_SIZE ?

Thanks & Regards,
Baisheng

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Re: Why prot_size subtract GRUB_DISK_SECTOR_SIZE in the file grub-1.98/loader/i386/linux.c ?

[Baisheng Wang]

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Let me clarify again.

In grub-1.98/loader/i386/linux.c, for the code lines：

"grub_file_seek (file, real_size + GRUB_DISK_SECTOR_SIZE);"

and

"prot_size = grub_file_size (file) - real_size - GRUB_DISK_SECTOR_SIZE;"

I want to know why there is another sector, I mean GRUB_DISK_SECTOR_SIZE ?

Thanks,
Baisheng


2011/2/10 Baisheng Wang <baisheng.wang.cn@gmail.com>

> Dear all:
>
> In the file grub-1.98/loader/i386/linux.c, for the variable prot_size, why
> subtract GRUB_DISK_SECTOR_SIZE ?
>
> Thanks & Regards,
> Baisheng
>
>

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Re: Why prot_size subtract GRUB_DISK_SECTOR_SIZE in the file grub-1.98/loader/i386/linux.c ?

[Vladimir 'φ-coder/phcoder' Serbinenko]

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On 02/10/2011 03:52 PM, Baisheng Wang wrote:
>
> Let me clarify again.
>
> In grub-1.98/loader/i386/linux.c, for the code lines：
>
> "grub_file_seek (file, real_size + GRUB_DISK_SECTOR_SIZE);"
>
> and
>
> "prot_size = grub_file_size (file) - real_size - GRUB_DISK_SECTOR_SIZE;"
>
> I want to know why there is another sector, I mean GRUB_DISK_SECTOR_SIZE ?
>
Trivial, Watson. first sector contains the part which is launched only
when dd'ing to floppy, not with a propoer bootloader. Actually recent
kernels just contain a stub instruction to use a bootloader
> Thanks,
> Baisheng
>
>
> 2011/2/10 Baisheng Wang <baisheng.wang.cn
> <http://baisheng.wang.cn>@gmail.com <http://gmail.com>>
>
>     Dear all:
>
>     In the file grub-1.98/loader/i386/linux.c, for the variable
>     prot_size, why subtract GRUB_DISK_SECTOR_SIZE ?
>
>     Thanks & Regards,
>     Baisheng
>
>
>
> _______________________________________________
> Grub-devel mailing list
> Grub-devel@gnu.org
> http://lists.gnu.org/mailman/listinfo/grub-devel
>   


-- 
Regards
Vladimir 'φ-coder/phcoder' Serbinenko



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Re: Why prot_size subtract GRUB_DISK_SECTOR_SIZE in the file grub-1.98/loader/i386/linux.c ?

[Baisheng Wang]

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Ok, It seems that I'v got it.

In file arch/x86/boot/tools/build.c, fill the setup_sects parameters in
header.S with "setup_sectors-1". Why build tool do this, It very strange!

Regards,
Baisheng

"buf[0x1f1] = setup_sectors-1;"

2011/2/11 Vladimir 'φ-coder/phcoder' Serbinenko <phcoder@gmail.com>

> On 02/10/2011 03:52 PM, Baisheng Wang wrote:
> >
> > Let me clarify again.
> >
> > In grub-1.98/loader/i386/linux.c, for the code lines：
> >
> > "grub_file_seek (file, real_size + GRUB_DISK_SECTOR_SIZE);"
> >
> > and
> >
> > "prot_size = grub_file_size (file) - real_size - GRUB_DISK_SECTOR_SIZE;"
> >
> > I want to know why there is another sector, I mean GRUB_DISK_SECTOR_SIZE
> ?
> >
> Trivial, Watson. first sector contains the part which is launched only
> when dd'ing to floppy, not with a propoer bootloader. Actually recent
> kernels just contain a stub instruction to use a bootloader
> > Thanks,
> > Baisheng
> >
> >
> > 2011/2/10 Baisheng Wang <baisheng.wang.cn
> > <http://baisheng.wang.cn>@gmail.com <http://gmail.com>>
> >
> >     Dear all:
> >
> >     In the file grub-1.98/loader/i386/linux.c, for the variable
> >     prot_size, why subtract GRUB_DISK_SECTOR_SIZE ?
> >
> >     Thanks & Regards,
> >     Baisheng
> >
> >
> >
> > _______________________________________________
> > Grub-devel mailing list
> > Grub-devel@gnu.org
> > http://lists.gnu.org/mailman/listinfo/grub-devel
> >
>
>
> --
> Regards
> Vladimir 'φ-coder/phcoder' Serbinenko
>
>
>
> _______________________________________________
> Grub-devel mailing list
> Grub-devel@gnu.org
> http://lists.gnu.org/mailman/listinfo/grub-devel
>
>

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