Re: Encryption Support for GRUB

[Javier Martín]

El mié, 06-08-2008 a las 10:11 -0700, Colin D Bennett escribió:
> On Wed, 6 Aug 2008 11:04:16 -0500 (CDT)
> "W. Michael Petullo" <address@hidden> wrote:
> 
> > 1.  How do I know exactly what subset of libc is available to me as a
> > GRUB developer? Obviously, system calls would not be expected to work
> > because the operating system has not yet been loaded, but I would
> > expect libmath routines to be usable by GRUB. What about other
> > libraries?
> 
> No libc is available.  Only functions implemented by GRUB itself are
> available.  See ``kern/misc.c`` and ``include/grub/misc.h`` in the GRUB
> 2 source tree for implementations of the most important things that are
> normally provided by libc, such as strcpy (grub_strcpy), memcmp
> (grub_memcmp), etc.
Maybe we should separate those headers in ANSI-like files, following a
structure like:

include/grub/gstdlib.h - grub_malloc et al
include/grub/gstdio.h - grub_printf and friends
etc

Of course, most of them would not be complete (i.e. gstdlib.h would not
have process control functions) but at least we'd separate "support"
functions from "pure GRUB" and questions like the OP's would be fast to
answer: "look at gstd*.h".

Furthermore, such a separation would "force" us to "commit" to a
semi-permanent specification of which subset of libc is available to
module writers, which is good if people wants to write and maintain
modules outside the GRUB tree.

-Habbit


> 
> link to online svn for misc.c:
> http://svn.savannah.gnu.org/viewvc/trunk/grub2/kern/misc.c?revision=1774&root=grub&view=markup
> 
> GRUB implements dynamic memory allocation through grub_malloc,
> grub_free, grub_realloc.  See ``kern/mm.c``.
> 
> No math library is available, but I think you could create a 'math'
> module in GRUB and implement the required math functions there.  The
> main thing is to keep the GRUB core small.  It needs to fit in 32 KB, I
> think.
> 
> GRUB has its own file I/O api (no stdio -- instead use grub_file_open,
> grub_file_read, etc.).
> 
> If you want to see how to use the GRUB library stuff, look at some of
> the built in commands such as ``commands/ls.c``, etc.
> 
> Regards,
> Colin
> 
> 
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