linux-embedded: smallest kernel for 2.4.0-test9

linux-embedded: smallest kernel for 2.4.0-test9

[Brendan J Simon]

I've ported the 2.4.0-test9 kernel to our MPC8260 board.  I have a 512K
boot flash and am trying to get the kernel to fit in it and then mount
the root file system via NFS.  I currently have the kernel down to 520K
but would like to get it under 448K (512K minus one 64K sector for a
bootloader).  Is this possible ???

Please CC to me as well as the list,
Thanks,
Brendan Simon.


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Re: linux-embedded: smallest kernel for 2.4.0-test9

[Dan Malek]

Brendan J Simon wrote:

> ....  I currently have the kernel down to 520K
> but would like to get it under 448K (512K minus one 64K sector for a
> bootloader).  Is this possible ???


Heh...I did this just the other day with a old -test2 kernel.

Did you remove the ELF header?

	dd if=zImage bs=64k skip=1 of=zImage.bin

The starting instruction is the first word of zImage.bin.


	-- Dan

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embedded gcc PPC toolchain questions

[Ron Flory]

  Hello;

  I have several low-level gcc toolchain questions.  I'm not new to
gcc or embedded programming, but this is the fist time I've tried
to use gcc for a stand-alone, non-linux embedded PPC project.

  Apologies in advance if these appear to be a little off-subject.
I welcome redirection to online FAQs or code snippets.  Thanks.

1.  How does one declare distinct data regions with GCC?  Consider
    the case where a separate non-cached memory region is needed
    for CPM/FEC use, I would do something like the following under
    GreenHills C/C++:

     #pragma ghs section data = ".nocacheram"
        static char fec_rbd_alloc[ <some length> ] = { 0 };
        static char fec_tbd_alloc[ <some length> ] = { 0 };
     #pragma ghs section

     Such distinct regions are generally collected and combined
    across modules, so the FEC and CPM drivers would place their
    buffers in the same non-cached area.

2.  Once I have defined and declared such regions, how does one
    instruct the linker to align and padd such regions?  Under
    Greenhills, this would be done in a linker control file, such
    as:

     .nocacheram  align(0x1000)   :
     .evtdata     align(0x1000)   :

       This would align ".nocacheram" on a 4kb boundary, and would
      ensure 4Kb length as well (since the following group was also
      4Kb aligned).

3.  Once I have defined, declared, and aligned these special memory
    regions, how would I determine their base/length?  Again, under
    GreenHills, we would declare:

      extern char __ghsbegin_nocacheram[];
      extern char __ghsend_nocacheram[];

     Which would provide the 'begin' and 'end' address of the region,
    allowing us to set the appropriate MMU attributes for this user-
    defined area.

4.  I know the question of embedded libc comes up often.  For
    the most part, we basically need the 'strxxx' and 'memxxx'
    functions, but 'sprintf' is quite a different critter.  Since
    we are running an 860, we won't have FP support (and we don't
    want to deal with emulation).  Do most folks use a hand-patched
    'sprintf' source file, manually removing the floating-point ops?
    I've looked into this a few years ago (the gcc sprintf source
    file is a horror).  Has the 'ulibc' that i've heard about been
    used with success by anybody on this list for embedded non-linux
    projects?

5.  We have access to many Macraigor 'Raven' BDM interfaces.  I've
    downloaded the x86 Linux support tools for this device.  Has
    anybody had good results with this device and support tools
    under Linux?

6.  OK, please don't flame me on this stupid question.  Does 'as'
    (the assembler) run its source input through the 'cpp' C
    PreProcessor?  I can always pipe through cpp myself with an
    implicit 'make' target if I need to...

  Thank you.

--

Ron Flory, Network Products.
email: mailto:ron.flory@adtran.com


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Re: embedded gcc PPC toolchain questions

[Wolfgang Denk]

Dear Ron,

in message <3ED6298C.3070901@adtran.com> you wrote:
>
>   I have several low-level gcc toolchain questions.  I'm not new to

Umm... did you read the info files for GCC and the GNU linker?

>   Apologies in advance if these appear to be a little off-subject.
> I welcome redirection to online FAQs or code snippets.  Thanks.

It is definitely useful to read existing code, too. The Linux  kernel
or the U-Boot bootloader are good places to start.

> 1.  How does one declare distinct data regions with GCC?  Consider

Use __attribute__ ((section("<name>")))

>     the case where a separate non-cached memory region is needed
>     for CPM/FEC use, I would do something like the following under
>     GreenHills C/C++:
>
>      #pragma ghs section data = ".nocacheram"
>         static char fec_rbd_alloc[ <some length> ] = { 0 };
>         static char fec_tbd_alloc[ <some length> ] = { 0 };
>      #pragma ghs section

static char fec_rbd_alloc[ <some length> ] __attribute__ ((section(".nocacheram"))) = { 0 };

etc.

It probably makes sense to define some macros, like this:

#define ___NOCACHERAM__ __attribute__ ((section(".nocacheram")))
...
static char fec_rbd_alloc[ <some length> ] ___NOCACHERAM__ = { 0 };


>      Such distinct regions are generally collected and combined
>     across modules, so the FEC and CPM drivers would place their
>     buffers in the same non-cached area.

Same here.

> 2.  Once I have defined and declared such regions, how does one
>     instruct the linker to align and padd such regions?  Under
>     Greenhills, this would be done in a linker control file, such
>     as:
>
>      .nocacheram  align(0x1000)   :
>      .evtdata     align(0x1000)   :

With GNU ld you will use a linker control file, too.

Something like this:

...
. = ALIGN(4 * 1024);
.nocacheram	:
{
	*(.nocacheram)
}
. = ALIGN(4 * 1024);
...

>        This would align ".nocacheram" on a 4kb boundary, and would
>       ensure 4Kb length as well (since the following group was also
>       4Kb aligned).

Same here.

> 3.  Once I have defined, declared, and aligned these special memory
>     regions, how would I determine their base/length?  Again, under
>     GreenHills, we would declare:
>
>       extern char __ghsbegin_nocacheram[];
>       extern char __ghsend_nocacheram[];
>
>      Which would provide the 'begin' and 'end' address of the region,
>     allowing us to set the appropriate MMU attributes for this user-
>     defined area.

You can define symbols in the linker script, too. Like this:

...
. = ALIGN(4 * 1024);
begin_nocacheram	:
{
	*(.nocacheram)
}
end_nocacheram:
. = ALIGN(4 * 1024);
...

> 4.  I know the question of embedded libc comes up often.  For
>     the most part, we basically need the 'strxxx' and 'memxxx'
>     functions, but 'sprintf' is quite a different critter.  Since
>     we are running an 860, we won't have FP support (and we don't
>     want to deal with emulation).  Do most folks use a hand-patched
>     'sprintf' source file, manually removing the floating-point ops?
>     I've looked into this a few years ago (the gcc sprintf source
>     file is a horror).  Has the 'ulibc' that i've heard about been
>     used with success by anybody on this list for embedded non-linux
>     projects?

Again, have a look at U-Boot and Linux. (U-Boot reuses the Linux code.)

> 5.  We have access to many Macraigor 'Raven' BDM interfaces.  I've
>     downloaded the x86 Linux support tools for this device.  Has
>     anybody had good results with this device and support tools
>     under Linux?

We prrefer the BDI2000.

> 6.  OK, please don't flame me on this stupid question.  Does 'as'
>     (the assembler) run its source input through the 'cpp' C
>     PreProcessor?  I can always pipe through cpp myself with an
>     implicit 'make' target if I need to...

"as" does not use "cpp". If you want  to  use  "cpp",  then  you  can
either  use "cpp" in a separate step, or use "gcc" which knows how to
deal with "*.S" source files.

Again, see Linux and U-Boot code for examples.

Best regards,

Wolfgang Denk

--
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd@denx.de
If I can have honesty, it's easier to overlook mistakes.
	-- Kirk, "Space Seed", stardate 3141.9

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Re: embedded gcc PPC toolchain questions

[Erik Christiansen]

in message <3ED6298C.3070901@adtran.com> Ron Flory wrote:

> 4.  I know the question of embedded libc comes up often.  For
>     the most part, we basically need the 'strxxx' and 'memxxx'
>     functions, but 'sprintf' is quite a different critter.  Since
>     we are running an 860, we won't have FP support (and we don't
>     want to deal with emulation).  Do most folks use a hand-patched
>     'sprintf' source file, manually removing the floating-point ops?
>     I've looked into this a few years ago (the gcc sprintf source
>     file is a horror).  Has the 'ulibc' that i've heard about been
>     used with success by anybody on this list for embedded non-linux
>     projects?

Ron,

   We're happily using newlib's sprintf on the mpc850, in a piece of
   seriously embedded non-linux equipment.

   According to my rough notes, µClibc is LGPL, so static linking may not
   be a good idea. Newlib's BSD-like terms seemed more appealing to me.

   http://sources.redhat.com/newlib

   Bill Gatliff wrote an article on it, in the December 2001 issue of
   Embedded Systems Programming.

   There's apparently also dietlibc and sglibc, but I haven't
   investigated either.

Regards,
Erik


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