SPARC linker command files

[Jiri Gaisler]

On 11/30/2013 02:31 AM, Gedare Bloom wrote:
> Does the NGMP allow for variant sizes of ROM and RAM? If so will we
> provide separate BSP variants for all possibilities, or how does the
> user select the right size for their board?

The boot loader (or gdb debug monitor) supplies the top-of-stack
address in %sp when the RTEMS binary is called. The area between
the start address and %sp indicates the size of RAM to be used.
In this way only one bsp is needed.

Jiri.

> 
> On Fri, Nov 29, 2013 at 8:20 AM, Sebastian Huber
> <sebastian.huber at embedded-brains.de> wrote:
>> Hello,
>>
>> most SPARC BSPs use current the following linker provided symbols to specify
>> the memory layout:
>>
>> _PROM_SIZE = DEFINED (_PROM_SIZE) ? _PROM_SIZE : 2M;
>> _PROM_START = DEFINED (_PROM_START) ? _PROM_START : 0x00000000;
>>
>> _RAM_SIZE = DEFINED (_RAM_SIZE) ? _RAM_SIZE : 4M;
>> _RAM_START = DEFINED (_RAM_START) ? _RAM_START : 0x40000000;
>>
>> So it is possible to define them as command line parameters.  There are two
>> problems with this approach.
>>
>> Firstly start address must be consistent with the memory area definition.
>> Due to this reason the NGMP linker command file looks like this:
>>
>> _PROM_SIZE = DEFINED (_PROM_SIZE) ? _PROM_SIZE : 0;
>> _RAM_SIZE = DEFINED (_RAM_SIZE) ? _RAM_SIZE : 64M;
>>
>> MEMORY {
>>   rom     : ORIGIN = 0xC0000000, LENGTH = 256M
>>   ram     : ORIGIN = 0x00000000, LENGTH = 2048M
>>   sram    : ORIGIN = 0xD0000000, LENGTH = 256M
>> }
>>
>> _PROM_START = ORIGIN (rom);
>> _RAM_START = ORIGIN (ram);
>>
>> INCLUDE linkcmds.base
>>
>> Secondly the size symbols don't allow region overflow checks by the linker.
>>
>> A better approach would be to remove the ability to define these symbols on
>> the command line and use a memory map definition via memory regions only.
>> For the NGMP as an example this would look like:
>>
>> MEMORY {
>>   rom     : ORIGIN = 0xC0000000, LENGTH = 8M
>>   ram     : ORIGIN = 0x00000000, LENGTH = 64M
>> }
>>
>> INCLUDE linkcmds.base
>>
>> This change makes it necessary to adopt user Makefiles to this new approach.
>>
>> --
>> Sebastian Huber, embedded brains GmbH
>>
>> Address : Dornierstr. 4, D-82178 Puchheim, Germany
>> Phone   : +49 89 189 47 41-16
>> Fax     : +49 89 189 47 41-09
>> E-Mail  : sebastian.huber at embedded-brains.de
>> PGP     : Public key available on request.
>>
>> Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.
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> 
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