[coreboot] a question about reset16.lds

[ali hagigat]

Thank you for the reply.

Lets consider the lines of that linker script again! First the
location counter is set to 0xfffffff0 and the output .reset section
starts from VMA=0xfffffff0. I think we both agree on that so far.
But after .reset section, .=15 forces the location counter to be 15!!
It means the location counter suddenly jumps from the top of memory to
some where in the bottom! and then linker asks for storing 0x00 in the
address of 15! or at the beginning of memory.
.=15 does not set the size of .reset as you wrote.
My suggestion was .=.+1 instead of .=15, or set VMA to one byte after
the final .reset and then ask for writing 0x00 at the address of
0xffffffff.
We are using . in the linker script file, it means VMA (virtual memory
address)    .....


On Tue, Feb 1, 2011 at 8:15 PM, Patrick Georgi <patrick at georgi-clan.de> wrote:
> Am 01.02.2011 12:46, schrieb ali hagigat:
>>
>> SECTIONS {
>>        /* Trigger an error if I have an unuseable start address */
>>        _bogus = ASSERT(_start>= 0xffff0000, "_start too low. Please
>> decrease CONFIG_ROM_IMAGE_SIZE");
>>        _ROMTOP = 0xfffffff0;
>>        . = _ROMTOP;
>>        .reset . : {
>>                *(.reset)
>>                . = 15 ;
>>                BYTE(0x00);
>>        }
>> }
>> ------------------------------------------------------------------
>> What does (.=15;) mean? It seems a mistake! and can be: . = .+1;
>
> . = 15; means "set the location pointer to 15". With the byte that's written
> right after that, this means that .reset is exactly 16 bytes.
> If it's less, ". = 15" pads the section to be larger, if it would have to be
> larger, ". = 15" makes the linker fail (because the location pointer must
> not go backwards).
>
> I guess that also answers why ". = .+1" is no adequate substitute.
>
>
> Patrick
>
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