Shinya Kuribayashi wrote: [snip]
Here's my proposal for RFC. This patch fixes
__got_start and _GLOBAL_OFFSET_TABLE_ miss-alignment, and
duplicated .sdata declaration.
[snip]
.got : {_gp = .;__got_start = .;*(.got)__got_end = .;}
[snip] That doesn't look right. Don't put _gp inside .got section.
I think this style is easier to understand than before.
But I'm still wondering where _gp can be used?
Any comments are welcome.
It should be loaded into the $gp register.
got[0](=0x00000000) and got[1](=0x80000000) are always reserved by
GNU ld. When updating the contents of GOT entries at in_ram:, leave
first two entries as they are. This is the reason for skipping two
entries. And as you know, this is nothing related with corrupting
command table. That's caused by relocation itself, not by updating
GOT entries.
.got it :-)
One more point: loading $gp with _GLOBAL_OFFSET_TABLE_ is not a good idea, it should be loaded with _gp. The value
is the same at the moment, but it's not guaranteed at all, someone could start playing with the link scripts and break this.
Hmm, I have to consider more.
Here's a good example:
http://www.sourceware.org/ml/ecos-discuss/2004-02/msg00327.html
There are some sections (.sdata/.sbss/.scommon) that contain objects referenced via $gp and not via GOT.
Try nm -n -f sysv u-boot|grep scommon.
I can also send you a patch with _gp != __got_start , and if you don't load $gp with _gp but with __got_start, it will crash and burn when doing
/* Initialize any external memory. */ la t9, lowlevel_init jalr t9
It will actually jump to _serial_puts(), believe it or not.
Vlad